JP7188693B2 - Electrode using graphene, method for producing same, and power storage device using same - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrode using graphene, a method for manufacturing the same, and an electric storage device using the same.

Electricity storage devices such as electric double layer capacitors (supercapacitors) and lithium ion batteries have large capacities and are attracting attention. The performance of such an electric storage device greatly depends on the electrode material, and development of electrode materials capable of improving the capacitance, energy density, and power density is still active.

It is known to use graphene as an electrode material for electric double layer capacitors. Graphene sheet films in which carbon nanotubes are interposed between graphene layers have been developed (see, for example, Patent Documents 1 and 2). According to Patent Document 1, a capacitance of 290.6 F/g and an energy density of 62.8 Wh/kg are achieved by utilizing the electrical conductivity of carbon nanotubes in addition to the properties of graphene. Patent Document 2 proposes a manufacturing method for mass-producing such graphene sheet films using high-pressure processing.

Furthermore, an electrode material composed of a laminate of graphene and carbon nanotubes into which pores are introduced has been developed (see, for example, Patent Document 3). According to Patent Document 3, an electrode material in which pores are introduced into graphene by adsorption and combustion of KOH and laminated with carbon nanotubes achieves an energy density of 100 Wh/kg or more.

However, when actually constructing an electric double layer capacitor using the electrode materials described in Patent Documents 1 to 3, the electrode material is mixed with a conductive material and a binder (binder) and processed into a film. be done. When the above-mentioned electrode materials are mixed with such conductive materials and binders, they may adsorb to the surface of graphene, affect the penetration and diffusion of electrolyte ions, and reduce the energy characteristics of the storage device. be.

Therefore, there is a demand for the development of an electrode that maintains the properties of the electrode materials described in Patent Documents 1 to 3 even when mixed with a conductive material and a binder.

On the other hand, it has been reported that graphene is vertically oriented in hydrogels by applying a magnetic field (see, for example, Non-Patent Document 1). Development of further applications using such knowledge is desired.

WO2015/129820 WO2017/110295 WO2017/163464

Wu et al., ACS Nano, Vol. 8, No. 5, 4640-4649, 2014

In view of the above, an object of the present invention is to provide an electrode using graphene for an electricity storage device that realizes high-speed charging and large capacity, a method for manufacturing the same, and an electricity storage device using the same.

ここで、Ｉは前記２次元小角Ｘ線散乱パターンの方位角依存性のピーク強度であり、Ａは前記２次元小角Ｘ線散乱パターンの方位角依存性のベースライン強度であり、Ｂは線形振幅パラメータであり、Ｃは前記２次元小角Ｘ線散乱パターンの方位角依存性のピークの分布幅を規定するパラメータであり、Ｄは前記２次元小角Ｘ線散乱パターンの方位角依存性の最大強度を有するピークの方位角であり、ψは方位角であり、Ｓは配向パラメータであり、Ｐ_２は配向秩序パラメータであり、ｘはｃｏｓψである。
前記複合体中の前記複数のグラフェンの少なくとも一部は、前記少なくとも一部のグラフェンの平面方向が前記シートの平面方向に対して３０°以上９０°以下の仰角を有する方向に向くように、前記シートを介して位置してもよい。
前記複合体中の前記複数のグラフェンの少なくとも一部は、前記少なくとも一部のグラフェンの平面方向が前記シートの平面方向に対して４５°以上９０°以下の仰角を有する方向に向くように、前記シートを介して位置してもよい。
前記複数のグラフェンのそれぞれの長手方向の大きさは、１０ｎｍ以上１０μｍ以下の範囲であってもよい。
前記複数のグラフェンのそれぞれの厚さは、０．３ｎｍ以上１００ｎｍ以下の範囲であってもよい。
前記複数のグラフェンの少なくとも一部は、貫通する孔を有してもよい。
前記複数のグラフェンのそれぞれは、互いに１ｎｍ以上１μｍ以下の間隔で位置してもよい。
さらに繊維状物質を含有してもよい。 前記繊維状物質は、カーボンナノチューブ、セルロースナノファイバおよび金属ナノワイヤからなる群から選択されてもよい。
本発明による電極を製造する方法は、複数のグラフェンと導電性ポリマーとを、アルコールと水とを含有する分散媒に分散させるステップであって、前記複数のグラフェンに対する前記導電性ポリマーの質量比は、０より大きく１以下である、ステップと、前記分散媒に磁場を印加し、加熱するステップとを包含し、これにより上記課題を解決する。
前記磁場を印加し、加熱するステップは、２テスラ（Ｔ）以上５０テスラ（Ｔ）以下の範囲の磁場を印加してもよい。
前記磁場を印加し、加熱するステップは、６テスラ（Ｔ）以上１６テスラ（Ｔ）以下の範囲の磁場を印加してもよい。
前記磁場を印加し、加熱するステップは、５０℃以上１００℃以下の範囲の温度に加熱してもよい。
前記アルコールは、メタノール、エタノール、１－プロパノール、１－ブタノール、２－メチル－１－プロパノール、２－ブタノール、および、２－メチル－２－プロパノールからなる群から選択されてもよい。
本発明による電極と電解質とを備えた蓄電デバイスは、前記電極が上述の電極からなり、これにより上記課題を解決する。
前記蓄電デバイスは、電気二重層キャパシタ、リチウムイオン電池またはリチウムイオンキャパシタであってもよい。 An electrode according to the present invention contains at least a composite of a plurality of graphenes and a sheet made of a conductive polymer, and at least a portion of the plurality of graphenes is such that the planar direction of the at least a portion of the graphenes is the plane of the sheet. A mass ratio of the sheet to the plurality of graphenes is greater than 0 and less than or equal to 1, thereby solving the above problem.
A mass ratio of the sheet to the plurality of graphenes may be 0.05 or more and 0.5 or less.
A mass ratio of the sheet to the plurality of graphenes may be 0.05 or more and 0.25 or less.
The conductive polymer is poly(4-styrenesulfonic acid) or tosylate-doped poly-3,4-ethylenedioxythiophene (PEDOT:PSS or PEDOT:Tos), polyaniline, polyacetylene, polyphenylene, polyfuran, polyselenophene. , polythiophene, polyacene, polyisothianaphthene, polyphenylene sulfide, polyphenylene vinylene, polythiophene vinylene, polyperinaphthalene, polyanthracene, polynaphthalene, polypyrene, polyazulene, polypyrrole, polyparaphenylene, poly(benzobisimidazobenzophenanthroline), organic boron It may be selected from the group consisting of polymers, polytriazoles, perylenes, carbazoles, triarylamines, tetrathiafulvalene, derivatives thereof, and copolymers thereof.
When the azimuth angle dependence of the two-dimensional small-angle X-ray scattering pattern of the composite is measured, the orientation parameter S obtained from the formulas (A) and (B) satisfies 0.25<S<0.50. good too.

