CN110337753B - Flexible rope-shaped supercapacitor with conformal shape - Google Patents

Abstract

Provided is a rope type supercapacitor including: (a) A first electrode comprising a first electrically conductive porous rod having pores, and a first mixture of a first electrode active material (e.g., activated carbon or isolated graphene sheets) and a first electrolyte present in the pores of the first porous rod; (b) A porous separator encapsulating the first electrode to form a separator protected first electrode; (c) A second electrode comprising a second electrically conductive porous rod having pores, and a second mixture of a second electrode active material and a second electrolyte present in the pores of the second porous rod; wherein the separator protected first and second electrodes combine to form a braid or twisted yarn; and (d) a protective sheath that wraps or encapsulates the braid or yarn.

Description

Flexible rope-shaped supercapacitor with conformal shape

Cross Reference to Related Applications

This application claims priority from U.S. patent application No. 15/398,416 filed on day 1, 4, 2017 and U.S. patent application No. 15/398,421 filed on day 1, 4, 2017, which are incorporated herein by reference.

Technical Field

The present invention relates generally to the field of supercapacitors (supercapacitors) or ultracapacitors (ultracapacitors), and more particularly to flexible and shape-conforming rope supercapacitors.

Background

Conventional supercapacitors and batteries (e.g., 18650 type cylindrical cells, rectangular pouch cells, and square cells) are mechanically rigid, and this inflexible feature has severely limited their adaptability or feasibility for implementation in confined spaces or for use in wearable devices. A flexible and shape-conformable power supply can be used to overcome these design limitations. These new power sources will enable the development of next generation electronic devices such as smart mobile gadgets, roll-up displays, wearable devices, and biomedical sensors. A flexible and conformable power supply will also save weight and space in an electric vehicle.

Electrochemical Capacitors (ECs), also known as supercapacitors or supercapacitors, are being considered for use in hybrid Electric Vehicles (EVs), where they can supplement the batteries used in electric vehicles to provide the power surge required for rapid acceleration, the biggest technical hurdle being to make battery-powered vehicles commercially viable. The battery will still be used for cruising, but the super capacitor (with its ability to release energy more quickly than the battery) will start to work when the car needs to accelerate to merge, pass, maneuver in emergency and climb a hill. The EC must also store sufficient energy to provide an acceptable vehicle range. In order to be cost-, volume-, and weight-efficient compared to the additional battery capacity, they must combine appropriate energy density (volumetric and gravimetric) and power density with long cycle life, and also meet cost targets.

As system designers become familiar with their attributes and benefits, ECs are also gaining acceptance in the electronics industry. ECs were originally developed to provide large bursts of drive energy for orbital lasers. For example, in Complementary Metal Oxide Semiconductor (CMOS) memory backup applications, a one farad EC with a volume of only one-half cubic inch can replace a nickel cadmium battery or a lithium battery and provide backup power for months. For a given applied voltage, the stored energy in the EC associated with a given charge is half the energy storable in the corresponding battery system for the same charge passed. Nonetheless, ECs are extremely attractive power sources. They do not require maintenance, provide much higher cycle life, require very simple charging circuits, do not experience "memory effects", and are generally much safer than batteries. Physical rather than chemical energy storage is a key reason for its safe operation and exceptionally high cycle life. Perhaps most importantly, the capacitor provides a higher power density than the battery.

The high volumetric capacitance density of ECs relative to conventional capacitors (10 to 100 times higher than conventional capacitors) results from the use of porous electrodes to create a large effective "plate area" and from storing energy in the diffused bilayer. Such bilayers, which naturally occur at the solid-electrolyte interface when a voltage is applied, have a thickness of only about 1nm, thus forming an extremely small effective "plate separation". Such supercapacitors are commonly referred to as Electric Double Layer Capacitors (EDLCs). Double layer capacitors are based on high surface area electrode materials, such as activated carbon, immersed in a liquid electrolyte. A polarized bilayer is formed at the electrode-electrolyte interface, providing high capacitance. This means that the specific capacitance of the supercapacitor is directly proportional to the specific surface area of the electrode material. The surface area must be accessible to the electrolyte and the resulting interface area must be large enough to accommodate the so-called double layer charge.

In some ECs, the stored energy is further increased by pseudocapacitance effects that occur again at the solid-electrolyte interface due to electrochemical phenomena such as redox charge transfer.

However, there are several serious technical problems associated with state-of-the-art ECs or supercapacitors:

(1) Experience with EC based on activated carbon electrodes shows that the experimentally measured capacitance is always much lower than the geometric capacitance calculated from the measured surface area and the width of the dipole layer. For very high surface area carbons, typically only about 10% -20% of the "theoretical" capacitance is observed. This disappointing behavior is related to the presence of micropores (< 2nm, mostly <1 nm) and is due to the difficulty of the electrolyte reaching some pores, wetting defects, and/or the inability of the electrolyte to successfully form bilayers in the pores in which oppositely charged surfaces are less than about 1-2nm apart. In activated carbon, depending on the source of the carbon and the heat treatment temperature, an unexpected amount of surface may be in the form of such micropores.

(2) Although high gravimetric capacitance (based on individual active material weight) at the electrode level is oftentimes claimed as in publications and patent documents, these electrodes unfortunately cannot provide energy storage devices with high capacity (based on total cell weight or component weight) at the supercapacitor cell or capacitor component level. This is due to the concept that the actual mass loading of the electrode and the apparent density of the active material are too low in these reports. In most cases, the active material mass loading (areal density) of the electrode is significantly below 10mg/cm ² (areal density = amount of active material per electrode cross-sectional area in the thickness direction of the electrode), and the apparent bulk or tap density of the active material is typically less than 0.75g/cm even for relatively large activated carbon particles ^-3 (more typically less than 0.5 g/cm) ^-3 And most typically less than 0.3g/cm ^-3 )。

The low mass loading is mainly due to the inability to obtain thicker electrodes (thicker than 100-200 μm) using conventional slurry coating procedures. This is not a trivial task as one might think, and for the purpose of optimizing cell performance, electrode thickness is not a design parameter that can be varied arbitrarily and freely. Conversely, thicker samples tend to become extremely brittle or have poor structural integrity, and will also require the use of large amounts of binder resin. These problems are particularly acute for electrodes based on graphene materials. It has not previously been possible to produce graphene-based electrodes that are thicker than 150 μm and remain highly porous, with pores that remain fully accessible to the liquid electrolyte. The low areal and bulk densities (associated with thin electrodes and poor packing density) result in relatively low volumetric capacitance and low volumetric energy density of the supercapacitor cell.

With the increasing demand for more compact and portable energy storage systems, there is a strong interest in increasing the volumetric utilization of energy storage devices. Novel electrode materials and designs that enable high volumetric capacitance and high mass loading are critical to achieving improved cell volumetric capacitance and energy density.

(3) During the past decade, much work has been done to develop electrode materials with increased volumetric capacitance using porous carbon-based materials (such as graphene), carbon nanotube-based composites, porous graphite oxide, and porous mesophase carbon. Although these experimental supercapacitors featuring such electrode materials can be charged and discharged at high rates, and also exhibit large volumetric electrode capacitances (100 to 200F/cm in most cases) ³ Based on electrode volume), but they are typically<1mg/cm ² Active mass loading of,<0.2g/cm ^-3 And a tap density of up to tens of microns (<<100 μm) electrode thicknesses still significantly lower than those used in most commercially available electrochemical capacitors (i.e., 10 mg/cm) ² 100-200 μm) which results in an energy storage device with relatively low area and volume capacitance and low volumetric energy density.

(4) For graphene-based supercapacitors, there are additional problems still to be solved, explained below:

it has recently been found that nanographene materials exhibit exceptionally high thermal conductivity, high electrical conductivity, and high strength. Another excellent feature of graphene is its exceptionally high specific surface area. About 1,300m provided by the corresponding single-wall CNT ² External surface area per g control (internal surface not accessible by electrolyte), a single graphene sheet provides approximately 2,675m ² Specific external surface area per gram (accessible for liquid electrolyte). The conductivity of graphene is slightly higher than that of CNTs.

The present applicant (a.zhamu and b.z.jang) and co-workers first studied graphene-based and other nanographite-based nanomaterials for supercapacitor applications [ see references 1-5 below; the first patent application was filed in 2006 and published in 2009 ]. After 2008, researchers began to recognize the importance of nanographene materials for supercapacitor applications.

List of references:

lulu Song, A. ZHamu, jiusheng Guo, and B.Z.Jang "Nano-scaled Graphene Plate Nanocomposites for supercapacitors" U.S. Pat. No. 7,623,340 (11/24/2009).

Arna Zhamu and Bor z. Jang, "Process for Producing Nano-scaled Graphene plate Nanocomposite Electrodes for Supercapacitors [ method for Producing Nano-scaled Graphene Platelet Nanocomposite Electrodes for Supercapacitors ]," U.S. patent application No. 11/906,786 (10/04/2007).

Arena Zhamu and Bor Z Jang, "Graphite-Carbon Composite Electrodes for Supercapacitors [ Graphite-Carbon Composite Electrodes for Supercapacitors ]" U.S. patent application Ser. No. 11/895,657 (08/27/2007).

Aruna Zhamu and Bor Z.Jang, "Method of Producing Graphite-Carbon Composite Electrodes for Supercapacitors [ Method for Producing Graphite-Carbon Composite Electrodes for Supercapacitors ]" U.S. patent application Ser. No. 11/895,588 (08/27/2007).

Arna Zhamu and Bor z. Jang, "Graphene Nanocomposites for Electrochemical cell Electrodes [ Graphene Nanocomposites for Electrochemical cell Electrodes ]," U.S. patent application No. 12/220,651 (07/28/2008).

However, individual nano-graphene sheets have a large tendency to re-stack themselves, effectively reducing the specific surface area accessible to the electrolyte in the supercapacitor electrodes. The significance of this graphene sheet overlap problem can be shown as follows: for nano-graphene platelets of dimensions l (length) × w (width) × t (thickness) and density ρ, the estimated surface area per unit mass is S/m = (2/ρ) (1/l +1/w + 1/t). In that

With l =100nm, w =100nm and t =0.34nm (monolayer), we have an impressive 2,675m ² S/m value per gram, which is much greater than the values of most commercially available carbon black or activated carbon materials used in state-of-the-art supercapacitors today. If two single-layer graphene sheets are stacked to form a bilayerGraphene, then the specific surface area is reduced to 1,345m ² (ii) in terms of/g. For three-layer graphene, t =1nm, we have S/m =906m ² (ii) in terms of/g. The specific surface area is further significantly reduced if more layers are stacked together.

These calculations indicate that it is extremely important to find a way to prevent individual graphene sheets from re-stacking, and even if they were partially re-stacked, the resulting multilayer structure would still have interlayer pores of sufficient size. These pores must be large enough to allow accessibility of the electrolyte and the ability to form an electric double layer charge, which typically requires a pore size of at least 1nm, more preferably at least 2 nm. However, these pores or inter-graphene spacings must also be small enough to ensure a large tap density. Unfortunately, typical tap densities of graphene-based electrodes are less than 0.3g/cm ³ And most typically<<0.1g/cm ³ . To a large extent, the requirements of having a large pore size and a high level of porosity and the requirements of having a high tap density are considered mutually exclusive on supercapacitors.

Another major technical obstacle to the use of graphene sheets as supercapacitor electrode active materials is the challenge of depositing thick layers of active materials onto the surface of a solid current collector (e.g., al foil) using conventional graphene-solvent slurry coating procedures. Among such electrodes, graphene electrodes typically require a large amount of binder resin (thus, significantly reducing the active material ratio relative to the inactive or non-contributing (over) material/component). Furthermore, any electrode made thicker than 50 μm in this way is brittle and weak. There has been no effective solution to these problems.

Thus, there is a clear and pressing need for supercapacitors with high active material mass loading (high areal density), active material with high apparent density (high tap density), high electrode thickness without significantly reducing electron and ion transport rates (e.g., without long electron transport distances), high volumetric capacitance, and high volumetric energy density. For graphene-based electrodes, several problems such as re-stacking of graphene sheets, the need for large proportions of binder resins, and the difficulty of producing thick graphene electrode layers must also be overcome.

In addition, the thick electrodes in conventional supercapacitors are also mechanically rigid, not flexible, inflexible, and do not conform to the desired shape. Thus, for conventional supercapacitors, the high volume/weight energy density and mechanical flexibility appear to be mutually exclusive.

With the increasing demand for more compact and portable energy storage systems, there is a strong interest in increasing the utilization of the volume of supercapacitors. Novel electrode materials and designs that enable high volumetric capacity and high mass loading are critical to achieving improved cell volumetric capacity and energy density of supercapacitors.

Thus, there is a clear and pressing need for supercapacitors with high active material mass loading (high areal density), active material with high apparent density (high tap density), high electrode thickness without significantly decreasing electron and ion transport rates (e.g., without high electron transport resistance or long ion diffusion paths), high gravimetric energy density, and high volumetric energy density. These properties must be achieved along with improved flexibility and shape conformability of the resulting supercapacitor.

Disclosure of Invention

The present invention provides a rope-like supercapacitor containing filament-like or rod-like anode and cathode electrodes combined to form a braid or twisted yarn shape (e.g., twisted 2-, 3-, 4-, 5-ply yarn or braid, etc.). The supercapacitor may be an electric double layer capacitor (EDLC, symmetric or asymmetric), a pseudocapacitor, a lithium ion capacitor, or a sodium ion capacitor. Lithium-ion or sodium-ion capacitors contain a pre-lithiated or pre-sodiated anode active material (i.e., a battery-type anode), and a cathode containing a high surface area carbon material such as activated carbon or graphene sheets (i.e., an EDLC-type cathode).

The supercapacitor includes: (a) A first electrode comprising a first electrically conductive porous rod (or filament) having pores, and a first mixture of a first electrode active material and a first electrolyte, wherein the first mixture is present in the pores of the first porous rod (e.g., a filament-shaped foam); (b) A porous separator wrapping or encapsulating the first electrode to form a separator protected first electrode; (c) A second electrode comprising a second electrically conductive porous rod (e.g., a foam in a filamentary shape) having pores, and a second mixture of a second electrode active material and a second electrolyte, wherein the second mixture is present in the pores of the second porous rod; wherein the separator protected first electrode and the second electrode are combined in a spiral manner to form a braid or twisted yarn; and (d) a protective sheath or sheath that wraps or encloses the braid or twisted yarn. The second electrolyte may be the same or different from the first electrolyte. The pores in the first or second electrode preferably contain interconnected pores and the porous rods/filaments are preferably open-cell foams.

The first active material and/or the second active material contain a plurality of carbon material particles and/or a plurality of isolated graphene sheets, wherein the plurality of graphene sheets contain single-layer graphene or few-layer graphene each having from 1 to 10 graphene planes, and the plurality of carbon material particles or graphene sheets have not less than 500m when measured in a dry state ² Per g (preference is given to>1,000m ² Per g and more preferably>2,000m ² Specific surface area of/g). These isolated graphene sheets are not part of the graphene foam (if the porous rod is a graphene-based foam structure). These isolated graphene sheets are the true electrode active material, separate from or attached to the porous rod.

In some preferred embodiments, the first electrode active material or the second electrode active material contains activated carbon particles or isolated graphene sheets having a length or width of less than 1 μ ι η to be easily impregnated into the pores of the first electrode or the second electrode, wherein the graphene sheets are selected from the group consisting of: native graphene, graphene oxide, reduced graphene oxide, fluorinated graphene, nitrided or nitrogen doped graphene, hydrogenated or hydrogen doped graphene, boron doped graphene, chemically functionalized graphene, or combinations thereof.

In some embodiments, the first or second electrode may further contain a redox pair partner material selected from a metal oxide, a conductive polymer, an organic material, a non-graphene carbon material, an inorganic material, or a combination thereof. The pairing material is combined with graphene or activated carbon to form a redox pair to provide a pseudocapacitance.

In certain embodiments, the first or second electrode contains as the only electrode active material in the first or second electrode: (ii) (a) individual graphene sheets; (b) Graphene sheets mixed with porous carbon materials (e.g., activated carbon); (c) Graphene sheets mixed with a pairing material that forms a redox pair with the graphene sheets to create a pseudocapacitance; or (d) graphene sheets and a porous carbon material mixed with a partner material that forms a redox pair with the graphene sheets or the porous carbon material to create a pseudo-capacitance; and wherein no other electrode active material is present in the first or second electrode.

The supercapacitor of the present invention may further comprise a porous separator wrapping or encapsulating the second electrode to form a separator protected second electrode. Thus, both the first and second electrodes (each with an active material-electrolyte mixture pre-impregnated into the pores of the porous rod) are encapsulated by a porous separator before being woven or interwoven to form a braid or twisted yarn. Preferably, the two electrodes are packed as close together as possible to maximize the contact or interface area between the electrodes.

In certain embodiments, the rope supercapacitor further comprises a third electrolyte disposed between the braid or yarn and the protective sheath. The third electrolyte may be the same as or different from the first electrolyte or the second electrolyte.

In the supercapacitor, the first electrode may be a negative electrode (or anode), and the second electrode may be a positive electrode (or cathode). Alternatively, the second electrode is a negative electrode or an anode and the first electrode is a positive electrode or a cathode.

The supercapacitor may comprise a plurality of said first electrodes and/or a plurality of said second electrodes. In other words, the supercapacitor may have filaments/rods of multiple anodes and/or multiple cathodes combined together to form a braid or twisted yarn structure. At least one of the electrodes is an anode and at least one of the electrodes is a cathode.

In certain embodiments, the rope supercapacitor has a length and diameter or thickness with a length to diameter or length to thickness aspect ratio of at least 5, preferably at least 10, and more preferably at least 20.

