JP2014103146A - Electricity storage device, and electrode and porous sheet used in the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel electricity storage device excellent in capacity density and cycle characteristics.SOLUTION: In an electricity storage device including an electrolyte layer 3 and a positive electrode 2 and a negative electrode 4 which are provided so as to sandwich the electrolyte layer, an electrode used in at least one of the positive electrode 2 and the negative electrode 4 comprises a composite including the following (A) and (B), and the following (B) is fixed within the electrode. (A) A porous carbon material having a surface coated with a conductive polymer. (B) A poly(meth)acrylic acid.

Description

  TECHNICAL FIELD The present invention relates to an electricity storage device, an electrode used therefor, and a porous sheet, and more particularly, a novel electric double layer capacitor type electricity storage device having both excellent characteristics of an electric double layer capacitor and excellent characteristics of a lithium ion secondary battery. And an electrode used therefor and a porous sheet.

  In recent years, 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. Lithium ion secondary batteries having high energy density are mainly used as power storage devices for hybrid vehicles and electric vehicles. In such a power storage device for automobiles, it is not sufficient that the energy density is high, but it is required to have a high output density that can cope with acceleration.

  However, although the lithium ion secondary battery has a high energy density, it has a problem that the output density is not so high. In view of this, lithium ion secondary batteries for automobiles have been devised in various ways to increase output density at the expense of energy density. For this reason, when the output density of the lithium ion secondary battery for automobiles is increased to an area exceeding 1000 W / kg, the energy density is reduced to a level of several tens of kWh / kg.

  On the other hand, as an energy storage device with high output characteristics and long life, a porous separator, a pair of polarizable electrodes arranged opposite to each other with the porous separator interposed therebetween, and impregnating the porous separator and polarizable electrode Attention has been focused on electric double layer capacitors having an electrolyte solution. An electric double layer capacitor has a very high output density, can easily reach several thousand W / kg, and is excellent in cycle characteristics, and thus is extremely excellent as an electricity storage device. However, since it also has a drawback of low energy density, it cannot be applied as it is to a power storage device for automobiles.

  That is, an electric double layer capacitor usually uses a polarizable electrode made of a conductive porous carbon material such as powdered activated carbon or fibrous activated carbon, and uses the physical adsorption characteristics of supporting electrolyte ions in the electrolyte solution to generate electricity. Since it is a storage device, it has an extremely low energy density and cannot sustain discharge over a long period of time compared to a device that stores electricity using a chemical reaction called a redox reaction.

  In order to improve the drawbacks of such electric double layer capacitors, it is essential to increase the specific surface area of activated carbon used for the electrodes. Therefore, various studies have been made to realize a high specific surface area of activated carbon. For example, a solvent extract of coal (ashless coal) is heated at a temperature of 800 to 950 ° C. in an inert atmosphere, and the resulting solid residue is alkali activated (Patent Document 1). In addition, heat treatment is performed on the coal-based pitch at two stages of 400 to 600 ° C. and 600 to 900 ° C., and the heat-treated coal-based pitch is alkali-activated (Patent Document 2), and the granular isotropic pitch is infusible. After that, treatment such as activation with a drug (Patent Document 3) has been studied. Attempts have also been made to chemically modify the surface of the activated carbon with a conductive polymer having redox properties (Patent Documents 4, 5, and 6).

  However, even with these improvements, the improvement in energy density is still not sufficient. Furthermore, in the conductive polymer system, the development of a rocking chair type using a polymer anion has been attempted, but its characteristics are not sufficient (Patent Document 7).

JP 2007-142204 A JP 2004-149399 A JP 2002-104817 A JP 2008-072079 A JP 2002-025865 A JP 2012-033783 A Japanese Patent Laid-Open No. 01-132052

  As described above, although various improvements have been made to the electric double layer capacitor, the current state is that the performance is still not sufficient as in the case of the lithium secondary battery.

  An object of the present invention is to solve such problems and to provide a novel electricity storage device that is excellent not only in capacity density but also in cycle characteristics and the like, an electrode used therefor, and a porous sheet.

In order to achieve the above object, the present invention provides an electricity storage device having an electrolyte layer, a positive electrode and a negative electrode provided therebetween, and the electrode used for at least one of the positive electrode and the negative electrode is the following (A) and An electrical storage device comprising a composite containing (B) and having the following (B) fixed inside the electrode is taken as a first gist.
(A) A porous carbon material whose surface is coated with a conductive polymer.
(B) Poly (meth) acrylic acid.

  An electrode for an electricity storage device, which is an electrode used for at least one of the positive electrode and the negative electrode, and is made of a composite containing the above (A) and (B), and (B) is fixed inside the electrode, This is the second gist.

  Furthermore, let the 3rd summary be the porous sheet for electrical storage device electrodes which consists of a composite containing said (A) and (B), and said (B) is being fixed inside the composite.