where I is the azimuth-dependent peak intensity of the 2D small-angle X-ray scattering pattern, A is the azimuth-dependent baseline intensity of the 2D small-angle X-ray scattering pattern, and B is the linear amplitude. is a parameter, C is a parameter that defines the distribution width of the peak of the azimuth angle dependence of the two-dimensional small-angle X-ray scattering pattern, and D is the maximum intensity of the azimuth dependence of the two-dimensional small-angle X-ray scattering pattern. is the azimuth angle of the peak with φ, is the azimuth angle, S is the orientation parameter, P2 is the orientation order parameter, and _x is cos φ.
At least some of the plurality of graphenes in the composite are arranged such that the plane direction of the at least some graphenes is oriented in a direction having an elevation angle of 30° or more and 90° or less with respect to the plane direction of the sheet. It may be positioned through the sheet.
At least part of the plurality of graphenes in the composite is arranged such that the planar direction of the at least part of the graphene faces in a direction having an elevation angle of 45° or more and 90° or less with respect to the planar direction of the sheet. It may be positioned through the sheet.
The longitudinal size of each of the plurality of graphenes may be in the range of 10 nm or more and 10 μm or less.
Each thickness of the plurality of graphenes may be in the range of 0.3 nm or more and 100 nm or less.
At least some of the plurality of graphenes may have holes therethrough.
Each of the plurality of graphenes may be positioned at intervals of 1 nm or more and 1 μm or less from each other.
Furthermore, it may contain a fibrous substance. The fibrous material may be selected from the group consisting of carbon nanotubes, cellulose nanofibers and metal nanowires.
A method of manufacturing an electrode according to the present invention comprises dispersing a plurality of graphenes and a conductive polymer in a dispersion medium containing alcohol and water, wherein the mass ratio of the conductive polymer to the plurality of graphenes is , is greater than 0 and less than or equal to 1, and a step of applying a magnetic field to the dispersion medium to heat it, thereby solving the above-mentioned problems.
The step of applying a magnetic field and heating may apply a magnetic field in the range of 2 Tesla (T) to 50 Tesla (T).
The step of applying a magnetic field and heating may apply a magnetic field in the range of 6 Tesla (T) to 16 Tesla (T).
In the step of applying the magnetic field and heating, the temperature may be in the range of 50°C to 100°C.
The alcohol may be selected from the group consisting of methanol, ethanol, 1-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol and 2-methyl-2-propanol.
A power storage device provided with an electrode and an electrolyte according to the present invention, in which the electrode is the above-described electrode, solves the above problems.
The electric storage device may be an electric double layer capacitor, a lithium ion battery or a lithium ion capacitor.

Since the electrode of the present invention contains at least a composite of a plurality of graphenes and a sheet made of a conductive polymer, the conductivity of the electrode can be improved. Furthermore, since at least some of the plurality of graphenes are positioned through the sheet such that the plane direction of the at least some graphenes is different from the plane direction of the sheet, the electrolyte can easily access the graphenes. . In addition, the sheet fixes the positions of the graphenes and improves the electrical conductivity, so that the electron transport properties between the current collector and the graphene can be improved. In particular, by setting the mass ratio of the sheet to the plurality of graphenes to be greater than 0 and equal to or less than 1, high-speed charging is possible when such electrodes are used in electric storage devices such as electric double layer capacitors, lithium ion batteries, and lithium ion capacitors. It has a large capacity and excellent retention characteristics. Moreover, since the sheet is made of a conductive polymer, the electrode of the present invention has excellent flexibility.

The electrode of the present invention comprises a step of dispersing a plurality of graphene and a conductive polymer (the mass ratio of the conductive polymer to graphene is greater than 0 and 1 or less) in a dispersion medium containing alcohol and water; and applying a magnetic field to the dispersion medium to heat it. According to the present invention, by applying a magnetic field, at least some of the plurality of graphenes can be oriented in the direction of the magnetic field. By heating at the same time, the dispersion medium can be evaporated and the oriented graphene can be fixed by the conductive polymer sheet. In this way, the electrodes described above can be easily manufactured.

