WO2014087858A1

WO2014087858A1 - Electricity storage device

Info

Publication number: WO2014087858A1
Application number: PCT/JP2013/081586
Authority: WO
Inventors: 阿部　正男; 大谷　彰; 岸井　豊; 植谷　慶裕
Original assignee: 日東電工株式会社
Priority date: 2012-12-04
Filing date: 2013-11-25
Publication date: 2014-06-12
Also published as: JP2014110221A

Abstract

Disclosed is an electricity storage device comprising: an electrolyte layer (3); and a positive electrode (2) and a negative electrode (4) that are provided so as to sandwich the electrolyte layer. The positive electrode (2) is an electrode made of a composite including at least (A) and (B) described below, wherein (B) is fixed within the composite. The negative electrode (4) is an electrode made of a composite including at least (B) and (C) described below, wherein (B) is fixed within the composite. Thus, an excellent output density per weight and excellent quick charging/discharging characteristics are obtained, and a high energy density per weight is obtained. (A) An electrode active material having an electroconductivity that changes according to the insertion/desorption of ions. (B) A polycarboxylic acid. (C) An electrode active material having an electroconductivity that changes according to the insertion/desorption of ions, the electrode active material having a lower oxidation-reduction potential than said (A).

Description

Power storage device

The present invention relates to an electricity storage device, and more specifically, while maintaining the excellent weight output density and rapid charge / discharge characteristics inherent in conventional electric double layer capacitors, the weight energy is significantly higher than that of conventional electric double layer capacitors. The present invention relates to an electric double layer capacitor type electricity storage device having a density.

In recent years, as an energy storage device having high output characteristics and long life, for example, a porous separator, a pair of polarizable electrodes disposed opposite to each other with the porous separator interposed therebetween, and the porous separator and polarizable electrode An electric double layer capacitor containing an electrolytic solution impregnated in has attracted attention.

Recently, technology development for realizing a low-carbon society has been actively carried out. In particular, in the automobile market, demand for hybrid cars and electric cars is rapidly increasing in place of gasoline cars. As power storage devices for hybrid and electric vehicles, lithium ion secondary batteries (lithium secondary batteries) are mainly used because of their high energy density. However, lithium ion secondary batteries are also currently used. The performance is still not enough. That is, the lithium ion secondary battery has a high energy density, but the output density is not so high.

Also, as a power source for automobiles, high power density that can cope with acceleration is required. Therefore, in the lithium secondary battery, various ideas have been devised for increasing the weight output density at the expense of energy density characteristics.

On the other hand, an electric double layer capacitor has a very low weight energy density, but inherently has a very high weight output density, and can easily obtain characteristics reaching several thousand mW / g. Are better. As described above, the electric double layer capacitor originally has a high weight output density and rapid charge / discharge characteristics, and has very excellent characteristics as an electric storage device. Have the disadvantages.

That is, conventionally, an electric double layer capacitor usually uses a polarizable electrode formed using a conductive porous carbon material such as powdered activated carbon or fibrous activated carbon, and exhibits physical adsorption characteristics of supporting electrolyte ions in an electrolytic solution. Since it is a device that uses electricity to store electricity, its weight energy density is extremely small compared to a battery using a chemical reaction called redox reaction, and it cannot maintain a long-term discharge in actual use. Have a problem.

In order to increase the capacity, it is essential to increase the specific surface area of the activated carbon used for the electrodes. Conventionally, activated carbon used for an electric double layer capacitor is generally manufactured by steam activation and chemical activation of raw materials such as coconut shell carbide, phenol resin carbide, and coal. As a method for producing such activated carbon, for example, a solvent extract of coal (ashless coal) is heated in a temperature range of 800 ° C. to 950 ° C. in an inert atmosphere, and the resulting solid residue is alkali activated. , A method in which the coal-based pitch is heat-treated in a two-step temperature range of 400 ° C. to 600 ° C. and 600 ° C. to 900 ° C., and the heat-treated coal-based pitch is alkali-activated. A method of activating with a drug has been studied (see Patent Documents 1 to 3). Furthermore, attempts have been made to increase the capacity by chemical modification by coating the surface of activated carbon with a conductive polymer having oxidation-reduction characteristics. (See Patent Documents 4 to 6).

However, electric double layer capacitors having polarizable electrodes formed in these methods are still not sufficiently improved in weight energy density. In addition, in order to improve the characteristics of conductive polymer systems, formation of a rocking chair type battery using a polymer anion has been attempted, but the characteristics are not sufficient (see Patent Document 7). Furthermore, although improvement was attempted by using conductive polymers having different characteristics for both the positive electrode and the negative electrode, the characteristics were not sufficient (see Patent Document 8).

JP 2007-142204 A JP 2004-149399 A JP 2002-104817 A JP 2008-72079 A Japanese Patent Laid-Open No. 2002-25865 JP 2012-33783 A Japanese Patent Laid-Open No. 1-132052 JP-A-63-69156

As described above, although the electric double layer capacitor has been improved in various ways, it is not yet sufficient in performance, and a lithium secondary battery using a lithium-containing transition metal oxide such as lithium manganate or lithium cobaltate for the electrode. Compared to batteries, the capacity density and energy density are low, and it is not possible to exhibit excellent performance as a power storage device for automobiles.

The present invention has been made to solve the above-described problems, and provides a novel power storage device having excellent weight output density and rapid charge / discharge characteristics and high weight energy density.

An electricity storage device of the present invention is an electricity storage device having an electrolyte layer, a positive electrode and a negative electrode provided therebetween, and the positive electrode is a composite electrode comprising at least the following (A) and (B): In addition, the following (B) is fixed in the composite, and the negative electrode is an electrode of a composite comprising at least the following (B) and (C), and the following (B) Is configured to be fixed.
(A) An electrode active material whose conductivity changes due to ion insertion / extraction.
(B) Polycarboxylic acid.
(C) An electrode active material whose conductivity is changed by insertion / extraction of ions, and has an oxidation-reduction potential lower than that of (A) above.