In some embodiments, the supercapacitor comprises: (a) A first electrode comprising a first conductive rod (not a porous foam), and a first mixture of a first electrode active material and a first electrolyte, wherein the first mixture is deposited on or in the first rod; (b) A porous separator wrapping or encapsulating the first electrode to form a separator protected first electrode; (c) A second electrode comprising a second conductive rod that is porous and has pores, and a second mixture of a second electrode active material and a second electrolyte, wherein the second mixture is present in the pores of the porous second rod; wherein the membrane-protected first electrode and the second electrode are interwoven or combined in a spiral or twisted manner to form a braid or yarn; and (d) a protective sheath or sheath that wraps or encloses the yarn or braid.

The first active material and/or the second active material may contain a plurality of carbon material particles and/or a plurality of isolated graphene sheets having a high specific surface area (not less than 500 m) ² Per g, preferably>1,000m ² Per g, and more preferably>2,000m ² In terms of/g). Again, these isolated graphene sheets are not part of the graphene foam (if the porous rod is a graphene-based foam structure). These isolated graphene sheets are the true electrode active material, separate from or attached to the porous rod. Also, the first electrode or the second electrode may further contain a material selected from the group consisting of metal oxides, conductive polymers, and organic materialsA material, a non-graphene carbon material, an inorganic material, or a redox pair partner material of a combination thereof. The pairing material is combined with graphene or activated carbon to form a redox pair to provide a pseudocapacitance.

Likewise, the supercapacitor of the present invention may further comprise a porous separator wrapping or encapsulating the second electrode to form a separator protected second electrode. In certain embodiments, the ultracapacitor further comprises a third electrolyte disposed between the braid or yarn and the protective sheath. The third electrolyte may be the same as or different from the first electrolyte or the second electrolyte.

In some embodiments of the invention, the first electrode or the second electrode (but not both) comprises a conductive rod (not foam) and the first mixture or the second mixture is coated or deposited on a surface of the conductive rod. The rod may simply be a metal wire, a conductive polymer fiber or yarn, a carbon or graphite fiber or yarn, or a plurality of wires, fibers or yarns.

In certain embodiments, the rope supercapacitor has a first end and a second end, and the first electrode contains a first terminal connector embedded in, connected to, or integral with the first electrode, the first terminal connector comprising at least one metal wire, conductive carbon/graphite fibers, or conductive polymer fibers. In certain preferred embodiments, the at least one metal wire, conductive carbon/graphite fiber, or conductive polymer fiber extends substantially from the first end to the second end. The wire or fiber preferably protrudes from the first or second end to be a terminal tab for connection to an electronic device or an external circuit or load.

Alternatively or additionally, the rope supercapacitor has a first end and a second end, and the second electrode contains a second terminal connector embedded in, connected to or integral with the second electrode, the second terminal connector comprising at least one metal wire, conductive carbon/graphite fibers, or conductive polymer fibers. In certain embodiments, at least one metal wire, conductive carbon/graphite fiber, or conductive polymer fiber extends substantially from the first end to the second end. The wire or fiber preferably protrudes from the first or second end to become a terminal tab for connection to an electronic device or an external circuit or load.

The first or second electrically conductive porous rods may contain a porous foam selected from: metal foam, metal mesh, metal fiber mat, metal nanowire mat, metal wire braid, conductive polymer fiber mat, conductive polymer foam, conductive polymer fiber braid, conductive polymer coated fiber foam, carbon foam, graphite foam, carbon aerogel, graphene aerogel, carbon xerogel, graphene foam, graphene oxide foam, reduced graphene oxide foam, carbon fiber foam, graphite fiber foam, expanded graphite foam, or combinations thereof. These foams can be made into highly deformable and conformable structures.

These foam structures can be readily made to porosity levels of >50%, typically and desirably >70%, more typically and preferably >80%, still more typically and preferably >90%, and most preferably >95% (graphene aerogels can be in excess of 99% porosity levels). The skeletal structure (pore walls) in these foams form a 3D network of electron conducting pathways, while the pores can accommodate a large proportion of electrode active material (anode active material in the anode or cathode active material in the cathode) without the use of any conductive additives or binder resins.

The foam rods/filaments may have a cross-section that is circular, oval, rectangular, square, hexagonal, hollow, or irregularly shaped. There is no particular limitation on the cross-sectional shape of the foam structure. The supercapacitor has a rope shape with a length and a diameter or thickness and an aspect ratio (length/thickness ratio or length/diameter ratio) of more than 10, preferably more than 15, more preferably more than 20, further preferably more than 30, even more preferably more than 50 or 100. There is no limitation on the length or diameter (or thickness) of the string-shaped battery. The thickness or diameter is typically and preferably from 100nm to 10cm, more preferably and typically from 1 μm to 1cm, and most typically from 10 μm to 1mm. The length may extend from 1 μm to tens or even hundreds of meters (if desired).

In certain embodiments of the invention, the supercapacitor is a lithium ion capacitor or a sodium ion capacitor having an anode active material selected from the group consisting of a pre-lithiated form or a pre-sodiated form of: (a) Particles of natural graphite, artificial graphite, mesocarbon microbeads (MCMB), and carbon; (b) Silicon (Si), germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), titanium (Ti), iron (Fe), and cadmium (Cd); (c) Alloys or intermetallic compounds of Si, ge, sn, pb, sb, bi, zn, al or Cd with other elements, wherein the alloys or compounds may be stoichiometric or non-stoichiometric; (d) Oxides, carbides, nitrides, sulfides, phosphides, selenides, and tellurides of Si, ge, sn, pb, sb, bi, zn, al, fe, ni, co, ti, mn, or Cd, and mixtures or composites thereof; and combinations thereof.

The lithium ion capacitor or sodium ion capacitor may contain as an anode active material a pre-lithiated or pre-sodiated graphene sheet selected from a pre-lithiated version or a pre-sodiated version of pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, boron doped graphene, nitrogen doped graphene, chemically functionalized graphene, a physical or chemical activation or etching version thereof, or a combination thereof.

In some embodiments, the supercapacitor is a sodium ion capacitor having an anode active material selected from: petroleum coke, carbon black, amorphous carbon, activated carbon, hard carbon, soft carbon, template carbon, hollow carbon nanowire, hollow carbon sphere, sodium titanate, and NaTi ₂ (PO ₄ ) ₃ 、Na ₂ Ti ₃ O ₇ 、Na ₂ C ₈ H ₄ O ₄ 、Na ₂ TP、Na _x TiO ₂ (x =0.2 to 1.0), na ₂ C ₈ H ₄ O ₄ Materials based on carboxylic acid salts, C ₈ H ₄ Na ₂ O ₄ 、C ₈ H ₆ O ₄ 、C ₈ H ₅ NaO ₄ 、C ₈ Na ₂ F ₄ O ₄ 、C ₁₀ H ₂ Na ₄ O ₈ 、C ₁₄ H ₄ O ₆ 、C ₁₄ H ₄ Na ₄ O ₈ Or a combination thereof.

In some preferred embodiments, the second electrode active material or the first electrode active material contains a lithium intercalation compound or a lithium-absorbing compound selected from the group consisting of: lithium cobalt oxide, doped lithium cobalt oxide, lithium nickel oxide, doped lithium nickel oxide, lithium manganese oxide, doped lithium manganese oxide, lithium vanadium oxide, doped lithium vanadium oxide, lithium mixed metal oxide, lithium iron phosphate, lithium vanadium phosphate, lithium manganese phosphate, lithium mixed metal phosphate, metal sulfide, lithium selenide, lithium polysulfide, and combinations thereof.

In certain embodiments, the second electrode active material or the first electrode active material contains a sodium intercalation compound or a potassium intercalation compound selected from: naFePO ₄ 、Na _(1-x) K _x PO ₄ 、KFePO ₄ 、Na _0.7 FePO ₄ 、Na _1.5 VOPO ₄ F _0.5 、Na ₃ V ₂ (PO ₄ ) ₃ 、Na ₃ V ₂ (PO ₄ ) ₂ F ₃ 、Na ₂ FePO ₄ F、NaFeF ₃ 、NaVPO ₄ F、KVPO ₄ F、Na ₃ V ₂ (PO ₄ ) ₂ F ₃ 、Na _1.5 VOPO ₄ F _0.5 、Na ₃ V ₂ (PO ₄ ) ₃ 、NaV ₆ O ₁₅ 、Na _x VO ₂ 、Na _0.33 V ₂ O ₅ 、Na _x CoO ₂ 、Na _2/3 [Ni _1/3 Mn _2/3 ]O ₂ 、Na _x (Fe _{1/ 2} Mn _1/2 )O ₂ 、Na _x MnO ₂ 、λ-MnO ₂ 、Na _x K _(1-x) MnO ₂ 、Na _0.44 MnO ₂ 、Na _0.44 MnO ₂ /C、Na ₄ Mn ₉ O ₁₈ 、NaFe ₂ Mn(PO ₄ ) ₃ 、Na ₂ Ti ₃ O ₇ 、Ni _1/3 Mn _1/3 Co _1/3 O ₂ 、Cu _0.56 Ni _0.44 HCF、NiHCF、Na _x MnO ₂ 、NaCrO ₂ 、KCrO ₂ 、Na ₃ Ti ₂ (PO ₄ ) ₃ 、NiCo ₂ O ₄ 、Ni ₃ S ₂ /FeS ₂ 、Sb ₂ O ₄ 、Na ₄ Fe(CN) ₆ /C、NaV _1-x Cr _x PO ₄ F、Se _z S _y (y/z =0.01 to 100), se, sodium polysulfide, foscarnosite, or a combination thereof, wherein x is from 0.1 to 1.0.

The first electrolyte and/or the second electrolyte may contain a lithium salt or a sodium salt dissolved in a liquid solvent, and wherein the liquid solvent is water, an organic solvent, an ionic liquid, or a mixture of an organic solvent and an ionic liquid. The liquid solvent may be mixed with the polymer to form a polymer gel.

The first electrolyte and/or the second electrolyte preferably contains a lithium salt or sodium salt dissolved in a liquid solvent, the lithium salt or sodium salt having a salt concentration of greater than 2.5M (preferably >3.0M, further preferably >3.5M, even more preferably >5.0M, still more preferably >7.0M, and most preferably >10M, up to 15M).

In the alkali metal battery, the first or second electrically conductive porous rod has at least 90% by volume of pores, the first or second electrode has a diameter or thickness of no less than 200 μ ι η, or has an active mass loading (anode or cathode active material) of at least 30% by weight or by volume of the entire battery cell, or the first and second electrode active materials combined comprise at least 50% by weight or by volume of the entire battery cell.

In some preferred embodiments, the first or second electrically conductive porous rod has at least 95% by volume of pores, the first or second electrode has a diameter or thickness of no less than 300 μ ι η, or has an active mass loading of at least 35% by weight or by volume of the entire battery cell, or the first and second electrode active materials combined comprise at least 60% by weight or by volume of the entire battery cell.

In some preferred embodiments, the first or second electrode active material comprises an alkali metal intercalation compound or alkali metal absorbing compound selected from: inorganic, organic or polymeric materials, metal oxide/phosphate/sulfide, or combinations thereof. The compound may be an anode active material (e.g., lithium titanate or lithiated graphite) in a lithium ion capacitor, wherein the cathode is of EDLC type (e.g., activated carbon) with a high specific surface area. The metal oxide/phosphate/sulfide contains a vanadium oxide selected from the group consisting of: VO (vacuum vapor volume) ₂ 、Li _x VO ₂ 、V ₂ O ₅ 、Li _x V ₂ O ₅ 、V ₃ O ₈ 、Li _x V ₃ O ₈ 、Li _x V ₃ O ₇ 、V ₄ O ₉ 、Li _x V ₄ O ₉ 、V ₆ O ₁₃ 、Li _x V ₆ O ₁₃ Doped forms thereof, derivatives thereof, and combinations thereof, wherein 0.1<x<5。

The compound may be an inorganic material selected from a transition metal dichalcogenide, a transition metal trichalcogenide, or a combination thereof. Preferably, the inorganic material is selected from TiS ₂ 、TaS ₂ 、MoS ₂ 、NbSe ₃ 、MnO ₂ 、CoO ₂ Iron oxide, vanadium oxide, or a combination thereof. In some embodiments, the inorganic material is selected from: (ii) (a) bismuth selenide or telluride, (b) transition metal dichalcogenide or trichalcogenide, (c) niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or transition metal sulfide, selenide, or telluride; (d) boron nitride, or (e) a combination thereof.

The redox couple partner material may be selected from an alkali metal intercalation compound or an alkali metal absorbing compound selected from: metal carbides, metal nitrides, metal borides, metal dichalcogenides, or combinations thereof. Further specifically, the cathode contains an alkali metal intercalation compound or an alkali metal absorption compound selected from: an oxide, dichalcogenide, trichalcogenide, sulfide, selenide, or telluride of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, vanadium, chromium, cobalt, manganese, iron, or nickel in the form of nanowires, nanodiscs, nanoribbons, or nanoplatelets.

In some embodiments, the redox couple partner material contains nanodiscs, nanoplatelets, nanocoatings, or nanoplatelets of an inorganic material selected from: (ii) (a) bismuth selenide or telluride, (b) transition metal dichalcogenide or trichalcogenide, (c) niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or transition metal sulfide, selenide, or telluride; (d) boron nitride, or (e) a combination thereof; wherein the disc, platelet, or sheet has a thickness of less than 100nm (preferably <10nm, and more preferably <3 nm) to ensure a high specific surface area.

Drawings

FIG. 1 (A) is a schematic of a prior art supercapacitor comprised of an anode current collector (e.g., a carbon-coated Al foil), an anode electrode (e.g., a layer of activated carbon particles and conductive additive bound by a resin binder), a porous separator, a cathode electrode (e.g., a layer of activated carbon particles and conductive additive bound by a resin binder), and a cathode current collector (e.g., an Al foil);

FIG. 1 (B) a schematic of a process for producing a rope-like flexible and shape conformable ultracapacitor;

FIG. 1 (C) four examples of procedures for producing electrodes (rod-shaped anodes or cathodes) in a continuous and automated manner; and

FIG. 1 (D) is a schematic of the process of the present invention for the continuous production of an alkali metal ion battery electrode.

Figure 2 electron microscope images of isolated graphene sheets.

Fig. 3 (a) example of conductive porous layer: metal grids/meshes and carbon nanofiber mats.

Fig. 3 (B) an example of a conductive porous layer: graphene foam and carbon foam.

Fig. 3 (C) an example of a conductive porous layer: graphite foam and Ni foam.

Fig. 3 (D) an example of a conductive porous layer: cu foam and stainless steel foam.

Fig. 4 (a) is a schematic of a common process for producing expanded graphite, expanded graphite flakes (thickness >100 nm) and graphene sheets (thickness <100nm, more typically <10nm, and can be as thin as 0.34 nm).

Fig. 4 (B) illustrates a schematic diagram of a process for producing expanded graphite, expanded graphite flakes, and isolated graphene sheets.

FIG. 5 contains Reduced Graphene Oxide (RGO) sheets and EMIMBF as electrode active materials ₄ Ralong (Ragone) plot (weight and volumetric power density versus energy density) of a symmetric supercapacitor (EDLC) cell of ionic liquid electrolyte. For comparison, data were obtained from both the rope-like supercapacitor and the prior art supercapacitor prepared by conventional electrode paste coating.

Fig. 6 contains a plot of the raleigh curve (weight and volumetric power density versus energy density) for a symmetric supercapacitor (EDLC) cell containing Activated Carbon (AC) particles and an organic liquid electrolyte as electrode active materials.

Fig. 7 (a) charting plots (weight and volumetric power density versus energy density) for Lithium Ion Capacitor (LIC) cells containing pristine graphene sheets as electrode active materials and a lithium salt-PC/DEC organic liquid electrolyte;

fig. 7 (B) charting plots (weight and volumetric power density versus energy density) for sodium ion capacitor (NIC) cells containing pristine graphene sheets and sodium salt-PC/DEC organic liquid electrolyte as electrode active materials.

Fig. 8 cell-level weight and volumetric energy densities plotted over the range of achievable electrode diameters for AC-based EDLC supercapacitors prepared by the conventional process and the process of the invention. With the method of the invention there is no theoretical limit to the electrode diameter that can be achieved. Typically, the actual electrode thickness is from 10 μm to 5,000 μm, more typically from 100 μm to 1,000 μm, and most typically from 200 μm to 800 μm.

FIG. 9 shows the results of a conventional method of preparing an RGO-based EDLC supercapacitor (organic liquid electrolyte) and a cord-like cell prepared by the method of the present invention (easily achievable electrode tap density of about 0.75 g/cm) ³ ) Cell-level weight and volumetric energy density plotted over the range of achievable electrode thicknesses.

FIG. 10 illustrates the formation of pristine graphene-based EDLC supercapacitors (organic liquid electrolytes) prepared by conventional methods and those rope-like cells (electrode tap density of about 0.85 g/cm) prepared by the method of the present invention ³ ) Cell-level weight and volumetric energy density plotted over the range of achievable electrode thicknesses.

FIG. 11 shows the state of the art in pristine graphene-based EDLC supercapacitors (ionic liquid electrolytes) prepared by conventional methods and those rope-like cells (electrode tap density of about 0.85 g/cm) prepared by the method of the invention ³ ) Cell-level weight and volumetric energy density plotted over the range of achievable electrode thicknesses.

Fig. 12 cell-level gravimetric energy densities plotted over the range of available active material ratios (active material weight/total cell weight) for an activated carbon-based EDLC supercapacitor (with organic liquid electrolyte).

Fig. 13 cell-level gravimetric energy densities plotted over the achievable active material ratio (active material weight/total cell weight) in supercapacitor cells for two series pristine graphene-based EDLC supercapacitors (all with organic liquid electrolyte).

