KR101025571B1 - Electrode for supercapacitor and the fabrication method thereof, and supercapacitor using the same - Google Patents

Abstract

The present invention relates to a supercapacitor electrode having excellent specific capacitance and electrical conductivity, a method for manufacturing the same, and a supercapacitor using the same, including a current collector; A porous metal oxide layer formed on at least one surface of the current collector and having a web structure of nanofibers including metal oxide nanoparticles, wherein the nanoparticles have an amorphous structure or are nanocrystalline in an amorphous structure. Provided is an electrode for a supercapacitor, which is formed partially.

Electrospinning, Metal Oxide Layers, Nanofibers, Amorphous, Web, Supercapacitors

Description

Supercapacitor Electrode and Manufacturing Method Thereof, and Supercapacitor Using the Subcapacitor {ELECTRODE FOR SUPERCAPACITOR AND THE FABRICATION METHOD THEREOF, AND SUPERCAPACITOR USING THE SAME}

The present invention relates to a supercapacitor electrode having excellent specific capacitance and electrical conductivity, a method of manufacturing the same, and a supercapacitor using the same.

With increasing interest in the environment and energy, studies on alternative energy and energy storage systems (lithium-based secondary batteries, electrochemical capacitors, etc.) are being actively conducted. In particular, supercapacitors that can be applied to fields requiring high capacity and high output characteristics have recently been attracting much attention.

Supercapacitors are electrochemical capacitors that store charge using pseudocapacitance by a reversible faradaic surface redox reaction at the interface between the electrode and the electrolyte. These supercapacitors are used alone or in combination with secondary batteries for power supplies for micro medical equipment and mobile communication devices, and may be used as power sources for electric and hybrid vehicles, and power supplies for military and aerospace equipment.

Representative electrode materials widely used in supercapacitors include transition metal oxides such as IrO ₂ and RuO ₂ , which exhibit pseudocapacitance characteristics. RuO ₂ , which has a specific capacitance and high electrical conductivity, is known to exhibit excellent characteristics as an electrode for supercapacitors. However, despite the excellent supercapacitor characteristics, RuO ₂ has great limitations in terms of mass production and low cost processes due to its high price.

Electrode materials for replacing them include MnO ₂ , NiO _x , CoO _x , V ₂ O ₅ , MoO _3, and the like. Among them, manganese oxide (MnO ₂ ) is environmentally friendly and inexpensive, many studies have been conducted. In order to have excellent supercapacitor properties (e.g. high specific capacitance), the electrode material has a large specific surface area and low internal resistance characteristics, the occurrence of surface oxidation / reduction reactions in the available potential region is continuous, and the reaction with the electrolyte It needs to be easy. Since the electrochemical reaction is mainly performed on the surface of the metal oxide or the surface layer of several nm thickness, the smaller the size of the metal oxide particles can be expected to have a larger capacity.

US Patent No. 7,084,002, which discloses a method for producing a metal oxide nanostructure, proposes a method for producing nanowires using an alumina membrane as a template. However, due to the size limitation of the alumina mold and the high price of the mold, there is a disadvantage in that mass productivity is greatly reduced.

In addition, in Korean Patent Laid-Open Publication No. 2008-0066495, an ultrafine fibrous or nanorod-like titanium oxide layer was prepared by electrospinning, and then sintered at 400-450 ° C. to form titanium oxide as a crystalline phase, followed by post-heat treatment at 700-1000 ° C. Next, a method of manufacturing an electrode for a supercapacitor by coating a metal oxide on the titanium oxide layer is disclosed. However, the two-step heat treatment process, and the additional metal oxide coating is a complicated process and high manufacturing cost disadvantages.

In addition, hydrothermal synthesis (CH Liang et al, Japanese Journal of Applied Physics, 47, 4682-4686, 2008) or microemulsion method (C. Xu et al, Journal of Power Source, 180, 664-670, 2008) has been proposed a method for producing manganese oxide nanoparticles. The manganese oxide nanoparticles thus obtained are mixed with a conductive material and a binder to paste into a current collector, but the specific capacitance value is reduced by the amount of the conductive material and the binder added.

The present invention has been made to solve these conventional problems, the object of the present invention,

Firstly, a metal oxide electrode having a large porosity and a high specific surface area (hereinafter, mixed with a 'metal oxide electrode') is manufactured to provide a supercapacitor electrode having excellent specific capacitance and electric conductivity.

Second, it provides a method for producing a simple and inexpensive mass production of the electrode for the supercapacitor,

Third, the present invention provides a supercapacitor electrode having excellent mechanical, thermal, and electrical stability by greatly increasing adhesion between a current collector and a metal oxide electrode.