That is, the present inventors have conducted intensive research to solve the above problems. In the course of that research, the present inventors configured both positive and negative electrodes in a capacitor-type electricity storage device using a composite of an electrode active material such as polyaniline and a polycarboxylic acid as a binder. In addition, by setting the electrode active material used on the negative electrode side to have a lower oxidation-reduction potential than the electrode active material used on the positive electrode side, both the weight output density and the weight energy density can be increased. I found out that I could do it. Accordingly, the present inventors have found that such an electrode configuration greatly improves the characteristics of the electricity storage device.

In the present invention, “(B) is fixed in the composite” means that the component (B) is fixed in the composite formed together with other electrode forming materials. Since the polycarboxylic acid (B), which is an anionic material, is fixed and does not move, the cation moves, and the electricity storage device using the same has a rocking chair type mechanism. Means that.

Thus, the electricity storage device of the present invention is an electricity storage device having an electrolyte layer, a positive electrode and a negative electrode provided therebetween, wherein the positive electrode is at least the specific electrode active material (A) and the polyelectrolyte. The composite electrode is composed of a carboxylic acid (B), the polycarboxylic acid (B) is fixed in the composite, and the negative electrode includes at least the polycarboxylic acid (B) and the specific electrode active material. (C) and the following (B) is being fixed in the composite. For this reason, while having the outstanding weight output density and rapid charge / discharge characteristic, it can be set as the high performance electrical storage device which has a high weight energy density.

Further, when at least one of the electrode active materials (A) and (C) is coated on the porous surface of the porous carbon material, the output characteristics are further improved.

Furthermore, when the oxidation-reduction potential difference between the electrode active materials (A) and (C) is 5 mV or more, the energy density is further improved.

It is sectional drawing which shows the structure of an electrical storage device.

Hereinafter, embodiments of the present invention will be described in detail. However, the description described below is an example of embodiments of the present invention, and the present invention is not limited to the following contents.

As shown in FIG. 1, the electricity storage device of the present invention is an electricity storage device having an electrolyte layer 3, a positive electrode 2 and a negative electrode 4 provided with the electrolyte layer 3 interposed therebetween, and the positive electrode 2 is at least the following (A): And (B), the following (B) is fixed in the composite, and the negative electrode 4 is at least a composite electrode comprising (B) and (C) below. In addition, the following (B) is fixed in the complex.
(A) An electrode active material whose conductivity changes due to ion insertion / extraction.
(B) Polycarboxylic acid.
(C) An electrode active material whose conductivity is changed by insertion / extraction of ions, and has an oxidation-reduction potential lower than that of (A) above.

Incidentally, 1 is a current collector (for positive electrode), and 5 is a current collector (for negative electrode). FIG. 1 schematically shows the structure of the electricity storage device, and the thickness of each layer is different from the actual one.

The present invention uses an electrode composed of a composite having the above components (A) and (B) as constituents for a positive electrode, and an electrode composed of a composite having the above (B) and (C) components as constituents Is the most important feature, but the materials used will be described in order.

<About electrode active materials (A) and (C)>
The above (A) and (C) are electrode active materials whose conductivity is changed by ion insertion / extraction (hereinafter sometimes referred to as “electrode active materials”). For example, polyacetylene, polypyrrole, polyaniline , Polythiophene, polyfuran, polyselenophene, polyisothianaphthene, polyphenylene sulfide, polyphenylene oxide, polyazulene, poly (3,4-ethylenedioxythiophene) (hereinafter abbreviated as “PEDOT”), and substituted polymers thereof Conductive polymer materials such as polyacene, graphite, carbon nanotubes, carbon nanofibers, graphene, and the like.

And for the electrode active material (A) used for the positive electrode, a material having a high redox potential is preferably used. Specifically, polythiophene-based or polyaniline-based materials are preferably used. On the other hand, a material having a low redox potential is preferably used for the electrode active material (C) used for the negative electrode. Specifically, polypyrrole-based or substituted polyaniline-based materials are preferably used.

As for the combination of the positive electrode and the negative electrode, if a material having a high redox potential is used for the positive electrode and a material having a low redox potential is used for the negative electrode, a battery having a high discharge voltage can be obtained and a battery having a high energy density can be obtained. Preferred examples include a combination using polythiophene-based PEDOT as the positive electrode and polypyrrole as the negative electrode, or a combination of the same polyaniline-based material using polyaniline as the positive electrode and poly (o-toluidine) as the negative electrode. Etc.

The redox potential difference of the electrode active materials (A) and (C) is preferably 5 mV or more, more preferably 10 mV or more. The redox potential difference between the electrode active materials (A) and (C) is preferably 2500 mV or less, more preferably 2000 mV or less. The oxidation-reduction potential difference is obtained from the difference between values obtained by measuring the average values of the peak values of the oxidation wave and the reduction wave by the cyclic voltammetry at the (A) electrode and the (C) electrode, respectively. The counter electrode at this time is lithium metal and is based on the oxidation-reduction potential of lithium. The electrolyte used is the same as that used when forming the battery cell, and the potential scanning speed is 20 mV / sec. By providing the oxidation-reduction potential difference in the above range, an energy storage device with higher energy density can be obtained.

The ion insertion / desorption in the above (A) and (C) is also referred to as so-called doping / dedoping as described above, and the doping / dedoping amount per certain molecular structure is called the doping rate. The higher the doping rate, the higher the capacity of the battery.

For example, the conductive polymer doping ratios of (A) and (C) are said to be 0.5 for polyaniline and 0.25 for polypyrrole. The higher the doping rate, the higher the capacity of the battery can be formed. For example, the conductivity of conductive polyaniline is about 10 ⁰ to 10 ³ S / cm in the doped state, and 10 ⁻¹⁵ to 10 ⁻² S / cm in the undoped state.

On the other hand, as a method of bringing the above (A) or (C) into the reduction-dedoped state in the initial stage, for example, there is a method of directly making the reduction-dedoped state, but there is a method of reducing after making the dedope state. This is common.