Detailed Description

The present invention relates to a flexible and shape conformable rope supercapacitor exhibiting exceptionally high volumetric energy density and high gravimetric energy density compared to conventional supercapacitors. The supercapacitor may be an EDLC supercapacitor (symmetric or asymmetric), a redox or pseudocapacitor, a lithium ion capacitor (not a lithium ion battery), or a sodium ion capacitor (not a sodium ion battery). Supercapacitors are based on aqueous, non-aqueous or organic electrolytes, gel electrolytes, ionic liquid electrolytes, or mixtures of organic and ionic liquids.

As schematically shown in fig. 1 (a), prior art supercapacitor cells are typically made up of: an anode current collector 202 (e.g., a 12-15 μm thick Al foil), an anode active material layer 204 (containing an anode active material, such as activated carbon particles 232, and a conductive additive, bound by a resin binder such as PVDF) coated on the current collector, a porous separator 230, a cathode active material layer 208 (containing a cathode active material, such as activated carbon particles 234, and a conductive additive, all bound by a resin binder (not shown)), a cathode current collector 206 (e.g., an Al foil), and a liquid electrolyte disposed in both the anode active material layer 204 (also referred to simply as an "anode layer") and the cathode active material layer 208 (or simply as a "cathode layer"). The entire cell is enclosed in a protective casing, such as an envelope based on a thin plastic-aluminum foil laminate. Prior art supercapacitor cells are typically made by a method comprising the steps of:

a) The first step is to mix particles of an anode active material (e.g., activated carbon), a conductive filler (e.g., graphite flake), a resin binder (e.g., PVDF) in a solvent (e.g., NMP) to form an anode slurry. On a separate basis, particles of a cathode active material (e.g., activated carbon), a conductive filler (e.g., acetylene black), a resin binder (e.g., PVDF), are mixed and dispersed in a solvent (e.g., NMP) to form a cathode slurry.

b) The second step includes coating the anode slurry onto one or both major surfaces of an anode current collector (e.g., cu or Al foil), and drying the coated layer by evaporating a solvent (e.g., NMP) to form a dried anode electrode coated on the Cu or Al foil. Similarly, the cathode slurry was coated and dried to form a dried cathode electrode coated on Al foil.

c) The third step involves laminating the anode/Al foil, porous separator layer and cathode/Al foil together to form a 3-or 5-layer assembly, which is cut and cut to the desired size and stacked to form a rectangular structure (as an example of a shape) or rolled into a cylindrical cell structure.

d) The rectangular or cylindrical laminate structure is then enclosed in an aluminum plastic laminate envelope or steel housing.

e) A liquid electrolyte is then injected into the laminate structure to make a supercapacitor cell.

There are several serious problems associated with this conventional method and the resulting supercapacitor cells:

1) It is very difficult to produce an activated carbon-based electrode layer (anode layer or cathode layer) thicker than 100 μm, and it is practically impossible or impractical to produce an electrode layer thicker than 200 μm. There are several reasons for this to occur:

a. electrodes with a thickness of 100 μm typically require heating zones 30-50 meters long in a slurry coating facility, which is too time consuming, too energy consuming, and not cost effective.

b. Thicker electrodes have a greater tendency to become delaminated and crack.

c. For some electrode active materials, such as graphene sheets, it has not been possible to produce electrodes thicker than 50 μm on a continuous basis in a practical manufacturing environment. This is true despite the following: some thicker electrodes have been claimed in the public or patent literature; but these electrodes were prepared in the laboratory on a small scale. In a laboratory environment, it is speculated that it may be possible to repeatedly add new material to the layers and manually consolidate the layers to increase the thickness of the electrode. However, even with such manual procedures (which are not suitable for mass production), the resulting electrodes become very brittle and fragile.

d. For graphene-based electrodes, this problem is even worse, since repeated compression results in re-stacking of the graphene sheets and thus significantly reduces the specific surface area and reduces the specific capacitance.

2) With conventional methods, as depicted in fig. 1 (a), the actual mass loading of the electrode and the apparent density of the active material are too low. In most cases, the electrodesHas an active material mass loading (areal density) of significantly less than 10mg/cm ² And even for relatively large activated carbon particles, the apparent bulk or tap density of the active material is typically less than 0.75g/cm ³ (more typically less than 0.5 g/cm) ³ And most typically less than 0.3g/cm ³ ). In addition, there are other inactive materials (e.g., conductive additives and resin binders) that add additional weight and volume to the electrode without contributing to the cell capacity. These low areal and volumetric densities result in relatively low volumetric capacitance and low volumetric energy density.

3) The conventional method requires that electrode active materials (an anode active material and a cathode active material) be dispersed in a liquid solvent (e.g., NMP) to manufacture a slurry, and when applied onto a current collector surface, the liquid solvent must be removed to dry the electrode layer. Once the anode and cathode layers are laminated together with the separator layer and encapsulated in a housing to make a supercapacitor cell, a liquid electrolyte is then injected into the cell. In practice, the two electrodes are wetted, then the electrodes are dried and finally they are wetted again. This wet-dry-wet process does not sound like a good process at all.

4) NMP is not an environmentally friendly solvent; which is known to cause birth defects.

5) Current supercapacitors (e.g. symmetric supercapacitors or electric double layer capacitors EDLCs) are still subject to relatively low gravimetric energy density and low volumetric energy density. Commercially available EDLCs exhibited gravimetric energy densities of about 6Wh/kg, and no experimental EDLC cells were reported to exhibit energy densities above 10Wh/kg (based on total cell weight) at room temperature. Although the experimental supercapacitors exhibited large volumetric electrode capacitances (in most cases 100 to 200F/cm) at the electrode level (rather than the cell level) ³ ) But of them<1mg/cm ² Typical active mass loading,<0.1g/cm ^-3 Yet the tap density and electrode thickness up to tens of microns are significantly lower than those used in most commercially available electrochemical capacitors, resulting in a capacitor with a relatively low face and area based on cell (device) weightVolumetric capacity and low volumetric energy density.

In the literature, energy density data reported based on active material weight or electrode weight alone cannot be directly translated into energy density of an actual supercapacitor cell or device. The "non-contributing weight" or weight of other device components (adhesives, conductive additives, current collectors, separators, electrolytes, and encapsulants) must also be taken into account. Conventional production methods result in an active material proportion of less than 30% by weight of the total cell weight (in some cases <15%; e.g., for graphene-based active materials).

The present invention provides a method for producing a flexible and shape conformable supercapacitor with rope form, high active material mass loading, low non-contributing weight and volume, high gravimetric energy density and high volumetric energy density. Furthermore, the manufacturing costs of the supercapacitors produced by the method of the invention can be significantly lower than those of conventional methods and are more environmentally friendly.

In one embodiment of the present invention, as shown in fig. 1 (C), the rope-type supercapacitor containing electrodes in a braid or yarn shape of the present invention may be manufactured by a method including a first step of supplying a first electrode 11 composed of a conductive porous rod (e.g., carbon foam, graphene foam, metal nanowire felt, etc.) having pores partially or completely loaded with a mixture of a first electrode active material (e.g., activated carbon particles or separated/divided graphene sheets having a size smaller than the pore size of the porous rod) and a first electrolyte. Optionally, a conductive additive or resin binder may be added to the mixture, but this is not necessary or even desirable. The first electrode 11 may optionally contain an active material-free and electrolyte-free end section 13, which may serve as a terminal tab for connecting the supercapacitor to an external load. The first electrode may take a cross-section having any shape; such as circular, rectangular, oval, square, hexagonal, hollow, or irregularly shaped.

Alternatively, in the first step, the first electrode comprises a conductive rod (not a porous foam) and the first mixture is coated or deposited on a surface of the conductive rod. The rod may simply be a metal wire, a conductive polymer fiber or yarn, a carbon or graphite fiber or yarn, or a plurality of thin wires, a plurality of fibers or a plurality of yarns. In this case, however, the second electrode must contain a porous foam structure.

The second step involves wrapping or encapsulating the first electrode 11 with a thin layer of porous separator 15 (e.g., porous plastic film, paper, fiber felt, non-woven fabric, fiberglass cloth, etc.) that is permeable to ions in the electrolyte. This step may simply be to wrap the first electrode with a thin porous plastic tape in one complete circle or slightly more than one complete circle, or in a spiral fashion. The main purpose is to electronically separate the anode and cathode to prevent internal short circuits. The porous separator layer may simply be deposited around the first electrode by spraying, printing, coating, dip casting, or the like.

The third step involves preparing a second electrode 17 comprising a mixture of a second active material and a second electrolyte and optionally a conductive additive or resin binder (although not necessary and not desired). The second electrode 17 may optionally contain an active material-free and electrolyte-free end section that may serve as a terminal tab for connection to an external load. The second electrode may optionally, but desirably, be encapsulated or wrapped by a porous separator layer 18.

This second electrode, with or without an encapsulating porous separator layer, is then combined with the first electrode using a weaving or yarn making procedure to make a 2-ply twisted yarn or braid. If the first electrode is an anode, the second electrode is a cathode; or vice versa. The yarn or braid may contain multiple anodes (i.e., multiple filaments or rods each containing an anode active material and electrolyte) in combination with a single cathode or multiple cathodes. The yarn or braid may contain multiple cathodes (i.e., multiple filaments or rods each containing a cathode active material and an electrolyte) in combination with a single anode or multiple anode filaments. As a final step, the braid or yarn structure is encapsulated or protected by an electrically insulating protective outer shell or sheath 19 (e.g. a plastic or rubber sheath).

It may be noted that some additional electrolyte may be incorporated between the n strands of braid/yarn (n ≧ 2) and the protective sheath. However, this is not a requirement as all electrode rods or filaments already contain active material and electrolyte in their pores.

In some embodiments, one of the electrodes comprises a porous rod having pores containing an active material-electrolyte mixture, and at least one of the electrodes is a non-porous rod (filament, fiber, wire, etc.) having an active material-electrolyte mixture coated on its surface.

The electrodes of the supercapacitor of the invention may be produced in a roll-to-roll manner. In one embodiment, as shown in fig. 1 (C) and 1 (D), the method of the present invention comprises continuously feeding an electrically conductive porous rod/filament (e.g., 304, 310, 322, or 330) from a feed roll (not shown) into an active material impregnation zone where a wet active material-electrolyte mixture (e.g., a slurry, suspension, or gelatinous substance, such as 306a, 306B, 312a, 312B) containing electrode active material (e.g., activated carbon particles and/or graphene sheets) and electrolyte, and optionally conductive additives, well mixed together, is delivered to the porous surface of a porous layer (e.g., 304 or 310 in schematic a and schematic B, respectively, of fig. 1 (C)). Using schematic a as an example, a wet active material-electrolyte mixture (306 a, 306 b) is forced into the porous layer from both sides using one or two pairs of rollers (302 a, 302b, 302c, and 302 d) to form an impregnated active electrode 308 (anode or cathode). The conductive porous layer contains interconnected electron-conducting pathways and preferably at least 70% (preferably >80%, more preferably > 90%) by volume of pores. The foam rods/filaments typically have a pore volume of from 50% to about 99%.

In schematic B, two feed rolls 316a, 316B are used to continuously release (pay out) two protective films 314a, 314B supporting wet active material-electrolyte mixture rods/filaments 312a, 312B. These wet active material-electrolyte mixture rods/ filaments 312a, 312b can be delivered to the protective (support) membranes 314a, 314b using a wide range of procedures (e.g., printing, spraying, casting, coating, etc., as is well known in the art). As the conductive porous layer 110 moves through the gap between the two sets of rollers (318 a, 318b, 318c, 318 d), the wet active material-electrolyte mixture is impregnated into the pores of the porous rod or filament 310 to form an active material electrode 320 (anode electrode or cathode electrode) that is temporarily covered by two protective films 314a, 314b.

Using schematic C as another example, two spray devices 324a, 324b are used to dispense wet active material-electrolyte mixtures (325 a, 325 b) to two opposing porous surfaces of the conductive porous layer 322. One or two pairs of rollers are used to force the wet active material-electrolyte mixture to impregnate into the porous rod from both sides to form impregnated active electrode 326 (anode or cathode). Similarly, in schematic D, two spray devices 332a, 332b are used to dispense a wet active material-electrolyte mixture (333 a, 333 b) to the porous surface of the conductive porous rod 330. One or two pairs of rollers are used to force the wet active material-electrolyte mixture to impregnate into the porous rod to form impregnated active electrode 338 (anode or cathode).

As another example, as shown in schematic E of fig. 1 (D), the electrode production process begins with continuous feeding of an electrically conductive porous rod 356 from a feed roll 340. The porous rod 356 is guided by the roller 342 to be immersed in the wet active material-electrolyte mixture substance 346 (slurry, suspension, gel, etc.) in the container 344. As the active material-electrolyte mixture travels toward the roller 342b and out of the container to feed into the gap between the two rollers 348a, 348b, the active material-electrolyte mixture begins to soak into the pores of the porous rod 356. Two protective films 350a, 350b are fed simultaneously from two respective rolls 352a, 352b to cover impregnated porous rods 354 which can be collected continuously on a rotating drum (take-up roll 355). The process is applicable to both the anode and cathode electrodes.

The resulting electrode rod or electrode filament (anode electrode or cathode electrode) may have a thickness or diameter of from 100nm to several centimeters (or more, if desired). For micro-cables (e.g., as flexible power supplies for microelectronic devices), the electrode thickness or diameter is from 100nm to 100 μm, more typically from 1 μm to 50 μm, and most typically from 10 μm to 30 μm. For macroscopic, flexible and conformable cable batteries (e.g., limited space for Electric Vehicles (EVs)), the electrodes typically and desirably have a thickness of no less than 100 μm (preferably >200 μm, further preferably >300 μm, more preferably >400 μm; further more preferably >500 μm, 600 μm, or even >1,000 μm; no theoretical limitation is placed on the electrode thickness.

The above are just a few examples of how the flexible and shape conformable rope-like alkali metal batteries of the present invention can be made. These examples should not be used to limit the scope of the present invention.

The electrically conductive porous rod or filament may be selected from the group consisting of a metal foam, a metal mesh or wire mesh, a perforated metal sheet based structure, a metal fiber mat, a metal nanowire mat, an electrically conductive polymer nanofiber mat, an electrically conductive polymer foam, an electrically conductive polymer coated fiber foam, a carbon foam, a graphite foam, a carbon aerogel, a carbon xerogel, a graphene aerogel, a graphene foam, a graphene oxide foam, a reduced graphene oxide foam, a carbon fiber foam, a graphite fiber foam, an expanded graphite foam, or a combination thereof. The porous rods or filaments must be made of a conductive material (such as carbon, graphite, metal coated fibers, conductive polymers or conductive polymer coated fibers) in the form of highly porous felts, meshes/nets, non-wovens, foams, and the like. Examples of conductive porous layers are presented in fig. 3 (a), 3 (B), 3 (C), and 3 (D). The porosity level must be at least 50% by volume, preferably more than 70% by volume, further preferably more than 90% and most preferably more than 95%. The skeleton or foam walls of the foam form an integral 3D network of electron conducting pathways.

It may be noted that the graphene material or the graphene oxide material in the structure of the graphene foam, the graphene oxide foam, or the graphene aerogel foam constitutes the pore walls of the foam. The graphene material or graphene oxide material in the described form is free of isolated or separated graphene sheets. The graphene material or graphene oxide material in the foam is not part of the active material-electrolyte mixture impregnated into the pores of the foam. The mixture may contain activated carbon particles, or isolated graphene sheets that are not part of the foam structure. These activated carbon particles or isolated graphene sheets are the primary electrode active materials for supercapacitors.

These foam structures can be readily made in any cross-sectional shape. They can also be very flexible; typically, non-metallic foams are more flexible than metallic foams. However, metal nanofibers can be made into highly flexible foams. Since the electrolyte is in a liquid or gel state, the resulting cable battery can be very flexible and can be made to conform to essentially any odd shape. Even when the salt concentration in the liquid solvent is high (e.g. from 2.5M to 15M), the foam structure containing the electrolyte within its pores is still deformable, bendable, twistable, and conformable to even odd shapes.

In some embodiments, the conductive porous rod in the first or second electrode contains a conductive polymer fiber mat, a carbon/graphite fiber mat, a fiber bundle with pores between fibers, a knitted structure or a nonwoven structure of conductive fibers with various fibers and pores. These various fibers may contain conductive polymer fibers, metal coated fibers, carbon coated polymer fibers, carbon fibers, or graphite fibers.

Preferably, substantially all of the pores in the original conductive porous rods or filaments are filled with an electrode active material (anode or cathode), an electrolyte, and optionally a conductive additive (binder resin is not required). Due to the large number of pores (more typically 70% -99% or preferably and more typically 85% -99%) relative to the pore walls or conductive pathways (1% -30%), very little space is wasted ("wasted" meaning not occupied by electrode active material and electrolyte), resulting in a high proportion of electrode active material-electrolyte mixture (high active material loading mass).

In such supercapacitor electrode configurations (e.g., fig. 1 (B)), the electrons only have to travel a short distance (on average half the pore size; e.g., nanometers or a few microns) before they are collected by the pore walls, since there are pore walls anywhere throughout the entire electrode structure (the conductive foam acting as a current collector). These pore walls form a 3-D network of interconnected electron transport pathways with minimal resistance. In addition, in each anode or cathode electrode, all electrode active material particles are pre-dispersed in the liquid electrolyte (no wettability issues), eliminating the presence of dry pockets typically found in electrodes prepared by conventional methods of wet coating, drying, packaging, and electrolyte injection. Thus, the method of the present invention delivers a completely unexpected advantage over conventional supercapacitor cell production methods.

