JP2012015377A - Power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power storage device having a high capacity and excellent pulse discharge characteristics.SOLUTION: The power storage device comprises: a positive electrode 10; a negative electrode 32; and a nonaqueous electrolyte. The positive electrode 10 contains a polymer which contains tetrachalcogenofulvalenes skelton in repeating unit, and an active carbon as an electrode active material. The active carbon and the polymer have a shape of particles, respectively, so that the nonaqueous electrolyte can touch the active carbon and the polymer directly. The positive electrode 10 in the power storage device has a structure where the polymer does not cover the surface of the active carbon.

Description

  The present invention relates to an electricity storage device having improved pulse discharge characteristics.

  In recent years, portable electronic devices such as portable audio devices, cellular phones, and laptop computers have become widespread. From the viewpoint of energy saving or the reduction of carbon dioxide emissions, hybrid vehicles using both an internal combustion engine and electric mobility are beginning to spread. With these spreads, there is an increasing demand for higher performance of power storage devices used as power sources. Under such circumstances, there is an increasing expectation for a capacitor as an electricity storage device having excellent output characteristics and repetition characteristics.

  Patent Document 1 discloses an electric double layer capacitor using activated carbon as an electrode active material for both a positive electrode and a negative electrode. Patent Literature 2 discloses a lithium ion capacitor using activated carbon as a positive electrode and a carbon electrode capable of inserting and extracting lithium ions into a negative electrode.

  However, only the surface of the activated carbon contributes to the storage capacity in the activated carbon. For this reason, the electric double layer capacitor using activated carbon for both positive and negative electrodes has a low capacity. The same applies to the lithium ion capacitor, and the capacity is low because activated carbon is used for the positive electrode.

  Patent Documents 3 and 4 describe a high-capacity capacitor using an organic compound having a π-electron conjugated cloud represented by tetrathiafulvalene (hereinafter referred to as TTF) instead of activated carbon. Among them, it is disclosed that a polymer compound into which a plurality of sites having a π-electron conjugated cloud are introduced is excellent in durability. For example, polyacetylene, a polymer compound having a polymethyl methacrylate chain as a main chain, and a polymer compound obtained by dehydrating condensation of a side chain having carboxytetrathiafulvalene to a polyvinyl alcohol main chain are disclosed.

  By using such an organic compound as an alternative electrode active material for activated carbon, it is possible to contribute to higher capacity, but the pulse discharge characteristics are lower than that of an electric double layer capacitor.

  Patent Document 4 discloses that activated carbon is used as a conductive base material of an electrode, and an organic compound that is an electrode active material is supported on the activated carbon, thereby suppressing capacity deterioration associated with a charge / discharge cycle. ing. Patent Document 5 discloses a capacitor electrode including an electric double layer capacitor material and activated carbon whose surface is coated with a pseudo-capacitance type organic capacitor material as a capacitor having a large capacity and improved output characteristics. Yes. Specifically, an electrode having a structure in which the surface of activated carbon is coated with an N-type or P-type conductive polymer is disclosed.

  However, if an electrode having a structure in which an organic compound is supported on activated carbon or an electrode having a structure in which the surface of activated carbon is coated with a conductive polymer can be used, it can contribute to higher capacity, but pulse discharge characteristics Is still lower than electric double layer capacitors.

International Publication No. 07/023664 International Publication No. 07/046382 JP 2007-281107 A JP 2004-111374 A JP 2003-92104 A

  As described above, it is difficult to increase the capacity of the electric double layer while maintaining the excellent pulse discharge characteristic which is an advantage of the electric double layer capacitor.

  This invention is made | formed in view of such a situation, and it aims at providing the electrical storage device which has the outstanding pulse discharge characteristic with high capacity | capacitance.

  In order to solve the above problems, the present inventors have conducted intensive studies on an electricity storage device using an electrode containing both a polymer containing a tetracargokenofulvalene skeleton in a repeating unit and activated carbon as an electrode active material. went. As a result of studies, it has been clarified that the performance of an electricity storage device using such an electrode greatly depends on the electrode structure. Furthermore, it has been clarified that depending on the specific electrode structure, an electricity storage device having the advantages of both electrode active materials, that is, having both high capacity and good pulse discharge characteristics can be obtained.

That is, the present invention
A positive electrode, a negative electrode, and a non-aqueous electrolyte;
The positive electrode includes, as an electrode active material, a polymer containing a tetrachalcogenofulvalene skeleton in a repeating unit, and activated carbon,
Provided is an electricity storage device in which the activated carbon and the polymer each have a particle shape so that the non-aqueous electrolyte can directly contact the activated carbon and the polymer, respectively.

In another aspect, the present invention provides:
A step of preparing a paste containing a solution in which a polymer containing a tetrachalcogenofulvalene skeleton in a repeating unit is dissolved in a solvent, and a conductive additive;
Removing the solvent from the paste to form composite particles containing the polymer and the conductive additive;
Using a mixture obtained by kneading the composite particles and activated carbon, and forming a mixture layer containing the composite particles and the activated carbon on a positive electrode current collector. I will provide a.

  The electricity storage device of the present invention includes activated carbon and a polymer as electrode active materials in the positive electrode. The polymer is a polymer containing a tetrachalcogenofulvalene skeleton as a redox site in a repeating unit. Therefore, according to the electricity storage device of the present invention, charging and discharging can be performed stably and repeatedly. The activated carbon and the polymer each have a particle shape. Preferably, the polymer does not coat the surface of the activated carbon. Therefore, charging / discharging derived from the electric double layer capacity of the activated carbon can be performed without reducing the surface area of the activated carbon. That is, excellent pulse discharge characteristics can be obtained. Furthermore, since the polymer is an electrode active material having a capacity higher than that of activated carbon, an electricity storage device having a capacity higher than that obtained when only activated carbon is used as the electrode active material in the positive electrode can be obtained. Thus, according to the present invention, an electric storage device having excellent pulse discharge characteristics and a high capacity can be realized.

It is typical sectional drawing which shows the positive electrode of the electrical storage device of Embodiment 1 by this invention. It is typical sectional drawing which shows the coin-type electrical storage device which is one Embodiment of the electrical storage device by this invention. It is typical sectional drawing which shows the positive electrode of the electrical storage device of Embodiment 2 by this invention. It is typical sectional drawing which expands and shows a part of active material layer of the electrode shown in FIG. It is a graph which shows the evaluation result of Examples 1, 2 and Comparative Examples 1-3.

  Hereinafter, embodiments of the electricity storage device of the present invention will be described.

(Embodiment 1)
FIG. 1 schematically shows a cross-sectional structure of a positive electrode 10 in an embodiment of an electricity storage device of the present invention. The positive electrode 10 includes a positive electrode current collector 11 and a positive electrode active material layer 12 provided on the positive electrode current collector 11.

  The positive electrode current collector 11 is not particularly limited as long as it is a material that can be used as a current collector in a low resistance substance having electrical conductivity, for example, a positive electrode or a negative electrode of a secondary battery or an electric double layer capacitor. The positive electrode current collector 11 is made of a metal foil, a metal mesh, a metal porous body, or a resin film containing a conductive filler made of metal. Examples of metals that can be used for the positive electrode current collector 11 include aluminum, gold, silver, stainless steel, and aluminum alloys. Among these, as the positive electrode current collector 11, an aluminum foil having a thickness of about 5 to 30 μm is preferably used. This is because the aluminum foil is excellent in electrochemical stability in the operating range of the positive electrode 10 and can maintain a sufficient strength even if it is a thin film having a thickness of about 5 to 30 μm. Further, the surface of the metal foil may be roughened by electrolytic etching treatment, blast treatment or the like.

  The positive electrode active material layer 12 includes at least two types of electrode active materials, that is, activated carbon 13 and a polymer 14. The polymer 14 includes a tetrachalcogenofulvalene skeleton, which will be described in detail below, in the repeating unit, and the polymer 14 does not cover the surface of the activated carbon 13 in the positive electrode active material layer 12. That the polymer 14 does not cover the surface of the activated carbon 13 means that the polymer 14 does not exist so as to cover the surface of the activated carbon 13, and the activated carbon 13 and the polymer 14 exist in different particles. State. In other words, the activated carbon and the polymer each have a particle shape so that the non-aqueous electrolyte can directly contact the activated carbon and the polymer, respectively. As long as the activated carbon 13 and the polymer 14 each form particles, the region where the particles are present in the positive electrode active material layer 12 is not limited and may be in contact with each other. Further, the positive electrode active material layer 12 has a substrate 17 containing a nonaqueous electrolyte. Activated carbon 13 and polymer 14 are dispersed in substrate 17. When the volume of the substrate 17 is sufficiently smaller than the volumes of the activated carbon 13 and the polymer 14, the substrate 17 fills the gap around the activated carbon 13 and the polymer 14. The substrate 17 may be composed of only a non-aqueous electrolyte, or may contain at least one selected from a binder and a conductive aid as necessary.