The latter method will be described. First, a dedope state is obtained by neutralizing the dopant which (A) or (C) has. For example, (A) or (C) in a dedope state is obtained by stirring in a solution for neutralizing the dopant (A) or (C) and then washing and filtering. Specifically, in order to dedope polyaniline having tetrafluoroboric acid as a dopant, a method of neutralizing by stirring in an aqueous sodium hydroxide solution can be mentioned.

Next, by reducing (A) or (C) in the dedope state, a reduced dedope state is obtained. For example, (A) or (C) in the reduced dedoped state is obtained by stirring in a solution for reducing (A) or (C) in the dedoped state, and then washing and filtering. Specifically, a method of reducing polyaniline in a dedoped state by stirring in an aqueous methanol solution of phenylhydrazine can be mentioned.

When forming a storage battery, the combinations shown in the following (1) and (2) are effective.
(1) The reduction-dedoped material (A) is used for the positive electrode, and the oxidation-doped material (C) is used for the negative electrode. This is charged and used first.
(2) The oxidation-doped material (A) is used for the positive electrode, and the reductive dedope material (C) is used for the negative electrode. This is first discharged and used.

Also, those obtained by coating the electrode active material (A) or (C) on the porous surface of a porous carbon material are preferably used as the electrode active material for the positive electrode or the negative electrode.

The porous carbon material is a material having a porous structure mainly composed of a carbon material, and activated carbon subjected to chemical or physical treatment (activation, activation) is preferably used in order to increase adsorption efficiency. . Examples of the activated carbon subjected to the chemical treatment include phenol resin activated carbon, coconut shell activated carbon, and petroleum coke activated carbon. Examples of the activated carbon subjected to the above physical treatment include activated carbon obtained from a steam activation treatment method, activated carbon obtained from a molten KOH activation treatment method, and the like. Among these, it is preferable to use activated carbon obtained by a steam activation treatment method in that a large capacity can be obtained.

Further, as the activated carbon, activated carbon for electric double layer capacitors having a large specific surface area is preferably used. It is preferable to use activated carbon having an average particle size of 20 μm or less and a specific surface area of 1000 to 3000 m ² / g so as to obtain an electricity storage device having a large capacity and a low internal resistance.

The electrode active material (A) or (C) is coated on the porous carbon material, for example, the porous carbon material in a solution obtained by dissolving the electrode active material (A) or (C) in an appropriate solvent. The porous carbon material is immersed in a polymerization solution at the time of chemical oxidative polymerization of the electrode active material of (A) or (C), a method of taking out and drying it, a method by an electrolytic method, Examples thereof include a method of attaching the electrode active material (A) or (C) to the surface (hereinafter abbreviated as “in situ polymerization method”). Among these, the in-situ polymerization method is particularly preferably used because a uniform thin film can be obtained. As the in-situ polymerization method, the method described in Patent Document 6 (Japanese Patent Laid-Open No. 2012-33783) can be used.

The coating thickness of the conductive polymer is usually 0.1 to 500 nm, preferably 0.5 to 50 nm. That is, if it is too thin, there is a tendency that a storage battery with a high capacity density cannot be obtained, and if it is too thick, it is difficult for ions to diffuse and a high capacity density tends not to be obtained.

The weight ratio of the conductive polymer to the composite of the conductive polymer and the porous carbon material is usually 0.5 to 40%, preferably 1 to 10%.

The electricity storage device of the present invention is a positive electrode made of a material containing the electrode active material (A) and the polycarboxylic acid (B) described below, and the electrode active material (C), A negative electrode is made from a material containing the polycarboxylic acid (B) to be described, and this is used. Both electrodes are made of a porous sheet or the like using at least an electrode active material and polycarboxylic acid.

<About polycarboxylic acid (B)>
Examples of the polycarboxylic acid (B) include a polymer, a carboxylic acid substitution compound having a relatively large molecular weight, and a carboxylic acid substitution compound having low solubility in an electrolytic solution. More specifically, a compound having a carboxyl group in the molecule is preferably used, and the polycarboxylic acid (B) as a polymer has an advantage that it can also serve as a binder.

Examples of the polycarboxylic acid (B) include polyacrylic acid, polymethacrylic acid, polyvinylbenzoic acid, polyallylbenzoic acid, polymethallylbenzoic acid, polymaleic acid, polyfumaric acid, polyglutamic acid, and polyaspartic acid. However, polyacrylic acid and polymaleic acid are particularly preferably used. These may be used alone or in combination of two or more.

In the electricity storage device of the present invention, when the polycarboxylic acid (B) is used together with the electrode active material (A) or (C), the polycarboxylic acid (B) has a function as a binder and a dopant. Therefore, it is considered that it has a rocking chair type mechanism and is involved in improving the characteristics of the electricity storage device according to the present invention.

As the polycarboxylic acid (B), those in which at least a part of the carboxyl group in the molecule is substituted with lithium to form a lithium type are preferably used. Such lithium substitution is preferably 40% or more of the carboxyl groups in the polymer, more preferably 100%.

The polycarboxylic acid (B) is usually 1 to 100 parts by weight, preferably 2 to 70 parts by weight, most preferably 5 parts per 100 parts by weight of the electrode active material (A) or (C). Used in the range of up to 40 parts by weight. If the amount of the polycarboxylic acid (B) with respect to the electrode active material (A) is too small, it tends to be difficult to obtain an electricity storage device with excellent energy density, while the polycarboxylic acid with respect to the electrode active material (A) tends to be difficult. Even if the amount of the acid (B) is too large, it tends to be difficult to obtain an electricity storage device having a high energy density.

<Other electrode forming materials>
Further, as the electrode forming material, the electrode active material (A) or (C), polycarboxylic acid (B), and a binder other than the polycarboxylic acid (B), a conductive auxiliary agent, etc., if necessary. It can mix | blend suitably.