A diagram schematically showing the electrode of the present invention Flow chart showing the manufacturing process of the electrode of the present invention Procedure showing the manufacturing process of the electrode of the present invention A diagram schematically showing an electric double layer capacitor of the present invention. A diagram schematically showing the state of the electrode of the present invention. FIG. 2 shows the state of the samples of Examples 6 and 9. FIG. 1 shows the XRD patterns of the samples of Examples 1, 3, 4, 6-8 and 10. 1 shows an SEM image of the sample of Example 2. SEM image of the sample of Example 12 2D-SAXS azimuth angle dependence of the samples of Examples 2 and 12. FIG. 2 shows electrochemical properties of coin cells using the samples of Examples 2 and 12. FIG. 2 shows electrochemical properties of coin cells using the samples of Examples 4 and 13. FIG. 2 shows electrochemical properties of coin cells using the samples of Examples 6 and 15. FIG. 2 shows electrochemical properties of coin cells using the samples of Examples 8 and 17. Current density dependence of specific capacity (a) and specific capacity retention characteristics ( Figure showing b) FIG. 2 shows Nyquist and Ragone plots of coin cells using the samples of Examples 2 and 12. FIG. 11 shows Nyquist plots of coin cells using the samples of Examples 6, 8, 15 and 17.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same number is given to the same element, and the description is omitted.

(Embodiment 1)
Embodiment 1 describes an electrode of the present invention and a method for manufacturing the same.
FIG. 1 is a diagram schematically showing an electrode of the present invention.

The electrode 100 of the present invention contains at least a composite of multiple graphenes 110 and a sheet 120 made of a conductive polymer. Hereinafter, for the sake of simplicity, a sheet made of a conductive polymer will simply be referred to as a sheet. By including the sheet 120 in the composite, the conductivity of the entire electrode 100 can be improved based on the conductive polymer. Note that in the specification of the present application, a plurality of graphenes is simply referred to as graphene unless otherwise specified.

In the electrode 100 of the present invention, at least a portion of the graphene 110 has a plane direction of the at least portion of the graphene 110 (the vertical direction of the paper in FIG. 1) is the plane direction of the sheet 120 (the horizontal direction of the paper in FIG. 1). are positioned across the sheet 120 so as to be different from . That is, although FIG. 1 shows that the entire graphene 110 is positioned perpendicular to the planar direction of the sheet 120 with the sheet 120 interposed therebetween, the present invention is not limited to this. As a result, when the electrode of the present invention is used as an electrode of an electricity storage device, the electrolyte ions can easily access the graphene and furthermore the current collector, so the electron transport properties can be improved. In FIG. 1, an electrode 100 of the present invention is shown positioned on a current collector 130 . In the present specification, “graphene is positioned through the sheet” means that the graphene is held by the sheet, and the graphene is in contact with the sheet, or part of the graphene is inside the sheet. It means that it is buried in

In the electrode 100 of the present invention, the mass ratio of the sheet 120 to the graphene 110 is adjusted to be greater than 0 and 1 or less. That is, by making the mass of the sheet 120 equal to or smaller than that of the graphene 110, a good film-like electrode 100 without cracks can be obtained. In addition, the electrode 100 as a whole maintains high conductivity, enabling large capacity and high retention characteristics when applied to an electricity storage device.

The mass ratio of the sheet 120 to the graphene 110 is preferably adjusted to 0.05 or more and 0.5 or less. As a result, the electrode 100 as a whole maintains a higher conductivity, enabling a large capacity and high retention characteristics when applied to an electricity storage device.

More preferably, the mass ratio of the sheet 120 to the graphene 110 is adjusted to 0.05 or more and 0.25 or less. As a result, the electrode 100 as a whole maintains high conductivity, and when applied to an electricity storage device, enables high-speed charging, large capacity, and high retention characteristics.

At least part of the graphene 110 in the composite preferably faces in a direction in which the plane direction of the graphene 110 has an elevation angle of 30° or more and 90° or less (indicating α in FIG. 1) with respect to the plane direction of the sheet 120. , through the sheet 120. As shown in FIG. This range facilitates access of the electrolyte ions to the graphene 110 . More preferably, at least part of the graphene 110 in the composite is oriented through the sheet 120 so that the planar direction of the graphene 110 faces in a direction having an elevation angle of 45° or more and 90° or less with respect to the planar direction of the sheet 120. located. Within this range, electrolyte ions can easily access the graphene 110, and when applied to an electricity storage device, a large capacity and high retention characteristics can be achieved. Note that the orientation of the graphene 110 (that is, the elevation angle with respect to the planar direction of the sheet 120) is, for example, an elevation angle with respect to the planar direction of the sheet (simply may be the angle of elevation with respect to the direction), and average them.

When the azimuth angle dependence of the two-dimensional small-angle X-ray scattering pattern of the composite is measured, the orientation parameter S obtained from the formulas (A) and (B) is preferably 0.25<S<0.50. Fulfill. This facilitates the access of the electrolyte ions to the graphene 110, and enables a large capacity and high retention characteristics when applied to an electricity storage device.

(where I is the azimuth-dependent peak intensity of the 2D small-angle X-ray scattering pattern, A is the azimuth-dependent baseline intensity of the 2D small-angle X-ray scattering pattern, and B is the linear amplitude parameter). where C is a parameter that defines the distribution width of the azimuth-dependent peaks of the two-dimensional small-angle X-ray scattering pattern, and D is the peak having the maximum intensity of the azimuth-dependent two-dimensional small-angle X-ray scattering pattern. is the azimuthal angle, ψ is the azimuthal angle, S is the orientation parameter, P2 is the orientational order parameter, and _x is cos ψ.)

Graphene 110 is a sheet-like material of sp2 ^- bonded carbon atoms and is a well-known material produced by, for example, the modified Hummers method. The longitudinal dimension of the graphene 110 is preferably in the range of 10 nm or more and 10 μm or less. Within this range, the electrode 100 of the present invention can be obtained by the manufacturing method described later. The longitudinal size of the graphene 110 is more preferably in the range of 0.5 μm or more and 5 μm or less. Within this range, it is easy to control the orientation of the graphene 110 such that the planar direction of the graphene 110 is different from the planar direction of the sheet 120 .

The thickness of the graphene 110 is preferably in the range of 0.3 nm or more and 100 nm or less. Within this range, the electrode 100 of the present invention can be obtained by the manufacturing method described later. More preferably, the thickness of the graphene 110 ranges from 0.5 nm to 10 nm. Within this range, the manufacturing efficiency is good.