  Hereinafter, the reaction mechanism of the positive electrode will be described. Hereinafter, a “polymer containing a tetrachalcogenofulvalene skeleton in a repeating unit” may be referred to as a “polymer containing a tetrachalcogenofulvalene skeleton”.

  Patent Document 5 discloses an electrode structure in which a surface of activated carbon that is an electric double layer capacitor material is coated with a conductive polymer compound that is an organic capacitor material. The present inventors used a polymer containing a tetrachalcogenofulvalene skeleton to form an electrode having the same structure as the electrode structure disclosed in Patent Document 5, that is, a structure in which a polymer is coated on the surface of activated carbon. The electricity storage device used was examined. As a result, it was found that the expected combined effect, that is, the effect of both high capacity and excellent pulse discharge characteristics, could not be obtained sufficiently compared with the electricity storage device using activated carbon as the electrode active material. .

  As a result of analyzing this cause, the polymer containing the tetrachalcogenofulvalene skeleton coated the surface of the activated carbon, which may be caused by filling the surface pores contributing to the charge / discharge capacity of the activated carbon. It was revealed. In addition, since the polymer containing the tetrachalcogenofulvalene skeleton does not have electronic conductivity, it is difficult to form a conductive path between the activated carbon and the positive electrode current collector, and the charge / discharge characteristics are also deteriorated. It was revealed. From the above, in a composite electrode using activated carbon and a polymer containing a tetrachalcogenofulvalene skeleton in the repeating unit as an electrode active material, it is important that the polymer does not cover the surface of the activated carbon. It became clear that there was.

  A polymer including a tetrachalcogenofulvalene skeleton has no conductivity compared to a conductive polymer, or a semiconductor level between a metal and an insulator even if it has a polymer. However, a polymer including a tetrachalcogenofulvalene skeleton is a higher-capacity electricity storage material than a conductive polymer. In the case of using a polymer containing a tetrachalcogenofulvalene skeleton and activated carbon, it is considered that an electrode structure different from that in the case of using a conventional conductive polymer is necessary.

  As shown in FIG. 1, in the positive electrode active material layer 12, the polymer 14 including the tetrachalcogenofulvalene skeleton does not cover the surface of the activated carbon 13. That is, the activated carbon 13 and the polymer 14 exist in different particles. The nonaqueous electrolyte can directly contact each of the activated carbon 13 and the polymer 14 in the active material layer 12. Therefore, the charge / discharge capacities of both the activated carbon 13 and the polymer 14 can be used, which can contribute to an increase in capacity. The excellent pulse characteristics of the activated carbon 13 are not impaired.

  As will be described in detail below, the polymer 14 undergoes a redox reaction with the movement of anions in the non-aqueous electrolyte. According to the electrode structure in the present embodiment, the surface of the activated carbon 13 is in contact with the nonaqueous electrolyte, and the pores of the activated carbon 13 include the nonaqueous electrolyte. Since many electrolytes are present in the surface pores of the activated carbon 13, the active material layer 12 can contain a sufficient amount of electrolyte. For this reason, at the time of the oxidation-reduction reaction, the polymer 14 in the active material layer 12 tends to react uniformly with the anion. Furthermore, since many anions exist around the polymer 14, the migration resistance of anions in the active material layer 12 decreases. That is, the resistance during charging / discharging is reduced. In addition, since the polymer 14 does not cover the activated carbon 13, a conductive path from the activated carbon 13 to the positive electrode current collector 11 is secured, and charging / discharging derived from the activated carbon 13 is not hindered. Therefore, excellent pulse discharge characteristics can be obtained as compared with the case where the positive electrode having only the polymer 14 is used as the electrode active material.

  As described above, according to this embodiment, the charge / discharge capacities of both the activated carbon 13 and the polymer 14 can be used while maintaining the pulse discharge characteristics of the activated carbon, and the excellent pulse discharge characteristics and high capacity can be achieved. A compatible positive electrode can be realized.

  The polymer 14 will be described in detail below. In the polymer 14, a portion having a tetrachalcogenofulvalene skeleton has a π-conjugated electron cloud and functions as a redox site. The structure of the part is preferably represented by the following formula (1).

In the formula (1), X ¹ , X ² , X ³ , and X ⁴ are each independently a sulfur atom, an oxygen atom, a selenium atom, or a tellurium atom. One or two selected from Ra, Rb, Rc, and Rd is a bond for bonding to the other part of the main chain or side chain of the polymer. The remaining three or two selected from Ra, Rb, Rc, and Rd are each independently a chained aliphatic group, cyclic aliphatic group, hydrogen atom, hydroxyl group, cyano group, amino group , A nitro group, a nitroso group, or an alkiothio group. The chain aliphatic group and the cyclic aliphatic group may each include at least one selected from the group consisting of an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, a phosphorus atom, and a boron atom. . Ra and Rb may be bonded to each other to form a ring, and Rc and Rd may be bonded to each other to form a ring.

In the formula (1), a compound in which X ¹ , X ² , X ³ , and X ⁴ are sulfur atoms, and Ra, Rb, Rc, and Rd are hydrogen atoms is a tetrathiafur represented by the following formula (2) Valene (hereinafter sometimes abbreviated as TTF). Hereinafter, taking TTF as an example, a mechanism in which a portion having a tetrachalcogenofulvalene skeleton functions as a redox site and reacts with an anion in an electrolyte will be described.

When TTF is subjected to one-electron oxidation in a state of being dissolved in an electrolytic solution, as shown in the following formula (3), one electron is extracted from one of the two five-membered rings, and a positive 1 Charged to the valence. As a result, one anion (PF ₆ ^{− in} the case of formula (3)) is coordinated to the tetrathiafulvalene skeleton as a counter ion. When one-electron oxidation is further performed from this state, one electron of the other five-membered ring is extracted and charged to a positive divalent value. As a result, another anion is coordinated to the tetrathiafulvalene skeleton as a counter ion.

  Even in the oxidized state, the cyclic skeleton is stable, and by receiving electrons again, the cyclic skeleton can be reduced to return to an electrically neutral original state. In other words, the oxidation-reduction reaction exemplified in the above formula (3) is reversible. The electricity storage device of the present invention utilizes such redox characteristics of the tetrathiafulvalene skeleton.

  For example, when TTF is used for the positive electrode of the electricity storage device, the tetrathiafulvalene skeleton moves toward an electrically neutral state in the discharge process. In other words, the reaction in the left direction proceeds in Equation (3). On the contrary, in the charging process, the tetrathiafulvalene skeleton proceeds to a positively charged state, that is, the reaction in the right direction proceeds in Formula (3).

In the formula (1), X ¹ , X ² , X ³ , and X ⁴ are each independently a sulfur atom, a selenium atom, a tellurium atom, or an oxygen atom, and Ra, Rb, Rc, and Rd are hydrogen Compounds that are atoms are collectively referred to as tetrachalcogenofulvalene or its oxygen-containing analogs. These compounds have redox properties similar to TTF. For example, TTF Chemistry: Fundamentals and Applications of Tetrathiafulvalene, Journal of the American Chemical Society, 97th edition. , Part 10, 1975, p. 2921-2922, and Chemical Communications, 1997, p. 1925-1926.

  In addition, a compound in which a functional group is bonded to a tetrachalcogenofulvalene skeleton, that is, a compound in which Ra, Rb, Rc, and Rd in the formula (1) have various structures is the same redox as tetrachalcogenofulvalene. Has characteristics. This has been reported, for example, in TTF Chemistry: Fundamentals and Applications of Tetrathiafulvalene, along with methods for synthesizing these compounds. Thus, an important structure for obtaining good redox characteristics is the structure of the tetrachalcogenofulvalene skeleton itself. Accordingly, Ra, Rb, Rc, and Rd in the formula (1) are not particularly limited as long as they are structures that do not contribute to the oxidation-reduction of the tetrachalcogenofulvalene skeleton.

  A molecule including a tetrachalcogenofulvalene skeleton has a lower solubility in an organic solvent as the molecular weight is increased. Therefore, when an organic solvent is contained in the electrolytic solution, by using a polymer containing a tetrachalcogenofulvalene skeleton as an electrode active material, the dissolution of the electrode active material in the electrolytic solution is suppressed, and cycle characteristics Can be prevented.