These objects can be achieved by the following configuration of the present invention.

(1) a current collector;

It is formed on at least one surface of the current collector, and comprises a porous metal oxide layer having a web structure of nanofibers including metal oxide nanoparticles,

The nanoparticles have an amorphous structure, or the electrode for a supercapacitor, characterized in that the nanocrystalline is partially formed in the amorphous structure.

(2) A supercapacitor comprising an electrode for a supercapacitor according to (1) above.

(3) (a) spinning a solution of a metal oxide precursor and a polymer on a current collector to prepare a web of composite fibers in which the metal oxide precursor and the polymer are mixed;

(B) thermocompressing, thermopressing or first heat treating the web of the composite fiber to partially or totally melt the polymer in the composite fiber;

(C) a porous metal oxide layer according to claim 1 to obtain a porous metal oxide layer according to claim 1 by removing the polymer from the web of the composite fiber by a second heat treatment of the web of the composite fiber passed through step (b). Manufacturing method.

First, since the metal oxide electrode prepared according to the present invention has a web structure of nanofibers including ultrafine metal oxide nanoparticles having a size of 2 to 30 nm, the specific surface area is greatly increased, and the electrolyte is nanofibers and It can easily penetrate between nanoparticles.

Second, since the metal oxide electrode is formed through a low temperature heat treatment of 400 ° C. or less, the metal oxide electrode has an amorphous, or a mixture of amorphous and nanocrystalline structures, and facilitates reaction with an electrolyte, thereby obtaining high capacity supercapacitor characteristics. Can be. In addition, the manufacturing process is simplified.

Third, the adhesiveness between the current collector (lower electrode) and the metal oxide layer is greatly improved through thermal compression, thermal pressing, or a low temperature heat treatment of 200 ° C. or less, thereby manufacturing a supercapacitor electrode having high electrical and mechanical stability. .

Fourth, it is possible to easily form a thin film or a thick film by easily controlling the thickness of the metal oxide film by adjusting the spinning time.

The supercapacitor electrode according to the present invention comprises a current collector and a porous metal oxide layer formed on at least one surface of the current collector.

Here, the porous metal oxide layer has a web or network structure of metal oxide nanofibers (nano wires). That is, the porous metal oxide layer has a form in which fibers are entangled by spinning (for example, electrospinning), and a web of metal oxide nanofibers in the form of a belt flattened by heat treatment (second heat treatment) after thermal compression or thermal pressing. Has a structure. The metal oxide nanofibers include metal oxide nanoparticles, and the metal oxide nanoparticles have an amorphous structure or a structure in which nanocrystals are partially formed in the amorphous structure. The average size of the nanoparticles is 2 ~ 30 nm, the average diameter of the nanofibers is preferably 50 ~ 3000 nm. The average diameter of the nanofibers and the size of the nanoparticles can be controlled by the content of the added precursor and the heat treatment temperature used.

The porous metal oxide layer may be a manganese oxide (MnO ₂ , Mn ₂ O ₃ or Mn ₃ O ₄ ), nickel oxide (NiO), vanadium oxide (V ₂ O ₅ ), tungsten oxide (WO ₃ ), cobalt oxide (CoO, Co ₂ O ₃ or Co ₃ O ₄ ) and molybdenum oxide (MoO ₃ ) may include any one or two or more mixed phases. However, the present invention is not limited thereto.

The current collector may be platinum (Pt), gold (Au), palladium (Pd), iridium (Ir), silver (Ag), ruthenium (Ru), nickel (Ni), stainless steel (STS), aluminum (Al) , Molybdenum (Mo), chromium (Cr), copper (Cu), titanium (Ti), tungsten (W), ITO (In doped SnO ₂ ) and FTO (F doped SnO ₂ ) Can be used.

In addition, the present invention provides a supercapacitor including the electrode for the supercapacitor. In general, a supercapacitor is composed of an electrode (including a current collector and a metal oxide electrode), an electrolyte, a separator, a case, a terminal, and the like. The supercapacitor of the present invention has the same configuration as that of a general supercapacitor except for the electrode. .