At least part of the graphene 110 may have pores (not shown) penetrating the surface. This promotes the penetration and migration of electrolyte ions, leading to improvements in energy density and power density. The pore diameter is in the range of 0.4 nm or more and 10 nm or less, more preferably in the range of 1 nm or more and 5 nm or less, from the viewpoint of passage of electrolyte solution ions. Graphene having such pores is produced, for example, according to WO2014/065241.

The graphene 110 may have functional groups (not shown) such as carboxy groups, hydroxyl groups, and carbonyl groups. Such functional groups remain on the surface of the graphene 110 during production, but even with these functional groups, the penetration and migration of electrolyte ions and the conductivity are not inferior.

The conductive polymer that constitutes the sheet is not particularly limited as long as it has conductivity. Thiophene (PEDOT:PSS or PEDOT:Tos), polyaniline, polyacetylene, polyphenyline, polyfuran, polyselenophene, polythiophene, polyacene, polyisothianaphthene, polyphenylene sulfide, polyphenylene vinylene, polythiophene vinylene, polyperinaphthalene, polyanthracene, polynaphthalene , polypyrene, polyazulene, polypyrrole, polyparaphenylene, poly(benzobisimidazobenzophenanthroline), organoboron polymer, polytriazole, perylene, carbazole, triarylamine, tetrathiafulvalene, derivatives thereof, and copolymers thereof selected from the group consisting of Among these, PEDOT:PSS or PEDOT:Tos is advantageous for manufacturing the electrode 100 of the present invention.

In the composite, the graphenes 110 are preferably spaced apart from each other by 1 nm or more and 1 μm or less. This facilitates access of the electrolyte ions to the graphene 110 . The graphenes 110 are more preferably spaced from each other by a distance of 1 nm or more and 100 nm or less, more preferably 1 nm or more and 20 nm or less.

The composite may further contain fibrous material (not shown). The fibrous material is located between the graphenes 110 and functions as a spacer, thus facilitating the access of the electrolyte ions to the graphenes 110 . From this point of view, the average value of the outer diameter of the fibrous substance is preferably in the range of 0.4 nm or more and 5.0 nm or less, and more preferably in the range of 1.0 nm or more and 3.0 nm or less. more preferred.

The mass ratio of graphene to fibrous substance (graphene/fibrous substance) is preferably 1 or more and 50 or less, more preferably 5 or more and 15 or less. Thereby, the function as a spacer is exhibited.

Such a fibrous substance preferably has conductivity or semi-conductivity in addition to the spacer function. Thereby, the conductivity of the entire electrode can be enhanced. Such fibrous substances are exemplified by carbon nanotubes, cellulose nanofibers, metal nanowires, and the like. Among them, carbon nanotubes are highly compatible with the graphene 110 . The carbon nanotubes are single-walled carbon nanotubes (SWNT), double-walled carbon nanotubes (DWNT) or multi-walled carbon nanotubes (MWNT), preferably single-walled carbon nanotubes. Single-walled carbon nanotubes have a high electrical conductivity of 10 ⁴ S/cm or more, which improves the electrical conductivity of the electrode, which can improve the performance of the capacitor.

Next, a method for manufacturing the electrode 100 of the present invention will be described.
FIG. 2 is a flow chart showing the manufacturing process of the electrode of the present invention.
FIG. 3 is a procedure showing the manufacturing process of the electrode of the present invention.

Step S210: A plurality of graphenes 110 and conductive polymers 310 are dispersed in a dispersion medium 320 containing alcohol and water. Here, the mass ratio of the conductive polymer to graphene is adjusted to be greater than 0 and 1 or less. By using alcohol and water for the dispersion medium 320, the graphene 110 can be well dispersed. Here, the graphene 110 and the conductive polymer 310 are omitted because they are as described with reference to FIG.

Alcohol is not particularly limited, but exemplified by the group consisting of methanol, ethanol, 1-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol, and 2-methyl-2-propanol is selected from These alcohols disperse graphene 110 and conductive polymer 310 well.

The ratio of alcohol and water is preferably 20-80:80-20 (volume ratio). This allows the graphene 110 and the conductive polymer 310 to be well dispersed. The ratio of alcohol and water is preferably 40-60:60-40 (volume ratio). Within this range, the dispersibility is excellent.

In step S210, further fibrous substances as described above may be added. In this case, it may be added so that the mass ratio of graphene to fibrous substance (graphene/fibrous substance) is 1 or more and 50 or less, preferably 5 or more and 15 or less.

Step S220: A magnetic field is applied to the dispersion medium 320 to heat it. As a result, the conductive polymer 310 is softened and melted to form the conductive polymer sheet 120 shown in FIG. 1, which is positioned at the bottom of the container. By applying a magnetic field, the graphene 110 is oriented such that the planar direction of the graphene 110 is the same as the direction of the magnetic field. FIG. 3 shows how the graphene 110 is oriented in the same manner as when a magnetic field is applied in the vertical direction with respect to the plane of the paper, as indicated by dotted arrows. Since the conductive polymer 310 softens and becomes the sheet 120 at the bottom of the container, it is preferable to apply the magnetic field in the vertical direction. Further heating evaporates the dispersion medium 320 and fixes the oriented graphene 110 to the sheet 120 to produce the electrode 100 of the present invention.

Preferably, the magnetic field is applied in the range of 2 Tesla (T) to 50 Tesla (T). Within this range, the graphene 110 can be oriented. More preferably, the magnetic field is applied in the range of 6T or more and 16T or less. Within this range, the graphene 110 can be efficiently oriented. More preferably, the magnetic field is applied in the range of 10T or more and 14T or less.