  The molecular weight of the polymer is preferably large. Specifically, it is preferable to have four or more tetrachalcogenofulvalene skeletons in one molecule. That is, the degree of polymerization of the polymer (n in formula (4) described later or the sum of n and m in formula (8) described later) is preferably 4 or more. Thereby, an electrode active material that is hardly soluble in an organic solvent can be realized. More preferably, the degree of polymerization of the polymer is 10 or more, and more preferably 20 or more. Although the upper limit of the polymerization degree of a polymer is not specifically limited, From viewpoints of manufacturing cost, a yield, etc., it is 500 or less, for example, Preferably it is 200 or less.

  The tetrachalcogenofulvalene skeleton may be contained in the main chain of the polymer, may be contained in the side chain, or may be contained in both the main chain and the side chain. . When the polymer contains a tetrachalcogenofulvalene skeleton in the main chain, the structure of the polymer is represented, for example, by the following formula (4).

In formula (4), X is an oxygen atom, a sulfur atom, a selenium atom or a tellurium atom. R ⁵ and R ⁶ are each independently a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, a cyclic saturated hydrocarbon group, a cyclic unsaturated hydrocarbon group, a phenyl group, a hydrogen atom, a hydroxyl group, cyano Group, amino group, nitro group, or nitroso group. The chain saturated hydrocarbon group, the chain unsaturated hydrocarbon group, the cyclic saturated hydrocarbon group, and the cyclic unsaturated hydrocarbon group are each selected from the group consisting of an oxygen atom, a nitrogen atom, a sulfur atom, and a silicon atom. At least one kind may be included. R ⁹ represents a linker, and is typically a chain unsaturated hydrocarbon group or a cyclic unsaturated hydrocarbon group containing at least one of an acetylene skeleton and a thiophene skeleton, and includes an oxygen atom, a nitrogen atom, a sulfur atom, And at least one selected from the group consisting of silicon atoms. n is an integer representing the number of repeating monomer units.

Formula (4) is an alternating copolymer in which repeating units including a tetrachalcogenofulvalene skeleton and repeating units not including a tetrachalcogenofulvalene skeleton (R ⁹ in Formula (4)) are alternately arranged. However, the order of the coupling is not particularly limited. That is, a polymer having a repeating unit containing a tetrachalcogenofulvalene skeleton and a repeating unit not containing a tetrachalcogenofulvalene skeleton in the main chain includes a block copolymer, an alternating copolymer, and a random copolymer. Any of copolymers may be used. In the case of a block copolymer, a unit in which repeating units including a tetrachalcogenofulvalene skeleton are directly bonded continuously and a unit in which repeating units not including a tetrachalcogenofulvalene skeleton are continuously bonded alternately It has an ordered structure. In addition, the random copolymer has a structure in which repeating units including a tetrachalcogenofulvalene skeleton and repeating units not including a tetrachalcogenofulvalene skeleton are randomly arranged.

For example, a polymer in which X in formula (4) is a sulfur atom, R ⁵ and R ⁶ are phenyl groups, and R ⁹ is a diethynylbenzene group is represented by the structural formula shown in formula (5). It is a polymer. The polymer represented by the formula (5) is an alternating copolymer of 4,4′-diphenyltetrathiafulvalene and 1,3-diethynylbenzene. N in the formula (5) is an integer representing the number of repeating monomer units.

  In addition, the polymer represented by the formula (4) includes a bond that forms the main chain of the polymer in five-membered rings having different tetrachalcogenofulvalene skeletons. It may contain a bond that forms the main chain of the coalescence. In the case where the same 5-membered ring of the tetrachalcogenofulvalene skeleton includes a bond that forms the main chain of the polymer, for example, a polymer having a structure represented by the following formula (6) can be given.

In formula (6), X is an oxygen atom, a sulfur atom, a selenium atom, or a tellurium atom. R ¹⁵ and R ¹⁶ are each independently a chain saturated hydrocarbon group, a chain unsaturated hydrocarbon group, a cyclic saturated hydrocarbon group, a cyclic unsaturated hydrocarbon group, a phenyl group, a hydrogen atom, a hydroxyl group, cyano Group, amino group, nitro group, or nitroso group. The chain saturated hydrocarbon group, the chain unsaturated hydrocarbon group, the cyclic saturated hydrocarbon group, and the cyclic unsaturated hydrocarbon group are each selected from the group consisting of an oxygen atom, a nitrogen atom, a sulfur atom, and a silicon atom. One kind may be included. R ¹⁹ represents a linker, which is typically a chain unsaturated hydrocarbon group or a cyclic unsaturated hydrocarbon group containing at least one of an acetylene skeleton and a thiophene skeleton, and includes an oxygen atom, a nitrogen atom, a sulfur atom, And at least one selected from the group consisting of silicon atoms. n is an integer representing the number of repeating monomer units.

For example, when X is a sulfur atom, R ¹⁵ and R ¹⁶ are thiohexyl groups (C ₆ H ₁₃ S—), and R ¹⁹ is diethynylbenzene, a polymer having a structure represented by the formula (7) It becomes. N in the formula (7) is an integer representing the number of repeating monomer units.

  When the polymer contains a tetrachalcogenofulvalene skeleton in the side chain, the structure of the polymer is represented, for example, by a structure in which two repeating units are bonded to each other in * as shown in the following formula (8). As in the above description, the order in which two repeating units are combined is not particularly limited.

In the formula (8), R ¹⁰ and R ¹² are trivalent groups constituting the main chain of the polymer, and are independently selected from the group consisting of carbon atom, oxygen atom, nitrogen atom and sulfur atom. Including at least one kind and at least one substituent selected from the group consisting of a saturated aliphatic group having 1 to 10 carbon atoms and an unsaturated aliphatic group having 2 to 10 carbon atoms, or at least one hydrogen atom . L ¹ is a monovalent group including an ester group, an ether group, a carbonyl group, a cyano group, a nitro group, a nitroxyl group, an alkyl group, a phenyl group, an alkylthio group, a sulfone group, or a sulfoxide group bonded to R ^12. is there. R ¹¹ is a divalent group bonded to R ¹⁰ and M ^1, and a group consisting of alkylene, alkenylene, arylene, ester, amide, and ether, which may have a substituent having 1 to 4 carbon atoms. It contains at least one selected from M ¹ is a monovalent group that can be represented by the formula (1) bonded to R ¹¹ . n and m are integers representing the number of repetitions of each monomer unit.

  For example, when X is a sulfur atom, a polymer having a structure represented by the following formula (9) is exemplified.

In formula (9), R ²¹ is a divalent group, optionally having 1 to 4 carbon atoms which may have a substituent; alkenylene having 1 to 4 carbon atoms which may have a substituent. An arylene which may have a substituent; an ester; an amide; and at least one selected from the group consisting of ethers. R ²⁰ and R ²² are each independently a saturated aliphatic group having 1 to 4 carbon atoms, a phenyl group, or a hydrogen atom. R ²⁵ , R ²⁶ , and R ²⁷ are each independently a chain aliphatic group, cyclic aliphatic group, hydrogen atom, hydroxyl group, cyano group, amino group, nitro group, nitroso group, or alkylothio group R ²⁵ and R ²⁶ may be bonded to each other to form a ring. L ¹ is a monovalent group including an ester group, an ether group, a carbonyl group, a cyano group, a nitro group, a nitroxyl group, an alkyl group, a phenyl group, an alkylthio group, a sulfone group, or a sulfoxide group. n and m are integers representing the number of repetitions of each monomer unit.

For example, L ¹ in formula (9) is a monovalent group containing an ester group, R ²¹ is a divalent ester group, R ²⁰ and R ²² are methyl groups, R ²⁵ , R ²⁶ , and The polymer in which R ²⁷ is a hydrogen atom has a structure represented by the following formula (10). In formula (10), n and m are integers representing the number of repetitions of each monomer unit.

Next, the activated carbon 13 will be described. The activated carbon 13 is not particularly limited as long as it is a known material used in an electric double layer capacitor, but activated carbon having a large specific surface area is preferable in order to perform charge / discharge with a large current, specifically, a BET specific surface area. It is desirable to use activated carbon of 1000 m ² / g or more. Examples of the activated carbon material include coconut shell, organic resin, petroleum pitch, sawdust, and the like. After carbonizing these raw materials at 900 to 1000 ° C. in an inert atmosphere such as nitrogen gas, activated carbon having an extremely high specific surface area of up to about 2000 m ² / g can be obtained by introducing water vapor as an activation treatment. . Moreover, as an activation process, you may employ | adopt the method using an alkaline solution other than the method by water vapor | steam. Examples of the shape of the activated carbon particles include powders, fibers, flakes (or scales), and the like.

