JP5211623B2 - Electricity storage device - Google Patents

Description

  The present invention relates to an electricity storage device.

Conventionally, various power storage devices using a polymer compound as a positive electrode active material have been developed. For example, Non-Patent Document 1 reports a secondary battery using a polymer compound having an oxoammonium structure in the molecule as a positive electrode. Specifically, a secondary battery in which poly (2,2,6,6-tetramethylpiperidinyloxymethacrylate) (PTMA), which is a nitroxyl polyradical, is synthesized as a positive electrode active material has an average discharge. The voltage was 3.5 V, the discharge capacity was 77 Ah / kg (corresponding to 70% of the theoretical capacity), and the capacity did not change significantly after repeated charging and discharging at a high current density of 1.0 mA / cm ² for 500 cycles or more. It has been reported.

  Non-Patent Document 2 reports a secondary battery using a polymer compound having a benzoquinone structure in the molecule as a positive electrode. Specifically, a secondary battery using a hybrid material of poly (2,5-dihydroxy-1,4-benzoquinone-3,6-methylene) (PDBM) and acetylene black as a positive electrode active material has a capacity of 150 mAh. / G.

Further, in Non-Patent Document 3, polyaniline, which is a conductive polymer, is used as a positive electrode, an alloy composed of lithium and aluminum is used as a negative electrode, and a mixed solvent of propylene carbonate and 1,2-dimethoxyethane is used as a nonaqueous electrolyte. It is described that a coin-shaped lithium battery using ₄ dissolved is practically used.
Chemical Physics Letters, 359, 351-354, 2002 Journal of Power Sources, 119-121, 316-320, 2003 The latest polymer battery technology, pages 42-54, supervision: Noboru Koyama, CM Publishing Co., Ltd., August 1998

By the way, in order to increase the capacity of the battery, it is only necessary to create an electrode with an electrochemically active structure that performs oxidation-reduction, but in order to prevent dissolution in the electrolyte when the active material is an organic compound. A method of reducing the solubility by polymerizing is employed. For this reason, there existed a problem that the electrochemically inactive structure occupied most and the capacity | capacitance of a battery fell. In fact, in Non-Patent Document 1, the theoretical capacity per weight is 111 mAh / g, which is smaller than the practical capacity of 140 to 160 mAh / g of LiCoO ₂ which is a typical positive electrode active material of a lithium ion battery. In addition, the polymer compounds described in Non-Patent Documents 1 and 2 are low even if they are not conductive. Therefore, when this is used as an active material, a conductive aid such as carbon must be mixed. However, when polymerized, it becomes difficult to uniformly disperse with the conductive additive, and there is a problem that the amount of active species that can be effectively used decreases. In order to increase the utilization efficiency of the active material, it is necessary to increase the amount of the conductive auxiliary agent to be mixed, but when it comes to the positive electrode material, it causes a decrease in capacity.

Regarding the output characteristics, when the active species is oxidized and reduced, the active species itself becomes a positive or negative ion. Therefore, an electrolyte ion as a counter ion (counter ion) (for example, BF ₄ ⁻ if the electrolyte is LiBF _4). ) Becomes the rate-determining rate, and this is a cause of a decrease in output particularly when the counter ion is a large anion. As in Non-Patent Document 3, a secondary battery using a conductive polymer polyaniline as a positive electrode has been reported. However, although the capacity is relatively large, it is slow for anions to enter and exit the polymer chain. The output is small. In addition, since the active species are often insulative and charge exchange is not sufficient, not all of the mixed active species can be used effectively, resulting in a reduction in capacity and low output characteristics. In Non-Patent Document 1, a high output is possible, but the capacity is small. If the capacity can be increased, it is considered that the exchange of charges becomes a resistance and it is difficult to improve the output.

  Regarding the cycle characteristics, in the case of organic substances, the concentration of the active species is often reduced by dissolving the active species in the solvent. When preventing only by high molecular weight, when the molecular weight is lowered due to partial decomposition by repeated charge and discharge, the capacity drop becomes significant. In Non-Patent Document 2, it is reduced to about 80% of the initial capacity after 100 cycles, and the durability is not sufficient.