In a preferred embodiment, the graphene electrode active material (instead of activated carbon) is selected from pristine graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, chemically functionalized graphene, or combinations thereof. The starting graphite material for producing any of the above graphene materials may be selected from natural graphite, artificial graphite, mesophase carbon, mesophase pitch, mesophase carbon microbeads, soft carbon, hard carbon, coke, carbon fibers, carbon nanofibers, carbon nanotubes, or combinations thereof.

The invention also provides a Lithium Ion Capacitor (LIC) or a sodium ion capacitor (NIC), wherein at least one of the two electrodes in the cell is produced by the method of the invention. More preferably, both the anode electrode and the cathode electrode for the LIC or NIC of the present invention are made by the above-described method of the present invention. The process of the invention comprises (a) continuously feeding an electrically conductive porous rod/filament to an anode material impregnation zone, wherein the electrically conductive porous rod/filament has a porous surface and contains interconnected electron-conducting pathways and preferably at least 70% by volume of pores; and (B) impregnating a wet anode active material-electrolyte mixture from at least one porous surface into the electrically conductive porous rod to form an electrode. For example, the wet anode active material mixture contains a liquid electrolyte and an anode active material preferably selected from: pre-lithiated or pre-sodiated versions of graphite particles, carbon particles, si nanoparticles, sn nanoparticles, or any other commonly used anode active material for lithium ion batteries or sodium ion batteries. These anode active materials can be made in the form of fine particles, and a plurality of particles together with conductive additive particles can be easily mixed with a liquid electrolyte to form a wet anode active material mixture (e.g., in the form of a slurry) to be impregnated into the conductive porous layer. The corresponding cathode may contain an EDLC type active material (e.g., activated carbon or isolated graphene sheets), with or without a redox pair partner material (e.g., an inherently conducting conjugated polymer or transition metal oxide).

In a Lithium Ion Capacitor (LIC), the anode active material may be selected from the group consisting of: (a) Natural graphite, artificial graphite, mesocarbon microbeads (MCMB), and pre-lithiated particles of carbon; (b) Pre-lithiated particles or coatings of silicon (Si), germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), titanium (Ti), iron (Fe), and cadmium (Cd); (c) Pre-lithiated alloys or intermetallic compounds of Si, ge, sn, pb, sb, bi, zn, al or Cd with other elements, wherein the alloys or compounds are stoichiometric or non-stoichiometric; (d) Prelithiated oxides, carbides, nitrides, sulfides, phosphides, selenides, and tellurides of Si, ge, sn, pb, sb, bi, zn, al, fe, ni, co, ti, mn, or Cd, and mixtures or composites thereof; and (e) pre-lithiated graphene sheets; and combinations thereof. Prelithiation can be accomplished electrochemically by using a compact mass of graphene sheets as the working electrode and lithium metal as the counter electrode. Prelithiation may also be accomplished by adding lithium powder or scrap to the liquid electrolyte along with the anode active material (e.g., si particles) and conductive additive particles.

In the sodium ion capacitor, the anode active material contains a pre-sodiated version of petroleum coke, carbon black, amorphous carbon, activated carbon, hard carbon, soft carbon, templated carbon, hollow carbon nanowires, hollow carbon spheres, or titanates, or a sodium intercalation compound selected from: naTi ₂ (PO ₄ ) ₃ 、Na ₂ Ti ₃ O ₇ 、Na ₂ C ₈ H ₄ O ₄ 、Na ₂ TP、Na _x TiO ₂ (x =0.2 to 1.0), na ₂ C ₈ H ₄ O ₄ Materials based on carboxylic acid salts, C ₈ H ₄ Na ₂ O ₄ 、C ₈ H ₆ O ₄ 、C ₈ H ₅ NaO ₄ 、C ₈ Na ₂ F ₄ O ₄ 、C ₁₀ H ₂ Na ₄ O ₈ 、C ₁₄ H ₄ O ₆ 、C ₁₄ H ₄ Na ₄ O ₈ Or a combination thereof.

In the sodium ion capacitor, the anode active material contains a sodium intercalation compound selected from the following group of materials: (a) Sodium-doped silicon (Si), germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), titanium (Ti), cobalt (Co), nickel (Ni), manganese (Mn), cadmium (Cd), and mixtures thereof; (b) Sodium-containing alloys or intermetallic compounds of Si, ge, sn, pb, sb, bi, zn, al, ti, co, ni, mn, cd, and mixtures thereof; (c) Sodium-containing oxides, carbides, nitrides, sulfides, phosphides, selenides, tellurides, or antimonides of Si, ge, sn, pb, sb, bi, zn, al, fe, ti, co, ni, mn, cd, and mixtures or composites thereof; (d) a sodium salt; and (e) graphene sheets pre-loaded with sodium or potassium. Pre-sodium modification can be accomplished electrochemically by using a compact block of graphene sheets as the working electrode and sodium metal as the counter electrode. Pre-sodium modification can also be accomplished by adding lithium powder or fragments to the liquid electrolyte along with anode active material (e.g., si particles) and conductive additive particles.

Bulk natural graphite is a 3-D graphite material, with each graphite particle being composed of a plurality of grains (the grains being graphite single crystals or crystallites) having grain boundaries (amorphous or defect regions) that define adjacent graphite single crystals. Each grain is composed of a plurality of graphene planes oriented parallel to each other. The graphene planes in the graphite crystallites are composed of carbon atoms occupying a two-dimensional hexagonal lattice. In a given grain or single crystal, graphene planes are stacked in the crystallographic c-direction (perpendicular to the graphene plane or basal plane) and bound by van der waals forces. While all graphene planes in one grain are parallel to each other, typically the graphene planes in one grain and the graphene planes in an adjacent grain are tilted in different orientations. In other words, the orientation of the different grains in the graphite particles typically differs from one grain to another.

The constituent graphene planes of graphite crystallites in natural or artificial graphite particles can be expanded and extracted or separated to obtain single graphene sheets of hexagonal carbon atoms that are monoatomic thick, provided that the interplanar van der waals forces can be overcome. The separate, single graphene plane of carbon atoms is commonly referred to as single-layer graphene. A stack of a plurality of graphene planes bonded by van der waals forces in the thickness direction with an inter-plane spacing of graphene of about 0.3354nm is generally referred to as multilayer graphene. The multi-layered graphene platelets have up to 300 graphene planes (< 100nm in thickness), but more typically up to 30 graphene planes (< 10nm in thickness), even more typically up to 20 graphene planes (< 7nm in thickness), and most typically up to 10 graphene planes (commonly referred to as few-layer graphene in the scientific community). Single-layer graphene sheets and multi-layer graphene sheets are collectively referred to as "nano-graphene platelets" (NGPs), as shown in fig. 2. Graphene sheets/platelets (collectively referred to as NGPs) are a new class of carbon nanomaterials (2-D nanocarbons) that differ from 0-D fullerenes, 1-D CNTs, or CNFs and 3-D graphites. For the purposes of defining the claims and as generally understood in the art, graphene materials (isolated graphene sheets) are not (and do not include) Carbon Nanotubes (CNTs) or Carbon Nanofibers (CNFs).

As early as 2002, our research group initiated the development of graphene materials and related production methods: (1) Jang and w.c. huang, "Nano-scaled Graphene Plates," U.S. Pat. No. 7,071,258 (07/04/2006), application filed 10/21/2002; (2) Jang et al, "Process for Producing Nano-scaled Graphene Plates [ method for Producing Nano-scaled Graphene Plates ]", U.S. patent application No. 10/858,814 (06/03/2004); and (3) b.z.jang, a.zhamu and j.guo, "Process for Producing Nano-scaled plates and Nanocomposites [ methods for Producing Nano-Platelets and Nanocomposites ]", U.S. patent application No. 11/509,424 (08/25/2006).

In one approach, graphene materials are obtained by intercalating natural graphite particles with strong acids and/or oxidants to obtain Graphite Intercalation Compounds (GICs) or Graphite Oxides (GO), as shown in fig. 4 (a) and 4 (B) (schematic diagrams). The presence of chemical species or functional groups in the interstitial spaces between graphene planes in a GIC or GO serves to increase the inter-graphene spacing (d) ₀₀₂ As determined by X-ray diffraction) to thereby significantly reduce van der waals forces that would otherwise hold the graphene planes together along the c-axis direction. GIC or GO is most often produced by immersing natural graphite powder (100 in fig. 4 (B)) in a mixture of sulfuric acid, nitric acid (the oxidant) and another oxidant (e.g., potassium permanganate or sodium perchlorate). If an oxidizing agent is present during the intercalation procedure, the resulting GIC (102) is actually some type of Graphite Oxide (GO) particles. The GIC or GO is then repeatedly washed and rinsed in water to remove excess acid, producing a graphite oxide suspension or dispersion containing discrete and visually identifiable graphite oxide particles dispersed in water. To produce graphene materials, one of two processing routes can be followed after this washing step, briefly described as follows:

route 1 involves removing water from the suspension to obtain "expandable graphite", which is essentially a mass of dried GIC or dried graphite oxide particles. Upon exposure of the expandable graphite to temperatures in the range of typically 800 c to 1,050 c for about 30 seconds to 2 minutes, the GIC undergoes 30-300 times rapid volume expansion to form "graphite worms" (104), each of which is an assemblage of expanded, yet interconnected, largely undivided graphite flakes.

In route 1A, these graphite worms (expanded graphite or "network of interconnected/undivided graphite flakes") can be recompressed to obtain flexible graphite sheets or foils (106), typically having a thickness in the range of 0.1mm (100 μm) to 0.5mm (500 μm). Alternatively, for the purpose of producing so-called "expanded graphite flakes" (108) which contain predominantly graphite flakes or platelets thicker than 100nm (and thus by definition not nanomaterials), the use of low intensity air mills or shears may be chosen to simply break down the graphite worms.

In route 1B, expanded graphite is subjected to high intensity mechanical shearing (e.g., using an ultrasonic generator, a high shear mixer, a high intensity air jet mill, or a high energy ball mill) to form separate single and multi-layered graphene sheets (collectively referred to as NGPs, 112), as disclosed in our U.S. application No. 10/858,814 (06/03/2004). Single-layer graphene can be as thin as 0.34nm, while multi-layer graphene can have a thickness of up to 100nm, but more typically less than 10nm (commonly referred to as few-layer graphene). A plurality of graphene sheets or platelets may be made into a sheet of NGP paper using a papermaking process. The NGP paper sheet is an example of a porous graphene structure layer used in the method of the present invention.

Route 2 requires ultrasonication of a graphite oxide suspension (e.g., graphite oxide particles dispersed in water) for the purpose of separating/isolating individual graphene oxide sheets from the graphite oxide particles. This is based on the following point: the spacing between graphene planes has increased from 0.3354nm in natural graphite to 0.6-1.1nm in highly oxidized graphite oxide, significantly reducing van der waals forces holding adjacent planes together. The ultrasonic power may be sufficient to further separate the graphene planar sheets to form completely separated, isolated, or discrete Graphene Oxide (GO) sheets. These graphene oxide sheets may then be chemically or thermally reduced to obtain "reduced graphene oxide" (RGO), typically having an oxygen content of 0.001-10% by weight, more typically 0.01-5% by weight, most typically and preferably less than 2% by weight oxygen.

For the purposes of defining the claims of the present application, NGP or graphene materials include single and multiple layers (typically less than 10 layers) of discrete sheets/platelets of pristine graphene, graphene oxide, reduced Graphene Oxide (RGO), graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, chemically functionalized graphene, doped graphene (e.g. doped with B or N). Pristine graphene has substantially 0% oxygen. RGO typically has an oxygen content of 0.001% -5% by weight. Graphene oxide (including RGO) may have 0.001% -50% oxygen by weight. All graphene materials, except pristine graphene, have 0.001% -50% by weight of non-carbon elements (e.g., O, H, N, B, F, cl, br, I, etc.). These materials are referred to herein as non-native graphene materials.

Pristine graphene, in the form of smaller discrete graphene sheets (typically 0.3 to 10 μm), can be produced by direct sonication (also known as liquid phase expansion or production) or supercritical fluid expansion of graphite particles. These methods are well known in the art.

Graphene Oxide (GO) may be obtained by immersing powders or filaments of a starting graphite material (e.g. natural graphite powder) in an oxidizing liquid medium (e.g. a mixture of sulfuric acid, nitric acid and potassium permanganate) at a desired temperature in a reaction vessel for a period of time (typically from 0.5 to 96 hours, depending on the nature of the starting material and the type of oxidant used). As previously described above, the resulting graphite oxide particles may then be subjected to thermal or ultrasound induced expansion to produce separated GO sheets. And then by using other chemical groups (e.g. -Br, NH) ₂ Etc.) substitution of-OH groups converts these GO sheets into various graphene materials.

Fluorinated graphene or graphene fluoride is used herein as an example of the halogenated graphene material group. There are two different methods that have been followed to produce fluorinated graphene: (1) fluorination of pre-synthesized graphene: the process requires the use of a fluorinating agent such as XeF ₂ Or F-based plasma treating graphene prepared by mechanical puffing or by CVD growth; (2) puffing of the multilayer graphite fluoride: both mechanical and liquid phase expansion of graphite fluoride can be readily achieved.

F ₂ Interaction with graphite at high temperatures results in covalent graphite fluoride (CF) _n Or (C) ₂ F) _n While forming Graphite Intercalation Compound (GIC) C at low temperature _x F (x is more than or equal to 2 and less than or equal to 24). In (CF) _n The carbon atoms are sp3 hybridized and thus the fluorocarbon layer is corrugated, consisting of trans-linked cyclohexane chairs. In (C) ₂ F) _n In which only half of the C atoms are coveredFluorinated and each pair of adjacent carbon sheets are linked together by a covalent C-C bond. Systematic studies of fluorination reactions have shown that the resulting F/C ratio depends to a large extent on the fluorination temperature, the partial pressure of fluorine in the fluorination gas, and the physical properties of the graphite precursor, including the degree of graphitization, particle size, and specific surface area. In addition to fluorine (F) ₂ ) In addition, other fluorinating agents may be used, although most of the prior art references refer to the use of F ₂ The gas is fluorinated (sometimes in the presence of fluoride).

In order to expand a layered precursor material into the state of a single layer or several layers, the attractive forces between adjacent layers must be overcome and the layers further stabilized. This can be achieved by covalent modification of the graphene surface with functional groups or by non-covalent modification using specific solvents, surfactants, polymers, or donor-acceptor aromatic molecules. The liquid phase expansion process involves ultrasonication of graphite fluoride in a liquid medium.

Nitridation of graphene can be performed by exposing a graphene material (e.g., graphene oxide) to ammonia at high temperatures (200-400 ℃). The graphene nitride can be formed at a lower temperature by a hydrothermal method; for example by sealing GO and ammonia in an autoclave and then warming to 150-250 ℃. Other methods of synthesizing nitrogen-doped graphene include nitrogen plasma treatment on graphene, arc discharge between graphite electrodes in the presence of ammonia, ammonolysis of graphene oxide under CVD conditions, and hydrothermal treatment of graphene oxide and urea at different temperatures.

The above features will be described and explained in further detail as follows: as shown in fig. 4 (B), the graphite particles (e.g., 100) are typically composed of a plurality of graphite crystallites or grains. Graphitic crystallites are composed of lamellar planes of hexagonal networks of carbon atoms. These layer planes of hexagonally arranged carbon atoms are substantially planar and are oriented or ordered so as to be substantially parallel and equidistant to one another within a particular crystallite. These hexagonal-structure carbon atom layers, which are generally called graphene layers or basal planes, are weakly bonded together in their thickness direction (crystallographic c-axis direction) by weak van der waals forces, and groups of these graphene layers are arranged in crystallites. Graphitic crystallite structure is generally characterized in two axes or directions: the c-axis direction and the a-axis (or b-axis) direction. The c-axis is the direction perpendicular to the base plane. The a-axis or b-axis is the direction parallel to the base plane (perpendicular to the c-axis direction).

Highly ordered graphitic particles can be composed of crystallites of considerable size having an L along the crystallographic a-axis direction _a Length, L along the crystallographic b-axis _b Width, and thickness L along crystallographic c-axis _c . The constituent graphene planes of the crystallites are highly aligned or oriented with respect to each other, and thus, these anisotropic structures give rise to a number of highly directional properties. For example, the thermal and electrical conductivity of crystallites has large magnitudes in the in-plane direction (a-or b-axis direction) but relatively low in the perpendicular direction (c-axis). As shown in the upper left portion of fig. 4 (B), the different crystallites in the graphite particle are typically oriented in different directions, and thus the particular characteristic of the multi-crystallite graphite particle is the directional average of all the constituent crystallites.

Natural graphite can be treated due to weak van der waals forces that hold parallel graphene layers, such that the spacing between graphene layers can be opened significantly to provide significant expansion in the c-axis direction, and thereby form an expanded graphite structure in which the laminar character of the carbon layers is substantially preserved. Methods of making flexible graphite are well known in the art. Typically, natural graphite flake (e.g., 100 in fig. 4 (B)) is intercalated in an acid solution to produce a graphite intercalation compound (GIC, 102). The GIC is washed, dried, and then puffed by exposure to elevated temperatures for short periods of time. This results in the flakes expanding or bulking up to 80-300 times their original size in the c-axis direction of the graphite. The exfoliated graphite flakes are vermiform in appearance, and are therefore commonly referred to as graphite worms 104. These graphite flake worms, which have been greatly expanded, can be formed into cohesive or integrated expanded graphite sheets without the use of a binder, e.g., having a typical density of about 0.04-2.0g/cm for most applications ³ A web, paper, strip, tape, foil, felt, etc. (typically referred to as "flexible graphite" 106).