  The positive electrode active material layer 12 may contain a conductive auxiliary agent that assists electronic conductivity in the electrode and / or a binder for maintaining the shape of the positive electrode active material layer 12 as necessary.

  As the conductive auxiliary agent, various electron conductive materials that do not cause a chemical change at the reaction potential of the electrode can be used. Examples of the conductive assistant include carbon materials such as carbon black, graphite, and carbon fiber, metal fibers, metal powders, conductive whiskers, and conductive metal oxides, and may be a mixture thereof. From the viewpoint that the energy density per weight can be increased, it is preferable to use carbon black as a conductive aid. Furthermore, in order to increase the contact area, it is desirable to use carbon black having a large specific surface area as a conductive aid.

  The binder may be either a thermoplastic resin or a thermosetting resin. Examples of the binder include polyolefin resins such as polyethylene and polypropylene; fluorine resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), hexafluoropropylene (HFP), and copolymer resins thereof; Examples thereof include styrene butadiene rubber, polyacrylic acid and copolymer resins thereof.

  The positive electrode 10 in Embodiment 1 can be manufactured by a method of forming a mixture layer including the polymer 14 that is an electrode active material and the activated carbon 13 on the positive electrode current collector 11. In addition, this mixture layer may contain a binder and / or a conductive aid as necessary. In this production method, a dry method or a wet method can be used. However, when the wet method is used, it is necessary not to use a solvent in which the polymer 14 is dissolved. In the dry method, for example, the polymer 14 and the activated carbon 13 are kneaded without using a solvent to obtain a mixture. A mixture layer can be formed by pressure-bonding the obtained mixture on the positive electrode current collector 11. In the wet method, a solvent in which the polymer 14 is not dissolved, for example, an aqueous solution or the like is used when the polymer 14 is dissolved in an organic solvent, and a paste in which the polymer 14 and the activated carbon 13 are dispersed in the solvent is prepared. A mixture layer can be formed on the positive electrode current collector 11 by applying the obtained paste on the positive electrode current collector 11 and removing the solvent in the paste.

  The order of mixing the materials is not particularly limited, but the polymer 14 is preferably made into particles of an appropriate size by grinding before mixing with other materials such as activated carbon. The particle diameter of the polymer 14 is preferably 0.03 μm to 20 μm. By adjusting the particle diameter of the polymer 14 within the above range, a large contact area between the polymer and the electrolytic solution is ensured, and the contact area between the polymer particles and the activated carbon or the conductive auxiliary agent is increased. Electron conductivity can be ensured.

  The particle diameter of the activated carbon 13 is preferably 0.05 μm to 20 μm. By adjusting the particle diameter of the activated carbon 13 within the above range, it is possible to ensure the double layer capacity due to the large specific surface area of the activated carbon, increase the contact area between the activated carbon and the polymer particles, and ensure the electron conductivity. it can.

  The particle diameter of the conductive assistant is preferably 0.03 μm to 20 μm, and more preferably 0.03 μm to 1 μm. By adjusting the particle diameter of the conductive auxiliary agent within the above range, the conductive auxiliary agent is filled in the gaps between the polymer particles and the activated carbon particles, and good conductivity of the electrode can be ensured.

  In the present specification, “particle diameter” means an average particle diameter. “Average particle size” means the particle size at 50% cumulative volume of the particle size distribution measured by Dynamic Light Scattering (DLS).

  In this way, in the positive electrode active material layer 12 formed on the positive electrode current collector 11, the polymer 14 and the activated carbon 13 each have a particle shape, and the polymer 14 covers the surface of the activated carbon 13. Thus, the positive electrode 10 having a structure not formed can be obtained.

  The content of the polymer 14 is preferably 5 to 80 parts by weight, and the content of the activated carbon 13 is preferably 5 to 80 parts by weight. Moreover, it is preferable that content of a conductive support agent is 10-60 weight part.

  FIG. 2 shows a schematic cross section of a coin-type electricity storage device which is an embodiment of the electricity storage device according to the present invention. The electricity storage device 20 has a structure in which the inside is sealed by a coin-type case 21, a sealing plate 25, and a gasket 28. Inside the electricity storage device 20, the positive electrode 10 including the positive electrode active material layer 12 and the positive electrode current collector 11, the negative electrode 32 including the negative electrode active material layer 26 and the negative electrode current collector 27, and the separator 24 are housed. . The positive electrode 10 and the negative electrode 32 face each other with the separator 24 in between, and the positive electrode active material layer 12 and the negative electrode active material layer 26 are disposed so as to be in contact with the separator 24. An electrode group including the positive electrode 10, the negative electrode 32, and the separator 24 is impregnated with an electrolytic solution 29. Since the separator 24 includes a fine space for holding the electrolytic solution 29, the electrolytic solution 29 is held in this fine space.

  The separator 24 is a resin layer made of a resin that does not have electronic conductivity, and is a microporous film that has a large ion permeability and has a predetermined mechanical strength and electrical insulation. From the viewpoint of excellent organic solvent resistance and hydrophobicity, a polyolefin resin in which polypropylene, polyethylene or the like is used alone or in combination is preferable. Instead of the separator 24, an ion conductive resin layer that swells and contains an electrolyte and functions as a gel electrolyte may be provided.

  The negative electrode active material layer 26 includes a negative electrode active material. As the negative electrode active material, activated carbon or a known negative electrode active material capable of reversibly occluding and releasing lithium ions is used. The negative electrode active material capable of reversibly occluding and releasing lithium ions is not particularly limited as long as it is a known negative electrode material in a lithium battery. For example, graphite materials such as natural graphite and artificial graphite, and amorphous carbon materials Lithium metal, lithium-containing composite nitride, lithium-containing titanium oxide, silicon, an alloy containing silicon, silicon oxide, tin, an alloy containing tin, and tin oxide. The negative electrode active material may be a mixture of these negative electrode materials. As the activated carbon used as the negative electrode active material, a known material used as the negative electrode of the electric double layer capacitor can be used. In addition, a known material having a pseudo capacity, which is known as an alternative material for activated carbon, can be used as the negative electrode active material. For the negative electrode current collector 27, for example, a material known as a current collector for a negative electrode for a lithium secondary battery such as copper, nickel, or stainless steel, or a material known as a current collector for an electric double layer capacitor negative electrode such as an aluminum foil is used. be able to.

  In addition to the negative electrode active material, the negative electrode active material layer 26 may include a conductive additive and / or a binder as necessary. As a conductive support agent and a binder, the same material as the conductive support agent and binder which can be used in the positive electrode active material layer 12 can be used.

  The electrolytic solution 29 includes at least one salt of a lithium ion and an anion and a salt of a quaternary ammonium cation and an anion. When the electrolytic solution 29 contains a salt of a quaternary ammonium cation and an anion, the negative electrode active material in the negative electrode has an electric double layer capacity capable of reversibly occluding and releasing the quaternary ammonium cation or anion. preferable. When the electrolytic solution 29 contains a salt of lithium ions and anions, the negative electrode preferably contains a negative electrode active material capable of inserting and extracting lithium ions.

The salt of lithium ion and anion is not particularly limited as long as it is a salt used in a lithium battery, and examples thereof include salts of lithium ions and the following anions. That is, as anions, halide anions, perchlorate anions, trifluoromethanesulfonate anions, tetrafluoroborate anions (BF ₄ ⁻ ), hexafluorophosphate anions (PF ₆ ⁻ ), bis (trifluoromethanesulfonyl) ) Imide anion, bis (perfluoroethylsulfonyl) imide anion, and the like. Two or more of these may be used in combination as a salt of lithium ions and anions.

  As a salt of a quaternary ammonium cation and an anion, a salt of a cation such as tetraethylammonium, tetrabutylammonium, 1-ethyl-3-methylimidazolium and the above-mentioned anion can be used. You may use it in combination.

The electrolyte may include a solid electrolyte. Examples of solid electrolytes include Li ₂ S—SiS ₂ , Li ₂ S—B ₂ S ₅ , Li ₂ S—P ₂ S ₅ —GeS ₂ , sodium / alumina (Al ₂ O ₃ ), amorphous or low phase transition temperature. (Tg) polyether, amorphous vinylidene fluoride-6-fluorinated propylene copolymer, heterogeneous polymer blend polyethylene oxide and the like.

  When the electrolyte is a liquid, the electrolyte itself may be used as the electrolyte solution 29, or the electrolyte may be dissolved in a solvent and used as the electrolyte solution 29. When the electrolyte is a solid, it is necessary to dissolve it in a solvent to obtain the electrolyte solution 29.