  That is, the present inventors have intensively studied in order to obtain an electricity storage device having excellent capacity density and cycle characteristics. In the process, the inventors of the present invention recalled that the target power storage device could be obtained by combining the excellent characteristics of the lithium secondary battery and the electric double layer capacitor. As a result, when a porous carbon material that has been specially treated is used as an electrode material and poly (meth) acrylic acid is fixed in the electrode, the capacity density of the electricity storage device is significantly larger than expected. As a result, the present invention has been found.

  In the present invention, “poly (meth) acrylic acid” means that either polyacrylic acid or polymethacrylic acid may be used.

  In the present invention, “poly (meth) acrylic acid (B) is fixed inside the electrode” means that the positive electrode forming material is related to the positive electrode forming material including the special porous carbon material (A). It is said that it is fixed in a more formed complex, and by this, an anionic material called poly (meth) acrylic acid (B) is fixed and does not move, so that it has a property that the cation moves. As a result, this means that an electricity storage device using the same has a rocking chair type mechanism.

Thus, in the electricity storage device of the present invention, the electrode used for at least one of the positive electrode and the negative electrode is composed of a composite containing the following (A) and (B), and the following (B) is fixed inside the electrode. Yes. For this reason, both energy density and capacity density are excellent.
(A) A porous carbon material whose surface is coated with a conductive polymer.
(B) Poly (meth) acrylic acid.

  That is, as the electrode material, a porous carbon material whose surface is coated with a conductive polymer is used, and poly (meth) acrylic acid is fixed inside the electrode. The acid has not only a rocking chair type function but also a binder function, which eliminates or reduces the need to use another binder for electrode formation. Therefore, the internal resistance of the electrode can be reduced, and an electricity storage device having a high energy density can be obtained. Furthermore, since the surface of the porous carbon material of the electrode material is coated with a conductive polymer, the conductivity of the electrode is improved, enabling high-speed charge / discharge of the electricity storage device, and greatly increasing its capacity density. Can be made.

  Further, in an electricity storage device having an electrolyte layer and a positive electrode and a negative electrode provided therebetween, the electrode is used for at least one of the positive electrode and the negative electrode, and is made of a composite containing the above (A) and (B). When the electrode for an electricity storage device in which (B) is fixed inside the electrode, the electricity storage device using the electrode has excellent charge / discharge characteristics and excellent capacity density.

  If the electrode used for at least one of the positive electrode and the negative electrode of these electricity storage devices is formed to be porous, the surface area becomes large and more ions can be adsorbed, so the high capacity density of the electricity storage device Can be realized further.

  Furthermore, when the porous sheet for an electricity storage device electrode is composed of a composite containing the following (A) and (B) and the following (B) is fixed inside the composite, the electricity storage device using this is charged. Excellent discharge characteristics and excellent capacity density.

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

  Embodiments of the present invention will be described in detail below. The electric storage device of the present invention is most characterized in that an electrode used for at least one of a positive electrode and a negative electrode is composed of a composite having the above (A) and (B) as constituent elements. Below, the structure of the electrical storage device of this invention which used the electrode which is this feature point as a positive electrode is demonstrated in order. However, the description described below is an example of an embodiment 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 has an electrolyte layer 3, a positive electrode 2 and a negative electrode 4 provided on both sides of the electrolyte layer 3, and at least one electrode has the following (A) and (B): The following (B) is being fixed inside the electrode. Reference numeral 1 denotes a current collector (for positive electrode). FIG. 1 schematically shows the structure of the electricity storage device, and the thickness of each layer is different from the actual one.
(A) A porous carbon material whose surface is coated with a conductive polymer.
(B) Poly (meth) acrylic acid.

<About positive electrode>
The positive electrode 2 is made of a composite containing the above (A) and (B) and the above (B) is fixed inside the electrode, and in particular, a porous one is preferably used. The thickness of such an electrode is preferably 1-1000 μm, more preferably 10-700 μm. That is, if the thickness is too thin, there is a tendency that an electric storage device cannot obtain a sufficient capacity. Conversely, if the thickness is too thick, it becomes difficult for ions to diffuse inside the positive electrode 2 and a desired output is obtained. This is because there is no tendency.

  The thickness of the positive electrode 2 was obtained by measuring the surface of the positive electrode 2 using a flat dial gauge (manufactured by Yazaki Mfg. Co., Ltd.) having a tip of 5 mm in diameter, and obtaining the average value of the 10 points. It is. When the positive electrode 2 is provided on the current collector 1 and these are integrated into a composite, the thickness of the composite is measured in the same manner as described above, and the average value of the 10 points is obtained. The value can be obtained by subtracting the thickness of the current collector 1.