Examples of the electrolyte used in the present invention include Na ₂ SO ₄ , (NH ₄ ) ₂ SO ₄ , KOH, LiOH, LiClO ₄ , KCl, Na ₂ SO ₄ , Li ₂ SO ₄ , KOH, NaCl and the like, manganese oxide (MnO ₂ , Mn ₂ O ₃ or Mn ₃ O ₄ ), nickel oxide (NiO), vanadium oxide (V ₂ O ₅ ), tungsten oxide (WO ₃ ), cobalt oxide (CoO, Co ₂ O ₃ or Co ₃ O ₄ ) and an electrolyte capable of causing an electrochemical reaction with a metal oxide electrode such as molybdenum oxide (MoO ₃ ), there is no restriction on a specific material.

On the other hand, the manufacturing method of the electrode for the supercapacitor according to the present invention is largely divided into (1) the step of forming the web of the composite fiber by spinning, (2) the step of thermal compression of the web of the spun composite fiber, (3) heat treatment It can be divided into the step of obtaining a porous metal oxide layer. Hereinafter, each step will be described in detail.

Formation of Composite Fibers by Spinning

1. Preparation of spinning solution

In the present invention, a spinning method is used to obtain a web structure of the metal oxide nanofibers, and a spinning solution is first prepared for spinning.

The spinning solution is prepared by mixing a sol-gel precursor of a metal oxide (hereinafter mixed with a 'metal oxide precursor') with a suitable polymer and a solvent. Here, the polymer increases the viscosity of the solution to form a fibrous phase when spinning, and serves to control the structure of the spun fiber by compatibility with the metal oxide precursor.

The metal oxide precursor is a precursor containing Mn, Ni, Co, W, and / or Mo ions, and is mixed with a polymer to produce manganese oxide (MnO ₂ , Mn) through a post-spinning heat treatment (eg, heat treatment at a temperature of 200 ° C. or higher). ₂ O ₃ or Mn ₃ O ₄ ), nickel oxide (NiO), vanadium oxide (V ₂ O ₅ ), tungsten oxide (WO ₃ ), cobalt oxide (CoO, Co ₂ O ₃ or Co ₃ O ₄ ) and molybdenum Any precursor capable of forming denium oxide (MoO ₃ ) is not constrained. For example, when manufacturing a web of manganese oxide nanofibers, manganese (III) acetylacetonate (Mn (C ₅ H ₇ O ₂ ) ₃ ), manganese (II) acetylacetonate (Manganese Acetylacetonate) as a manganese oxide precursor _{, [CH 3 COCH = C (} O) CH 3] 2Mn), manganese (ⅲ) acetate hydrate (manganese acetate hydrate, Mn (CH 3 COO) 3 · xH 2 O), manganese (ⅲ) acetate dihydrate (manganese acetate dihydrate, Mn (CH ₃ COO) ₃ .2H ₂ O), Manganese acetate tetrahydrate, Mn (CH ₃ COO) ₂ 4H ₂ O) hydrate, Mn (NO ₃ ) ₂ xH ₂ O), manganese chloride (MnCl ₂ ), manganese chloride hydrate (MnCl ₂ xH ₂ O), manganese (III) Manganese chloride tetrahydrate (MnCl ₂ · 4H ₂ O), under manganese (II) sulfate At least one selected from the group consisting of manganese sulfate hydrate (MnSO ₄ .xH ₂ O) and manganese sulfate monohydrate (MnSO ₄ .H ₂ O) may be used.

In addition, the polymer may be a polyvinyl acetate, polyurethane, polyurethane copolymer including polyetherurethane, cellulose acetate and cellulose derivatives such as cellulose acetate butyrate and cellulose acetate propionate, polymethylmethacrylate (PMMA), Polymethyl acrylate (PMA), polyacrylic copolymer, polyvinylacetate copolymer, polyvinyl alcohol (PVA), polyfuryl alcohol (PPFA), polystyrene (PS), polystyrene copolymer, polyethylene oxide (PEO), poly Propylene oxide (PPO), polyethylene oxide copolymer, polypropylene oxide copolymer, polycarbonate (PC), polyvinylchloride (PVC), polycaprolactone, polyvinylpyrrolidone (PVP), polyvinyl fluoride, poly Selected from the group consisting of vinylidene fluoride copolymer and polyamide The can at least use of any of them. However, the present invention is not limited thereto, and no particular limitation is imposed on the polymer surface capable of maintaining a viscosity capable of being formed into ultrafine fibers by electrospinning or the like.

In addition, any one selected from the group consisting of dimethylformamide (DMF), acetone, detrahydrofuran, toluene, water and mixtures thereof may be used as the solvent. However, the present invention is not limited thereto.

Furthermore, additives may be added to the spinning solution for smooth spinning. As the additive, acetic acid, stearic acid, adipic acid, ethoxyacetic acid, benzoic acid, nitric acid and the like can be used. For example, cetyltrimethyl ammonium bromide (CTAB) may be used as the additive.