  As the solvent for dissolving the electrolyte, a known nonaqueous solvent that can be used in a nonaqueous secondary battery or a nonaqueous electric double layer capacitor can be used. As a specific non-aqueous solvent, a solvent containing a cyclic carbonate can be suitably used. This is because cyclic carbonates have a very high dielectric constant, as typified by ethylene carbonate and propylene carbonate. Among the cyclic carbonates, propylene carbonate is preferable. This is because propylene carbonate has a freezing point of −49 ° C., which is lower than that of ethylene carbonate, so that the electricity storage device can be operated even at a low temperature.

  Moreover, as the non-aqueous solvent, a solvent containing a cyclic ester can also be suitably used. This is because the cyclic ester has a very high dielectric constant as represented by γ-butyrolactone.

  By including these solvents as components of the non-aqueous solvent, the entire non-aqueous solvent in the electrolyte solution 29 can have a very high dielectric constant. As the non-aqueous solvent, only one of these solvents may be used, or two or more may be mixed and used. In addition to the components listed above, examples of the non-aqueous solvent include a chain carbonate ester, a chain ester, a cyclic or chain ether, and the like. Specific examples include dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. , Dioxolane, sulfolane and the like.

(Embodiment 2)
The electricity storage device in the second embodiment is different from the first embodiment only in the positive electrode. Therefore, the description other than the positive electrode is omitted, and only the positive electrode will be described below.

  FIG. 3 schematically shows a cross-sectional structure of the positive electrode 10 ′ of one embodiment of the electricity storage device according to the present invention. The positive electrode 10 ′ includes a positive electrode current collector 11 and a positive electrode active material layer 12 ′ provided on the positive electrode current collector 11. The positive electrode active material layer 12 ′ includes activated carbon 13 and composite particles 15. An enlarged cross-sectional view of the composite particle 15 is schematically shown in FIG. In FIG. 4, a polymer 14 ′ including a tetrachalcogenofulvalene skeleton is coated on at least a part of the surface of the conductive additive 16.

  Further, the positive electrode active material layer 12 ′ has a substrate 17 containing a nonaqueous electrolyte. Activated carbon 13 and composite particles 15 are dispersed in the substrate 17. When the volume of the substrate 17 is sufficiently smaller than the volumes of the activated carbon 13 and the composite particles 15, the substrate 17 fills the gaps around the activated carbon 13 and the composite particles 15. The substrate 17 may be composed of only a non-aqueous electrolyte, or may contain at least one selected from a binder and a conductive aid as necessary. When the substrate 17 contains a conductive auxiliary other than the conductive auxiliary agent 16 forming the composite particles 15, the gap between the polymer particles and the activated carbon particles is filled with the conductive auxiliary agent, so that the electrode has good conductivity. Sex can be secured. When a conductive aid other than the conductive aid 16 is contained in the substrate 17, the conductive aid 16 forming the composite particle 15 and the conductive aid contained in the substrate 17 are the same kind of conductive aid. They may be different from each other or may be different from each other.

  The positive electrode active material layer 12 ′ includes at least two kinds of electrode active materials, that is, activated carbon 13 and polymer 14 ′, and further includes a conductive additive 16. The polymer 14 'includes a polymer containing a tetrachalcogenofulvalene skeleton in a repeating unit. The polymer 14 ′ is included as composite particles 15 in which the polymer 14 ′ covers at least a part of the surface of the conductive additive. That is, the surface of the conductive auxiliary agent 16 is covered with the polymer 14 ′ so that the conductive auxiliary agent 16 and the polymer 14 ′ form the composite particles 15.

  In the second embodiment, since the polymer 14 ′ including the tetrachalcogenofulvalene skeleton does not cover the surface of the activated carbon 13, it is possible to develop good pulse discharge characteristics possessed by the activated carbon 13. In addition, since the polymer 14 ′ including the tetrachalcogenofulvalene skeleton is included together with the activated carbon 13, the capacity of the electricity storage device can be increased. Furthermore, as compared with the case where the particles are made of the polymer 14 (Embodiment 1), the polymer 14 ′ is present so as to cover a part of the surface of the conductive additive 16 as shown in FIG. As a result, the pulse discharge characteristics of the polymer 14 'are also improved. This is because the contact area between the polymer 14 ′ and the conductive auxiliary agent 16 increases because the polymer 14 ′ exists so as to cover a part of the surface of the conductive auxiliary agent 16. Therefore, the electron transfer accompanying the oxidation / reduction is smoothly performed between the conductive auxiliary agent 16 and the polymer 14 ', and the oxidation-reduction reaction in the polymer 14' proceeds smoothly.

  Further, a reaction occurs in which the anion in the electrolytic solution enters the polymer 14 ′ with charging / discharging. When the polymer 14 ′ is coated with the conductive additive 16 to form the composite particle 15, the thickness of the polymer 14 ′ is smaller than when the polymer 14 ′ is forming a particle alone. Therefore, the movement distance of the anion is shortened and the oxidation-reduction reaction rate is improved.

  For these reasons, the polymer containing the tetrachalcogenofulvalene skeleton does not coat the surface of the activated carbon and coats at least a part of the surface of the conductive auxiliary agent, so that the high capacity and good An electricity storage device having pulse discharge characteristics can be provided.

  In FIG. 4, the conductive auxiliary agent 16 is shown in an elliptical cross section, but the shape of the conductive auxiliary agent 16 is not limited to an elliptical shape, and has various shapes that are commonly used as conductive auxiliary agents for electrode materials. You may do it. Further, the polymer 14 ′ may not completely cover the particles of the conductive auxiliary agent 16, and there may be a portion where the particles of the conductive auxiliary agent 16 are in contact with each other. Further, the polymer 14 ′ may cover the entire surface of the conductive auxiliary agent 16 as shown in FIG. 4, or may cover a part of the surface of the conductive auxiliary agent 16.

  Further, instead of the polymer 14 ′, a coating layer containing the polymer 14 ′ and a binder may cover the conductive additive 16. When the coating layer covers the conductive auxiliary agent 16, the coating layer is in a state where the polymer 14 'and the binder are mixed.

  Next, a method for manufacturing the positive electrode 10 'will be described. The positive electrode 10 ′ can be manufactured through first to third steps described below. In the first step and the second step, composite particles in which at least a part of the surface of the conductive additive is coated with a polymer are prepared. In the third step, the obtained composite particles and activated carbon are mixed so that the polymer does not cover the surface of the activated carbon, and a mixture layer is formed on the current collector.

  In the first step, a paste containing a conductive additive and a solution in which a polymer containing a tetrachalcogenofulvalene skeleton is dissolved in a solvent is prepared. The solvent is a solvent in which a polymer containing a tetrachalcogenofulvalene skeleton is soluble. That is, the polymer is in a dissolved state in the paste. Therefore, it is important that the polymer containing the tetrachalcogenofulvalene skeleton is soluble in some solvent. In addition, when the electrolytic solution contains a nonaqueous solvent, it is also important that the polymer does not dissolve in the nonaqueous solvent in the electrolyte. The structure of the polymer that satisfies these conditions and the nonaqueous solvent will be described below.

  In order for a polymer containing a tetrachalcogenofulvalene skeleton to be soluble in any solvent, the polymer is a repeating unit containing a tetrachalcogenofulvalene skeleton, and a repeat containing no tetrachalcogenofulvalene skeleton. A copolymer with the unit is preferable. The tetrachalcogenofulvalene skeleton is a highly planar skeleton. Therefore, a polymer composed only of a repeating unit containing a tetrachalcogenofulvalene skeleton tends to stack between tetrachalcogenofulvalene skeletons due to intermolecular forces, and therefore, there are often few choices of soluble solvents. . On the other hand, in the case of having a repeating unit that does not contain a tetrachalcogenofulvalene skeleton, the solubility of the polymer can be adjusted by changing the structure of this part, and the choice of soluble solvent can be increased.

  Further, such a copolymer may be a copolymer having a repeating unit including a tetrachalcogenofulvalene skeleton in a side chain branched from the main chain, as represented by the formula (10), for example. Further, for example, as represented by the formula (5), a copolymer having a repeating unit containing a tetrachalcogenofulvalene skeleton in the main chain may be used. From the viewpoint of charge / discharge capacity and charge / discharge repeatability of the polymer, a copolymer having a repeating unit containing a tetrachalcogenofulvalene skeleton in the main chain is desirable.