  As described above, the positive electrode 2 is composed of a composite containing the porous carbon material (A) and the poly (meth) acrylic acid (B) whose surfaces are coated with a conductive polymer. These will be described in order.

[Porous carbon material (A) whose surface is coated with a conductive polymer]
The porous carbon material whose surface is coated with the conductive polymer is one in which the conductive polymer enters the inner peripheral wall of the pores of the porous carbon material and coats a thin film along the inner peripheral wall. . That is, since the pores of the porous carbon material are not blocked by the conductive polymer, the porous carbon material is formed into a conductive polymer / porous carbon material composite having a large specific surface area. In addition, the inner peripheral wall of the pore of the porous carbon material means the inner surface of the pore extending inward from the surface of the porous carbon material.

  The thickness of the conductive polymer covering the surface of the porous carbon material is preferably 0.1 to 500 nm, and more preferably 0.5 to 50 nm. If the coating of the conductive polymer is too thin, there is a tendency that an electricity storage device with a high capacity density cannot be obtained, and if the coating of the conductive polymer is too thick, it becomes difficult for ions to diffuse, resulting in a high capacity density. This is because there is a tendency that cannot be achieved. The ratio of the conductive polymer to the composite of the conductive polymer and the porous carbon material is preferably 0.5 to 40% by weight, and more preferably 1 to 10% by weight.

(Porous carbon material)
The porous carbon material used for the special porous carbon material (A) is a porous structure material mainly composed of a carbon material, and examples of the carbon material include powdered activated carbon and fibrous activated carbon. Examples include activated carbon, conductive carbon black having a hollow shape such as ketjen black, so-called carbon blacks such as Vulcan XC72, Denka Black, and the like, and preferably activated carbon is used. These may be used alone or in combination of two or more. The porous structure is formed mainly due to a porous carbon material, but is not limited thereto. Here, the main component means a component that occupies the majority of the whole, and includes the case where the whole consists of only the main component.

  Moreover, as said activated carbon, what performed the chemical or physical process (activation, activation) in order to improve adsorption efficiency, such as a dopant, is used preferably. 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 diameter of 20 μm or less and a specific surface area of 1000 to 3000 m ² / g so as to obtain a large capacity and low internal resistance electric storage device.

Moreover, the electrical conductivity of such a porous carbon material is preferably greater than 10 ⁻³ S / cm, and more preferably greater than 10 ⁻² S / cm. This is because if the electrical conductivity is too small, even if it is coated with a conductive polymer and formed into a special porous carbon material, it is difficult to obtain the effect of increasing the weight output density of the electricity storage device. The conductivity of such a porous carbon material can be measured by a pressure cylinder method or the like. For example, the conductivity of powdered activated carbon measured by the pressure cylinder method is about 10 ⁻² S / cm.

(Conductive polymer)
The conductive polymer used for the special porous carbon material (A) is an ionic species inserted into the polymer in order to compensate for a change in charge generated or lost by an oxidation reaction or reduction reaction of the polymer main chain. Or a group of polymers in which the conductivity of the polymer itself changes when detached from the polymer.

  In such a polymer, a state with high conductivity is referred to as a doped state, and a state with low conductivity is referred to as a dedope state. Even if a polymer having conductivity loses conductivity by an oxidation reaction or a reduction reaction and becomes insulative (that is, in a dedoped state), such a polymer is reversibly conductive again by the oxidation-reduction reaction. Therefore, the insulating polymer in such a dedope state is also included in the category of the conductive polymer in the present invention.

  Further, as one of the preferred conductive polymers of the present invention, at least one proton acid selected from the group consisting of inorganic acid anions, fatty acid sulfonate anions, aromatic sulfonate anions, polymer sulfonate anions and polyvinyl sulfate anions is preferable. A polymer having an anion as a dopant. Further, another conductive polymer preferable in the present invention is a polymer in a dedope state obtained by dedoping the conductive polymer.

  Specific examples of the conductive polymer include, for example, polyacetylene, polypyrrole, polyaniline, polythiophene, polyfuran, polyselenophene, polyisothianaphthene, polyphenylene sulfide, polyphenylene oxide, polyazulene, and poly (3,4-ethylenedioxythiophene). And various derivatives thereof. Of these, polyaniline, polyaniline derivatives, polypyrrole, and polypyrrole derivatives having a large electrochemical capacity are preferably used, and polyaniline and polyaniline derivatives are more preferably used.

  In the present invention, the polyaniline means a polymer obtained by electrolytic polymerization or chemical oxidative polymerization of aniline, and the polyaniline derivative is obtained by electrolytic polymerization or chemical oxidative polymerization of an aniline derivative, for example. Refers to the polymer produced.