2. Web Preparation of Metal Oxide Precursor / Polymer Composite Fibers

The spinning solution obtained above is spun onto the current collector. When spinning, a web of ultrafine metal oxide precursor / polymer composite fiber (hereinafter referred to as “network”) is formed by a phase separation or mutual mixing process between the metal oxide precursor and the polymer.

The spinning may be performed by any one method selected from electrospinning, melt-blown, flash spinning, and electrostatic melt-blown.

Among them, the radiation by the electrospinning method is shown in FIG. The electrospinning apparatus includes a spinning nozzle connected to a metering pump capable of quantitatively introducing the spinning solution, a high voltage generator, an electrode (i.e., a current collector) to form a layer of spun fiber, and the like. The current collector is used as the cathode, and the spinning nozzle with the pump to control the discharge amount per hour is used as the anode. When a voltage of 7 to 30 kV is applied and the discharge rate of the solution is adjusted to 10 to 50 µl / min, ultrafine fibers having an average diameter of the composite fiber of 50 to 3000 nm can be prepared. In addition, electrospinning conditions, such as the distance between a tip and an electrode, are a normal range. The electrospinning is preferably carried out until the composite fiber layer is formed on the current collector to a thickness of 0.5 ~ 100 ㎛.

Of composite fiber web  Thermal crimping etc

Next, the web of the composite fiber obtained above is thermally compressed, thermally pressurized, or the first heat treatment. In this case, the thermal compression or thermal pressurization may be performed by applying a pressure at a temperature above the glass transition temperature of the polymer used.

If it is possible to induce partial and total melting of the polymer without pressing, the web of the composite fiber is heated to a temperature slightly higher than the glass transition temperature of the polymer or heat pressurized using hot compressed air on the current collector. Compression can also be done (this is called 'thermopressing', apart from thermocompression). At this time, in order to suppress the rapid volatilization process of the polymer, it may be subjected to thermal pressurization at a high temperature after a stepwise heat treatment process at a low temperature (for example 50 ~ 200 ℃). In addition, the adhesive properties may be improved by dissolving the polymer through an evaporation process in a closed vessel of vapor such as ethanol and methanol.

The pressure, temperature and time of the thermal compression or thermal pressurization are appropriately selected in consideration of the type of polymer used and the glass transition temperature. Preferably, it is carried out for 30 seconds at a pressure of 0.1 MPa. Considering the type of polymer used and the glass transition temperature, the pressure range can be selected from 0.001 to 10 MPa, and the compression time can be selected from 5 seconds to 10 minutes.

By thermal compression, thermal pressing, or the first heat treatment, flow between the metal oxide precursor and the polymer separated from the phase during spinning is suppressed, and then a web of nanofibers including nanometer-sized metal oxide nanoparticles is subjected to a heat treatment process. Is formed.

This thermal compression or thermal pressurization process melts or partially melts the polymer in the web of the composite fiber, improves the adhesion with the current collector, and the specific surface area after the subsequent heat treatment (second heat treatment). And it is possible to have a unique structure with a significantly improved density per unit volume, thereby providing a metal oxide network consisting of ultra-fine nanoparticles with a significantly increased specific surface area. Since the metal oxide fibers that have not undergone the thermal compression or thermal pressurization process can be easily detached from the substrate after the heat treatment, it is necessary to undergo the thermal compression or thermal pressurization process to provide a stable supercapacitor device.

In some cases, the effect of the thermocompression or thermocompression may be achieved through the first heat treatment without the thermocompression or thermocompression. In this case, the first heat treatment is preferably performed at a temperature of more than 200 ℃ ℃ glass transition temperature of the polymer. For the first heat treatment, during the spinning, it may be spinning while maintaining the temperature of the current collector at a temperature higher than the glass transition temperature of the polymer used. In particular, in the case of using a polymer having a low glass transition temperature, for example, a polymer such as polyvinyl acetate (PVAc), the polymer may be melted through a low temperature heat treatment at 50 ° C. to 80 ° C., thereby improving adhesion to the current collector.

Web Fabrication of Porous Metal Oxide Nanofibers

Subsequently, the web of the composite fiber subjected to the previous step is heat treated (second heat treatment) to remove the polymer from the web of the composite fiber.