  In the case where the copolymer has a repeating unit including a tetrachalcogenofulvalene skeleton in the main chain of the copolymer, the repeating unit not including the tetrachalcogenofulvalene skeleton includes an acetylene skeleton or a thiophene skeleton. Repeating units are preferred. When the copolymer has a repeating unit containing a tetrachalcogenofulvalene skeleton in the side chain branched from the main chain of the copolymer, the repeating unit not containing the tetrachalcogenofulvalene skeleton is an ester group, It preferably contains an ether group, carbonyl group, cyano group, nitro group, nitroxyl group, alkyl group, phenyl group, alkylthio group, sulfone group, or sulfoxide group.

  In the first step, as a solvent for preparing a paste by dissolving a polymer containing a tetrachalcogenofulvalene skeleton, a solvent having high affinity for the polymer is preferable. Specifically, the solvent is N-methylpyrrolidone (NMP), 1,3-dimethyl-2-imidazolidinone (DMI), tetrahydrofuran (THF), toluene, dimethylformamide (DMF), dimethylacetamide (DMAc), It is preferable to include at least one selected from non-aqueous solvents such as dimethyl sulfoxide (DMSO). Among these, it is more preferable that the polymer contains at least one selected from the group consisting of N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethylacetamide, dimethylformamide, dimethylsulfoxide, and tetrahydrofuran. NMP and DMI are more preferable from the viewpoint that can be dissolved at a higher concentration. In other words, from the viewpoint of the polymer, the polymer containing a tetrachalcogenofulvalene skeleton is preferably soluble in a solvent containing at least one selected from the group.

  The paste may be prepared by first dissolving the polymer in a solvent and mixing the resulting solution with a conductive aid, or by first mixing the solvent and the conductive aid. The polymer may be dissolved in the paste.

  The paste may further contain a binder. As the binder, the above-described binder can be used. The conductive auxiliary agent and the binder may not be dissolved in the solvent. Moreover, when a paste contains a binder, the order which adds a binder in a 1st process is arbitrary. The polymer is desirably uniformly dispersed in the solvent. Therefore, the paste is preferably prepared by first dissolving the polymer in a solvent and mixing the resulting solution, the conductive additive and the binder. As a mixing method, a mixing method commonly used in this field can be used as long as the polymer is dissolved in a solvent. For example, dissolution and mixing can be performed using a kneader such as a planetary mixer.

  In the second step, composite particles containing a polymer and a conductive additive are formed by drying the paste obtained in the first step. The method for drying the paste, that is, the method for removing the solvent from the paste (removal method) is not particularly limited, and a method commonly used in this field can be used. For example, the removal method includes solvent removal by high-temperature drying in which the paste is dried using a drying furnace. As described above, composite particles in which a polymer containing a tetrachalcogenofulvalene skeleton covers at least a part of the surface of the conductive additive can be obtained.

  In the third step, the mixture containing the composite particles and activated carbon obtained in the second step is kneaded, and a mixture layer containing the composite particles and activated carbon is formed on the positive electrode current collector. In this step, a dry method or a wet method can be used. However, when the wet method is used, it is necessary not to use a solvent in which the polymer is dissolved.

  In the dry method, for example, the composite particles obtained in the second step and activated carbon are mixed without using a solvent to obtain a mixture. A mixture layer can be formed by solidifying the obtained mixture with a binder such as PTFE and pressing the mixture onto a positive electrode current collector. In the wet method, a paste is prepared by dispersing composite particles and activated carbon in a solvent using a solvent in which the polymer does not dissolve, for example, water when the polymer is dissolved in an organic solvent. A mixture layer can be formed on the positive electrode current collector by applying the obtained paste on the positive electrode current collector and removing the solvent in the paste.

  The materials that can be used in the second embodiment, which are preferable as the polymer containing a tetrachalcogenofulvalene skeleton, activated carbon, a conductive additive, and a binder, are the same as those in the first embodiment.

  In the composite particle 15, the content of the polymer 14 ′ is preferably 10 to 90 parts by weight, and the content of the conductive additive 16 is preferably 10 to 90 parts by weight. Further, the content of the composite particles 15 is preferably 5 to 90 parts by weight, the content of the activated carbon 13 is preferably 5 to 80 μm, and the conductive assistant contained in the substrate 17 (forms the composite particles 15 is formed). The content is preferably 10 to 60 parts by weight.

  Preferred particle diameters of the activated carbon and the conductive additive (those not forming the composite particles 15) used in the second embodiment are the same as those in the first embodiment. The particle diameter of the composite particles 15 is preferably 0.03 μm to 10 μm. By adjusting the particle diameter of the composite particles 15 within the above range, the contact area with the electrolytic solution can be increased, and the effects of the present invention can be significantly obtained. The particle size of the composite particle means the particle size of the composite particle that is a single particle. The composite particle that is a single particle may be a single particle in which a single conductive aid particle is coated with a polymer, or a single particle in which a plurality of conductive aid particles are coated with a polymer. May be.

  Thus, in the positive electrode active material layer formed on the positive electrode current collector, the positive electrode has a structure in which the polymer covers the surface of the conductive additive and the polymer does not cover the surface of the activated carbon. Can be obtained.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to a following example.

Example 1
As an electrode active material, it contains a polymer containing a tetrachalcogenofulvalene skeleton in the repeating unit and activated carbon, the polymer does not cover the surface of the activated carbon, and the polymer covers a conductive aid other than activated carbon An electricity storage device was fabricated using the positive electrode having the above structure.

[Production of positive electrode]
First, as a polymer containing a tetrachalcogenofulvalene skeleton in a repeating unit, a copolymer represented by the following formula (10) (hereinafter referred to as copolymer 11c) was synthesized.

  In Formula (10), the number of units m of the repeating unit (second unit) not including the tetrachalcogenofulvalene skeleton is smaller than the number of units n of the repeating unit (first unit) including the tetrachalcogenofulvalene skeleton. The composition ratio m / n is approximately 1.

  The copolymer 11c was synthesized by coupling the tetrathiafulvalene precursor 11a to the compound 11b constituting the main chain of the copolymer 11c as shown in the following formula (11). In formula (11), n and m are integers representing the number of repetitions of each monomer unit.

  Next, using the synthesized copolymer 11c, a positive electrode was produced under an argon atmosphere in a glow box equipped with a gas purification device. This will be described in detail below.

  200 mg of the copolymer 11c was pulverized in a mortar, and 600 mg of NMP (manufactured by Wako Pure Chemical Industries, Ltd.), which is an aprotic solvent, was added thereto and kneaded to dissolve the copolymer 11c in NMP. A paste was prepared by adding 160 mg of acetylene black as a conductive additive, 40 mg of polyvinylidene fluoride as a binder, and 2.3 g of NMP to this solution and kneading. The obtained paste was applied to an aluminum foil. This was put in a thermostat and dried at a temperature of 80 ° C. for 1 hour to remove NMP contained in the paste. After drying, the composite film containing the conductive assistant and the copolymer 11c was obtained by peeling off the film of the mixture containing the copolymer 11c and the conductive assistant formed on the aluminum foil. 100 mg of this composite was placed in a mortar and pulverized to obtain composite particles containing a conductive additive and copolymer 11c. To the composite particles, 50 mg of activated carbon (MSP-20 manufactured by Kansai Thermal Chemical Co., Ltd.) and 360 mg of acetylene black as a conductive assistant were added and mixed uniformly. Further, 90 mg of polytetrafluoroethylene was added as a binder and mixed uniformly to obtain a positive electrode mixture.

The obtained positive electrode mixture was pressure-bonded onto a positive electrode current collector made of an aluminum wire mesh, vacuum-dried, and punched into a disk shape having a diameter of 13.5 mm to produce a positive electrode. The total weight of the activated carbon and the copolymer in the positive electrode was 1.0 mg / cm ² per electrode plate unit area.

  About the cross section of the produced positive electrode, the shape analysis (cross-sectional SEM observation) by a scanning electron microscope (SEM) and the elemental analysis by an electron beam microanalyzer (EPMA) were performed. As a result of cross-sectional SEM observation, carbon particles of several μm derived from activated carbon were confirmed. Further, as a result of elemental analysis by EPMA, it was confirmed from the distribution of sulfur element that the copolymer 11c was distributed in a region where no activated carbon was present. For further detailed observation, cross-sectional SEM observation at high magnification and elemental analysis by Auger electron spectroscopy were performed. As a result, the distribution of several tens to several hundreds of nanometers of carbon particles derived from acetylene black, which is a conductive additive, was confirmed, and it was confirmed that the copolymer 11c was distributed so as to almost overlap with it.

  From the above, it was confirmed that the produced positive electrode had a structure in which the copolymer 11c did not cover the activated carbon and the copolymer 11c covered the conductive additive.