The conductive auxiliary agent may be any conductive material whose properties do not change depending on the potential applied during the discharge of the electricity storage device, and examples thereof include conductive carbon materials and metal materials, among which acetylene black and ketjen black A conductive carbon black such as carbon fiber, or a fibrous carbon material such as carbon fiber or carbon nanotube is preferably used. Particularly preferred is conductive carbon black.

The conductive assistant is preferably 1 to 30 parts by weight, more preferably 4 to 20 parts by weight, and particularly preferably 8 parts by weight based on 100 parts by weight of the electrode active material (A) or (C). ~ 18 parts by weight. When the blending amount of the conductive aid is within this range, the shape and characteristics as the active material can be prepared without abnormality, and the rate characteristics can be effectively improved.

Examples of the binder other than the polycarboxylic acid (B) include vinylidene fluoride.

<About electrodes>
The electrode according to the electricity storage device of the present invention is composed of a composite comprising at least the electrode active material (A) or (C) and the polycarboxylic acid (B), and is preferably formed on a porous sheet. Usually, the thickness of the electrode is preferably 1 to 1000 μm, and more preferably 10 to 700 μm.

The thickness of the electrode is obtained by measuring the electrode using a dial gauge (manufactured by Ozaki Mfg. Co., Ltd.), which is a flat plate having a tip shape of 5 mm in diameter, and obtaining an average of 10 measurement values with respect to the surface of the electrode. . As shown in FIG. 1, when an electrode (porous layer) is provided on the current collector and composited, the thickness of the composite is measured in the same manner as described above, and the average of the measured values is obtained. Thereafter, the thickness of the electrode is obtained by subtracting the thickness of the current collector.

The electrode according to the electricity storage device of the present invention is produced, for example, as follows. That is, the polycarboxylic acid (B) is dissolved in water to form an aqueous solution, and an electrode active material (A) or (C) and, if necessary, a conductive assistant such as conductive carbon black are added thereto. To prepare a paste. After applying this on the current collector, water is evaporated to form a composite (porous sheet) of a mixture of the electrode active material and polycarboxylic acid (conducting aid if necessary) on the current collector. ) Can be obtained as an electrode (sheet electrode).

In the electrode formed as described above, the polycarboxylic acid (B) is present as a composite of a mixture with the electrode active material (A) or (C), thereby fixing in the composite, and thus the electrode. Fixed inside. The polycarboxylic acid (B) fixedly arranged in the vicinity of the electrode active material (A) or (C) in this way is used for charge compensation during oxidation / reduction of the electrode active material (A) or (C). The

Although the reason why it becomes an energy storage device with a high energy density by using such an electrode has not yet been fully elucidated, a suitable electrode can be obtained by placing a polycarboxylic acid in the vicinity of the electrode active material. Factors such as an active material concentration environment and facilitating the movement of ions that are inserted and desorbed from the electrode active material can be considered. Furthermore, the polycarboxylic acid, which is an anionic material, becomes a counter ion of a cation such as lithium ion, contributes to the so-called rocking chair type ion transfer, and prevents a decrease in capacity even when the total amount of electrolyte is reduced. Conceivable.

<About the electrolyte layer>
The electrolyte layer according to the electricity storage device of the present invention is composed of an electrolyte. For example, a sheet formed by impregnating a separator with an electrolytic solution or a sheet formed of a solid electrolyte is preferably used. The sheet made of the solid electrolyte itself also serves as a separator.

As the electrolyte layer, for example, as described above, when using a separator impregnated with an electrolytic solution, examples of the electrolyte constituting such an electrolytic solution include protons, alkali metal ions, quaternary ammonium ions, At least one cation such as quaternary phosphonium ion, sulfonate ion, perchlorate ion, tetrafluoroborate ion, hexafluorophosphate ion, hexafluoroarsenic ion, halogen ion, phosphate ion, sulfate ion, A combination of at least one anion such as nitrate ion is preferably used.

As the solvent constituting the electrolytic solution, at least one organic solvent such as carbonates, alcohols, nitriles, amides, ethers and the like is used in addition to water. In addition, what melt | dissolved the said electrolyte in the solvent may be called "electrolytic solution."

In the present invention, the separator can be used in various modes. As the separator, it is possible to prevent an electrical short circuit between the positive electrode and the negative electrode that are arranged to face each other across the separator. Furthermore, the separator is electrochemically stable, has a large ion permeability, and has a certain level. Any insulating porous sheet having mechanical strength may be used. Therefore, as a material for the separator, for example, a porous porous sheet made of a resin such as paper, nonwoven fabric, polypropylene, polyethylene, or polyimide is preferably used. These may be used alone or in combination of two or more.

<About electricity storage devices>
The production of an electricity storage device using the above materials will be described with reference to FIG. The device is preferably assembled in a glove box under an inert gas atmosphere such as ultra-high purity argon gas.

In FIG. 1, metal foils and meshes such as nickel, aluminum, stainless steel, and copper are appropriately used as current collectors of positive electrode 2 and negative electrode 4 (1, 5 in FIG. 1).

The power storage device of the present invention is formed in various shapes such as a laminate cell, a porous sheet type, a sheet type, a square type, a cylindrical type, and a button type.

The electricity storage device of the present invention is the energy per total weight of the positive electrode and the negative electrode of the specific electrode active materials (A) and (C), that is, the “electrode active material whose conductivity is changed by insertion / extraction of ions”. The density is usually 30 mWh / g or more, preferably 40 mWh / g or more.

Since the electricity storage device of the present invention has such an excellent energy density, even if the amount of the electrolytic solution is reduced, the total weight of the used electrolytic solution and the weight of the electrode active materials (A) and (C) The capacity density is not greatly reduced.

Furthermore, since the electricity storage device of the present invention uses electrodes in combination with the A component and B component, and in combination with the B component and C component, it has excellent charge / discharge characteristics like an electric double layer capacitor. The capacitance density is higher than that of the conventional electric double layer capacitor. From this, it can be said that the electrical storage device according to the present invention is a capacitor-like secondary battery.