The second heat treatment temperature and time are determined in consideration of the temperature at which the polymer is removed and the degree of crystallization of the metal oxide. Since the metal oxide having an amorphous structure rather than the crystalline structure has excellent supercapacitor characteristics, it is preferable to proceed with the second heat treatment at a relatively low temperature of 250 to 400 ° C. Depending on the second heat treatment temperature, it may be amorphous, and nanocrystalline may be partially formed in the amorphous structure. Preferably, the heat treatment temperature is performed at 400 ° C. or lower, and the heat treatment time is long to allow the polymer to be sufficiently removed to form a web of amorphous nanofibers.

Hereinafter, the present invention will be described in detail with reference to examples, but these examples are only presented to more clearly understand the present invention, and are not intended to limit the scope of the present invention. It will be determined within the scope of the technical spirit of the claims.

[ Example  One] Web Preparation of Manganese Oxide Precursor-Polyvinylacetate Composite Fiber after  Fabrication of Manganese Oxide Nanofiber Web Structure by Heat Treatment Process

2 g (Aldrich) of manganese (III) acetylacetonate was placed in a 100 mL bottle. Then add 15 g of Dimethyformamide (J.T.Baker) and dissolve until completely dissociated. At this time, for smooth electrospinning, 1 ml of acetic acid was added and stirred for 1 minute, followed by 2.5 g of polyvinyl acetate (PVAc, Polyvinylacetate) (molecular weight: 500,000) and dissolved for 2 hours or more. Through this process, a manganese oxide precursor / PVAc complex solution was prepared. At this time, for smooth spinning, a small amount of cetyltrimethyl ammonium bromide (CTAB) may be added. The manganese oxide precursor / PVAc complex solution thus obtained was placed in a 20 mL syringe (syringe) and flowed through a needle (30 G) at a rate of 10 μl / min. The voltage difference was maintained at about 13-15 kV. A stainless steel (SUS) substrate was used as the current collector. At this time, the thickness of the composite fiber layer can be adjusted by changing the discharge amount.

2A is a scanning electron microscope (SEM) photograph (× 3,000 magnification) of a manganese oxide precursor / PVAc composite fiber web electrospun onto a current collector according to Example 1 of the present invention. FIG. 2B is an enlarged photograph (× 10,000 magnification) of the image of FIG. 2A. It can be seen that the manganese oxide precursor / PVAc composite fiber having a size of 50 to 1000 nm is well formed. The diameter of the composite fiber can be adjusted by changing the spinning conditions.

The manganese oxide precursor / PVAc composite fiber web obtained above was raised to 180 ° C. in an electric furnace at a rate of 5 ° C./min and maintained for 10 minutes (first heat treatment). Then, after raising to 250 ~ 400 ℃ at a rate of 5 ℃ / min and heat treatment for 1 hour (second heat treatment).

An SEM image (× 3,000 magnification) of the manganese oxide (MnO ₂ ) nanofiber web obtained by heat treatment at 300 ° C. can be seen in FIG. 3A. It can be seen that the continuous nanofiber network is well formed. In particular, in the enlarged SEM photograph (× 10,000 magnification) of FIG. 3B, it can be seen that nanofibers are entangled with each other to form a porous structure well. When the SEM picture of FIG. 3B is enlarged at a magnification of × 100,000, the web structure of the nanofibers composed of ultrafine particles having a size of 2 to 10 nm can be clearly observed as shown in the SEM picture of FIG. 3C.

PVAc polymers with a low glass transition temperature undergo a melting process for 10 minutes at 180 ° C. The complete decomposition of PVAc was observed at 300 ℃ TGA results. Therefore, in FIGS. 2A and 2B, the manganese oxide / PVAc composite fiber shows a clear nanowire structure, whereas in FIGS. 3A to 3C, the manganese oxide heat treated through the melting process of the polymer has a nanowire web structure.

[ Example  2] Thermocompression Process of Manganese Oxide Precursor-Polyvinylacetate Composite Fiber Layer and Post heat treatment  Fabrication of the Web Structure of Manganese Oxide Nanofibers Through the Process

 After pressing the web of manganese oxide precursor / polyvinylacetate composite fiber obtained in Example 1 by using a lamination machine (60 ℃, pressing pressure: 0.1 MPa, pressing time: 60 seconds), and then again 300 ℃ It was calcined for 1 hour at to obtain a manganese oxide network composed of nanoparticles. At this time, it was found that the surface structure changed depending on the applied pressure and time. In addition, different thermocompression or thermopressurization temperatures may be determined according to the glass transition temperature of the polymer used. In particular, depending on the heat treatment (second heat treatment) temperature, the size of the nanocrystals can also be easily adjusted.