Acids (such as sulfuric acid) are not the only type of intercalating agent (intercalant) that penetrates into the spaces between graphene planes to obtain GIC. Many other types of intercalation agents may be used, such as alkali metals (Li, K, na, cs and alloys or eutectics thereof) to intercalate graphite into stage 1, stage 2, stage 3, and the like. Stage n means one intercalator layer per n graphene planes. For example, stage 1 potassium intercalated GIC means one K layer for each graphene plane; alternatively one K atomic layer interposed between two adjacent graphene planes can be found in the G/K/G/KG … sequence, where G is a graphene plane and K is a potassium atom plane. A stage 2GIC will have a sequence of GG/K/GG/K/GG …. And stage 3GIC will have the sequence GGG/K/GGG/K/GGG …. These GICs can then be contacted with water or water-alcohol mixtures to produce expanded graphite and/or separated/isolated graphene sheets.

The expanded graphite worms may be subjected to high intensity mechanical shearing/separation processes using high intensity air jet mills, high intensity ball mills, or ultrasonic devices to produce separated nano-graphene platelets (NGPs), all of which are thinner than 100nm, mostly thinner than 10nm, and in many cases single layer graphene (also shown as 112 in fig. 4 (B)). NGPs are composed of one graphene sheet or multiple graphene sheets, where each sheet is a two-dimensional, hexagonal structure of carbon atoms. A large number of multiple NGPs (including single and/or few-layer graphene or discrete sheets/platelets of graphene oxide) can be made into graphene films/papers (114 in fig. 4 (B)) using a film-making or paper-making process. Alternatively, under low intensity shear, the graphite worms tend to separate into so-called expanded graphite flakes (108 in fig. 4 (B), having a thickness >100 nm). These sheets may be formed into graphite paper or felt 106 using a paper or felting process with or without a resin binder.

Despite the fact that: graphene sheets alone have an exceptionally high specific surface area, but graphene sheets have a large tendency to be re-stacked together or to overlap one another, thereby significantly reducing the specific capacitance due to the significantly reduced specific surface area available for electrolytes. This tendency to re-stack is particularly acute during the supercapacitor cell electrode production process. In this process, graphene sheets are dispersed in a solvent (typically NMP) together with other conductive additives and a resin binder (e.g., PVDF) to form a slurry, which is then coated on the surface of a solid current collector (e.g., al foil). The solvent is then removed (evaporated) to form a dried active material electrode layer, which is then fed through a pair of rollers in a compressor to consolidate the electrode layer. These drying and compression procedures resulted in severe graphene re-stacking. In many scientific reports, although graphene sheets in the original powder form were found to exhibit exceptionally high specific surface areas, the resulting electrodes only show unexpectedly lower specific capacitances. Theoretically, the maximum specific capacitance of supercapacitors based on single-layer graphene is as high as 550F/g (based on EDLC structures, without redox couples or pseudocapacitances), but the values achieved in experiments have only been in the range of 90-170F/g. This has been a long standing problem in the field of supercapacitors.

The present invention provides a highly innovative and elegant method to overcome this graphene sheet re-stacking problem. The process of the present invention completely eliminates the need to undergo slurry coating, drying and compression procedures. Instead of forming a slurry containing an environmentally hazardous solvent (i.e., NMP), the method requires that graphene sheets be dispersed in a liquid electrolyte to form a slurry of an electrode active material-liquid electrolyte mixture. Then injecting the mixture slurry into pores of a conductive foam based current collector; no subsequent drying and compression is required and the graphene sheets are not or hardly likely to be re-stacked together. In addition, the graphene sheets have been pre-dispersed in the liquid electrolyte, meaning that substantially all of the graphene surface is naturally accessible to the electrolyte, leaving no "dry pockets. This approach also enables us to pack graphene sheets (with electrolyte in between) in a very compact manner, resulting in an unexpectedly high tap density of the electrode active material.

The graphene sheets used in the above-mentioned method may be subjected to the following processes, either alone or in combination:

(a) Chemically functionalized or doped with atomic, ionic, or molecular species. Useful surface functional groups may include quinones, hydroquinones, quaternary aromatic amines, thiols, or disulfides. Such functional groups can impart pseudocapacitance to graphene-based supercapacitors.

(b) Coated or grafted with inherently conductive polymers (conductive polymers such as polyacetylene, polypyrrole, polyaniline, polythiophene and their derivatives, are good choices for the present invention); these processes aim to further increase the capacitance value by pseudocapacitance effects such as redox reactions.

(c) For the purpose of forming redox pairs with graphene sheets, transition metal oxides or sulfides such as RuO are used ₂ 、TiO ₂ 、MnO ₂ 、Cr ₂ O ₃ And Co ₂ O ₃ Carrying out deposition so as to endow pseudo capacitance to the electrode; and

(d) Subjected to an activation treatment (similar to the activation of carbon black materials) to create additional surfaces and possibly impart functional groups to these surface chemistries. The activation treatment may be by CO ₂ Physical activation, KOH chemical activation, or exposure to nitric acid, fluorine, or ammonia plasma.

We have found that a wide variety of two-dimensional (2D) inorganic materials can be used in the supercapacitors of the invention prepared by the active material-electrolyte mixture impregnation process of the invention. Layered materials represent a diverse source of 2D systems that can exhibit unexpected electronic properties and high specific surface areas that are important for supercapacitor applications. Although graphite is the best known layered material, transition Metal Dichalcogenides (TMD), transition Metal Oxides (TMO) and various other compounds such as BN, bi ₂ Te ₃ And Bi ₂ Se ₃ And is also a potential source of 2D material.

Non-graphene 2D nanomaterials (single or few layers (up to 20 layers)) can be produced by several methods: mechanical cleaving, laser ablation (e.g., ablation of TMD into a single layer using laser pulses), liquid phase expansion, and synthesis by thin film techniques such as PVD (e.g., sputtering), evaporation, vapor phase epitaxy, liquid phase epitaxy, chemical vapor phase epitaxy, molecular Beam Epitaxy (MBE), atomic Layer Epitaxy (ALE), and plasma assisted versions thereof.

We have surprisingly found that although these inorganic materials are generally considered to be non-conductive and therefore not candidate supercapacitor electrode materials, most of these inorganic materials exhibit significant EDLC values when in the form of 2D nanodiscs, nanoplatelets, nanoribbons (nanobelts) or nanoribbons (nanobibons). When these 2D nanomaterials are used in combination with a small number of nano-graphene sheets (especially single layer graphene), the supercapacitance value is exceptionally high. The desired single layer graphene may be from 0.1% to 50% by weight, more preferably from 0.5% to 25%, and most preferably from 1% to 15% by weight.

In the present invention, there is no limitation on the type of liquid electrolyte that can be used in the supercapacitor: aqueous, organic, gel, and ionic liquids. Typically, electrolytes for supercapacitors consist of a solvent and a dissolved chemical (e.g. a salt) that dissociates into positive ions (cations) and negative ions (anions), thereby making the electrolyte conductive. The more ions the electrolyte contains, the better its conductivity, which also affects the capacitance. In a supercapacitor, the electrolyte provides molecules to separate monolayers in a helmholtz bilayer (electric double layer) and delivers ions for pseudocapacitance.

Water is a preferred solvent for dissolving inorganic chemicals. When reacted with an acid, e.g. sulfuric acid (H) ₂ SO ₄ ) Bases, e.g. potassium hydroxide (KOH), or salts, e.g. quaternary phosphonium salts, sodium perchlorate (NaClO) ₄ ) Lithium perchlorate (LiClO) ₄ ) Or lithium hexafluoroarsenate (LiAsF) ₆ ) When added together, water provides relatively high conductivity values. The aqueous electrolyte has a dissociation voltage of 1.15V per electrode and a relatively low operating temperature range. The aqueous electrolyte based supercapacitors exhibit low energy density.

Alternatively, the electrolyte may contain an organic solvent such as acetonitrile, propylene carbonate, tetrahydrofuran, diethyl carbonate, γ -butyrolactone, and a quaternary ammonium salt or an alkylammonium salt such as tetraethylammonium tetrafluoroborate (N (Et) ₄ BF ₄ ) Or triethyl (methyl) tetrafluoroborate (NMe (Et) ₃ BF ₄ ) The solute of (1). Organic electrolytes are more expensive than aqueous electrolytes, but they have typically 1.35V/electrode (2.7V electricity)Container voltage) and a higher temperature range. The lower conductivity of the organic solvent (10 to 60 mS/cm) results in a lower power density, but a higher energy density, since the energy density is proportional to the square of the voltage.

Ionic liquids are composed of ions only. Ionic liquids are low melting point salts that are molten or liquid when above a desired temperature. For example, a salt is considered an ionic liquid if it has a melting point below 100 ℃. If the melting temperature is equal to or lower than room temperature (25 ℃), the salt is referred to as a Room Temperature Ionic Liquid (RTIL). Due to the combination of large cations and charge delocalized anions, IL salts are characterized by weak interactions. This results in a low tendency to crystallize due to flexibility (anions) and asymmetry (cations).

Typical and well-known ionic liquids are formed by the combination of a 1-ethyl-3-methylimidazolium (EMI) cation and an N, N-bis (trifluoromethane) sulfonamide (TFSI) anion. This combination results in a fluid having an ionic conductivity comparable to many organic electrolyte solutions and a low decomposition tendency and low vapor pressure of up to about 300-400 ℃. This means an electrolyte that is generally low in volatility and non-flammability, and is therefore much safer for batteries.

Ionic liquids are essentially composed of organic ions, and have an essentially infinite number of structural changes due to the ease of preparation of their various components. Thus, various salts can be used to design ionic liquids with desired properties for a given application. These include inter alia imidazolium, pyrrolidinium and quaternary ammonium salts as cations and bis (trifluoromethanesulfonyl) imide, bis (fluorosulfonyl) imide and hexafluorophosphate as anions. Ionic liquids have different classes based on their composition, including essentially aprotic, protic and zwitterionic types, each suitable for a particular application.

Common cations for Room Temperature Ionic Liquids (RTILs) include, but are not limited to, tetraalkylammonium, di-, tri-and tetra-alkylimidazolium, alkylpyridinium, dialkyl-pyrrolidinium, dialkyl piperidinium, tetraalkylphosphonium and trisAlkyl sulfonium. Common anions for RTILs include, but are not limited to, BF ₄ ^- 、B(CN) ₄ ^- 、CH ₃ BF ₃ ^- 、CH2CHBF ₃ ^- 、CF ₃ BF ₃ ^- 、C ₂ F ₅ BF ₃ ^- 、n-C ₃ F ₇ BF ₃ ^- 、n-C ₄ F ₉ BF ₃ ^- 、PF ₆ ^- 、CF ₃ CO ₂ ^- 、CF ₃ SO ₃ ^- 、N(SO ₂ CF ₃ ) ₂ ^- 、N(COCF ₃ )(SO ₂ CF ₃ ) ^- 、N(SO ₂ F) ₂ ^- 、N(CN) ₂ ^- 、C(CN) ₃ ^- 、SCN ^- 、SeCN ^- 、CuCl ₂ ^- 、AlCl ₄ ^- 、F(HF) _2.3 ^- And the like. In contrast, imidazolium or sulfonium cations are reacted with, for example, alCl ₄ ^- 、BF ₄ ^- 、CF ₃ CO ₂ ^- 、CF ₃ SO ₃ ^- 、NTf ₂ ^- 、N(SO ₂ F) ₂ ^- Or F (HF) _2.3 ^- The combination of isocomplex halide anions results in an RTIL with good working conductivity.

RTILs can have typical characteristics such as high intrinsic ionic conductivity, high thermal stability, low volatility, low (almost zero) vapor pressure, non-flammability, ability to remain as liquids over a wide range of temperatures above and below room temperature, high polarity, high viscosity, and a wide electrochemical window. These properties are desirable attributes in addition to high viscosity when it comes to using RTILs as electrolyte components (salts and/or solvents) in supercapacitors.

To make a pseudocapacitor (a supercapacitor that works by creating a pseudocapacitance through redox couple formation), the anode active material or cathode active material can be designed to contain graphene sheets and a redox couple partner material selected from: a metal oxide, a conductive polymer, an organic material, a non-graphene carbon material, an inorganic material, or a combination thereof. Many materials that can be paired with reduced graphene oxide sheets are well known in the art. In this study, we recognize that graphene halides (e.g., graphene fluoride), graphene hydride, and graphene nitride can work with a wide variety of partner materials to form redox pairs for creating pseudocapacitance.

For example, the metal oxide or inorganic material that plays such a role includes RuO ₂ 、IrO ₂ 、NiO、MnO ₂ 、VO ₂ 、V ₂ O ₅ 、V ₃ O ₈ 、TiO ₂ 、Cr ₂ O ₃ 、Co ₂ O ₃ 、Co ₃ O ₄ 、PbO ₂ 、Ag ₂ O、MoC _x 、Mo ₂ N or a combination thereof. Typically, the inorganic material may be selected from metal carbides, metal nitrides, metal borides, metal dichalcogenides, or combinations thereof. Preferably, the desired metal oxide or inorganic material is selected from the group consisting of oxides, dichalcogenides, trichalcogenides, sulfides, selenides, or tellurides of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, vanadium, chromium, cobalt, manganese, iron, or nickel in the form of nanowires, nanodiscs, nanoribbons, or nanoplatelets. These materials may be in the form of simple mixtures with sheets of graphene material, but are preferably in the form of nanoparticles or nanocoatings (physically or chemically bonded to the surface of the graphene sheets prior to forming the wet active material mixture (e.g., in the form of a slurry) and impregnating into the pores of the conductive porous layer).

The cord battery of the present invention has a number of unique features, and some of these features and advantages are summarized below:

by definition, a rope supercapacitor is meant a supercapacitor containing at least a rod-like or filament-like anode and a rod-like or filament-like cathode combined into a braid or twisted yarn. The supercapacitor has a length and a diameter or a thickness wherein the aspect ratio (length to diameter ratio or length to thickness ratio) is at least 10 and preferably at least 20. The rope-like supercapacitor may have a length of more than 1m, or even more than 100 m. The length may be as short as 1 μm, but is typically from 10 μm to 10m, and more typically from micrometers to several meters. In fact, there is no theoretical limit to the length of this type of rope supercapacitor.

The rope-shaped supercapacitor of the present invention is so flexible that the supercapacitor can be easily bent to have a radius of curvature of more than 10 cm. The ultracapacitor may be bent to substantially conform to the shape of a void or interior compartment in a vehicle. The void or interior compartment may be a trunk, door, hatch, spare tire compartment, under seat area, or under dashboard area. The ultracapacitor is detachable from the vehicle and bendable to conform to the shape of different voids or interior compartments.

One or more units of the rope supercapacitor of the invention may be incorporated into a garment, belt, carrying strap, luggage strap, weapons strap, musical instrument strap, helmet, hat, boot, foot cover, glove, wrist cover, watchband, jewelry item, animal collar, or animal harness.

One or more units of the rope supercapacitor of the invention may be removably attached to a garment, belt, carrying strap, luggage strap, weapons strap, musical instrument strap, helmet, hat, boot, foot cover, glove, wrist cover, wristband, jewelry item, animal collar, or animal harness.

In addition, the rope-like supercapacitor of the present invention conforms to the inside radius of a hollow bicycle frame.

In the following, we provide examples of a number of different types of anode active materials, cathode active materials, and conductive porous rods (e.g., graphite foam, graphene foam, and metal foam) to illustrate the best mode of practicing the invention. These illustrative examples, as well as other portions of the specification and drawings, alone or in combination, are sufficient to enable one of ordinary skill in the art to practice the invention. However, these examples should not be construed as limiting the scope of the invention.

Example 1: illustrative examples of conductive porous rods or filaments as porous current collectors to contain active material-electrolyte mixtures

Various types of metal foams, carbon foams, and fine metal meshes are commercially available as conductive porous rods (acting as current collectors) in anodes or cathodes; such as Ni foam, cu foam, al foam, ti foam, ni mesh/net, stainless steel fiber mesh, etc. Metal coated polymer foams and carbon foams may also be used as current collectors. For the manufacture of macroscopic rope-like flexible and shape-conformable supercapacitors, the most desirable thickness/diameter range of these conductive porous rods is 50-1000 μm, preferably 100-800 μm, more preferably 200-600 μm. To fabricate a microscopic rope supercapacitor (e.g., having a diameter of from 100nm to 100 μm), graphene foam, graphene aerogel foam, porous carbon fibers (e.g., made by electrospinning polymer fibers, carbonizing polymer fibers, and activating the resulting carbon fibers), and porous graphite fibers may be used to contain the electrode active material-electrolyte mixture.

Example 2: ni foam and CVD graphene foam based porous rod loaded on Ni foam template

The procedure for producing CVD graphene foam was adapted according to the methods disclosed in the following publications: three-dimensional flexible and conductively interconnected graphene network growth by chemical vapor deposition]", nature Materials [ Natural Materials],10,424-428 (2011). Nickel foam (porous structure with interconnected 3D nickel scaffold) was chosen as template for graphene foam growth. Briefly, by decomposing CH at 1,000 ℃ under ambient pressure ₄ Carbon is introduced into the nickel foam, and then a graphene film is deposited on the surface of the nickel foam. Due to the difference in thermal expansion coefficient between nickel and graphene, waviness and wrinkles are formed on the graphene film. The following four types of foams made in this example were used as current collectors in the lithium batteries of the invention: ni foam, CVD graphene coated Ni form, CVD graphene foam (Ni etched away), and conductive polymer bonded CVD graphene foam.

To recover (separate) the graphene foam from the supporting Ni foam, the Ni frame is etched away. In the procedure proposed by Chen et al, the reaction is carried out by hot HCl (or FeCl) ₃ ) Before the solution etches away the nickel skeleton,a thin layer of poly (methyl methacrylate) (PMMA) was deposited on the surface of the graphene film as a support to prevent collapse of the graphene network during the nickel etch. After careful removal of the PMMA layer by hot acetone, a brittle graphene foam sample was obtained. The use of a PMMA support layer is believed to be critical to the preparation of free standing films of graphene foam. Instead, a conductive polymer is used as a binder resin to hold the graphene together while etching away the Ni. The thickness/diameter of the graphene foam or Ni foam ranges from 35 μm to 600 μm.