  The present invention has been made to solve such problems, and a main object of the present invention is to provide an electricity storage device having high capacity and output and excellent cycle characteristics.

  In order to achieve the main object described above, the present inventors used a polyion complex formed from polyaniline and poly (2,5-dihydroxy-1,4-benzoquinone-3,6-methylene) as a positive electrode active material. As a result, it was found that the lithium secondary battery has higher capacity and output than those of the prior art and has good cycle characteristics, and the present invention has been completed.

  That is, each of the electricity storage devices of the present invention uses a polyion complex composed of a cationic organic compound having redox properties and an anionic organic compound as an electrode active material.

  According to the electricity storage device of the present invention, it is possible to obtain the effects that the capacity and output are higher than those of the prior art and the cycle characteristics are also improved. The mechanism by which these effects can be obtained is not clear, but is presumed as follows.

That is, in the electricity storage device of the present invention, by adopting a polyion complex as an electrode active material, it is possible to suppress the dissolution of the electrode active material in the electrolyte and prevent the decrease in the concentration of the electrode active material, thereby improving cycle characteristics. It is thought that. Further, at the time of charge / discharge, counter ions enter and exit in order to maintain electrical neutrality against the valence change of the electrode active material due to oxidation / reduction, but as the counter ions, anions that are large ions (for example, the electrolyte is LiBF ₄₎ . If there is a metal ion (for example, Li ⁺ ) which is a smaller cation than BF ₄ ⁻ ), the capacity per weight including the counter ion is larger, the diffusion is faster and the output is higher, and there is no change in the electrolyte concentration. It works in terms of Therefore, an anion exchange type electrode active material in which an anion enters and exits as a counter ion as the electrode active material becomes a cation by oxidation is generally disadvantageous, but a polyion complex that maintains electrical neutrality during oxidation is used as an electrode. When used as an active material, it is considered that a metal cation enters during reduction and exits during oxidation, thereby maintaining the overall electrical neutrality. Thus, in the polyion complex, a metal cation can be used as a counter ion, so it is considered that high capacity and high output are possible.

  The electricity storage device of the present invention uses a polyion complex composed of a cationic organic compound having an oxidation-reduction property and an anionic organic compound as an electrode active material. Examples of the power storage device include a secondary battery and an electric double layer capacitor, and a secondary battery is preferable. Hereinafter, as a typical example, a lithium ion battery that is a secondary battery will be described as an example. However, the metal species is not particularly limited, and Mg, Al, Zn, or the like may be used instead of Li.

  When the electricity storage device of the present invention is configured as a lithium ion battery, a material that occludes and releases lithium ions is used for the negative electrode. Here, examples of materials that occlude and release lithium ions include metal lithium and lithium alloys, metal oxides, metal sulfides, and carbonaceous substances that occlude and release lithium ions. Examples of lithium alloys include alloys of lithium with aluminum, tin, magnesium, indium, calcium, silicon, and the like. Examples of the metal oxide include tin oxide, silicon oxide, lithium titanium oxide, niobium oxide, and tungsten oxide. Examples of the metal sulfide include tin sulfide and titanium sulfide. Examples of the carbonaceous material that absorbs and releases lithium ions include graphite, coke, mesophase pitch-based carbon fiber, spherical carbon, and resin-fired carbon.

  When the electricity storage device of the present invention is configured as a lithium ion battery, a polyion complex composed of a cationic organic compound and an anionic organic compound each having redox properties is used for the positive electrode.