In the present invention, the weight of the electrode active material is the weight including the dopant for the oxidized state (A) or (C), and the weight not including the dopant for the reduced state (A) or (C). Calculate based on the original. Further, the same applies to (A) or (C) coated with the porous carbon material. In this case, the weight of the porous carbon material is also summed up.

Next, examples will be described together with comparative examples. However, the present invention is not limited to these examples.

First, prior to the examples and comparative examples, each material was manufactured according to the following manufacturing examples 1 to 7.

[Production Example 1: Production of polyaniline powder]
To a glass beaker having a capacity of 138 g of ion-exchanged water, 84.0 g (0.402 mol) of a 42 wt% tetrafluoroboric acid aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd., special grade) was added. While stirring, 10.0 g (0.107 mol) of aniline was added thereto. When aniline was first added to an aqueous tetrafluoroboric acid solution, the aniline was dispersed as oily droplets in the aqueous tetrafluoroboric acid solution, but then dissolved in water within a few minutes, resulting in a uniform and transparent aniline. It became an aqueous solution. The aniline aqueous solution thus obtained was cooled to −4 ° C. or lower using a low-temperature thermostatic bath.

Next, 11.63 g (0.134 mol) of manganese dioxide powder (1st grade, manufactured by Wako Pure Chemical Industries, Ltd.) as an oxidizing agent was added little by little to the aniline aqueous solution, and the temperature of the mixture in the beaker was −1 ° C. Not to exceed. Thus, by adding an oxidizing agent to the aniline aqueous solution, the aniline aqueous solution immediately turned black-green. Thereafter, when stirring was continued for a while, a black-green solid started to be formed.

Thus, after adding an oxidizing agent over 80 minutes, it stirred for further 100 minutes, cooling the reaction mixture containing the produced | generated reaction product. Thereafter, using a Buchner funnel and a suction bottle, the obtained solid was No. Suction filtration was performed with two filter papers (manufactured by ADVANTEC) to obtain a powder. This powder was stirred and washed in a tetrafluoroboric acid aqueous solution of about 2 mol / dm ³ using a magnetic stirrer, then stirred and washed several times with acetone, and this was filtered under reduced pressure. The obtained powder was vacuum-dried at room temperature for 10 hours to obtain 12.5 g of conductive polyaniline (oxidized polyaniline) having tetrafluoroborate anion as a dopant as a bright green powder.

After pulverizing 130 mg of the conductive polyaniline powder in a smoked mortar, vacuum-pressing was performed for 10 minutes under a pressure of 300 MPa using a KBr tablet molding machine for infrared spectrum measurement, and a conductive polyaniline disk having a thickness of 720 μm was formed. Obtained. The conductivity of the disk measured by the 4-terminal method conductivity measurement by the Van der Pau method was 19.5 S / cm.

The conductive polyaniline powder in the doped state thus obtained was put into a 2 mol / dm ³ sodium hydroxide aqueous solution and stirred for 30 minutes to neutralize the conductive polyaniline. Thereby, the tetrafluoroboric acid which is a dopant was dedope from polyaniline.

The dedoped polyaniline was washed with water until the filtrate became neutral, then stirred and washed in acetone, and then filtered under reduced pressure using a Buchner funnel and a suction bottle. 2 A polyaniline powder was obtained which was dedoped on the filter paper. This was vacuum-dried at room temperature for 10 hours to obtain undoped polyaniline as a brown powder.

Next, the dedope polyaniline powder thus obtained was put in a methanol solution of phenylhydrazine and subjected to a reduction treatment with stirring for 30 minutes. The polyaniline powder changed its color from brown to gray.

After such a reduction treatment, the obtained polyaniline powder is washed with methanol and then with acetone, filtered, and then vacuum-dried at room temperature to obtain a reduced dedope polyaniline (reduced polyaniline). It was.

After pulverizing 130 mg of the above polyaniline powder in a reduced dedope state in a smoked mortar, vacuum reduced pressure molding was performed for 10 minutes under a pressure of 300 MPa using a KBr tablet molding machine for infrared spectrum measurement, and a reduced dedope having a thickness of 720 μm. A polyaniline disk in state was obtained. The electric conductivity of the disk measured by the 4-terminal conductivity measurement by the Van der Pau method was 5.8 × 10 ⁻³ S / cm.

That is, this polyaniline has a higher electrical conductivity in an oxidized state in which ions are inserted than in a reduced state in which ions are desorbed. Therefore, it is an electrode active material whose conductivity is changed by ion insertion / extraction.

[Production Example 2: Production of poly (o-toluidine) powder]
In Production Example 1, in place of 10.0 g of aniline, 11.47 g of o-toluidine was used. Otherwise, in the same manner as in Production Example 1, conductive poly (o-toluidine) (oxidized poly (o-toluidine)) having tetrafluoroborate anion as a dopant was obtained as a powder. The conductivity was 0.8 S / cm as a result of measurement by the same method as in Production Example 1.

The doped conductive poly (o-toluidine) powder thus obtained was put into a 2 mol / dm ³ aqueous sodium hydroxide solution and stirred for 30 minutes to obtain conductive poly (o-toluidine). Neutralized. As a result, the dopant tetrafluoroborate anion was dedoped from poly (o-toluidine).

The dedoped poly (o-toluidine) was washed with water until the filtrate became neutral, then stirred and washed in acetone, and then filtered under reduced pressure using a Buchner funnel and a suction bottle. 2 Poly (o-toluidine) powder was obtained which was dedope on the filter paper. The poly (o-toluidine) powder was vacuum-dried at room temperature for 10 hours to obtain undope poly (o-toluidine) as a brown powder.

Next, the undoped poly (o-toluidine) powder thus obtained was placed in a methanol solution of phenylhydrazine and subjected to a reduction treatment for 30 minutes with stirring. The poly (o-toluidine) powder changed its color from brown to gray.

The thus-reduced poly (o-toluidine) powder is washed with methanol and then with acetone, filtered, and then vacuum-dried at room temperature to obtain poly (o-toluidine) (reduced state) in a reduced and undoped state. Of poly (o-toluidine). The electrical conductivity was 2.5 × 10 ⁻⁴ S / cm as a result of measurement by the same method as in Production Example 1.