Ni foam or CVD graphene foam as used herein is intended to be a Conductive Porous Rod (CPR) to accommodate the components of the anode or cathode or both (anode or cathode active material + optional conductive additive + liquid electrolyte). For example, pre-lithiated Si nanoparticles dispersed in an organic liquid electrolyte (as an anode active material for lithium ion capacitors) (e.g., 1-5.5M LiPF dissolved in PC-EC) ₆ ) A gelatinous mass was produced which was delivered to the porous surface of Ni foam, which was continuously fed from a feed roll to make an anode electrode (as in schematic a of fig. 1 (D)).

Graphene sheets (300-750 nm long) dispersed in the same liquid electrolyte were made into a cathode slurry that was sprayed onto the porous surface of a continuous Ni foam rod to form a cathode electrode. A porous foam rod (first electrode) containing a prelithiated Si nanoparticle-electrolyte mixture impregnated into the foam pores was wound through a porous separator layer (porous PE-PP copolymer). The two electrodes were then assembled into a twisted yarn and then encapsulated in a thin polymer sheath to obtain a rope-like lithium ion capacitor.

On an individual basis, a mixture of separated graphene sheets and liquid electrolyte is impregnated into the pores of a rod of graphene foam, which is then wound with a separator film to fabricate one electrode. Another electrode with the same porous rod and the same mixture was made in a similar manner. The two rods are then combined to make a twisted yarn, which is then encased in a plastic sheath.

Example 3: conductive porous rods based on graphite foam from pitch-based carbon foam

The asphalt powder, granules or pellets are placed in an aluminum mold having the desired final foam shape. Mitsubishi ARA-24 mesophase pitch was used. The sample was evacuated to less than 1 torr and then heated to a temperature of about 300 ℃. At this point, the vacuum was released to a nitrogen blanket and then pressure was applied up to 1,000psi. The temperature of the system was then raised to 800 ℃. This was done at a rate of 2 deg.C/min. The temperature was held for at least 15 minutes to achieve soaking and then the furnace power was turned off and cooled to room temperature at a rate of about 1.5 deg.c/min, releasing the pressure at a rate of about 2 psi/min. The final foam temperatures were 630 ℃ and 800 ℃. During the cooling cycle, the pressure is gradually released to atmospheric conditions. The foam was then heat treated to 1050 ℃ (carbonized) under a nitrogen blanket and then heat treated to 2500 ℃ and 2800 ℃ (graphitized) in a separate operation in argon in a graphite crucible. Graphite foam rods can be obtained in the thickness range of 75-500 μm.

Example 4: preparation of Graphene Oxide (GO) and Reduced Graphene Oxide (RGO) nanoplates from natural graphite powder

Natural Graphite from Huadong Graphite co (Huadong Graphite co.) (celand china) was used as the starting material. GO is obtained by following the well-known modified helmholtz method, which involves two oxidation stages. In a typical procedure, the first oxidation is effected under the following conditions: 1100mg of graphite was placed in a 1000mL long-necked flask. Then, 20g of K was added to the flask ₂ S ₂ O ₈ 20g of P ₂ O ₅ And 400mL of concentrated H ₂ SO ₄ Aqueous solution (96%). The mixture was heated at reflux for 6 hours and then left undisturbed at room temperature for 20 hours. The graphite oxide was filtered and rinsed with copious amounts of distilled water until neutral pH. The wet cake-like material is recovered at the end of this first oxidation.

For the second oxidation process, the previously collected wet cake was placed in a container containing 69mL of concentrated H ₂ SO ₄ Aqueous solution (96%) in a long-necked flask. The flask was kept in an ice bath while slowly adding 9g KMnO ₄ . Care is taken to avoid overheating. The resulting mixture was heated to 35 deg.CStir for 2 hours (sample color turned dark green) then add 140mL of water. After 15min, the reaction mixture was purified by adding 420mL of water and 15mL of 30wt.% H ₂ O ₂ To stop the reaction. At this stage the color of the sample turned bright yellow. To remove the metal ions, the mixture was filtered and washed with 1. The collected material was gently centrifuged at 2700g and rinsed with deionized water. The final product was a wet cake containing 1.4wt.% GO (as estimated from dry extract). Subsequently, a liquid dispersion of GO sheets was obtained by mild sonication of wet-cake material diluted in deionized water.

Surfactant stabilized RGO (RGO-BS) is obtained by diluting the wet cake in an aqueous solution of a surfactant, rather than pure water. A mixture of commercially available sodium cholate (50 wt.%) and sodium deoxycholate (50 wt.%) salts supplied by Sigma Aldrich (Sigma Aldrich) was used. The surfactant weight fraction was 0.5wt.%. The fraction remained constant for all samples. Sonication was performed using a Branson Sonifier S-250A equipped with a 13mm step disruptor horn and a 3mm conical microtip operating at a frequency of 20 kHz. For example, 10mL of an aqueous solution containing 0.1wt.% GO was sonicated for 10min and then centrifuged at 2700g for 30min to remove any undissolved large particles, aggregates and impurities. Chemical reduction to obtain as-received GO to produce RGO was performed by following the following method, which involved placing 10mL of a 0.1wt.% GO aqueous solution in a 50mL long-necked flask. Then, 10 μ L of 35wt.% N ₂ H ₄ (hydrazine) aqueous solution and 70mL of 28wt.% NH ₄ An aqueous OH (ammonia) solution is added to the mixture and stabilized by a surfactant. The solution was heated to 90 ℃ and refluxed for 1h. The pH value measured after the reaction was about 9. The color of the sample turned dark black during the reduction reaction.

RGO is used as an electrode active material (alone or together with a redox pair partner material) in either or both of the anode and cathode in several of the inventive supercapacitors. The wet anode active-electrolyte mixture and cathode active material-electrolyte mixture are separately delivered to the surface of the graphite foam to form an anode and a cathode, respectively. A rope-like battery is then manufactured in which one filamentary electrode (e.g., anode) and one filamentary electrode (cathode) are combined to form a braid, twisted yarn, or the like.

For comparison purposes, a slurry coating and drying procedure was performed to produce a conventional electrode. The electrodes and separator disposed between the two dried electrodes were then assembled and encapsulated in an Al plastic laminate encapsulation envelope, and then injected with liquid electrolyte to form a conventional supercapacitor cell.

Example 5: preparation of pristine graphene sheets (0% oxygen)

Recognizing the possibility that the high defect number in GO sheets acts to reduce the electrical conductivity of individual graphene planes, we decided to investigate whether using pristine graphene sheets (non-oxidized and oxygen-free, non-halogenated and halogen-free, etc.) could yield active materials with high electrical and thermal conductivity to achieve electric double layer capacitors (EDLC supercapacitors). The prelithiated native graphene and the pre-sodiated native graphene are also used as anode active materials for lithium ion capacitors and sodium ion capacitors, respectively. Pristine graphene sheets are produced using direct sonication or a liquid phase production process.

In a typical procedure, 5 grams of graphite flakes milled to a size of about 20 μm or less are dispersed in 1,000ml deionized water (containing 0.1% by weight dispersant, from DuPont) containing

FSO) to obtain a suspension. An ultrasonic energy level of 85W (Branson S450 ultrasonicator) was used for puffing, separation and size reduction of graphene sheets for a period of 15 minutes to 2 hours. The resulting graphene sheets are pristine graphene that has never been oxidized and is oxygen-free and relatively defect-free. The pristine graphene is substantially free of any non-carbon elements.

The pristine graphene sheets are incorporated into a supercapacitor along with the electrolyte using both the procedure of the present invention and the conventional slurry coating, drying and lamination procedures.

Example 6: moS as cathode active material for pseudo-supercapacitor ₂ hybrid/RGO materialsPreparation of

In this example, various inorganic materials were studied. For example, by (NH) at 200 ℃ ₄ ) ₂ MoS ₄ One-step solvothermal reaction of hydrazine and oxidized Graphene Oxide (GO) in N, N-Dimethylformamide (DMF) solution to synthesize ultrathin MoS ₂ a/RGO impurity. In a typical procedure, 22mg of (NH) ₄ ) ₂ MoS ₄ To 10mg GO dispersed in 10ml DMF. The mixture was sonicated at room temperature for approximately 10min until a clear and homogeneous solution was obtained. Thereafter, 0.1ml of N was added ₂ H ₄ ·H ₂ And O. The reaction solution was further sonicated for 30min before transferring into a 40mL teflon lined autoclave. The system was heated in an oven at 200 ℃ for 10h. The product was collected by centrifugation at 8000rpm for 5min, washed with DI water and re-collected by centrifugation. The washing step was repeated at least 5 times to ensure removal of most of the DMF. Finally, the product is dried and mixed with a liquid electrolyte to produce an active cathode mixture slurry for impregnation into carbon foam.

Example 7: preparation of Graphene Fluoride (GF) sheets as supercapacitor active materials

We have used several methods to produce GF, but only one method is described here as an example. In a typical procedure, highly Expanded Graphite (HEG) is prepared from an intercalation compound ₂ F·xClF ₃ And (4) preparation. HEG was further fluorinated with chlorine trifluoride vapor to produce Fluorinated Highly Expanded Graphite (FHEG). The precooled Teflon reactor is filled with 20-30mL of liquid precooled ClF ₃ The reactor was closed and cooled to liquid nitrogen temperature. Then, no more than 1g of HEG was placed in a container with a container for ClF ₃ The gas enters the reactor and is located in an aperture within the reactor. Form a product with approximate formula C in 7-10 days ₂ F as a grey beige product.

Subsequently, a small amount of FHEG (approximately 0.5 mg) was mixed with 20-30mL of organic solvent (methanol and ethanol respectively) and subjected to sonication (280W) for 30min, resulting in the formation of a homogeneous yellowish dispersion. After removal of the solvent, the dispersion turned brown GF powder.

Example 8: preparation of graphene nitride sheet as electrode active material of supercapacitor

Graphene Oxide (GO) synthesized in example 2 was finely ground with urea in different proportions and the granulated mixture was heated (900W) in a microwave reactor for 30s. The product was washed several times with deionized water and dried in vacuo. In this method, graphene oxide is simultaneously reduced and doped with nitrogen. The obtained products with graphene to urea mass ratios of 1.5, 1:1 and 1:2 were named NGO-1, NGO-2 and NGO-3, respectively, and the nitrogen content of these samples was found to be 14.7wt%, 18.2wt% and 17.5wt%, respectively, as by elemental analysis. These graphene nitride sheets remain dispersed in water. The resulting suspension was then dried to obtain a nitrided graphene powder. The powders are mixed in a liquid electrolyte to form a slurry for impregnation into the pores of the conductive porous rods/filaments.

Example 9: two-dimensional (2D) layered Bi ₂ Se ₃ Preparation of chalcogenide nanoribbons

(2D) Layered Bi ₂ Se ₃ The preparation of chalcogenide nanoribbons is well known in the art. For example, growing Bi using the vapor-liquid-solid (VLS) method ₂ Se ₃ A nanoribbon. On average, the nanoribbons produced herein are 30-55nm thick, with widths and lengths ranging from hundreds of nanometers to several microns. The longer nanobelts were subjected to ball milling to reduce the lateral dimensions (length and width) to below 200nm. Nanoribbons prepared by these procedures (with or without graphene sheets or expanded graphite flakes) are used as supercapacitor electrode active materials.

Example 10: MXene powder + chemically activated RGO

MXene is selected from metal carbides such as Ti ₃ AlC ₂ Is produced by partially etching away some elements. For example, 1M NH is used at room temperature ₄ HF ₂ Aqueous solution as Ti ₃ AlC ₂ The etchant of (1). Typically, MXene surfaces are terminated by O, OH and/or F groups, which is why they are commonly referred to as M _n+1 X _n T _x Wherein M is the first transition metal,x is C and/or N, T represents an end capping group (O, OH and/or F), N =1, 2 or 3, and X is the number of end capping groups. MXene materials of interest include Ti ₂ CT _x 、Nb ₂ CT _x 、V ₂ CT _x 、Ti ₃ CNT _x And Ta ₄ C ₃ T _x . Typically, 35% -95% mxene and 5% -65% graphene sheets are mixed in a liquid electrolyte and impregnated into the pores of the conductive porous filaments.

Example 11: mnO as pseudocapacitance active material ₂ Preparation of graphene redox couple

MnO ₂ Powders were synthesized by two methods, each with or without graphene sheets present. In one method, 0.1mol/L KMnO is prepared by dissolving potassium permanganate in deionized water ₄ An aqueous solution. While 13.32g of a high purity sodium bis (2-ethylhexyl) sulfosuccinate surfactant was added to 300mL of isooctane (oil) and stirred well to obtain an optically clear solution. Then, 32.4mL of 0.1mol/L KMnO was added ₄ The solution and a selected amount of GO solution were added to the solution, which was sonicated for 30min to prepare a dark brown precipitate. The product was isolated, washed several times with distilled water and ethanol and dried at 80 ℃ for 12h. The sample is graphene-supported MnO in powder form ₂ It is dispersed in a liquid electrolyte to form a slurry and impregnated into the pores of the foamed current collector.

Example 12: evaluation of various supercapacitor cells

In most of the examples studied, both the supercapacitor cells of the invention and their conventional counterparts were made and evaluated. For comparison purposes, the latter cells were prepared by a conventional procedure of slurry coating of the electrodes, drying of the electrodes, assembly of the anode, separator and cathode layers, encapsulation of the assembled laminate, and injection of the liquid electrolyte. In a conventional cell, the electrode (cathode or anode) is typically composed of 85% electrode active material (e.g., graphene, activated carbon, inorganic nanodisks, etc.), 5% super-P (acetylene black-based conductive additive), and 10% ptfe (which are mixed and coated on aluminum foil). The thickness of the electrode is about 100 μm. For each sample, both coin-sized and soft-packed cells were assembled in a glove box. Capacity was measured with a constant current experiment using an Arbin SCTS electrochemical tester. Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) were performed on an electrochemical workstation (CHI 660 system, usa).

Galvanostatic charge/discharge tests were performed on the samples to evaluate electrochemical performance. For the galvanostatic test, the specific capacity (q) was calculated as

q＝I*t/m (1)

Where I is a constant current in mA, t is a time in hours, and m is the mass of the cathode active material in grams. For the voltage V, the specific energy (E) is calculated as,

E＝∫Vdq (2)

the specific power (P) can be calculated as P = (E/t) (W/kg) (3)

Where t is the total charge or discharge step time in hours.

The specific capacitance (C) of the cell is represented by the slope at each point of the voltage versus specific capacity diagram,

C＝dq/dV (4)

for each sample, several current densities (representing charge/discharge rates) were applied to determine the electrochemical response, allowing the energy density and power density values required to construct a ravigneaux plot (power density versus energy density) to be calculated.

The plot of the radon force (weight and volumetric power density versus energy density) for two sets of symmetric supercapacitor (EDLC) cells containing Reduced Graphene Oxide (RGO) sheets as electrode active material and EMIMBF4 ionic liquid as electrolyte is shown in fig. 5. One of the two series of supercapacitors was prepared according to an embodiment of the invention and the other series of supercapacitors was prepared by conventional electrode paste coating. From these data several important observations can be made:

(A) Both the weight and volumetric energy density and the power density of the supercapacitor cells prepared by the process of the invention (rope cells) are significantly higher than their counterparts prepared by conventional processes (denoted "conventional")Weight and volumetric energy density of the object and power density. The differences are highly significant and are primarily due to the high active material mass loading associated with the cells of the present invention: (>20mg/cm ² ) Reduced proportion of non-contributing (inactive) components relative to active material weight/volume, no need to have a binder resin, ability of the inventive method to more effectively pack graphene sheets in the pores of a foamed current collector.

(B) For cells prepared by conventional methods, the very low tap density (0.25 g/cm) of RGO-based electrodes prepared by conventional slurry coating methods is due to ³ Bulk density) of the bulk energy density and bulk power density are significantly lower than their gravimetric energy density and gravimetric power density.

(C) In contrast, for cells prepared by the method of the present invention, the relatively high tap density (bulk density of 1.05 g/cm) of the RGO-based electrodes prepared by the method of the present invention is due to ³ ) The absolute magnitudes of the volumetric energy density (23.8 Wh/L) and volumetric power density (9,156W/L) are higher than the absolute magnitudes of their gravimetric energy density and gravimetric power density.

(D) The volumetric energy density and volumetric power density of the corresponding supercapacitor prepared by the conventional method were 3.1Wh/L and 1,139W/L, respectively, one order of magnitude lower. These are significant and unexpected.

Fig. 6 shows a raleigh plot (both weight and volumetric power density versus energy density) of a symmetric supercapacitor (EDLC) cell containing Activated Carbon (AC) particles as electrode active material and an organic liquid electrolyte. Experimental data were obtained from supercapacitors (rope cells) prepared by the method of the invention and supercapacitors prepared by conventional electrode paste coating.

These data also indicate that the weight and volumetric energy density and power density of the supercapacitor cells prepared by the method of the present invention are significantly higher than the weight and volumetric energy density and power density of their counterparts prepared by conventional methods. Also, the difference is great and is mainly due to the rope shape of the inventionCell-associated high active material mass loading (>15mg/cm ² ) Reduced proportion of non-contributing (inactive) components relative to active material weight/volume, no need to have a binder resin, ability of the inventive method to more effectively pack graphene sheets in the pores of a foamed current collector. Highly porous activated carbon particles are not as suitable for more compact packing as graphene sheets. Thus, for an AC-based ultracapacitor, the absolute magnitudes of the volumetric energy density and volumetric power density are lower than the absolute magnitudes of the corresponding gravimetric energy density and gravimetric power density. However, the process of the present invention still unexpectedly enables AC particles to be produced at tap densities (0.55 g/cm) that are greater than those achieved in the present study with conventional slurry coating methods ³ ) Significantly higher tap density (0.75 g/cm) ³ ) And (4) stacking.