  Here, the cationic organic compound means an organic compound having a site dissociated into a cation in the structure, and examples thereof include a nitrogen-containing organic compound containing an amine site or an ammonium site. Moreover, an anionic organic compound means the organic compound which has the site | part dissociated into the anion in a structure, For example, the organic compound containing a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, and a phenolic hydroxyl group is mentioned. In addition, these compounds may have both a site dissociating into a cation and a site dissociating into an anion. In this case, when the compound functions as a cation as a whole, it becomes a cationic organic compound. If it functions as an anion, it belongs to an anionic organic compound. For example, a nitrogen-containing (or sulfur-containing) organic compound containing a sulfonic acid group belongs to the anionic organic compound because it functions as an anion as a whole.

  The polyion complex is a polyion structure in which at least one of a cationic organic compound and an anionic organic compound has a plurality of ionic sites in the molecule, and the cationic organic compound and the anionic organic compound Refers to a complex in which ions are bonded. Such polyion complexes have a lower solubility in non-aqueous solvents than in the case where a cationic organic compound or an anionic organic compound is present alone, thereby preventing a decrease in concentration in the electrode due to dissolution in non-aqueous solvents. be able to. Moreover, since both form ionic bonds, the physical positional relationship between the two is fixed at a close position, and as a result, the mutual interaction becomes stronger and affects each other. It is considered to be. In addition, since a polyion complex should just form a complex with a cationic organic compound and an anionic organic compound, it is not necessary to make equivalent of both, For example, the range of 0.1-10 is equivalent ratio preferable.

  In the present invention, it is preferable that at least one of the cationic organic compound and the anionic organic compound forming such a polyion complex is a conductive polymer compound. When the electrode active material is insulative, it takes the form of being supported around the carbon as a conductive aid, but the exchange of electric charges is not successful, the active material cannot be used effectively, and resistance is increased, so the output is increased. As a result, the active material concentration cannot be increased. On the other hand, when at least one of the cationic organic compound and the anionic organic compound is a conductive polymer compound, since efficient charge exchange is possible, higher capacity and higher output are achieved. It becomes possible to do. Moreover, since it becomes possible to reduce the conductive support agent which was difficult until now due to a decrease in utilization efficiency, the capacity of the electrode material as a whole also increases. When such a polyion complex is used as the positive electrode of a lithium secondary battery, charge exchange at the positive electrode occurs easily, and the active material can be used efficiently. As a result, higher output and higher capacity can be achieved.

  Here, the conductive polymer compound is preferably, for example, polyanilines, polythiophenes, or polypyrroles. In order to efficiently prepare the polyion complex, it is preferable to use a conductive polymer compound that is soluble in a solvent. However, a polyion complex can be prepared by electrolytic polymerization or chemical polymerization even for a conductive polymer compound that is insoluble or hardly soluble in a solvent.

When the cationic organic compound is a conductive polymer, it is preferable to employ polyanilines, polypyrroles, and polythiophenes. Examples of such conductive polymers include polyaniline (soluble in water, toluene, N-methylpyrrolidone, dimethyl sulfoxide) and polypyrrole (soluble in methyl ethyl ketone), as well as SSPY (3- And a copolymer of ethyl methyl-4-pyrrolecarboxylate and butyl 3-methyl-4-pyrrolecarboxylate, soluble in dimethylacetamide). These are all available from TA Chemical Co., Ltd. PEDOT obtained by polymerizing 3,4-ethylenedioxythiophene in the presence of an anionic organic compound can also be used as a cationic conductive polymer. On the other hand, when an anionic organic compound is used as a conductive polymer, it is preferable to employ polyanilines, polythiophenes or polypyrroles having an acidic group. Examples of the acidic group include a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, and a phenolic hydroxyl group. Such conductive polymers include polyaniline sulfonic acid (soluble in water), polythiophene (soluble in water) and polyisothianaphthene (soluble in water) having a methylsulfonic acid group as shown in the following formula. And the like. These are all available from TA Chemical Co., Ltd.