  More specifically, as a derivative of aniline, a substituent such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group, an aryloxy group, an alkylaryl group, an arylalkyl group, or an alkoxyalkyl group is provided at a position other than the 4-position of aniline. What has at least one can be illustrated. Preferable specific examples include, for example, o-substituted anilines such as o-methylaniline, o-ethylaniline, o-phenylaniline, o-methoxyaniline, o-ethoxyaniline, m-methylaniline, m-ethylaniline, m And m-substituted anilines such as -methoxyaniline, m-ethoxyaniline, m-phenylaniline and the like. These may be used alone or in combination of two or more. In the present invention, p-phenylaminoaniline having a substituent at the 4-position can be suitably used as an aniline derivative because polyaniline is obtained by oxidative polymerization.

(Preparation of porous carbon material (A) whose surface is coated with a conductive polymer)
A porous carbon material (conductive polymer / porous carbon material composite having a large specific surface area) (A) that has been specially treated in this manner is porous, for example, in a solvent in which a conductive polymer is dissolved. It can be produced by a method in which a carbon material is immersed and taken out and dried, or a method in which chemical oxidation polymerization of a monomer forming a conductive polymer is initiated in a solvent in which a porous carbon material is present (polymerization method).

  In particular, in the above polymerization method, with respect to 100 parts by weight of the monomer that forms the conductive polymer, the porous carbon material is blended in an amount of 25 to 55 parts by weight, and the monomer is oxidatively polymerized in an appropriately selected solvent. This is preferable because a uniform thin film can be formed on the surface of the porous carbon material. The solvent is usually water, but a mixed solvent of a water-soluble organic solvent and water can also be used. Moreover, you may add surfactant etc. in a solvent as needed.

  In more detail, the method for producing the porous carbon material (A) will be described below using an example in which aniline is used as a monomer for providing a conductive polymer and activated carbon is used as a porous carbon material.

  That is, aniline is chemically treated with a chemical oxidant having a standard electrode potential of 0.6 V or higher with respect to a standard hydrogen electrode in water (solvent) containing activated carbon and a protonic acid having a pKa value of 0.3 or lower. Oxidative polymerization is performed. At this time, when the proportion of activated carbon is 25 to 55 parts by weight with respect to 100 parts by weight of aniline, polyaniline enters not only the surface of the activated carbon but also the inner peripheral wall of the pores, and covers the thin film along the inner peripheral wall. Thus, a polyaniline / activated carbon composite (porous carbon material (A)) having a large specific surface area can be obtained.

  Examples of the protonic acid having a pKa value of 0.3 or less include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, perchloric acid, tetrafluoroboric acid, hexafluorophosphoric acid, hydrogen fluoride, and hydroiodic acid, and benzene. Sulfonic acids, aromatic sulfonic acids such as p-toluenesulfonic acid, alkanesulfonic acids such as methanesulfonic acid and ethanesulfonic acid, phenols such as picric acid, aromatic carboxylic acids such as m-nitrobenzoic acid, dichloroacetic acid, Examples thereof include aliphatic carboxylic acids such as malonic acid. A polymer acid can also be used. Examples of such polymer acids include polystyrene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyvinyl sulfuric acid, poly (acrylamide-t-butyl sulfonic acid), phenol sulfonic acid, and perfluorosulfonic acid represented by Nafion. Etc.

  Examples of the chemical oxidant having a standard electrode potential of 0.6 V or higher with respect to the standard hydrogen electrode include ammonium peroxodisulfate (2.0), hydrogen peroxide (1.78), potassium dichromate (1 .3), potassium permanganate (1.49), sodium chlorate (1.45), ceric ammonium nitrate (1.44), sodium iodate (1.085), iron chloride (0.68), etc. can give. In addition, the numerical value in the said parenthesis is a value of the standard electrode potential on the basis of a standard hydrogen electrode.

[Poly (meth) acrylic acid (B)]
The said poly (meth) acrylic acid means the polyacrylic acid and polymethacrylic acid which have a carboxyl group in the structure, or the derivative induced | guided | derived from these, These can be used individually or in combination. In particular, those in which at least a part of the carboxyl group in the polymer 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 poly (meth) acrylic acid (B) is used in a range of 1 to 100 parts by weight, preferably 2 to 100 parts by weight with respect to 100 parts by weight of the porous carbon material (A) whose surface is coated with a conductive polymer. 70 parts by weight, more preferably 5 to 40 parts by weight. That is, there is a tendency that an electricity storage device excellent in energy density cannot be obtained if the poly (meth) acrylic acid (B) is too much or too little.

[Production of electrodes]
The positive electrode 2 can be produced, for example, as follows. That is, the poly (meth) acrylic acid (B) is dissolved in water, the porous carbon material (A) whose surface is coated with a conductive polymer in this aqueous solution, and, if necessary, a conductive assistant such as carbon black. A paste in which a binder such as an agent and vinylidene fluoride is added and these are sufficiently dispersed is prepared. The paste is applied to the current collector 1 to a predetermined thickness and dried to produce a porous and thin-film positive electrode 2 containing the component (A) and the component (B) on the current collector 1. Can do.