Fig. 7 (a) shows a liquid electrolyte composition containing pristine graphene sheets as a cathode active material, prelithiated graphite particles as an anode active material, and a lithium salt (LiPF) as an organic liquid electrolyte ₆ ) Latong plots for Lithium Ion Capacitor (LIC) cells of PC/DEC. The data are for both LIC prepared by the method of the present invention and LIC prepared by conventional electrode paste coating. These data indicate that the weight and volumetric energy density and power density of LIC cells prepared by the method of the present invention are significantly higher than their counterparts prepared by conventional methods. Again, the difference is large and is primarily due to the high active material mass loading (on the anode side) associated with the rope cells of the invention>15mg/cm ² And on the cathode side>25mg/cm ² ) Reduced proportion of non-contributing (inactive) components relative to active material weight/volume, lack of binder resin, ability of the inventive method to more effectively pack graphene sheets in the pores of a foamed current collector.

For LIC cells prepared by conventional methods, due to the very low tap density (0.75 g/cm) of pristine graphene-based electrodes prepared by conventional slurry coating methods ³ Average bulk density) of the bulk energy density and the volumetric power density are significantly lower than their gravimetric energy in absolute orderAbsolute magnitude of the mass density and gravimetric power density. In contrast, for the rope-like LIC cells prepared by the inventive method, the absolute magnitudes of the volumetric energy density and the volumetric power density are higher than the absolute magnitudes of their gravimetric energy density and gravimetric power density due to the relatively high tap density of the pristine graphene-based cathodes prepared by the inventive method.

Fig. 7 (B) shows a liquid electrolyte composition containing pristine graphene sheets as a cathode active material, pre-sodium graphite particles as an anode active material, and sodium salt (NaPF) as an organic liquid electrolyte ₆ ) Ragong plots for sodium ion capacitor (NIC) cells of PC/DEC. The data are for both LIC prepared by the method of the present invention and LIC prepared by conventional electrode paste coating. These data indicate that the weight and volumetric energy density and power density of NIC cells (rope cells) made by the process of the present invention are significantly higher than their counterparts made by conventional processes. Again, the difference is significant and is primarily due to the high active material mass loading (on the anode side) associated with the cells of the invention>15mg/cm ² And on the cathode side>25mg/cm ² ) Reduced proportion of non-contributing (inactive) components relative to active material weight/volume, no need to have a binder resin, ability of the inventive method to more effectively pack graphene sheets in the pores of a foamed current collector.

It is important to note that reporting the energy density and power density per weight of active material alone on the largong graph, as done by many researchers, may not give a realistic picture of the performance of the assembled supercapacitor cell. The weight of the other apparatus components must also be taken into account. These non-contributing components, including current collectors, electrolytes, separators, adhesives, connectors, and encapsulants, are inactive materials and do not contribute to charge storage. They merely add weight and bulk to the device. Therefore, it is desirable to reduce the relative proportion of the weight of the non-contributing components and increase the proportion of the active material. However, this goal has not been possible using conventional supercapacitor production methods. The present invention overcomes this long standing most serious problem in the field of supercapacitors.

In commercial supercapacitors having an electrode thickness of 150-200 μm (75-100 μm on each side of the Al foil current collector), the weight of the active material (i.e. activated carbon) accounts for about 25-30% of the total mass of the encapsulated cell. Therefore, a factor of 3 to 4 is often used to extrapolate the energy density or power density of the device (cell) from the characteristics based solely on the weight of the active material. In most scientific papers, the reported characteristics are typically based on the active material weight alone, and the electrodes are typically very thin (< 100 μm, and mostly < <50 μm). The active material weight is typically from 5% to 10% of the total device weight, which means that the actual cell (device) energy density or power density can be obtained by dividing the corresponding value based on the active material weight by a factor of 10 to 20. Taking this factor into account, the properties reported in these papers do not actually look better than those of commercial supercapacitors. Therefore, great care must be taken in reading and interpreting the performance data of supercapacitors reported in scientific papers and patent applications.

Example 13: achievable electrode thickness and its effect on electrochemical performance of supercapacitor cells

One may tend to think that the electrode thickness of a supercapacitor is a design parameter that can be freely adjusted to optimize device performance; however, in practice, supercapacitor thickness is limited by manufacturing and electrodes with good structural integrity beyond a certain thickness level cannot be produced. Our studies further show that this problem is more severe in the case of graphene-based electrodes. The present invention addresses this crucial problem associated with supercapacitors.

Fig. 8 shows cell-level weight (Wh/kg) and volumetric energy density (Wh/L) plotted over the achievable electrode thickness range for activated carbon-based symmetric EDLC supercapacitors prepared by conventional methods and those rope-like cells prepared by the method of the present invention. The activated carbon-based electrode can be fabricated to a thickness of 100-200 μm using a conventional slurry coating method. In contrast, however, there is no theoretical limit to the electrode thickness that can be achieved with the method of the present invention. Typically, the actual electrode thickness is from 10 μm to 5000 μm, more typically from 50 μm to 2,000 μm, even more typically from 100 μm to 1,000 μm, and most typically from 200 μm to 800 μm.

These data further demonstrate the surprising effectiveness of the method of the present invention in ultra-thick supercapacitor electrodes that could not be achieved prior to production. These ultra-thick electrodes result in exceptionally high active material mass loadings, typically significant>10mg/cm ² (more typically>15mg/cm ² Further typically>20mg/cm ² Often times, the>25mg/cm ² And even>30mg/cm ² ). These high active material mass loadings have not been possible to achieve with conventional supercapacitors made by slurry coating processes.

More importantly, typical cell level energy densities of commercial AC-based supercapacitors are from 3 to 8Wh/kg and from 1 to 4Wh/L. In contrast, the method of the invention enables supercapacitors containing the same type of electrode active material (AC) to provide energy densities of up to 19.5Wh/kg or 14.6 Wh/L. This increase in energy density is not considered possible in the supercapacitor industry.

The data summarized in fig. 9 is also highly significant and unexpected for EDLC supercapacitors based on reduced graphene oxide. The cell-level gravimetric and volumetric energy densities are plotted over the range of achievable electrode thicknesses for RGO-based EDLC supercapacitors (organic liquid electrolytes) prepared by conventional methods and those prepared by the method of the invention. In this graph, the weight (. Diamond-solid.) and volume (. Tangle-solidup.) energy densities of conventional supercapacitors are based on approximately 0.25g/cm ³ And the energy density of the weight (■) and volume (X) of the rope supercapacitor of the present invention comes from having about 0.75g/cm ³ (by no means the highest) of the tap densities of the electrodes. No one has previously reported such high tap densities for untreated, unactivated RGO electrodes.

These data indicate that the highest gravimetric energy density achieved with RGO-based EDLC supercapacitor cells produced by the conventional slurry coating process is about 12Wh/kg, but those supercapacitor cells prepared by the process of the present invention exhibit gravimetric energy densities of up to 25.6Wh/kg at room temperature. For EDLC supercapacitors, this is an unprecedented high energy density value (based on the total cell weight, rather than just the electrode weight or active material weight). Even more impressive are the following observations: the volumetric energy density of the supercapacitor cells of the invention is as high as 19.2Wh/L, which is over 6 times higher than the 3.0Wh/L achieved by the conventional counterparts.

The data for cell-level weight and volumetric energy density plotted over the achievable electrode thickness range for pristine graphene-based EDLC supercapacitors (organic liquid electrolytes) prepared by the conventional process and those rope cells prepared by the process of the present invention are summarized in fig. 10. The legend includes the energy densities of the weight (. Diamond-solid.) and volume (. Tangle-solidup.) of the conventional supercapacitor (the highest achieved electrode tap density was approximately 0.25 g/cm) ³ ) And the energy density (about 0.85 g/cm) of the weight (■) and volume (X) of the inventive supercapacitor ³ Electrode tap density).

Very significantly, these EDLC supercapacitors (without any redox or pseudocapacitance) deliver gravimetric energy densities of up to 32.3Wh/kg, which are already within the energy density of advanced lead acid batteries (20-40 Wh/kg). Since EDLC supercapacitors can be charged and discharged for 250,000-500,000 cycles, this has a high practical value compared to the typical 100-400 cycles of lead acid batteries. This achievement is very significant and completely unexpected in the field of supercapacitors. Furthermore, carbon or graphene based EDLC supercapacitors can be recharged in seconds compared to the typical several hours of recharge time required for lead acid batteries. Lead acid batteries are notorious for their highly negative environmental impact, but the supercapacitors of the invention are environmentally friendly.

Further notable examples include those data summarized in FIG. 11 for those based on proto-base prepared by conventional methodsCell-level weight and volumetric energy density plotted over the achievable electrode thickness range for raw graphene EDLC supercapacitors (ionic liquid electrolytes) and those rope cells made by the method of the invention. The weight (. Diamond-solid.) and volume (. Tangle-solidup.) energy densities were for those conventional supercapacitors (the highest achieved electrode tap density was about 0.25 g/cm) ³ ) And the energy density of the weight (■) and volume (X) is for a fuel cell having a density of about 0.85g/cm ³ Of the electrode tap density of the invention. The pristine graphene-based EDLC supercapacitors of the invention are capable of storing an energy density at the cell level of 38.6Wh/kg, which is 6 times higher than that possible by conventional AC-based EDLC supercapacitors. The volumetric energy density value of 32.8Wh/L is also unprecedented and 10 times greater than 3-4Wh/L for commercial AC-based supercapacitors.

Example 14: achievable weight percent of active material in a cell and its effect on electrochemical performance of a supercapacitor cell

Since the active material weight accounts for up to about 30% of the total mass of the encapsulated commercial supercapacitor, a factor of 30% must be used to infer the energy or power density of the device from the performance data of the active material alone. Thus, an energy density of 20Wh/kg of activated carbon (i.e., based on the weight of active material alone) would translate to about 6Wh/kg of encapsulated cells. However, this inference is only for thicknesses and densities that are present and commercial electrodes (150 μm or about 10mg/cm for carbon electrodes) ² ) Similar electrodes are effective. A thinner or lighter electrode of the same active material would mean an even lower energy or power density based on the cell weight. It is therefore desirable to produce supercapacitor cells with a high proportion of active material. Unfortunately, it has not been previously possible to achieve active material ratios of greater than 30% by weight for activated carbon-based supercapacitors or greater than 15% by weight for graphene-based supercapacitors.

The method of the present invention makes supercapacitors far beyond these limitations of all active materials studied. In fact, the invention makes it possible to increase the proportion of active material to more than 90%, if desired; but typically from 15% to 85%, more typically from 30% to 80%, even more typically from 40% to 75%, and most typically from 50% to 70%.

As shown in fig. 12, the cell-level gravimetric energy density of the activated carbon-based EDLC supercapacitors (with organic liquid electrolyte) was plotted within the achievable active material ratio (active material weight/total cell weight), which was from 4.2% to 33.3%, yielding an energy density of from 1.3 to 8.4 Wh/kg. The invention allows us to achieve a pristine graphene content of from 17.5 to 79% by weight in supercapacitor cells, resulting in a gravimetric energy density of from 4.9 to 19.5 Wh/kg. For example, fig. 13 shows cell-level gravimetric energy densities plotted over the achievable active material ratio (active material weight/total cell weight) in supercapacitor cells for two series of pristine graphene-based EDLC supercapacitors (all with organic liquid electrolyte). Likewise, cord cells of the present invention comprising filament electrodes pre-impregnated with an active material-electrolyte mixture can be made to contain exceptionally high proportions of active material, and therefore exceptionally high energy densities.

Example 15: electrochemical performance of supercapacitor cells based on various electrode active materials and/or different porous or foamed structures (as current collectors)

To evaluate the impact of foam structure, we chose to use RGO as an example of electrode active material, but varying the type and properties of the current collector (porous rods or filaments). A wide variety of foams were selected, ranging from metal foams (e.g., ni and Ti foams), metal meshes (e.g., stainless steel mesh), perforated metal sheet-based 3-D structures, metal fiber mats (steel fibers), metal nanowire mats (Cu nanowires), conductive polymer nanofiber mats (polyaniline), conductive polymer foams (e.g., PEDOT), conductive polymer coated fiber foams (polypyrrole coated nylon fibers), carbon foams, graphite foams, carbon aerogels, carbon xerogels, graphene foams (from Ni-loaded CVD graphene), graphene oxide foams (obtained by freeze-drying GO-water solution), reduced graphene oxide foams (RGO mixed with polymer and then carbonized), carbon fiber foams, graphite fiber foams, and expanded graphite foams (expanded graphite worms bonded by carbonized resin). This extensive and intensive study led to the following important observations:

(A) The conductivity of the foam is an important parameter, with higher conductivity tending to result in higher power density and faster supercapacitor response time.

(B) Porosity level is also an important parameter, where a higher pore content leads to a higher amount of active material, and thus a higher energy density, given the same volume. However, higher porosity levels may result in slower response times, possibly due to lower electron conductivity.

(C) Graphite foam and graphene foam provide better supercapacitor response times. However, the metal foam enables easier formation or connection to the tab (end lead). Two leads are required for each cell.

Various electrode active materials have been investigated for both EDLC and redox supercapacitors, covering organic and inorganic materials, in combination with aqueous, organic and ionic liquid electrolytes. Summarized in the following table (table 1) are some examples of different classes of supercapacitors for illustrative purposes. These should not be construed as limiting the scope of the application.

Table 1: examples of supercapacitors prepared by the novel process and their counterparts prepared by conventional slurry coating processes.

These data further demonstrate the unexpected superiority of the rope supercapacitor cells and the production process of the invention in significantly improving mass loading (ratio), electrode diameter/thickness, gravimetric energy density and volumetric energy density. The rope-like supercapacitors of the invention (with active material/electrolyte-pre-impregnated braid/yarn electrodes) are consistently much better than conventional supercapacitors in terms of electrochemical properties. The difference is surprisingly significant.

In summary, we have successfully developed a new and novel class of supercapacitors that are flexible and shape-conformable and have unexpectedly large active material mass loading (not previously achievable), excellent gravimetric energy density (not previously achievable), and unprecedentedly high volumetric energy density. The method of the present invention of pre-impregnating the active material-electrolyte mixture into the foamed current collector to make an electrode also overcomes the long-standing problems associated with graphene sheet-based supercapacitors (i.e., inability to make thick electrodes, difficulty in preventing graphene sheet re-stacking, low tap density, and low volumetric energy density).

Claims (64)

1. A rope supercapacitor, comprising:

(a) A first electrode comprising a first electrically conductive porous rod having pores, and a first mixture of a first electrode active material and a first electrolyte, wherein the first mixture is present in the pores of the first electrically conductive porous rod;

(b) A porous separator wrapping or encapsulating the first electrode to form a separator protected first electrode;

(c) A second electrode comprising a second electrically conductive porous rod having pores, and a second mixture of a second electrode active material and a second electrolyte, wherein the second mixture is present in the pores of the second electrically conductive porous rod; wherein the separator protected first electrode and the second electrode are combined or interwoven together to form a braid or yarn; and

(d) A protective outer shell or sheath that wraps or encases the braid or yarn;

wherein the first electrode active material and/or the second electrode active material contains a plurality of carbon material particles and/or a plurality of graphene sheets, wherein the plurality of graphene sheets contain single-layer graphene or few-layer graphene each having from 1 to 10 graphene planes, and the plurality of carbon material particles or graphene sheets have a structure having, when measured in a dry stateNot less than 500m ² Specific surface area in g.

2. The rope-like supercapacitor of claim 1 comprising a plurality of the first electrodes and/or a plurality of the second electrodes, wherein at least one of the electrodes is an anode and at least one is a cathode.

3. The rope supercapacitor of claim 1 further comprising a porous separator wrapping or encapsulating the second electrode to form a separator protected second electrode.

4. The rope supercapacitor of claim 3 further comprising a third electrolyte disposed between the braid or yarn and the protective shell or sheath.

5. The rope-like supercapacitor of claim 1, wherein the first or second electrode active material contains activated carbon particles or isolated graphene sheets having a length or width of less than 1 μ ι η to impregnate into the pores of the first or second electrode, wherein the graphene sheets are selected from the group consisting of: pristine graphene, graphene oxide, reduced graphene oxide, fluorinated graphene, nitrided or nitrogen doped graphene, hydrogenated or hydrogen doped graphene, boron doped graphene, chemically functionalized graphene, and combinations thereof.

6. The rope-shaped supercapacitor according to claim 1, wherein the first electrode or the second electrode contains, as the only electrode active material in the first electrode or the second electrode: (a) individual graphene sheets; (b) graphene sheets mixed with a porous carbon material; (c) Graphene sheets mixed with a pairing material that forms a redox pair with the graphene sheets to create a pseudocapacitance; or (d) graphene sheets and a porous carbon material mixed with a partner material that forms a redox pair with the graphene sheets or the porous carbon material to create a pseudo-capacitance; and wherein no other electrode active material is present in the first or second electrode.

7. A rope supercapacitor having a length to diameter aspect ratio or a length to thickness aspect ratio of greater than 10; the rope-shaped supercapacitor comprises:

(a) A first electrode comprising a first collector bar, and a first mixture of a first electrode active material and a first electrolyte, wherein the first mixture is deposited on or in the first collector bar;

(b) A porous separator wrapping or encapsulating the first electrode to form a separator protected first electrode;

(c) A second electrode comprising a second electrically conductive porous rod having pores, and a second mixture of a second electrode active material and a second electrolyte, wherein the second mixture is present in the pores of the second electrically conductive porous rod; wherein the membrane protected first electrode and the second electrode are interwoven or combined in a twisted or spiral manner to form a braid or yarn; and

(d) A protective outer shell or sheath that wraps or encases the braid or yarn;

wherein the first electrode active material and/or the second electrode active material contains a plurality of carbon material particles and/or a plurality of graphene sheets, wherein the plurality of graphene sheets contain single-layer graphene or few-layer graphene each having from 1 to 10 graphene planes, and the plurality of carbon material particles or the graphene sheets have not less than 500m when measured in a dry state ² Specific surface area in g.