That is, this poly (o-toluidine) has a higher electrical conductivity in an oxidized state in which ions are inserted than in a reduced state in which ions are desorbed. Therefore, it is an electrode active material whose conductivity is changed by ion insertion / extraction.

[Production Example 3: Production of poly (3,4-ethylenedioxythiophene) <PEDOT>]
Under a nitrogen atmosphere, 73.9 g of iron trichloride was dissolved in 900 g of acetonitrile in a three-necked flask. Thereafter, the flask was immersed in an ice bath containing sodium chloride and kept at 0 ° C. or lower.

In addition, 26.0 g of 3,4-ethylenedioxythiophene (manufactured by Junsei Co., Ltd.) was dissolved in 20 g of acetonitrile, and this was dropped into the above-prepared solution of iron trichloride and acetonitrile over 2 hours. did. After completion of the dropwise addition, stirring was continued for 30 minutes at room temperature.

Subsequently, the solution was filtered, and the solid content was washed with a large amount of water and acetone and then vacuum-dried at room temperature. The thus obtained PEDOT powder in the oxidized state had a conductivity of 30.1 S / cm as a result of measurement by the same method as in Production Example 1.

Next, the oxidized PEDOT powder was placed in a 2N aqueous sodium hydroxide solution and stirred for 30 minutes. And after washing with water until the filtrate became neutral, it was stirred and washed in acetone, and then filtered.

Next, the PEDOT powder was put in a methanol solution of phenylhydrazine and subjected to a reduction treatment for 30 minutes with stirring. After the reaction, the product was washed with methanol and acetone in this order, filtered and vacuum dried at room temperature. In this way, reduced PEDOT powder was obtained. The yield was 15.5 g. And the electrical conductivity of the said PEDOT powder of the said reduction | restoration was 1.8 * 10 < ^-1 > S / cm as a result of measuring by the method similar to manufacture example 1. FIG.

That is, this PEDOT has higher electrical conductivity in the oxidized state in which ions are inserted than in the reduced state in which ions are desorbed. Therefore, it is an electrode active material whose conductivity is changed by ion insertion / extraction.

[Production Example 4: Production of polypyrrole]
Under a nitrogen atmosphere, 3 g of pyrrole (manufactured by Wako Pure Chemical Industries, Ltd.) was dropped into 300 g of a 0.5 mol / dm ³ aqueous iron trichloride solution over 2 hours. After completion of the dropwise addition, stirring was continued for 30 minutes at room temperature. Subsequently, the solution was filtered, and the solid content was washed with a large amount of water and acetone and then vacuum-dried at room temperature. The conductivity of the polypyrrole powder in the oxidized state thus obtained was 10.3 S / cm as a result of measurement by the same method as in Production Example 1.

Next, the oxidized polypyrrole powder was put in a 2N aqueous sodium hydroxide solution and stirred for 30 minutes. And after washing with water until the filtrate became neutral, it was stirred and washed in acetone, and then filtered.

Next, the polypyrrole powder was put into a methanol solution of phenylhydrazine and subjected to a reduction treatment with stirring for 30 minutes. After the reaction, the product was washed with methanol and acetone in this order, filtered and vacuum dried at room temperature. In this way, a reduced polypyrrole powder was obtained. The yield was 15.5 g. And the electric conductivity of the polypyrrole powder in the reduced state was 3.1 × 10 ⁻² S / cm as a result of measurement by the same method as in Production Example 1.

That is, this polypyrrole has a higher electrical conductivity in an oxidized state in which ions are inserted than in a reduced state in which ions are desorbed. Therefore, it is an electrode active material whose conductivity is changed by ion insertion / extraction.

[Production Example 5: Production of activated carbon coated with polyaniline]
To 243.6 g of ion-exchanged water in a 1 L-capacity glass beaker, 5.13 g (0.0245 mol) of 42 wt% concentration tetrafluoroboric acid aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd., special grade) Mixed. While stirring the tetrafluoroboric acid aqueous solution thus obtained, 1.25 g (0.0134 mol) of aniline was added to obtain a transparent aqueous solution of aniline salt.

Next, an oxidizing agent aqueous solution in which 1.53 g (0.0067 mol) of ammonium peroxodisulfate was dissolved in 13.8 g of ion-exchanged water was added to the aqueous solution of the aniline salt, and the mixture was stirred and mixed uniformly. An aniline / oxidizer aqueous solution was obtained. While this aniline / oxidant aqueous solution is colorless and transparent, that is, within the polymerization induction period before the aniline oxidative polymerization begins, 50 g of steam-activated activated carbon (JSC 18 manufactured by JFE Chemical Co., Ltd.) is used as the porous carbon material. (Activated carbon / aniline weight ratio 40) was added and subjected to ultrasonic dispersion treatment with an ultrasonic homogenizer for 2 minutes to suspend the activated carbon in the aqueous aniline / oxidant solution.

The aniline / oxidant aqueous solution in which the activated carbon was suspended as described above was placed under a reduced pressure of 30 hPa, defoamed for 5 minutes, and impregnated with the aniline / oxidant aqueous solution into the pores of the activated carbon. The aqueous aniline / oxidant solution was then returned to atmospheric pressure and stirring was continued. The aniline / oxidant aqueous solution, which was initially colorless and transparent, continued to be transparent during the treatment so far. Thereafter, oxidative polymerization of aniline was started in the aniline / oxidant aqueous solution, and as the water proceeded, the water-soluble color changed from blue to blue-green and further to black-green.

The oxidized polymer of aniline thus obtained was filtered under reduced pressure to obtain a black powder. This was washed with acetone and filtered again under reduced pressure. This operation was performed three times in total, and the resulting black powder was vacuum-dried at room temperature for 10 hours in a desiccator, and a conductive polyaniline / activated carbon composite having tetrafluoroboric acid as a dopant, that is, oxidized polyaniline. 51.2 g of activated carbon coated with was obtained.