  In the electricity storage device of the present invention, benzoquinones having a basic group may be used as the cationic organic compound. At this time, the basic group is preferably an amino group. Alternatively, as the anionic organic compound, benzoquinones or dihydrobenzoquinones having an acidic group may be used. At this time, the acidic group is preferably a sulfonic acid group, a carboxylic acid group, a phosphoric acid group or a phenolic hydroxyl group. The benzoquinone skeleton is a typical electrochemically active structure that performs redox, and is a structure that is expected to have a high capacity for performing redox of two electrons. Therefore, a compound that forms a polyion complex used in the electricity storage device of the present invention It is suitable as. In addition, since dihydrobenzoquinone has an acidic group (OH group), it may have an acidic group as a substituent separately, but does not need to have it.

  In the electricity storage device of the present invention, oxoammonium compounds may be used as the cationic organic compound. At this time, the oxoammoniums may have a basic group such as an amino group. Alternatively, as the anionic organic compound, oxoammonium having an acidic group may be used. At this time, the acidic group is preferably a sulfonic acid group, a carboxylic acid group, a phosphoric acid group or a phenolic hydroxyl group. Since the oxoammonium ion structure has a high redox rate and is expected to have a high output, it is suitable as a compound that forms a polyion complex used in the electricity storage device of the present invention.

  In the polyion complex used in the electricity storage device of the present invention, any of the cationic organic compound and the anionic organic compound may be a monomer, but the valence changes due to the point of suppressing solubility or redox. Considering that it is difficult to elute, at least one of them is preferably a polymer.

  In the electricity storage device of the present invention, the positive electrode may contain a conductive material. The conductive material is not particularly limited as long as it is a conductive material. For example, carbon blacks such as ketjen black, acetylene black, channel black, furnace black, lamp black and thermal black may be used, and natural graphite such as flake graphite, graphite such as artificial graphite and expanded graphite may be used. Conductive fibers such as carbon fibers and metal fibers may be used, metal powders such as copper, silver, nickel, and aluminum may be used, and organic conductive materials such as polyphenylene may be used. These may be used alone or in combination.

  Further, the positive electrode may contain a binder. Although it does not specifically limit as a binder, A thermoplastic resin, a thermosetting resin, etc. are mentioned. For example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), styrene butadiene rubber, tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE resin) , Polychlorotrifluoroethylene (PCTFE), vinylidene fluoride-pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrif Examples include olefin copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, and ethylene-acrylic acid copolymer. . These materials may be used alone or in combination.

Further, the positive electrode may be formed by mixing a polyion complex, a binder, and a conductive material used as necessary, and then press-molding the current collector. At this time, although the usage-amount of a polyion complex is not specifically limited, For example, it is good also as 10-90 weight part with respect to the whole. As a mixing method, wet mixing may be performed in a solvent such as N-methylpyrrolidone, or dry mixing may be performed using a mortar or the like. Although it does not specifically limit as a collector, Metal plates and metal meshes, such as stainless steel, aluminum, copper, and nickel, can be used. Among these, it is preferable in terms of stability to use a stainless steel plate, a stainless steel mesh, an aluminum plate, or an aluminum mesh. In addition to these metals, carbon paper and oxide conductors can also be used. For example, transparent conductive materials such as InSnO ₂ , SnO ₂ , ZnO, In ₂ O ₂ , fluorine-doped tin oxide (SnO ₂ : F), antimony-doped tin oxide (SnO ₂ : Sb), tin-doped indium oxide (In ₂ O ₃ : Sn), ZnO, Al-doped zinc oxide (ZnO: Al), Ga-doped zinc oxide (ZnO: Ga) and other materials doped with a single layer or laminated layer such as glass or polymer What was formed in can be used. The film thickness is not particularly limited, but is preferably about 3 nm to 10 μm. The glass or polymer surface may be flat, or the surface may be uneven.