8. The rope supercapacitor of claim 7 further comprising a porous separator wrapping or encapsulating the second electrode to form a separator protected second electrode.

9. The rope supercapacitor of claim 8 further comprising a third electrolyte disposed between the braid or yarn and the protective sheath.

10. The rope supercapacitor of claim 1, wherein the rope supercapacitor has a first end and a second end, and the first electrode contains a first terminal connector embedded in, connected to, or integral with the first electrode, the first terminal connector comprising at least one of metal wire, conductive carbon/graphite fiber, or conductive polymer fiber.

11. The rope supercapacitor of claim 10, wherein the at least one metal wire, conductive carbon/graphite fiber, or conductive polymer fiber extends substantially from the first end to the second end.

12. The rope supercapacitor of claim 1, wherein the first or second conductive porous rod contains a porous foam selected from: metal foams, metal meshes, metal fiber mats, metal nanowire mats, conductive polymer fiber mats, conductive polymer foams, conductive polymer coated fiber foams, carbon aerogels, carbon xerogels, and combinations thereof.

13. The rope supercapacitor of claim 1, wherein the first or second conductive porous rod contains a porous foam selected from: graphite foam, graphene aerogel, carbon fiber foam, and combinations thereof.

14. The rope supercapacitor of claim 1, wherein the first or second conductive porous rod contains a porous foam selected from: graphene foam, graphite fiber foam, expanded graphite foam, and combinations thereof.

15. The rope supercapacitor of claim 1, wherein the first or second conductive porous rod contains a porous foam selected from: graphene oxide foam, reduced graphene oxide foam, and combinations thereof.

16. The rope supercapacitor of any one of claims 12 to 15, wherein the porous foam has a cross-section that is circular, elliptical, rectangular, hexagonal, hollow, or irregularly shaped.

17. The rope supercapacitor of any one of claims 12 to 15, wherein the porous foam has a square cross-section.

18. The rope supercapacitor of claim 1, wherein the rope supercapacitor has a length/thickness aspect ratio or a length/diameter aspect ratio greater than 10.

19. The rope supercapacitor of claim 5, wherein the first or second electrode further comprises a redox pair partner material selected from an organic material, an inorganic material, or a combination thereof, wherein the partner material in combination with graphene or activated carbon forms a redox pair for pseudocapacitance.

20. The rope supercapacitor of claim 5, wherein the first or second electrode further comprises a redox pair partner material selected from a metal oxide, a conductive polymer, a non-graphene carbon material, or a combination thereof, wherein the partner material in combination with graphene or activated carbon forms a redox pair for pseudo-capacitance.

21. The rope supercapacitor of claim 20, wherein the metal oxide is selected from the group consisting of: ruO ₂ 、IrO ₂ 、NiO、MnO ₂ 、VO ₂ 、V ₂ O ₅ 、V ₃ O ₈ 、TiO ₂ 、Cr ₂ O ₃ 、Co ₂ O ₃ 、Co ₃ O ₄ 、PbO ₂ 、Ag ₂ O and combinations thereof.

22. The rope supercapacitor of claim 19 wherein the inorganic material is selected from the group consisting of metal carbides, metal nitrides, metal borides, metal dichalcogenides, and combinations thereof.

23. The rope supercapacitor of claim 19 wherein the inorganic material is selected from oxides, dichalcogenides, trichalcogenides, sulfides, selenides, or tellurides of an element selected from the group consisting of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, vanadium, chromium, cobalt, manganese, iron, nickel, and combinations thereof, in the form of nanowires, nanodiscs, nanoribbons, or nanoplatelets.

24. The rope supercapacitor of claim 19, wherein the inorganic material is selected from nanodiscs, nanoplatelets, nanocoatings, or nanoplatelets of an inorganic material selected from the group consisting of: bismuth selenide, bismuth telluride, transition metal dichalcogenides, transition metal trichalcogenides, sulfides of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or transition metals, selenides of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or transition metals, tellurides of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or transition metals, boron nitride, and combinations thereof; wherein the nanodisk, nanoplatelet, nanocoating, or nanoplatelet has a thickness of less than 100 nm.

25. The rope supercapacitor of claim 1, wherein the first or second electrode active material contains nanodiscs, nanoplatelets, nanocoatings, or nanoplatelets of an inorganic material selected from the group consisting of: bismuth selenide, bismuth telluride, transition metal dichalcogenides, transition metal trisalcogenides, niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel or peroxoniumA sulfide of a transition metal, a selenide of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or a transition metal, a telluride of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or a transition metal, boron nitride, and combinations thereof, wherein the disc, platelet, coating, or sheet has a thickness of less than 100nm and no less than 200m when measured in a dry state ² Specific surface area in g.

26. The rope supercapacitor of claim 1, which is a lithium ion capacitor or a sodium ion capacitor, and wherein the first or second electrode active material is an anode selected from the group consisting of:

(a) Natural graphite, artificial graphite, mesocarbon microbeads (MCMB), and pre-lithiated and pre-sodiated particles of carbon;

(b) Pre-lithiated and pre-sodiated silicon (Si), germanium (Ge), tin (Sn), lead (Pb), antimony (Sb), bismuth (Bi), zinc (Zn), aluminum (Al), nickel (Ni), cobalt (Co), manganese (Mn), titanium (Ti), iron (Fe), and cadmium (Cd);

(c) Pre-lithiated and pre-sodiated alloys or intermetallic compounds of Si, ge, sn, pb, sb, bi, zn, al or Cd with other elements, wherein said alloys or compounds are stoichiometric or non-stoichiometric;

(d) Pre-lithiated and pre-sodiated oxides, carbides, nitrides, sulfides, phosphides, selenides, and tellurides of Si, ge, sn, pb, sb, bi, zn, al, fe, ni, co, ti, mn, or Cd, and mixtures or composites thereof; and

(e) Combinations thereof.

27. The rope supercapacitor of claim 1, which is a lithium ion capacitor or a sodium ion capacitor, and wherein the first or second electrode is an anode containing: native graphene, graphene oxide, reduced graphene oxide, graphene fluoride, graphene chloride, graphene bromide, graphene iodide, hydrogenated graphene, nitrogenated graphene, boron-doped graphene, nitrogen-doped graphene, chemically functionalized graphene, physically or chemically activated or etched versions thereof, and pre-lithiated versions or pre-sodiated versions of combinations thereof.

28. The rope supercapacitor of claim 1, which is a sodium-ion capacitor, and wherein the first or second electrode is an anode comprising an anode active material selected from the group consisting of: petroleum coke, carbon black, amorphous carbon, activated carbon, hard carbon, soft carbon, template carbon, hollow carbon nanowire, hollow carbon sphere, or sodium titanate, naTi ₂ (PO ₄ ) ₃ 、Na ₂ Ti ₃ O ₇ 、Na ₂ C ₈ H ₄ O ₄ 、Na ₂ TP、Na _x TiO ₂ Materials based on carboxylic acid salts, C ₈ H ₄ Na ₂ O ₄ 、C ₈ H ₆ O ₄ 、C ₈ H ₅ NaO ₄ 、C ₈ Na ₂ F ₄ O ₄ 、C ₁₀ H ₂ Na ₄ O ₈ 、C ₁₄ H ₄ O ₆ 、C ₁₄ H ₄ Na ₄ O ₈ And combinations thereof, wherein in Na _x TiO ₂ Wherein x =0.2 to 1.0.

29. The rope-shaped supercapacitor of claim 1, wherein the first or second conductive porous rod has from 70 to 99% by volume of pores.

30. The rope supercapacitor of claim 1, wherein the rope supercapacitor is greater than 1m in length.

31. The rope supercapacitor of claim 1, wherein the rope supercapacitor is curved with a radius of curvature greater than 10 cm.

32. The rope supercapacitor of claim 1, wherein the rope supercapacitor is bendable to substantially conform to a shape of a void or interior compartment in a vehicle, the void or interior compartment comprising a trunk, a door, a hatch, a spare tire compartment, an under seat area, or an under dashboard area.

33. The rope supercapacitor of claim 32, wherein the rope supercapacitor is detachable from a vehicle and bendable to conform to the shape of different voids or interior compartments.

34. The rope supercapacitor of claim 1, wherein one or more cells of the rope supercapacitor are incorporated into a garment, belt, carrying strap, luggage strap, weapons strap, musical instrument strap, helmet, hat, boot, foot cover, glove, wrist cover, watch strap, jewelry item, animal collar, or animal harness.

35. The rope supercapacitor of claim 1, wherein one or more cells of the rope supercapacitor are removably coupled to a garment, belt, carrying strap, luggage strap, weapons strap, musical instrument strap, helmet, hat, boot, foot cover, glove, wrist cover, watch strap, jewelry item, animal collar, or animal harness.

36. The rope supercapacitor of claim 1, wherein the rope supercapacitor conforms to an inner radius of a hollow bicycle frame.

37. A method for producing a rope supercapacitor, the method comprising:

(a) Impregnating a first mixture of a first electrode active material and a first electrolyte into pores of a first electrically conductive porous rod to form a first electrode;

(b) Wrapping or encapsulating a porous separator around the first electrode to form a separator-protected first electrode;

(c) Impregnating a second mixture of a second electrode active material and a second electrolyte into pores of a second electrically conductive porous rod to form a second electrode;

(d) Combining or interweaving the separator protected first electrode and the second electrode together to form a braid or twisted yarn; and

(e) Wrapping or encapsulating a protective outer shell or protective sheath around the braid or twisted yarn to form the rope supercapacitor;

wherein the first electrode active material and/or the second electrode active material contains a plurality of carbon material particles and/or a plurality of graphene sheets, wherein the plurality of graphene sheets contain single-layer graphene or few-layer graphene each having from 1 to 10 graphene planes, and the plurality of carbon material particles or graphene sheets have not less than 500m when measured in a dry state ² Specific surface area in g.

38. The method of claim 37, comprising the procedure of combining a plurality of said first electrodes and/or a plurality of said second electrodes to form said rope supercapacitor, wherein at least one of said electrodes is an anode and at least one is a cathode.

39. The method of claim 37, further comprising the step of wrapping or encapsulating a porous separator around the second electrode to form a separator protected second electrode.

40. The method of claim 39, further comprising the step of disposing a third electrolyte between the braid or yarn and the protective sheath.

41. The method of claim 37, wherein the first or second electrode active material contains activated carbon particles or isolated graphene sheets having a length or width of less than 1 μ ι η to impregnate into the pores of the first or second electrode, wherein the graphene sheets are selected from the group consisting of: native graphene, graphene oxide, reduced graphene oxide, fluorinated graphene, nitrided or nitrogen doped graphene, hydrogenated or hydrogen doped graphene, boron doped graphene, chemically functionalized graphene, or combinations thereof.

42. A method for producing a rope supercapacitor having a length to diameter aspect ratio or a length to thickness aspect ratio of greater than 10; the method comprises the following steps:

(a) Providing a first electrode comprising a first conductive rod, and a first mixture of a first electrode active material and a first electrolyte, wherein the first mixture is deposited on or in the first conductive rod;

(b) Wrapping or encapsulating a porous separator around the first electrode to form a separator-protected first electrode;

(c) Impregnating a second mixture of a second electrode active material and a second electrolyte into pores of a second electrically conductive porous rod to form a second electrode;

(d) Combining or interweaving the membrane protected first electrode and the second electrode in a twisted or spiral manner to form a braid or yarn; and

(e) Wrapping or encapsulating a protective outer shell or protective sheath around the braid or yarn to form the rope supercapacitor;

wherein the first electrode active material and/or the second electrode active material contains a plurality of carbon material particles and/or a plurality of graphene sheets, wherein the plurality of graphene sheets contain single-layer graphene or few-layer graphene each having from 1 to 10 graphene planes, and the plurality of carbon material particles or graphene sheets have not less than 500m when measured in a dry state ² Specific surface area in g.

43. The method of claim 42, further comprising the step of wrapping or encapsulating a porous separator around the second electrode to form a separator protected second electrode.

44. The method of claim 37, wherein the rope supercapacitor has a first end and a second end, and the method further comprises the step of connecting a first terminal connector to the first electrode, wherein the first terminal connector comprises at least one of a metal wire, a conductive carbon/graphite fiber, or a conductive polymer fiber, the first terminal connector being embedded in, connected to, or integral with the first electrode.

45. The method of claim 44, wherein the at least one metal wire, conductive carbon/graphite fiber, or conductive polymer fiber extends substantially from the first end to the second end.

46. The method of claim 37, wherein the first or second electrically conductive porous rods contain a porous foam selected from: metal foams, metal meshes, metal fiber mats, metal nanowire mats, conductive polymer fiber mats, conductive polymer foams, conductive polymer coated fiber foams, carbon aerogels, carbon xerogels, and combinations thereof.

47. The method of claim 37, wherein the first or second electrically conductive porous rods contain a porous foam selected from: graphite foam, graphene aerogel, carbon fiber foam, and combinations thereof.

48. The method of claim 37, wherein the first or second electrically conductive porous rods contain a porous foam selected from: graphene foam, graphite fiber foam, expanded graphite foam, and combinations thereof.

49. The method of claim 37, wherein the first or second electrically conductive porous rods contain a porous foam selected from: graphene oxide foam, reduced graphene oxide foam, and combinations thereof.

50. The method of claim 37, wherein the rope supercapacitor has a length/thickness aspect ratio or a length/diameter aspect ratio greater than 10.

51. The method of claim 41, wherein the first or second electrode further comprises a redox pair partner material selected from an organic material, an inorganic material, or a combination thereof, wherein the partner material in combination with graphene or activated carbon forms a redox pair for pseudocapacitance.

52. The method of claim 41, wherein the first or second electrode further comprises a redox pair partner material selected from a metal oxide, a conductive polymer, a non-graphene carbon material, or a combination thereof, wherein the partner material in combination with graphene or activated carbon forms a redox pair for pseudocapacitance.

53. The method of claim 52, wherein the metal oxide is selected from RuO ₂ 、IrO ₂ 、NiO、MnO ₂ 、VO ₂ 、V ₂ O ₅ 、V ₃ O ₈ 、TiO ₂ 、Cr ₂ O ₃ 、Co ₂ O ₃ 、Co ₃ O ₄ 、PbO ₂ 、Ag ₂ O and combinations thereof.

54. The method of claim 51, wherein the inorganic material is selected from the group consisting of metal carbides, metal nitrides, metal borides, metal dichalcogenides, and combinations thereof.

55. The method of claim 51, wherein the inorganic material is selected from an oxide, dichalcogenide, trichalcogenide, sulfide, selenide, or telluride of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, vanadium, chromium, cobalt, manganese, iron, or nickel in the form of nanowires, nanodiscs, nanoribbons, or nanoplatelets.

56. The method of claim 51, wherein the inorganic material is selected from nanodiscs, nanoplatelets, nanocoatings, or nanoplatelets of an inorganic material selected from the group consisting of: bismuth selenide, bismuth telluride, transition metal dichalcogenides, transition metal trichalcogenides, sulfides of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or transition metals, selenides of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or transition metals, tellurides of niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or transition metals, boron nitride, and combinations thereof; wherein the disc, platelet or sheet has a thickness of less than 100 nm.

57. The method of claim 37, wherein the first or second electrode active material contains nanodiscs, nanoplatelets, nanocoatings, or nanoplatelets of an inorganic material selected from the group consisting of: bismuth selenide, bismuth telluride, transition metal dichalcogenide, transition metal trisulfide, niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or a sulfide of a transition metal, niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or a selenide of a transition metal, niobium, zirconium, molybdenum, hafnium, tantalum, tungsten, titanium, cobalt, manganese, iron, nickel, or a telluride of a transition metal, boron nitride, and combinations thereof, wherein the disc, platelet, coating, or sheet has a thickness of less than 100nm and a thickness of not less than 200m when measured in a dry state ² Specific surface area in g.

58. The method of claim 37, wherein the first or second electrically conductive porous rods have from 70 to 99% pores by volume.

59. The method of claim 37, wherein step (a) comprises (i) continuously feeding the electrically conductive porous rod containing interconnected electron-conducting pathways and having at least one porous surface to a first electrode active material impregnation zone; and (ii) impregnating the first mixture from the at least one porous surface into the electrically conductive porous rod to form the first electrode.

60. The method of claim 59, wherein step (a) comprises continuously or intermittently delivering the first mixture to the at least one porous surface on demand by spraying, printing, coating, casting, conveyor film delivery, and/or roller surface delivery.

61. The method of claim 37, wherein step (c) comprises (i) continuously feeding the electrically conductive porous rod containing interconnected electron-conducting pathways and having at least one porous surface to an impregnation zone of the second electrode active material; and (ii) impregnating the second mixture from the at least one porous surface into the electrically conductive porous rod to form the second electrode.

62. The method of claim 61, wherein step (c) comprises continuously or intermittently delivering the second mixture to the at least one porous surface on demand by spraying, printing, coating, casting, conveyor film delivery, and/or roller surface delivery.

63. The method of claim 37, wherein step (b) comprises winding the first electrode with a porous separator strip in a coiled or spiral manner to form the porous separator protected first electrode.

64. The method of claim 37, wherein step (b) comprises spraying an electrically insulating material to encapsulate the first electrode, forming a porous shell structure overlying the first electrode to form the porous separator protective structure.

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