The weight increase of the conductive polyaniline / activated carbon composite thus obtained was an increase of 1.2 g based on the weight of the activated carbon used. That is, the proportion of the weight increase in the composite was 2.3% by weight. The specific surface area of this conductive polyaniline / activated carbon composite by BET method was 1600 m ² / g.

[Production Example 6: Production of activated carbon coated with poly (o-toluidine)]
Instead of 1.25 g of aniline used in Production Example 5, 1.43 g of o-toluidine was used. Other than that, through the same production process as in Production Example 5, the conductive poly (o-toluidine) / activated carbon composite with tetrafluoroboric acid as a dopant, ie, oxidized poly (o-toluidine) was coated. 45.5g of activated carbon was obtained.

The weight increase of the conductive poly (o-toluidine) / activated carbon composite thus obtained was an increase of 1.5 g relative to the weight of the activated carbon used. That is, the proportion of the weight increase in the composite was 3.2% by weight. The conductive poly (o-toluidine) / activated carbon composite had a specific surface area of 1400 m ² / g as measured by the BET method.

[Production Example 7]
The conductive polyaniline / activated carbon composite powder having tetrafluoroboric acid as a dopant obtained in Production Example 5 is put into a 2 mol / dm ³ aqueous sodium hydroxide solution and stirred for 30 minutes to obtain conductive polyaniline. After neutralization, tetrafluoroboric acid as a dopant was dedoped from polyaniline.

The activated carbon powder coated with the dedoped polyaniline was washed with water until the filtrate became neutral, then stirred and washed in acetone, filtered under reduced pressure using a Buchner funnel and a suction bottle. 2 Activated carbon powder coated with de-doped polyaniline was obtained on filter paper. This was vacuum-dried at room temperature for 10 hours to obtain activated carbon powder coated with dedope polyaniline.

Next, the thus obtained activated carbon powder coated with polyaniline in a dedope state was placed in a methanol solution of phenylhydrazine and subjected to a reduction treatment for 30 minutes with stirring.

After the reduction treatment, the obtained polyaniline powder is washed with methanol and then with acetone, filtered, and then vacuum-dried at room temperature to obtain activated carbon powder coated with polyaniline in a reduced dedope state (reduced state). Obtained.

[Example 1]
(Preparation of positive electrode sheet)
0.1 g of polyacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight: 1,000,000) was added to 3.9 g of ion-exchanged water and allowed to stand overnight to swell. Then, it processed for 1 minute using the ultrasonic homogenizer, and it was made to melt | dissolve, and obtained the polyacrylic acid aqueous solution 4g of 2.5 weight% density | concentration uniformly.

Next, 0.8 g of the reduced polyaniline powder obtained in Production Example 1 was mixed with 0.1 g of conductive carbon black (Denka Black, Denki Kagaku Kogyo Co., Ltd.), and the resulting mixture was mixed with 2.5 wt. It was kneaded well with a spatula in addition to 4 g of a polyacrylic acid aqueous solution with a% concentration. Thereafter, a dispersion treatment was performed for 1 minute with an ultrasonic homogenizer to obtain a paste having fluidity. This paste was further defoamed using a vacuum suction bell and a rotary pump.

Subsequently, an etching aluminum foil for electric double layer capacitor having a thickness of 50 μm (manufactured by Hosen Co., Ltd., 30CB) was prepared as a current collector. And the said defoaming paste was apply | coated on the said electrical power collector with the application speed | rate of 10 mm / sec with the doctor blade type applicator with a micrometer using the desktop type | mold automatic coating apparatus by a tester industry company. Subsequently, after leaving at room temperature for 45 minutes, it dried on the hotplate with a temperature of 100 degreeC. Then, using a vacuum press (Kitagawa Seiki Co., Ltd., KVHC), it was sandwiched between 15 cm square stainless steel plates and pressed at a temperature of 140 ° C. and a pressure of 1.49 MPa for 5 minutes to obtain a composite sheet. The thickness of the electrode calculated by subtracting the thickness of the current collector from the thickness of the composite sheet was 265 μm.

The composite sheet was punched into a disk shape with a punching jig on which a punching blade having a diameter of 15.95 mm was installed, and this was used as a positive electrode sheet.

(Preparation of negative electrode sheet)
Instead of 0.8 g of the reduced polyaniline powder obtained in Production Example 1 used as the positive electrode active material, 1.2 g of oxidized poly (o-toluidine) obtained in Production Example 2 was used as the electrode active material. Used as (negative electrode active material). Other than that was carried out similarly to the said positive electrode sheet, and produced the composite sheet (negative electrode sheet). The thickness was 270 μm.

(Production of cell (electric storage device))
As a separator, a non-woven fabric having a porosity of 68% (manufactured by Hosen Co., Ltd., TF40-50) was prepared, and dried together with the positive electrode sheet and the negative electrode sheet in a vacuum dryer at 100 ° C. for 5 hours. Thereafter, the following assembly was performed in a glove box having a dew point of −100 ° C. in an ultrahigh purity argon gas atmosphere. First, a positive electrode sheet and a negative electrode sheet were placed facing each other in a stainless steel HS cell (manufactured by Hosen Co., Ltd.) for a non-aqueous electrolyte secondary battery experiment, and the separator was positioned so that they did not short-circuit. Thereafter, an electrolytic solution of 1 mol / dm ³ lithium tetrafluoroborate (LiBF ₄ ) in ethylene carbonate / dimethyl carbonate (manufactured by Kishida Chemical Co., Ltd.) was injected.

The electrolyte amount (mg) was set to be 4.50 times the total weight (mg) of the positive electrode and negative electrode active material. That is, the total weight of electrolytic solution weight (mg) / active material of both positive and negative electrodes (mg) = 4.50 (mg / mg).

After injecting the electrolyte, the HS cell was sealed by heat-sealing the injection port portion to complete the cell.