[Production of electricity storage device]
A negative electrode mixture was prepared by uniformly mixing 400 mg of activated carbon as a negative electrode active material, 100 mg of acetylene black as a conductive additive, and 100 mg of polytetrafluoroethylene as a binder. The obtained negative electrode mixture was pressure-bonded onto a negative electrode current collector made of an aluminum wire mesh, and this was punched into a disc shape having a diameter of 13.5 mm to produce a negative electrode.

  In a non-aqueous solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed at a volume ratio of 1: 3, lithium hexafluorophosphate as a salt is dissolved so as to have a concentration of 1.25 mol / L. This was used as an electrolytic solution.

  As the separator, a porous polyethylene sheet having a thickness of 20 μm was used.

  By impregnating the positive electrode, the negative electrode, and the separator with an electrolyte, and storing them in a coin-type case shown in FIG. 2, sandwiching the opening of the case with a sealing plate equipped with a gasket, and caulking and sealing with a press machine, A coin-type electricity storage device was produced.

(Example 2)
As an electrode active material, it contains a polymer containing tetrachalcogenofulvalene skeleton in the repeating unit and activated carbon, the polymer does not cover the surface of the activated carbon, and the polymer and activated carbon form different particles. An electricity storage device was manufactured using the positive electrode having the structure described above.

[Production of positive electrode]
Copolymer 11c was synthesized in the same manner as in Example 1. 50 mg of the copolymer 11c was pulverized in a mortar, and 50 mg of activated carbon and 400 mg of acetylene black as a conductive assistant were added thereto and mixed uniformly. Furthermore, 100 mg of polytetrafluoroethylene was added as a binder and mixed uniformly to obtain a positive electrode mixture.

The obtained positive electrode mixture was pressure-bonded onto a positive electrode current collector made of an aluminum wire mesh, vacuum-dried, and punched into a disk shape having a diameter of 13.5 mm to produce a positive electrode. The total weight of the activated carbon and the copolymer in the positive electrode was 1.0 mg / cm ² per electrode plate unit area.

  The fabricated positive electrode was subjected to cross-sectional SEM observation and elemental analysis by EPMA. As a result of cross-sectional SEM observation, carbon particles of several μm derived from activated carbon were confirmed. Further, as a result of elemental analysis by EPMA, it was confirmed from the distribution of elemental sulfur that the copolymer 11c also exists as particles of several μm.

  From the above, it was confirmed that the produced positive electrode had a structure in which the copolymer 11c did not cover the activated carbon, and the activated carbon and the copolymer 11c formed different particles.

[Production of electricity storage device]
An electricity storage device was produced in the same manner as in Example 1 except that the above positive electrode was used as the positive electrode.

(Comparative Example 1)
As an electrode active material, an electricity storage device was manufactured using a positive electrode including only a polymer including a tetrachalcogenofulvalene skeleton in a repeating unit.

[Production of positive electrode]
Copolymer 11c was synthesized in the same manner as in Example 1. 100 mg of the copolymer 11c was pulverized in a mortar, and 400 mg of acetylene black as a conductive auxiliary agent was added thereto and mixed uniformly. Furthermore, 100 mg of polytetrafluoroethylene was added as a binder and mixed uniformly to obtain a positive electrode mixture.

The obtained positive electrode mixture was pressure-bonded onto a positive electrode current collector made of an aluminum wire mesh, vacuum-dried, and punched into a disk shape having a diameter of 13.5 mm to produce a positive electrode. The weight of the copolymer 11c in the positive electrode was 1.0 mg / cm ² per electrode plate unit area. The produced positive electrode is an electrode containing only the copolymer 11c as an electrode active material.

[Production of electricity storage device]
An electricity storage device was produced in the same manner as in Example 1 except that the above positive electrode was used as the positive electrode.

(Comparative Example 2)
An electricity storage device was fabricated using a positive electrode containing only activated carbon as an electrode active material.

[Production of positive electrode]
100 mg of activated carbon and 400 mg of acetylene black as a conductive assistant were placed in a mortar and mixed uniformly. Furthermore, 100 mg of polytetrafluoroethylene was added as a binder and mixed uniformly to obtain a positive electrode mixture.

The obtained positive electrode mixture was pressure-bonded onto a positive electrode current collector made of an aluminum wire mesh, vacuum-dried, and punched into a disk shape having a diameter of 13.5 mm to produce a positive electrode. The weight of the activated carbon in the positive electrode was 1.0 mg / cm ² per electrode plate unit area. The produced positive electrode is an electrode containing only activated carbon as an electrode active material.

[Production of electricity storage device]
An electricity storage device was produced in the same manner as in Example 1 except that the above positive electrode was used as the positive electrode.

(Comparative Example 3)
As an electrode active material, a power storage device was fabricated using a positive electrode having a structure in which a polymer including a tetrachalcogenofulvalene skeleton in a repeating unit and activated carbon, and the polymer covering the surface of the activated carbon.

[Production of positive electrode]
Copolymer 11c was synthesized in the same manner as in Example 1. 200 mg of the copolymer 11c is pulverized in a mortar, and 600 mg of NMP (manufactured by Wako Pure Chemical Industries, Ltd.), which is an aprotic solvent, is added thereto and kneaded in the mortar, whereby the copolymer 11c is aprotic. Dissolved in polar solvent. In this solution, 200 mg of activated carbon, 40 mg of polyvinylidene fluoride as a binder, and 2.3 g of NMP were added and kneaded to prepare a paste. The obtained paste was applied to an aluminum foil. This was put in a thermostat and dried at a temperature of 80 ° C. for 1 hour to remove NMP in the paste. After drying, the film of the mixture containing copolymer 11c and activated carbon formed on the aluminum foil was peeled off to obtain a mixture containing copolymer 11c and activated carbon.

  110 mg of the obtained mixture was pulverized in a mortar, and 400 mg of acetylene black was added as a conductive aid and mixed uniformly. Furthermore, 90 mg of polytetrafluoroethylene was added as a binder to produce a positive electrode mixture.

The obtained positive electrode mixture was pressure-bonded onto a positive electrode current collector made of an aluminum wire mesh, vacuum-dried, and punched into a disk shape having a diameter of 13.5 mm to produce a positive electrode. The total weight of the activated carbon and the copolymer 11c in the positive electrode was 1.0 mg / cm ² per electrode plate unit area.

  About the cross section of the produced positive electrode, cross-sectional SEM observation and elemental analysis by EPMA were performed. As a result of cross-sectional SEM observation, carbon particles of several μm derived from activated carbon were confirmed. Further, as a result of elemental analysis by EPMA, it was confirmed from the distribution of sulfur element that the copolymer 11c was present so as to cover the activated carbon. For further detailed observation, cross-sectional SEM observation at high magnification and elemental analysis by Auger electron spectroscopy were performed. As a result, it was confirmed that the copolymer 11c exists only on the surface of the activated carbon, and the copolymer 11c does not cover the conductive additive.

  From the above, it was confirmed that the produced positive electrode had a structure in which the copolymer 11c was coated with activated carbon.

[Production of electricity storage device]
An electricity storage device was produced in the same manner as in Example 1 except that the above positive electrode was used as the positive electrode.

  About the electrical storage device of Examples 1, 2 and Comparative Examples 1-3, charging / discharging capacity | capacitance and output characteristics were evaluated.

  In the charge / discharge capacity evaluation, a value obtained by dividing the charge / discharge capacity at the first charge / discharge by the total weight of the copolymer 11c and the activated carbon in the positive electrode, that is, the charge / discharge capacity per unit weight of the active material was measured. Charging / discharging was performed by constant current charging / discharging of 0.1 mA. The charge / discharge conditions were a charge upper limit voltage of 2.3 V and a discharge lower limit voltage of 1.0 V. The rest time from the end of charging to the start of discharging was set to zero.

  In output (pulse discharge) evaluation, a constant voltage discharge test of 1.7 V was performed, and a current value after 3 seconds was measured. Charging was performed by constant current charging of 0.1 mA. The charging conditions were such that the charging upper limit voltage was 2.3 V, and the rest time until the discharge was started after the end of charging was zero.

  These evaluation results are summarized in Table 1. Moreover, the result of Table 1 is shown in FIG.

  Comparative Example 1 is an electricity storage device using a positive electrode containing only the copolymer 11c as an electrode active material, and the charge / discharge capacity was as large as 110 mAh / g, but the pulse discharge was as small as 6 mA. On the other hand, Comparative Example 2 is an electricity storage device using a positive electrode containing only activated carbon as an electrode active material, and the pulse discharge was as large as 38 mA, but the charge / discharge capacity was as small as 45 mAh / g. The dotted line in FIG. 5 is a line connecting Comparative Example 1 and Comparative Example 2, and the characteristics of the electricity storage device using the positive electrode containing activated carbon and copolymer 11c as the electrode active material are expected to be on the dotted line. Is done.