Preferably, the heating is performed at a temperature in the range of 50°C to 100°C. Within this range, the conductive polymer 310 is softened and melted, and the dispersion medium 320 can be evaporated. More preferably, it is carried out at a temperature in the range of 55°C or higher and 70°C or lower. Within this range, the conductive polymer 310 is softened and melted, and the dispersion medium 320 can be evaporated while maintaining the orientation of the graphene 110 .

In step S220, the heating and magnetic field application time varies depending on the heating temperature and the magnitude of the magnetic field, but is illustratively in the range of 30 minutes to 48 hours. If the time is shorter than 30 minutes, the graphene 110 may not be sufficiently oriented. Beyond 48 hours, the reaction is unchanged and inefficient. Preferably, it is in the range of 5 hours or more and 12 hours or less. Within this range, the graphene 110 is satisfactorily oriented, and the electrode 100 fixed by the sheet 120 is obtained.

Although graphene is used in step S210 in FIG. 2, graphene oxide may be used instead of graphene. When graphene oxide is used, reduction treatment may be performed after step S220. The reduction treatment is exemplified by chemical reduction using a reducing agent such as hydrazine, or thermal reduction by heating, which can be appropriately adopted by those skilled in the art.

(Embodiment 2)
Embodiment 2 describes an electric double layer capacitor using the electrode of the present invention.
FIG. 4 is a diagram schematically showing the electric double layer capacitor of the present invention.
FIG. 5 is a diagram schematically showing the state of the electrode of the present invention.

The electric double layer capacitor 400 of the present invention includes at least electrodes and an electrolytic solution. In the electric double layer capacitor 400 of FIG. 3, a positive electrode 410 and a negative electrode 420 are immersed in an electrolytic solution 430 as electrodes. These positive electrode 410 and negative electrode 420 are made of the electrode 100 of the present invention described in the first embodiment.

The electrolytic solution 430 is not particularly limited as long as it can be used for an electric double layer capacitor, but examples include sulfuric acid aqueous solution, sodium sulfate aqueous solution, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, ammonium hydroxide aqueous solution, chloride Potassium aqueous solution, potassium carbonate aqueous solution, or 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI-TFSI), 1-ethyl-3-methylimidazolium borofluoride (EMI-BF ₄ ) and 1 -methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide (MPPp-TFSI) ionic liquid.

Electric double layer capacitor 400 further has separator 440 between positive electrode 410 and negative electrode 420 to separate positive electrode 410 and negative electrode 420 .

Materials of the separator 440 include, for example, fluorine-based polymers, polyethers such as polyethylene oxide and polypropylene oxide, polyolefins such as polyethylene and polypropylene, polyacrylonitrile, polyvinylidene chloride, polymethyl methacrylate, polymethyl acrylate, polyvinyl alcohol, and polymethacrylonitrile. A material selected from nitrile, polyvinyl acetate, polyvinylpyrrolidone, polyethyleneimine, polybutadiene, polystyrene, polyisoprene, polyurethane polymers and their derivatives, cellulose, paper, and non-woven fabric.

In electric double layer capacitor 400 , positive electrode 410 , negative electrode 420 , electrolyte 430 and separator 440 described above are accommodated in cell 450 . Also, the positive electrode 410 and the negative electrode 420 each have an existing current collector.

Such an electric double layer capacitor 400 may be a chip-type, coin-type, mold-type, pouch-type, laminate-type, cylindrical-type, rectangular-type capacitor, etc., and is used in a module in which a plurality of these are connected. may

Next, the operation of the electric double layer capacitor 400 of FIG. 4 will be described.

When a voltage is applied to the electric double layer capacitor 400, electrolyte ions (anions) of the electrolyte 430 are adsorbed to the positive electrode 410, and electrolyte ions (cations) of the electrolyte 430 are adsorbed to the negative electrode 420. do. As a result, an electric double layer is formed on each of the positive electrode 410 and the negative electrode 420 and charged. Here, since the positive electrode 410 and the negative electrode 420 are formed from the electrode 100 described in Embodiment 1, as shown in FIG. becomes easy, and an electric double layer is formed. As a result, the exchange of electrons between the graphene 110 and electrolyte ions is increased, and a large capacity and high retention characteristics can be achieved.

When the charged electric double layer capacitor 400 is connected to a circuit such as a resistor, the anions and cations adsorbed to the positive electrode 410 and the negative electrode 420 are desorbed and discharged. Again, since the positive electrode 410 and the negative electrode 420 are formed from the electrode 100 described in Embodiment 1, the desorption/diffusion of electrolyte solution ions is facilitated, and high rate characteristics and large capacity can be achieved. Moreover, since it is excellent in conductivity, the power density can be improved with the easiness of desorption/diffusion.

As described above, the electric double layer capacitor 400 of the present invention can be quickly charged, and can achieve large capacity and high retention characteristics. In addition, since the formation of an electric double layer is used for charging and discharging, it is excellent in repeated use. The electric double layer capacitor 400 of the present invention can be used for wind power generation, electric vehicles, and the like.

Here, the explanation is limited to the electric double layer capacitor, but it goes without saying that the electrode of the present invention can be applied to electric storage devices such as lithium ion batteries and lithium ion capacitors (LIC) in addition to electric double layer capacitors. . For example, when applied to a lithium ion battery, at least electrodes and an electrolytic solution are provided in the same manner as the electric double layer capacitor 400 of FIG. different. A lithium ion capacitor is known as a hybrid of an electric double layer capacitor and a lithium ion battery, and for example, an electrolytic solution containing a lithium salt (LiBF ₄ , LiPF ₆ , etc.) is employed together with the electrode of the present invention.

The present invention will now be described in detail using specific examples, but it should be noted that the present invention is not limited to these examples.