[Example 2]
Instead of the reduced polyaniline powder used as the positive electrode active material of Example 1, the polyaniline (reduced state) -coated activated carbon obtained in Production Example 7 was used, and the negative electrode active material of Example 1 was used. Instead of 1.2 g of the oxidized polyaniline powder, 1.0 g of poly (o-toluidine) (oxidized state) -coated activated carbon obtained in Production Example 6 was used. Moreover, the thickness of the positive electrode sheet was 315 μm, and the thickness of the negative electrode sheet was 305 μm. Otherwise, the cell was fabricated in the same manner as in Example 1.

Example 3
Instead of the reduced polyaniline powder used as the positive electrode active material in Example 1, the oxidized PEDOT obtained in Production Example 3 was used, and the oxidation used as the negative electrode active material in Example 1 Instead of the polyaniline powder in the state, the reduced state polypyrrole obtained in Production Example 4 was used. The thickness of the positive electrode sheet was 270 μm, and the thickness of the negative electrode sheet was 285 μm. Otherwise, the cell was fabricated in the same manner as in Example 1.

[Comparative Example 1]
Instead of 4 g of 2.5 wt% polyacrylic acid aqueous solution used as the positive electrode / negative electrode material of Example 1, 0.31 g of SBR emulsion (manufactured by JSR, TRD2001, SBR content: 48 wt%) and poly A solution obtained by mixing 0.21 g of an (N-vinylpyrrolidone) aqueous solution (manufactured by Nippon Shokubai Co., Ltd., K-90W, content: 19.8% by weight) was used. Moreover, the thickness of the positive electrode sheet was 265 μm, and the thickness of the negative electrode sheet was 250 μm. Otherwise, the cell was fabricated in the same manner as in Example 1.

[Comparative Example 2]
Instead of 4 g of the 2.5 wt% polyacrylic acid aqueous solution used as the positive electrode / negative electrode material of Example 2, 0.31 g of SBR emulsion (manufactured by JSR, TRD2001, SBR content: 48 wt%) and poly A solution obtained by mixing 0.21 g of an (N-vinylpyrrolidone) aqueous solution (manufactured by Nippon Shokubai Co., Ltd., K-90W, content: 19.8% by weight) was used. Moreover, the thickness of the positive electrode sheet was 295 μm, and the thickness of the negative electrode sheet was 225 μm. Otherwise, the cell was fabricated in the same manner as in Example 2.

[Comparative Example 3]
Instead of 4 g of the 2.5 wt% polyacrylic acid aqueous solution used as the positive electrode / negative electrode material of Example 3, 0.31 g of SBR emulsion (manufactured by JSR, TRD2001, SBR content: 48 wt%) and poly A solution obtained by mixing 0.21 g of an (N-vinylpyrrolidone) aqueous solution (manufactured by Nippon Shokubai Co., Ltd., K-90W, content: 19.8% by weight) was used. The thickness of the positive electrode sheet was 280 μm, and the thickness of the negative electrode sheet was 290 μm. Other than that was carried out similarly to Example 3, and produced the cell.

For the cells of Examples and Comparative Examples thus obtained, the cells were evaluated according to the following criteria.

<Evaluation of cell>
Each cell obtained above is placed in a constant temperature bath at 25 ° C. and measured in a constant current / constant voltage charge / constant current discharge mode using a battery charging / discharging device (Hokuto Denko, SD8). It was. That is, first, constant current charging was performed up to 3.5 V at a current value of 0.14 mA (Example 3 and Comparative Example 3 were first charged and then charged). After reaching 3.5V, switch to constant voltage charging of 3.5V, perform constant voltage charging until the current value becomes 20% of the current value at the time of constant current discharge, leave for 30 minutes after charging, Thereafter, discharging was performed at a current value of 0.14 mA until the voltage reached 2.0V.

The discharge energy density (mWh / g) after the fifth charge / discharge cycle was measured. Based on this, the energy density of each cell of the above Examples and Comparative Examples is shown in Table 1 below as a result of conversion per active material (total of both electrodes).

From the above results, it was found that Examples 1 to 3 had a higher energy density per weight of the active material (total of both electrodes) than the comparative example.

The present inventors confirmed that Examples 1 to 3 were excellent in charge / discharge rate, and found that the battery was a capacitor-like secondary battery. Furthermore, the electricity storage device of the present invention was more effective than the capacitor. It was confirmed to have a high energy density.

In addition, although the specific form in this invention was shown in the said Example, the said Example is only a mere illustration and is not interpreted limitedly. Various modifications apparent to those skilled in the art are contemplated to be within the scope of this invention.

The electricity storage device of the present invention can be suitably used as an electricity storage device such as a lithium secondary battery or a high-capacity capacitor. In addition, the electricity storage device of the present invention can be used for the same applications as conventional secondary batteries and electric double layer capacitors. For example, portable electronic devices such as portable PCs, cellular phones, and personal digital assistants (PDAs), Widely used in driving power sources for hybrid electric vehicles, electric vehicles, fuel cell vehicles and the like.

1 Current collector (for positive electrode)
2 Positive electrode 3 Electrolyte layer 4 Negative electrode 5 Current collector (for negative electrode)

Claims

An electricity storage device having an electrolyte layer, a positive electrode and a negative electrode provided therebetween, wherein the positive electrode is an electrode of a composite composed of at least the following (A) and (B), and the composite (B) below is fixed, and the negative electrode is an electrode of a composite comprising at least the following (B) and (C), and the following (B) is fixed in the composite A power storage device characterized.
(A) An electrode active material whose conductivity changes due to ion insertion / extraction.
(B) Polycarboxylic acid.
(C) An electrode active material whose conductivity is changed by insertion / extraction of ions, and has an oxidation-reduction potential lower than that of (A) above.
2. The electric storage device according to claim 1, wherein at least one of the electrode active materials (A) and (C) is coated on a porous surface of a porous carbon material.
The electrical storage device according to claim 1 or 2, wherein the redox potential difference between the electrode active materials (A) and (C) is 5 mV or more.