  Examples 1 and 2 and Comparative Example 3 are power storage devices using positive electrodes including activated carbon and a copolymer 11c as electrode active materials. Example 1 is an electricity storage device using a positive electrode having a structure in which the copolymer 11c does not cover the surface of the activated carbon and the copolymer 11c covers the surface of the conductive additive. Example 2 is an electricity storage device using a positive electrode having a structure in which the copolymer 11c does not cover the surface of the activated carbon and the activated carbon and the copolymer 11c form particles. Comparative Example 3 is an electricity storage device using a positive electrode having a structure in which a polymer coats the surface of activated carbon. As can be confirmed from FIG. 5, the characteristics of Examples 1 and 2 and Comparative Example 3 were greatly different. In Comparative Example 3, the characteristics inferior to the dotted line connecting Comparative Example 1 and Comparative Example 2 with a straight line were shown, but in Example 2, the characteristics exceeding the dotted line connecting Comparative Example 1 and Comparative Example 2 with a straight line were shown. . Moreover, it can confirm that Example 1 has shown the pulse discharge characteristic which exceeds Example 2 further.

  Examples 1 and 2 and Comparative Example 3 differ only in the positive electrode structure. Therefore, it is considered that the difference in characteristics of the electricity storage device is derived from the electrode structure of the positive electrode.

  In the positive electrode of Comparative Example 3, the surface of the activated carbon is covered with the copolymer 11c. For this reason, it is considered difficult to form a conductive path between the activated carbon and the positive electrode current collector. Moreover, it is thought that the pore which exists in the surface of activated carbon is filled up with the copolymer 11c. Therefore, it is considered that the charge / discharge capacity and pulse discharge characteristics derived from activated carbon cannot be fully utilized.

  In the positive electrode of Example 2, the copolymer 11c does not coat the surface of the activated carbon and forms different particles. Therefore, the pulse discharge characteristics of activated carbon and the charge / discharge capacity of copolymer 11c can be fully utilized. Moreover, since the surface pores of the activated carbon are not covered with the copolymer 11c, a large amount of electrolytic solution exists in the positive electrode. Therefore, it is considered that the migration resistance of the anion in the positive electrode accompanying charging / discharging of the copolymer 11c is reduced, and the pulse discharge characteristics derived from the copolymer 11c are improved. As a result, it is thought that the characteristic which exceeded the dotted line which connected the comparative example 1 and the comparative example 2 with the straight line was shown.

  In the positive electrode of Example 1, the copolymer 11c does not cover the surface of the activated carbon, and the copolymer 11c covers the conductive additive. Therefore, the pulse discharge characteristics of activated carbon and the charge / discharge capacity of the copolymer 11c can be fully utilized. Moreover, since the surface pores of the activated carbon are not covered with the copolymer 11c, a large amount of electrolytic solution exists in the positive electrode. Therefore, it is considered that the migration resistance of the anion in the positive electrode accompanying charging / discharging of the copolymer 11c is reduced, and the pulse discharge characteristics derived from the copolymer 11c are improved. Furthermore, the copolymer 11c exists as a thin film on the surface of the conductive additive. Therefore, the electron transfer between the polymer and the conductive agent is smoothly performed during charging / discharging of the copolymer 11c. As a result, it exceeded the dotted line connecting Comparative Example 1 and Comparative Example 2 with a straight line, which is considered to indicate better characteristics than Example 2.

  As described above, according to the present invention, it is possible to provide a high-capacity electricity storage device having excellent pulse discharge characteristics. In addition, since the electrode and the electricity storage device used in the present invention can perform a stable and reversible oxidation-reduction reaction, it is possible to provide an electricity storage device having high capacity, excellent pulse discharge characteristics, and excellent repetition characteristics. it can.

  Since the electricity storage device of the present invention is a high-capacity electricity storage device with excellent pulse characteristics, it is suitably used for vehicles such as hybrid vehicles and portable electronic devices. The vehicle and the portable electronic device provided with the electricity storage device of the present invention are characterized in that the electricity storage device is lightweight, has a large output, and is excellent in repetition characteristics. In particular, since the electricity storage device of the present invention is excellent in pulse characteristics, it is suitably used for various portable electronic devices and uninterruptible power supplies.

DESCRIPTION OF SYMBOLS 10, 10 'Positive electrode 11 Positive electrode collector 12, 12' Positive electrode active material layer 13 Activated carbon 14, 14 'Polymer 15 Composite particle | grains 16 of a polymer and a conductive support agent 16 Conductive support agent 17 Substrate 20 Coin type electrical storage device 21 Coin Mold case 24 Separator 25 Sealing plate 26 Negative electrode active material layer 27 Negative electrode current collector 28 Gasket 29 Electrolytic solution 32 Negative electrode

Claims (15)

A positive electrode, a negative electrode, and a non-aqueous electrolyte;
The positive electrode includes, as an electrode active material, a polymer containing a tetrachalcogenofulvalene skeleton in a repeating unit, and activated carbon,
An electricity storage device in which each of the activated carbon and the polymer has a particle shape so that the non-aqueous electrolyte can be in direct contact with each of the activated carbon and the polymer.   The electricity storage device according to claim 1, wherein the polymer does not cover the surface of the activated carbon. The positive electrode further includes a conductive additive,
The electricity storage device according to claim 1 or 2, wherein at least a part of a surface of the conductive auxiliary agent is coated with the polymer so that the conductive auxiliary agent and the polymer form composite particles.   The electricity storage device according to claim 3, wherein the conductive additive is carbon black. 5. The electricity storage device according to claim 1, wherein a structure of a portion having the tetrachalcogenofulvalene skeleton in the polymer is represented by the following formula (1).
Wherein ^(1), X 1 ~X ⁴ independently of one another, a sulfur atom, an oxygen atom, a selenium atom or a tellurium atom,
One or two selected from Ra, Rb, Rc, and Rd is a bond for binding to the other part of the main chain or side chain of the polymer, and is selected from Ra, Rb, Rc, and Rd The remaining three or two are independently of each other a chain aliphatic group, a cyclic aliphatic group, a hydrogen atom, a hydroxyl group, a cyano group, an amino group, a nitro group, a nitroso group, or an alkiothio group. The chain aliphatic group and the cyclic aliphatic group each include at least one selected from the group consisting of an oxygen atom, a nitrogen atom, a sulfur atom, a silicon atom, a phosphorus atom, and a boron atom. You may,
Ra and Rb may be bonded to each other to form a ring, and Rc and Rd may be bonded to each other to form a ring. ]

The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent,
The electricity storage device according to claim 1, wherein the polymer is insoluble in the non-aqueous solvent. The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent,
The polymer is insoluble in the non-aqueous solvent;
The electricity storage device according to claim 3, wherein the polymer is soluble in a first solvent other than the non-aqueous solvent.   The first solvent includes at least one selected from the group consisting of N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethylacetamide, dimethylformamide, dimethylsulfoxide, and tetrahydrofuran. The electricity storage device described in 1.   The electricity storage according to any one of claims 1 to 8, wherein the polymer is a copolymer of a repeating unit including a tetrachalcogenofulvalene skeleton and a repeating unit not including the tetrachalcogenofulvalene skeleton. device.   The electricity storage device according to claim 9, wherein the copolymer has a repeating unit including the tetrachalcogenofulvalene skeleton in a side chain of the copolymer.   The electricity storage device according to claim 9, wherein the copolymer has a repeating unit including the tetrachalcogenofulvalene skeleton in a main chain of the copolymer. The non-aqueous electrolyte includes a salt of a quaternary ammonium cation and an anion,
The negative electrode includes a negative electrode active material,
The electricity storage device according to claim 1, wherein the negative electrode active material has an electric double layer capacity capable of reversibly occluding and releasing the quaternary ammonium cation or the anion. The non-aqueous electrolyte includes a salt of lithium ions and anions,
The electricity storage device according to claim 1, wherein the negative electrode includes a negative electrode active material capable of inserting and extracting lithium ions. A step of preparing a paste containing a solution in which a polymer containing a tetrachalcogenofulvalene skeleton in a repeating unit is dissolved in a solvent, and a conductive additive;
Removing the solvent from the paste to form composite particles containing the polymer and the conductive additive;
Using a mixture obtained by kneading the composite particles and activated carbon, and forming a mixture layer containing the composite particles and the activated carbon on a positive electrode current collector. .   15. The solvent according to claim 14, wherein the solvent comprises at least one selected from the group consisting of N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethylacetamide, dimethylformamide, dimethylsulfoxide, and tetrahydrofuran. Production method.

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