[Examples 1 to 18]
In Examples 1 to 18, graphene and PEDOT:PSS as a conductive polymer were mixed at various mass ratios shown in Table 1, and subjected to magnetic field and heating under the conditions shown in Table 1 to produce electrodes.

Graphene was prepared as follows. Graphene oxide (GO) was synthesized from graphite by the Hummers method. GO was diluted with 0.1 mol/L hydrochloric acid aqueous solution and centrifuged 5 times, then diluted with deionized water and subjected to high speed centrifugation (35,000 rpm) until the pH of the supernatant reached 7. rice field. The resulting GO dispersion was reduced with hydrazine, washed with ethanol and dried in a vacuum freeze dryer (Eyla, FDU-1200). Thus, reduced graphene oxide (rGO, ie graphene) was obtained.

The obtained rGO was evaluated by Fourier transform infrared spectroscopy (FTIR, manufactured by Shimadzu Corporation, IRTracer-100) and a transmission electron microscope (TEM, manufactured by JEOL Ltd., JEM-2100). It was confirmed that the graphene had a length of 1 nm or more and 100 nm or less, a longitudinal size of 1 μm or more and 5 μm or less, and had a very small amount of carbonyl groups. The rGO was dispersed in ethanol (0.1 mg/mL).

A 13 mg/mL PEDOT:PSS aqueous solution (PEDOT:PSS (PH1000, Clevios) was purchased from HC Starck Company) was mixed with the rGO ethanol dispersion so as to satisfy the mass ratio shown in Table 1, and ultrasonically processed to obtain a mixture containing rGO and PEDOT:PSS (step S210 in FIG. 2). Here, the ratio of alcohol and water was 50:50 (volume ratio). The mixture was transferred to a cylindrical evaporating dish with a removable polyvinylidene fluoride (PVDF) film bottom.

This evaporating dish was placed in a magnetic field generator, a magnetic field of 12 tesla (T) was applied in the vertical direction, and the inside was heated to 60° C. and held for 8 hours (step S220 in FIG. 2). In Examples 11 to 18, heating was performed under the same conditions as in Examples 1 to 10 except that no magnetic field was applied.

After that, the evaporating dish was taken out, and it was confirmed that the dispersion medium had evaporated. This state is shown in FIG. 6 and will be described later.

Next, the film bottom of the evaporating dish was removed, and the resulting product was used as a sample. For each sample, X-ray diffraction was measured using a desktop X-ray diffractometer (MiniFlex 600 manufactured by Rigaku Corporation). Each sample was observed using a scanning electron microscope (SEM, manufactured by JEOL Ltd., JSM-6500F/JSM-7001F). These results are shown in FIGS. 7-9. A two-dimensional small-angle X-ray scattering apparatus (2D-SAXS, manufactured by Bruker, Nanostar) was used to investigate the orientation of graphene in the sample. The results are shown in FIG. The sheet resistance of each sample was measured by the four probe method. Table 2 shows the results.

Next, an electric double layer capacitor (coin cell) was manufactured using each sample as an electrode, and its electrical characteristics were evaluated. Specifically, the product was cut to 15 mmφ and placed _on a carbon _- coated aluminum foil current collector to form a positive electrode and a negative electrode. As a separator, the positive electrode and the negative electrode were partitioned by a glass fiber nonwoven fabric, and sealed with a stainless steel coin cell.

The electrochemical properties of the coin cell were measured using an electrochemical workstation (BioLogic, VSP-300). Cyclic voltammetry was measured at various voltage rates ranging from 200 mV/s to 4 V/s. Charge-discharge cycle characteristics were measured at various current densities ranging from 0.5 A/g to 50 A/g. Based on the results of charge-discharge cycle characteristics, the specific capacity, power density and energy density of the coin cell were calculated from the following equations.

C=4JΔt/ΔU
P=2JΔU
E=JΔtΔU/1.8
where C is the specific capacity, P is the power density, E is the energy density, J is the current density, Δt is the discharge time and ΔU is the voltage change.

Potential-mode electrochemical impedance spectroscopy (PEIS) measurements were also performed. These results are shown in FIGS. 11-17.

The results will be summarized and explained.
FIG. 6 is a diagram showing the state of the samples of Examples 6 and 9. FIG.

According to FIG. 6, the sample of Example 6 yielded a uniform film without cracks. Although not shown, the samples of Examples 2 to 5 were in a similar manner. On the other hand, the sample of Example 9 had cracks throughout and was poor in film quality. This indicates that the mass ratio of the conductive polymer sheet to graphene must be greater than 0 and equal to or less than 1 in order to obtain a good film.

FIG. 7 shows the XRD patterns of the samples of Examples 1, 3, 4, 6-8 and 10;

According to FIG. 7, all samples showed a clear peak near 23.7°. This peak corresponds to the (002) diffraction peak of graphene. Focusing on the (002) diffraction peak of graphene, as the content of PEDOT:PSS increases, the (002) diffraction peak of graphene shifts to the characteristic peak (25.88°) of PEDOT:PSS. I found out. This indicates that samples with different ratios of graphene and PEDOT:PSS were obtained according to the design composition in Table 1.

According to Table 2, it was found that the sheet resistance decreased as the content of PEDOT:PSS increased. This also indicates that samples with different ratios of graphene and PEDOT:PSS were obtained according to the design composition in Table 1.

8 is a SEM image of the sample of Example 2. FIG.
9 is a SEM image of the sample of Example 12. FIG.

8(a) and (b) are SEM images of the cross section of the sample of Example 2, and FIGS. 8(c)-(f) are SEM images of the surface of the sample of Example 2. FIG. 9A is a SEM image of the surface of the sample of Example 12, and FIG. 9B is a SEM image of the cross section of the sample of Example 12. FIG.