  The porosity of the positive electrode 2 is preferably 50 to 80%, more preferably 60 to 70%.

  The porosity (%) of the electrode (positive electrode 2) can be calculated by [(apparent volume of electrode−true volume of electrode) / apparent volume of electrode] × 100. Here, the true volume of the electrode refers to the “volume of the electrode constituent material”. Specifically, using the weight ratio of the constituent material of the electrode and the value of the true density of each constituent material, the average of the entire electrode constituent material is obtained. It can be obtained by calculating the density and dividing the total weight for the electrode component by this average density. The apparent volume of the electrode refers to “electrode area of the electrode × electrode thickness”. Specifically, the volume of the electrode substance, the volume of the void in the electrode, and the volume of the space of the uneven portion on the electrode surface The sum of

  Moreover, the true density (true specific gravity) of each constituent material used above was activated carbon 2.0, polyacrylic acid 1.2, Denka black (acetylene black) 2.0.

  In the positive electrode 2 thus produced, poly (meth) acrylic acid (B) exists in the electrode as a mixture with the porous carbon material (A) whose surface is coated with the conductive polymer. , Fixed in the electrode. The poly (meth) acrylic acid (B) thus fixed in the vicinity of the component (A) is used for charge compensation during oxidation / reduction of the component (A).

  In addition, it is unclear why the electricity storage device using the positive electrode 2 has a high capacity. However, the B component is fixedly arranged in the vicinity of the A component, so that an appropriate electrode active material concentration environment can be obtained. In addition, it is conceivable that the ions that are inserted and desorbed from the A component can be easily moved.

  Furthermore, the polyacrylate anion, which is a B component fixed in the electrode, becomes a fixed ion of a cation such as lithium ion, contributing to the so-called rocking chair type ion transfer, and the capacity is reduced even if the total electrolyte weight is reduced. It is thought that it is preventing the decline.

<About negative electrode>
As the negative electrode 4, metallic lithium, a carbon material into which lithium ions can be inserted / extracted during oxidation / reduction, silicon, tin, and the like are preferably used. A porous carbon material may be used. In the present invention, “use” not only means that only the forming material is used, but also includes the case where the forming material is used in combination with another forming material. The use ratio of the other forming material is set to less than 50 parts by weight of the forming material. And when negative electrode 4 itself has high electroconductivity, it is not necessary to use a collector.

<About the electrolyte layer>
The electrolyte layer 3 is composed of an electrolyte, and in particular, a sheet formed by impregnating a separator with an electrolytic solution or a sheet formed of a solid electrolyte is preferably used. In addition, the sheet | seat which consists of solid electrolyte itself serves as the separator itself.

  The electrolyte is composed of a solute and, if necessary, a solvent and various additives. Examples of the solute include at least one cation such as proton, alkali metal ion, quaternary ammonium ion, quaternary phosphonium ion, sulfonate ion, perchlorate ion, tetrafluoroborate ion, hexafluorophosphorus A combination of at least one anion such as acid ion, hexafluoroarsenic ion, halogen ion, phosphate ion, sulfate ion or nitrate ion is preferably used.

  Water can be used as a solvent for dissolving the solute. In addition, organic solvents such as carbonates, alcohols, nitriles, amides, ethers and the like can also be used. Furthermore, the above-mentioned solvent includes an operating voltage such as an interfacial controller for electrodes such as vinylene carbonate, an overcharge inhibitor such as biphenyl, cyclohexylbenzene, and anisole fluoride, and a flame retardant such as phosphate ester and phosphazene, Various additives for ensuring charge / discharge speed, safety, life characteristics and the like may be added. In addition, what melt | dissolved the said solute in the solvent may be called electrolyte solution.

<Current collector>
As the current collectors 1 and 5 in FIG. 1, those having characteristics such as excellent electronic conductivity, volume reduction inside the battery (thinning), and easy processing can be used. Examples of those satisfying such characteristics include metal foils and meshes such as nickel, aluminum, stainless steel, and copper. The positive electrode current collector (for example, current collector 1) and the negative electrode current collector (for example, current collector 5) may be made of the same material or different materials.

  The power storage device uses a separator (not shown) in addition to the current collector 1, the positive electrode 2, the electrolyte layer 3, and the negative electrode 4. As such a separator, for example, an electrical short circuit between the positive electrode and the negative electrode can be prevented, and further, an electrochemically stable, high ion permeability, and a certain mechanical strength. A porous sheet can be used. Especially, the porous sheet which consists of resin, such as paper, a nonwoven fabric, a polypropylene, polyethylene, a polyimide, is used preferably. These may be used alone or in combination of two or more. Moreover, as above-mentioned, when the electrolyte layer 3 is a sheet | seat which consists of solid electrolytes, since it itself serves as a separator, it is not necessary to use another separator separately.