FIG. 4 is a scanning electron micrograph of a web of manganese oxide precursor / PVAc composite fiber obtained after electrospinning according to Example 2 after thermal compression at a pressure of 0.1 MPa for 60 seconds at 60 ° C. FIG. As shown in FIG. 4, it can be seen that PVAc having a low glass transition temperature is completely melted to have a structure in which all of them are connected. When the manganese oxide precursor / PVAc composite fiber subjected to the thermal compression process as shown in FIG. 4 is heat-treated at 300 ° C., as shown in the SEM photograph (× 3,000 magnification) of FIG. 5A, the web structure has a fine nanofiber web structure. It can be seen that the nanofiber web is more densely formed than the manganese oxide nanofiber web (see FIG. 3A) without heat compression. In FIG. 5b, the magnification of the manganese oxide nanofibers composed of very fine nanoparticles can be clearly confirmed.

The web of manganese oxide nanofibers composed of nanoparticles formed by heat treatment (second heat treatment) formed through the thermal compression process of the second embodiment has excellent adhesion to a substrate, and thus, makes a supercapacitor having excellent thermal, mechanical, and electrical contacts. It is possible.

[ Experimental Example  One] Fabrication of Supercapacitor Electrode Using Web of Manganese Oxide Nanofibers

Electrochemical properties were evaluated using the web of manganese oxide nanofibers formed in Example 2 described above as an electrode for a supercapacitor.

Cyclic voltammetry is one of the ways to measure capacitive behavior. This shows a large amount of current density in the cyclic voltammogram (CV), and in the anodic and cathodic sweeps, it is advantageous for the supercapacitor characteristic to show the shape of the rectangle and the symmetry of the left and right. Electrochemical properties were measured using a three-electrode electrochemical measurement. SCE ranges from 0 to 1.0 V and scan rate is 10 to 2000 mV / s. As the electrolyte, Na ₂ SO ₄ 0.1 ~ 1 M solution was used, and the working electrode was a web of manganese oxide nanofibers. In this case, the electrolyte used may be used to control the concentration of Na ₂ SO ₄ as well as (NH ₄ ) ₂ SO ₄ KOH, LiOH, LiClO ₄ , KCl, Na ₂ SO ₄ , Li ₂ SO ₄ , KOH, NaCl and the like. It does not limit the specific electrolyte. Ag / AgCl was used as the reference electrode and Pt was used as the counter electrode. In Experimental Example 1, the supercapacitor characteristics of the manganese oxide nanofiber web were evaluated using a stainless steel current collector, but Pt current collector and F-doped SnO ₂ were evaluated. (FTO) The use of current collectors is also possible and does not place restrictions on specific current collectors. An optical photograph of a manganese oxide nanofiber web formed in accordance with Example 2 on a stainless steel, Pt, FTO current collector can be seen in FIG. 6. 6 shows an image formed by spinning a manganese oxide nanofiber web on a 1 cm × 3 cm sized stainless steel, Pt, and FTO current collector. An image of the supercapacitor electrode cell used for CV measurement can be seen in the bottom photo of FIG. 6, leaving only a 1 cm × 1 cm manganese oxide nanofiber web for electrochemical measurements.

In particular, Figure 7a shows the supercapacitor characteristics of the thin manganese oxide nanofiber web layer made through Experimental Example 1. The thin manganese oxide nanofiber web layer composed of nanoparticles prepared by electrospinning, thermocompression, and 300 ° C. heat treatment has a large specific surface area. In addition, since it has a nanofiber web structure, electrolyte penetration and high reactivity can be expected. As shown in FIG. 7A, when the sweep rate was measured from 10 mV / S to 2000 mV / s, rectangular CV characteristics were observed.

Figure 7b shows the specific capacitance characteristics measured by changing the scan rate to 10 ~ 500 mV / s. It shows a high initial capacity of 250 F / g at a sweep rate of 10 mV / s. Considering the point obtained from the simple manganese oxide obtained through heat treatment at 300 ° C. without other additives, the value is quite high. As the scan rate increased, the specific capacitance value gradually decreased, and at the scan speed of 500 mV / s, the specific capacitance value was 120 F / g. This is observed because the electrical conductivity of the pure manganese oxide used without the addition of the conductive material is low, it is possible to overcome the reduction of the specific capacitance according to the scan speed by improving the electrical conductivity by the addition of the conductive material.