In the sample of Example 2 to which a magnetic field was applied, the graphene in the cross section stood up in the vertical direction with respect to the paper surface (FIGS. 8A and 8B), and it was found that the graphene was also fluffed on the surface. Although not shown, the samples of Examples 3 to 8 exhibited similar behavior. In particular, from FIG. 8B, when 300 pieces of graphene were investigated, it was found that the graphene was positioned so that the plane direction of the graphene was oriented in a direction having an elevation angle of 45° or more and 90° or less with respect to the plane direction of the sheet. Do you get it.

On the other hand, in the sample of Example 12 where no magnetic field was applied, the surface was smooth without fluff of graphene (Fig. 9(A)), and the graphene in the cross section was also laminated in the horizontal direction to the paper surface. was found (FIG. 9(B)). Although not shown, Examples 1, 11, and 13 to 17 also showed similar aspects. In the sample of Example 1, although a magnetic field was applied, the graphene aligned in the direction of the magnetic field could not be fixed because there was no PEDOT:PSS.

From these, by performing the method shown in FIGS. 2 and 3, at least a composite of a plurality of graphenes and a sheet made of a conductive polymer, wherein at least a part of the graphene is a part of the graphene It has been shown that composites can be obtained that are placed through the sheets such that the planar direction is different from the planar direction of the sheets.

FIG. 10 shows the 2D-SAXS azimuth dependence of the samples of Examples 2 and 12;

The 2D-SAXS pattern of the sample of Example 12 showed distinct peaks at 90° and 270°. This indicates that in the sample of Example 12, the graphene is laminated so that the plane direction thereof is the same as the plane direction of the sheet (same as the plane direction of the electrode). On the other hand, according to the 2D-SAXS pattern of the sample of Example 2, the intensity of the peaks at 90° and 270° of the sample of Example 2 was significantly reduced compared to that of the sample of Example 12. This suggests that the planar direction of at least a portion of the graphene in the sample of Example 2 is located in a different direction from the planar direction of the sheet, which agrees well with the results in FIG.

Furthermore, for the samples of Examples 2 and 12, the orientation parameter S obtained from the above formulas (A) and (B) was calculated. As shown in Table 3, the S-value of the sample of Example 2 was 0.47 and the S-value of the sample of Example 12 was 0.50. In calculating the S value, for the sample of Example 2, I is the peak intensity of the azimuth dependence of the two-dimensional small-angle X-ray scattering pattern, and A is the azimuth dependence of the two-dimensional small-angle X-ray scattering pattern. is the baseline intensity (25.424), B is the linear amplitude parameter (0.087), and C is the parameter defining the distribution width of the azimuthally dependent peaks of the two-dimensional small-angle X-ray scattering pattern (3. 276), D is the azimuth angle (4.573) of the peak with maximum intensity of the azimuth dependence of the two-dimensional small-angle X-ray scattering pattern, ψ is the azimuth angle (0° to 360°), P2 was the orientational order parameter ₍ 0.47). For the sample of Example 12, I is the relative value, A is 49.6, B is 0.171, C is 3.470, D is 4.782 and ψ is 0°. ~360° and _P2 was 0.50. The S values of the samples of Examples 3 to 6 all satisfied 0.25<S<0.50.

FIG. 11 is a diagram showing the electrochemical properties of coin cells using the samples of Examples 2 and 12;
FIG. 12 is a diagram showing the electrochemical properties of coin cells using the samples of Examples 4 and 13;
FIG. 13 is a diagram showing the electrochemical properties of coin cells using the samples of Examples 6 and 15;
FIG. 14 is a diagram showing the electrochemical properties of coin cells using the samples of Examples 8 and 17;
FIG. 15 shows the current density dependence (a) of the specific capacity of coin cells using the samples of Examples 2, 4, 6, 8, 10 to 13, 15, 17 and 18 and specific capacity is a diagram showing a retention characteristic (b) of .

Focusing on the cyclic voltammetry plots (a) and (b) of FIGS. 11-14, the coin cell with the magnetic field applied sample maintained its rectangular shape even with increasing sweep speed. In particular, this tendency was remarkable when the PEDOT:PSS content was 50% or less, preferably 30% or less, and more preferably around 10%. From this, it was shown that the electricity storage device using the composite of the present invention as an electrode has excellent rate characteristics.

Focusing on the galvanostat charge-discharge plots (c) and (d) in FIGS. 11 to 14, when the current density is small, the behavior of the sample to which the magnetic field is applied and the sample to which the magnetic field is not applied is similar, and there is a large change. However, when the current density was high, the sample with applied magnetic field showed longer discharge time than the sample without applied magnetic field. This suggests that an electricity storage device using the composite of the present invention as an electrode can be charged at high speed. Table 4 summarizes the specific capacities obtained from these charge-discharge plots.

Current density dependence of specific capacitance (e) and specific capacitance retention characteristics (f) in FIGS. 11 to 14, and current density dependence of specific capacitance (a) and specific capacitance retention characteristics (b) in FIG. Focusing on , coin cells using samples to which a magnetic field is applied tend to have high specific capacity and high retention characteristics, and in particular, the content of PEDOT:PSS is 50% or less, preferably 30% or less, more preferably This tendency was remarkable at around 10%. The above results are summarized in Table 4.

FIG. 16 is a diagram showing Nyquist plots and Ragone plots of coin cells using the samples of Examples 2 and 12;
17 is a diagram showing Nyquist plots of coin cells using the samples of Examples 6, 8, 15 and 17. FIG.

According to the Nyquist plot (a) of FIG. 16, the charge transfer resistances of the coin cells using the samples of Example 2 and Example 12, respectively, were 0.66Ω and 1.04Ω. The charge transfer resistance of the coin cells using samples with applied magnetic field was smaller than that using samples without applied magnetic field. In addition, the 45° linear portion (corresponding to 0.64 Ω) when using the sample of Example 2 is shorter than that (corresponding to 2.49 Ω) when using the sample of Example 12, and the ion diffusion resistance was found to be small.