  The assembly of the electricity storage device is preferably performed in an atmosphere of an inert gas such as an ultrahigh purity argon gas in a glove box.

  According to the electricity storage device of the present invention, the positive electrode 2 is composed of a composite containing a porous carbon material (A) and a poly (meth) acrylic acid (B), the surfaces of which are coated with a conductive polymer. Since the poly (meth) acrylic acid (B) is fixed to the poly (meth) acrylic acid, the poly (meth) acrylic acid has a binder function, and it is not necessary to separately use another binder when forming the positive electrode 2. Or it can be reduced. Therefore, the internal resistance of the positive electrode 2 can be reduced, and a high energy density can be obtained.

  Furthermore, since the surface of the porous carbon material of the positive electrode 2 is coated with a conductive polymer, the conductivity of the positive electrode 2 is improved, high-speed charge / discharge of the electricity storage device is possible, and the capacity density is greatly increased. Has improved. Further, since the positive electrode 2 is formed to be porous, the surface area thereof is increased, more ions can be adsorbed, and the capacity density of the electricity storage device is further improved. Since the negative electrode 4 used together with the special positive electrode 2 is made of lithium metal, not only charging / discharging by adsorption / desorption of ions in the positive electrode 2 but also a Faraday reaction in the negative electrode 4 can be used. Has a higher energy density.

  Moreover, in the said embodiment, although the electrode for electrical storage devices of this invention is used as the positive electrode 2, it can be used not only as a positive electrode but as a negative electrode. However, it is preferable to use it as a positive electrode.

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

  First, prior to the production of electricity storage devices (cells) as examples and comparative examples, the following components were prepared and prepared.

[Preparation of porous carbon material (A) whose surface is coated with a conductive polymer]
To 423.6 g of ion-exchanged water, 5.12 g (0.0245 mol) of 42 wt% tetrafluoroboric acid (made by Wako Pure Chemical Industries, Ltd., special grade) was added and stirred to obtain an aqueous tetrafluoroboric acid solution. . To this tetrafluoroboric acid aqueous solution, 1.25 g (0.0134 mol) of aniline was added and stirred to obtain a transparent aniline salt aqueous solution.

  Next, an aqueous oxidizing agent solution in which 1.53 g (0.0067 mol) of ammonium peroxodisulfide was dissolved in 13.8 g of ion-exchanged water was prepared, added to the obtained aniline salt aqueous solution and stirred, and colorless and transparent An aniline / oxidant 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 starts, this aniline / oxidant aqueous solution is treated with a steam activated activated carbon (JFE Chemical) as a porous carbon material. 50 g (activated charcoal / aniline weight ratio 40) manufactured by Kogyo Co., Ltd. was added, and the mixture was dispersed for 2 minutes with an ultrasonic homogenizer, and the activated carbon was suspended in the aniline / oxidant aqueous solution.

  The aniline / oxidant aqueous solution in which the activated carbon was suspended was defoamed for 5 minutes under a reduced pressure of 30 hPa, and the aniline / oxidant aqueous solution was introduced into the pores of the activated carbon. Thereafter, when the pressure is returned to atmospheric pressure and stirring is continued, oxidative polymerization of aniline is started, and as it progresses, the initially colorless and transparent aniline / oxidant aqueous solution turns blue, and further, blue-green, It changed to blackish green.

The aniline oxidation polymer thus obtained was filtered under reduced pressure to obtain a black powder. The black powder was washed with acetone and then filtered under reduced pressure, and this was repeated three times. The washed black powder was vacuum-dried in a desiccator at room temperature (approximately 25 ° C.) for 10 hours, thereby conducting a conductive polyaniline / activated carbon composite having tetrafluoroboric acid as a dopant (the surface was coated with a conductive polymer). 51.2 g of porous carbon material (A)) was obtained. The weight of the conductive polyaniline / activated carbon composite thus obtained was increased by 1.2 g relative to the activated carbon used. That is, the ratio of the weight increase to the conductive polyaniline / activated carbon composite was 2.3% by weight. The specific surface area of the conductive polyaniline / activated carbon composite was 1600 m ² / g according to the BET method.

[Preparation of poly (meth) acrylic acid (B)]
Polyacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight 800,000) is dissolved in water. To this aqueous solution, 1/2 equivalent of lithium hydroxide of carboxylic acid is added and stirred, and the concentration is 4.5% by weight. A viscous polyacrylic acid aqueous solution was obtained. In this polyacrylic acid aqueous solution, about 50% of the carboxyl groups of polyacrylic acid were lithium chloride.