[ Experimental Example  2] At 400 ℃ Heat-treated  Manganese oxide Nanowire  Fabrication of Supercapacitor Electrodes Using Web

The same procedure as in Example 2 was carried out in the same manner, but the electrochemical properties were evaluated in the same manner as in Experiment 1 using the web of manganese oxide nanofibers obtained at the heat treatment temperature of 400 ° C. as the electrode for the supercapacitor. The manganese oxide heat treated at 300 ° C. has an amorphous structure or a crystal structure in which the amorphous structure and the ultrafine nanocrystalline are mixed due to the low heat treatment temperature. In comparison, the web of manganese oxide nanofibers heat treated at 400 ° C. has a more advanced crystallinity as the heat treatment temperature increases.

In particular, Figure 8a shows the supercapacitor characteristics of the thin manganese oxide nanofiber web layer made through Experimental Example 2. The thin manganese oxide nanofiber web layer composed of nanoparticles prepared by electrospinning, thermocompression, and 400 ° C. heat treatment has a large specific surface area. In addition, since it has a nanofiber web structure, electrolyte penetration and high reactivity can be expected. As shown in Figure 8a, when the sweep rate was measured from 10 mV / S to 2000 mV / s, the rectangular CV characteristics were observed.

Figure 8b shows the specific capacitance characteristics measured while changing the scan rate from 0 to 500 mV / s. The initial capacity is somewhat lower than that of supercapacitor using manganese oxide heat treated at 300 ℃ at 220 F / g at a sweep rate of 10 mV / s. Considering the point obtained from pure manganese oxide obtained through heat treatment at 400 ° C. without other additives, the value is quite high. As the scan rate increased, the specific capacitance value decreased gradually, and the scan rate of 500 mV / s showed a specific capacitance of 110 F / g. This is observed because the electrical conductivity of the pure manganese oxide used without the addition of the conductive material is low, it is possible to overcome the reduction in specific capacitance according to the scanning speed by the addition of the conductive material.

[ Experimental Example  3] At 300 ℃ Heat-treated  Fabrication of Supercapacitor Electrode Using Manganese Oxide Nanofiber Web

The same process as in Example 1 above, but using a Pt-coated Si wafer as a current collector, using a web of manganese oxide nanofibers obtained by the heat treatment temperature of 300 ℃ without a thermal compression process, using as a supercapacitor electrode The electrochemical properties were evaluated in the same manner as in Experiment 1. The Pt current collector has better electrical conductivity than the stainless steel current collector, and does not deteriorate the electrical conductivity of the current collector due to the second heat treatment, thereby maintaining high electrical conductivity of the current collector.

In particular, FIG. 9A shows the supercapacitor characteristics of the thin manganese oxide nanofiber web layer formed on the Pt current collector through Experimental Example 1. FIG. The thin manganese oxide nanofiber web layer composed of nanoparticles prepared by electrospinning, 180 ° C. heat treatment, and 300 ° C. heat treatment has a large specific surface area. In addition, since it has a nanofiber web structure, electrolyte penetration and high reactivity can be expected. As shown in Figure 9a, when the sweep rate was measured from 10 mV / S to 2000 mV / s, the rectangular CV characteristics were observed.

Figure 9b shows the specific capacitance characteristics measured while changing the scan rate from 10 to 2000 mV / s. High specific capacitance values were obtained even at low temperature heat treatment at 300 ° C at 253 F / g at a sweep rate of 10 mV / s. In particular, as shown in Fig. 9b, even at a scan rate of 2000 mV / s showed a high specific storage capacity of 141 F / g. It can be seen that high capacitance and excellent scan characteristics can be observed even in the heat-treated manganese oxide nanofiber web without improving the electrical conduction characteristics and the thermal compression process of the current collector.

In the above, the present invention has been described with reference to the illustrated examples, which are merely examples, and the present invention may be embodied in various modifications and other embodiments that are obvious to those skilled in the art. Understand that you can.

1 is a view schematically showing a manufacturing process of a porous metal oxide (manganese oxide) nanofiber web according to the present invention.

2A and 2B are scanning electron micrographs of a manganese oxide precursor / PVAc composite fiber web electrospun according to Example 1 of the present invention.

3a to 3c are scanning electron micrographs of the manganese oxide nanofiber web heat treated after electrospinning according to Example 1 of the present invention.

FIG. 4 is a scanning electron micrograph of a manganese oxide precursor / PVAc composite fiber web subjected to thermal compression after electrospinning according to Example 2 of the present invention.

5A and 5B are scanning electron micrographs of manganese oxide nanofiber webs heat-treated at 300 ° C. after a thermal compression process after electrospinning according to Example 2 of the present invention.