According to FIG. 17(a), a tendency similar to that of FIG. 16(a) was shown, but according to FIG. 17(b), no significant difference was obtained in charge transfer resistance and ion diffusion resistance.

According to the Ragone plot (b) of FIG. 16, it was found that the coin cell using the sample of Example 2 can maintain a constant energy density while extracting a higher power density than that using the sample of Example 12. .

From these, the coin cell using the sample to which the magnetic field is applied as the electrode tends to have a high power density and a small diffusion resistance. Preferably, this tendency was remarkable at around 10%.

INDUSTRIAL APPLICABILITY The electrode of the present invention has easy access to the graphene in the electrolyte, excellent conductivity, and is applicable to electric double layer capacitors. An electric double layer capacitor to which the electrode of the present invention is applied achieves high-speed charging, large capacity and high retention characteristics, and is advantageous for wind power generation, electric vehicles, and the like. Further, the electrode of the present invention is applied to lithium ion batteries and lithium ion capacitors in addition to electric double layer capacitors.

REFERENCE SIGNS LIST 100 electrode 110 graphene 120 conductive polymer sheet 130 current collector 310 conductive polymer 320 dispersion medium

Claims (19)

An electrode containing at least a composite of a plurality of graphene and a sheet made of a conductive polymer,
at least some of the plurality of graphenes are positioned through the sheet such that the planar direction of the at least some graphenes is different from the planar direction of the sheet;
The electrode, wherein a mass ratio of the sheet to the plurality of graphenes is 0.05 or more and 0.5 or less . 2. The electrode according to claim 1 , wherein a mass ratio of said sheet to said plurality of graphenes is 0.05 or more and 0.25 or less. The conductive polymer is poly(4-styrenesulfonic acid) or tosylate-doped poly-3,4-ethylenedioxythiophene (PEDOT:PSS or PEDOT:Tos), polyaniline, polyacetylene, polyphenylene, polyfuran, polyselenophene. , polythiophene, polyacene, polyisothianaphthene, polyphenylene sulfide, polyphenylene vinylene, polythiophene vinylene, polyperinaphthalene, polyanthracene, polynaphthalene, polypyrene, polyazulene, polypyrrole, polyparaphenylene, poly(benzobisimidazobenzophenanthroline), organic boron 3. Electrode according to claim 1 or 2 , selected from the group consisting of polymers, polytriazoles, perylenes, carbazoles, triarylamines, tetrathiafulvalene, derivatives thereof and copolymers thereof. When the azimuth angle dependence of the two-dimensional small-angle X-ray scattering pattern of the composite is measured, the orientation parameter S obtained from the formulas (A) and (B) satisfies 0.25<S<0.50. The electrode according to any one of claims 1-3 .

(where I is the azimuth-dependent peak intensity of the 2D small-angle X-ray scattering pattern, A is the azimuth-dependent baseline intensity of the 2D small-angle X-ray scattering pattern, and B is linear). is an amplitude parameter, C is a parameter that defines the distribution width of the peaks of the azimuth angle dependence of the two-dimensional small-angle X-ray scattering pattern, and D is the maximum intensity of the azimuth-angle dependence of the two-dimensional small-angle X-ray scattering pattern. is the _azimuth angle of the peak with At least some of the plurality of graphenes in the composite are arranged such that the plane direction of the at least some graphenes is oriented in a direction having an elevation angle of 30° or more and 90° or less with respect to the plane direction of the sheet. 5. The electrode according to any one of claims 1 to 4 , positioned via a sheet. At least part of the plurality of graphenes in the composite is arranged such that the planar direction of the at least part of the graphene faces in a direction having an elevation angle of 45° or more and 90° or less with respect to the planar direction of the sheet. 6. Electrode according to claim 5, located through a sheet. 7. The electrode according to any one of claims 1 to 6, wherein each of the plurality of graphenes has a longitudinal size in the range of 10 nm or more and 10 µm or less. 8. The electrode according to any one of claims 1 to 7, wherein each of said plurality of graphenes has a thickness in the range of 0.3 nm or more and 100 nm or less. 9. The electrode according to any one of claims 1 to 8, wherein at least some of said plurality of graphenes have through holes. 10. The electrode according to any one of claims 1 to 9, wherein each of said plurality of graphenes is positioned at intervals of 1 nm or more and 1 µm or less from each other.
The electrode according to any one of claims 1 to 10 , further comprising a fibrous substance. 12. The electrode of claim 11, wherein said fibrous material is selected from the group consisting of carbon nanotubes, cellulose nanofibers and metal nanowires. A step of dispersing a plurality of graphenes and a conductive polymer in a dispersion medium containing alcohol and water, wherein the mass ratio of the conductive polymer to the plurality of graphenes is 0.05 or more and 0.5 or less . a step that is
and applying a magnetic field to the dispersion medium to heat it. 14. The method of claim 13, wherein the applying a magnetic field and heating step applies a magnetic field in the range of 2 Tesla (T) to 50 Tesla (T). 15. The method of claim 14, wherein the applying a magnetic field and heating step applies a magnetic field in the range of 6 Tesla (T) to 16 Tesla (T). The method according to any one of claims 13 to 15, wherein said step of applying a magnetic field and heating heats to a temperature in the range of 50°C to 100°C. Claims 13-16 , wherein the alcohol is selected from the group consisting of methanol, ethanol, 1-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol and 2-methyl-2-propanol. The method according to any one of An electricity storage device comprising an electrode and an electrolyte,
An electricity storage device, wherein the electrode comprises the electrode according to any one of claims 1 to 12 . 19. The electricity storage device according to claim 18, wherein said electricity storage device is an electric double layer capacitor, a lithium ion battery or a lithium ion capacitor.

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