[Preparation of negative electrode]
A 50 μm thick metal lithium foil (Honjo Metal Co., Ltd.) was prepared.

[Preparation of electrolyte]
An ethylene carbonate / dimethyl carbonate solution (manufactured by Kishida Chemical Co., Ltd.) of 1 mol / dm ³ concentration of lithium tetrafluoroborate (LiBF ₄ ) was prepared.

[Preparation of separator]
A nonwoven fabric (manufactured by Hosen Co., Ltd., TF40-50, porosity: 55%) was prepared.

  Using the materials prepared and prepared, cells of Examples 1 to 4 and Comparative Examples 1 to 8 were produced by the following method. The obtained cell was evaluated by calculating the capacity density per activated carbon weight (mAh / g) and the capacity density per total weight of the activated carbon and the electrolyte (mAh / g) by the method described below. .

[Example 1]
<Preparation of positive electrode sheet>
A positive electrode sheet that is a composite of the current collector 1 and the positive electrode 2 was produced according to the following methods (1) to (3). That is, first, (1) a paste for forming the positive electrode 2 is prepared, and then (2) the paste is applied onto the current collector 1, and a composite sheet of the current collector 1 and the positive electrode 2 is formed. Make it. Then, (3) the obtained composite sheet was punched into a predetermined shape to produce a target positive electrode sheet. Details are shown below.

(1) Preparation of positive electrode 2 forming paste 4.00 g of the conductive polyaniline / activated carbon composite powder (component A) prepared above and 0.53 g of conductive carbon black powder (Denka Black, Denki Kagaku Kogyo Co., Ltd.) were mixed. Then, 19 g of the 4.5 wt% lithium polyacrylate aqueous solution prepared above and 16.0 g of distilled water were added thereto and mixed with a spatula to obtain a paste. Next, this paste was treated with an ultrasonic homogenizer for 5 minutes, and further subjected to mild dispersion treatment (manufactured by Primix Co., Ltd., Fillmix 40-40 type) to obtain a paste having fluidity. This fluid paste was defoamed (Shinky Corp., Awatori Nertaro) to obtain a positive electrode 2 forming paste.

(2) Production of Composite Sheet of Current Collector 1 and Positive Electrode 2 Using a desktop automatic coating apparatus (manufactured by Tester Sangyo Co., Ltd.), the paste for forming the positive electrode 2 after the defoaming is used. Coating was performed on the prepared current collector 1 at a coating speed of 10 mm / second using a doppling applicator. This was allowed to stand at room temperature (approximately 25 ° C.) for 45 minutes, then placed on a hot plate adjusted to a temperature of 100 ° C. for 1 hour, and dried to form a composite of current collector 1 and positive electrode 2 A sheet was produced.

(3) Preparation of positive electrode sheet 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, thereby preparing a positive electrode sheet. The thickness of the positive electrode 2 calculated by subtracting the thickness of the current collector 1 from the thickness of the positive electrode sheet was 366 μm. Moreover, the porosity of the positive electrode 2 was 70%.

<Assembly of cell>
Using the prepared material and the produced positive electrode sheet, a cell as an electricity storage device was assembled according to the following method.

  First, before assembling to a cell, the produced positive electrode sheet and the prepared separator were vacuum-dried at 100 degreeC for 5 hours using the vacuum dryer. Then, 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. Then, the prepared electrolytic solution is injected into the cell so as to be 4.5 times the weight (mg) of the conductive polyaniline / activated carbon composite powder (component A) that forms the positive electrode 2, and is a power storage device. Completed the cell. That is, the injected electrolyte weight (mg) is electrolyte weight (mg) / [conductive polyaniline / activated carbon composite powder (component A)] weight (mg) = 4.5 (mg / mg). .

[Examples 2 to 4]
Except for changing the weight of the electrolyte (mg) to the weight (mg) of the conductive polyaniline / activated carbon composite powder (component A) as shown in Table 1 below, the same as in Example 1 A cell was produced.

[Comparative Example 1]
In Example 1, instead of the conductive polyaniline / activated carbon composite powder (component A), water vapor activated activated carbon (manufactured by JFE Chemical Co., JSC18) was used, and a 4.5 wt% aqueous lithium polyacrylate solution (component B) ) Instead of 19 g, SBR emulsion (manufactured by JSR, TRD2001: SBR content 48 wt%) 0.31 g and poly (N-vinylpyrrolidone)
A cell was produced in the same manner as in Example 1 except that a mixed solution with 1.76 g of an aqueous solution (manufactured by Nippon Shokubai Co., Ltd., K-90W: poly (N-vinylpyrrolidone) content 19.8% by weight) was used. .