6 is an optical picture of a manganese oxide nanofiber web formed on a stainless steel, Pt, FTO current collector according to Example 2 of the present invention.

7A and 7B show a supercapacitor characteristic using a manganese oxide nanofiber web (300 ° C. heat treatment) prepared according to Experimental Example 1 of the present invention as an electrode.

8a and 8b show the characteristics of the supercapacitor using the manganese oxide nanofiber web (400 ℃ heat treatment) prepared according to Experimental Example 2 of the present invention as an electrode.

9A and 9B show a supercapacitor characteristic using a manganese oxide nanofiber web (300 ° C. heat treatment) prepared according to Experimental Example 3 of the present invention as an electrode.

Claims (11)

delete delete delete delete (A) spinning a solution in which the metal oxide precursor and the polymer are mixed on the current collector to prepare a web of composite fibers in which the metal oxide precursor and the polymer are mixed; (B) thermocompressing, thermopressing or first heat treating the web of the composite fiber to partially or totally melt the polymer in the composite fiber; (C) characterized in that to obtain a porous metal oxide layer by removing the polymer from the web of the composite fiber by a second heat treatment of the web of the composite fiber passed through the (b) step, The thermal compression or thermal pressurization is carried out by applying a pressure at a temperature higher than the glass transition temperature of the polymer used, The first heat treatment is to be carried out at a temperature of more than 200 ℃ ℃ glass transition temperature of the polymer, The second heat treatment is performed at a temperature of 250 to 400 ° C., such that the nanoparticles constituting the web of the metal oxide nanofibers have an amorphous structure, or have a structure in which the amorphous structure and the nanocrystalline structure are mixed. The porous metal oxide layer includes a current collector and a porous metal oxide layer formed on at least one surface of the current collector and having a web structure of nanofibers including metal oxide nanoparticles, wherein the nanoparticles are amorphous. The manufacturing method of the electrode for supercapacitors which has a structure or the nanocrystalline part was formed partially in an amorphous structure. The method of claim 5, wherein the metal oxide precursor is a manganese oxide precursor, the manganese oxide precursor is manganese (III) acetylacetonate (Mn (C ₅ H ₇ O ₂ ) ₃ ), manganese (II) acetylaceto Manganese Acetylacetonate, [CH ₃ COCH = C (O) CH ₃ ] 2 Mn, Manganese acetate hydrate, Mn (CH ₃ COO) ₃ xH ₂ O, Manganese (III) acetate die Manganese acetate dihydrate (Mn (CH ₃ COO) ₃ · 2H ₂ O), Manganese acetate tetrahydrate (Mn (CH ₃ COO) ₂ · 4H ₂ O), Manganese (II) nitrate hydrate (manganese nitrate hydrate, Mn (NO 3) 2 · xH 2 O), manganese (ⅱ) chloride (manganese chloride, MnCl _2), manganese (ⅱ) chloride hydrate _{(manganese chloride hydrate, MnCl 2 ·} xH 2 O), manganese (ⅲ) chloride tetrahydrate _{(manganese chloride tetrahydrate, MnCl 2 ·} 4H 2 O), network (Ⅱ) sulfate hydrate _{(Manganese sulfate hydrate, MnSO 4 ·} xH 2 O) and manganese (Ⅱ) sulfate monohydrate from the group consisting of _{(Manganese sulfate monohydrate, MnSO 4 ·} H 2 O) , characterized in that the selected at least one The manufacturing method of the electrode for supercapacitors. The method of claim 5, wherein the polymer is polyvinyl acetate, polyurethane, polyurethane copolymer including polyetherurethane, cellulose acetate and cellulose derivatives such as cellulose acetate butylate and cellulose acetate propionate, polymethylmethacrylate ( PMMA), polymethylacrylate (PMA), polyacryl copolymer, polyvinylacetate copolymer, polyvinyl alcohol (PVA), polyperfuryl alcohol (PPFA), polystyrene (PS), polystyrene copolymer, polyethylene oxide (PEO ), Polypropylene oxide (PPO), polyethylene oxide copolymer, polypropylene oxide copolymer, polycarbonate (PC), polyvinylchloride (PVC), polycaprolactone, polyvinylpyrrolidone (PVP), polyvinyl pullo Ride, polyvinylidene fluoride copolymer and polyamide Method for producing an electrode for a supercapacitor, characterized in that at least one selected from. delete delete delete The method of claim 5, wherein the radiation is selected from electrospinning, melt-blown, flash spinning, and electrostatic melt-blown. The manufacturing method of the electrode for supercapacitors characterized by the above-mentioned.

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