[Comparative Examples 2 to 4]
Except for changing the weight of the electrolyte (mg) to the weight (mg) of the conductive polyaniline / activated carbon composite powder (component A) as shown in Table 2 below, the same as in Comparative Example 1 A cell was produced.

[Comparative Example 5]
In Example 1, instead of 19 g of 4.5 wt% lithium polyacrylate aqueous solution (component B), 0.31 g of SBR emulsion (manufactured by JSR, TRD2001: SBR content 48 wt%) and poly (N-vinylpyrrolidone) ) A cell was prepared in the same manner as in Example 1 except that a mixed solution with 1.76 g of an aqueous solution (manufactured by Nippon Shokubai Co., Ltd., K-90W: poly (N-vinylpyrrolidone) content 19.8% by weight) was used. did.

[Comparative Examples 6-8]
The electrolyte solution weight (mg) was changed in the same manner as in Comparative Example 5 except that it was changed as shown in Table 3 below with respect to the conductive polyaniline / activated carbon composite powder (component A) weight (mg). A cell was produced.

<Evaluation of cell>
The battery was charged with a constant current of 3.8 V at a current of 0.77 mA, and after reaching 3.8 V, the battery was switched to a constant voltage of 3.8 V and charged until the current value reached 0.15 mA. Then, after a 30-minute interval, constant current discharge was performed until the voltage became 2.0 V at a current of 0.77 mA. This charging / discharging was made into 1 cycle and this was repeated 15 cycles. An interval of 30 minutes is provided between the above cycles. And the discharge capacity of 1st cycle and 15th cycle was measured, and electroconductive polyaniline / activated carbon composite powder (component A) per weight (mg) (in Comparative Examples 1 to 4, per steam activated carbon weight (mg)) Calculated. Further, the capacity density (mAh / g) per total weight of the conductive polyaniline / activated carbon composite powder (component A) and the electrolytic solution (in Comparative Examples 1 to 4, per total weight (mg) of the steam activated activated carbon and the electrolytic solution. ) Was also calculated. These results are summarized in Tables 1 to 3 below. The “activated carbon” in Tables 1 to 3 is activated carbon used for each positive electrode material, that is, one of conductive polyaniline / activated carbon composite powder (component A) and water vapor activated activated carbon.

  From the above results, it was found that Examples 1 to 4 had a large capacity density (mAh / g) per total weight of the activated carbon and the electrolyte solution, and did not decrease even when the electrolyte solution weight decreased. Furthermore, the reduction rate after 15 cycles was low, indicating excellent cycle characteristics. In contrast, Comparative Examples 1 to 8 had a small capacity density (mAh / g) per total weight of the activated carbon and the electrolytic solution, and decreased in proportion to the decrease in the electrolytic solution weight. Further, the reduction rate after 15 cycles was high, and it was found that the cycle characteristics were inferior. As described above, according to the present invention, an electricity storage device having excellent capacity density and cycle characteristics can be realized. Further, since the capacity density does not decrease even when the weight of the electrolytic solution is reduced, it is possible to prevent deterioration due to depletion of the electrolytic solution and to reduce the size of the electricity storage device.

  In addition, even when polymethacrylic acid was used as the (B component) of the present invention, results almost the same as in the above examples were obtained.

  The power storage device of the present invention can be used in the same applications as conventional secondary batteries and high-capacity capacitors. For example, portable electronic devices such as portable PCs, cellular phones, and personal digital assistants (PDAs), and hybrid electric vehicles It can be widely used as a driving power source for 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 (5)

An electricity storage device having an electrolyte layer and a positive electrode and a negative electrode provided therebetween, wherein the electrode used for at least one of the positive electrode and the negative electrode is made of a composite containing the following (A) and (B) and the electrode An electrical storage device characterized in that the following (B) is fixed therein.
(A) A porous carbon material whose surface is coated with a conductive polymer.
(B) Poly (meth) acrylic acid.   The electricity storage device according to claim 1, wherein an electrode used for at least one of a positive electrode and a negative electrode of the electricity storage device is formed to be porous. In an electricity storage device having an electrolyte layer and a positive electrode and a negative electrode provided therebetween, the electrode is used for at least one of the positive electrode and the negative electrode, and is composed of a composite containing the following (A) and (B) and the electrode An electrode for an electricity storage device, wherein the following (B) is fixed inside.
(A) A porous carbon material whose surface is coated with a conductive polymer.
(B) Poly (meth) acrylic acid.   The electrode for an electrical storage device according to claim 3, wherein the electrode used for at least one of the positive electrode and the negative electrode of the electrical storage device is formed to be porous. A porous sheet for an electricity storage device electrode, comprising a composite containing the following (A) and (B), and the following (B) being fixed inside the composite: .
(A) A porous carbon material whose surface is coated with a conductive polymer.
(B) Poly (meth) acrylic acid.

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