In the electricity storage device of the present invention, the positive electrode and the negative electrode are arranged via a non-aqueous electrolyte. At this time, although it does not specifically limit about a non-aqueous electrolyte, The electrolyte solution containing a support salt, a gel electrolyte, a solid electrolyte, etc. can be used. Examples of the supporting salt include LiPF ₆ , LiClO ₄ , LiBF ₄ , Li (CF ₃ SO ₂ ) ₂ N, (C ₂ H ₅ ) ₄ NBF ₄ , (C ₄ H ₉ ) ₄ NBF ₄ , (C ₂ H ₅ ) Known supporting salts such as ₄ NPF ₆ and (C ₄ H ₉ ) ₄ NPF ₆ can be used. As the supporting salt, ionic liquids such as 1-methyl-3-propylimidazolium bis (trifluorosulfonyl) imide and 1-ethyl-3-butylimidazolium tetrafluoroborate can also be used. The concentration of the supporting salt is preferably 0.1 to 2.0M, and more preferably 0.8 to 1.2M. Examples of the solvent for the electrolyte include conventional secondary batteries and capacitors such as ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (γ-BL), diethyl carbonate (DEC), and dimethyl carbonate (DMC). The organic solvent used is mentioned. These may be used alone or in combination. The gel electrolyte is not particularly limited. For example, a polymer such as polyvinylidene fluoride, polyethylene glycol, or polyacrylonitrile, or a saccharide such as an amino acid derivative or sorbitol derivative is added with an electrolyte containing a supporting salt. And a gel electrolyte. Examples of the solid electrolyte include inorganic solid electrolytes and organic solid electrolytes. Well-known inorganic solid electrolytes include, for example, Li nitrides, halides, oxyacid salts, and the like. Among _{them, Li 4 SiO 4, Li 4} SiO 4 -LiI-LiOH, xLi 3 PO 4 - (1-x) Li 4 SiO 4, Li 2 SiS 3, Li 3 PO 4 -Li 2 S-SiS 2, sulfide Examples thereof include phosphorus compounds. These may be used alone or in combination. Examples of the organic solid electrolyte include polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyvinylidene fluoride, polyphosphazene, polyethylene sulfide, polyhexafluoropropylene, and derivatives thereof. These may be used alone or in combination.

  The electricity storage device of the present invention may include a separator between the negative electrode and the positive electrode. The separator is not particularly limited as long as it has a composition that can withstand the range of use of the non-aqueous secondary battery. A porous film is mentioned. These may be used alone or in combination.

  The shape of the electricity storage device of the present invention is not particularly limited, and examples thereof include a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, and a square type. Moreover, you may apply to the large sized thing etc. which are used for an electric vehicle etc.

[Examples 1 and 2]
Soluble deprotonated polyaniline (PAn) was synthesized according to Nitto Giho, Vol. 28, p. 63 (1990). Further, poly (2,5-dihydroxy-1,4-benzoquinone-3,6-methylene (PDBM) represented by the following formula was synthesized according to Non-Patent Document 2.

  Then, an N-methylpyrrolidone (NMP) solution containing 2% by weight of PAn and an NMP solution containing 2% by weight of PDBM were prepared and mixed so that PAn and PDBM were in equal parts. , A precipitate that turned to dark green, the protonated color of PAn, was formed. This suggested that a polyion complex was formed. Also, spin coating with a PAn solution on a glass substrate (PAn film), spin coating with a PDBM solution (PDBM film), and spin coating with the PDBM solution overlaid on the PAn film Absorption spectra in the visible to near-infrared region for each of the film (PAn + PDBM) film and the PAn film immersed in 0.2N sulfuric acid aqueous solution for 5 minutes and protonated (PAn acid-treated film). Was measured. The measurement was performed with UV-3600 manufactured by Shimadzu Corporation. The result is shown in FIG. As is clear from FIG. 1, the absorption spectrum of the (PAn + PDBM) film is not the sum of the absorption spectrum of the PAn film and the absorption spectrum of the PDBM film, but the sum of the absorption spectrum of the PAn acid-treated film and the absorption spectrum of the PDBM film. It was close to. Further, when only the NMP solvent was spin-coated on the PAn film, PAn dissolved and disappeared, whereas the film remained in the (PAn + PDBM) film. From these facts, it is considered that the (PAn + PDBM) film is a polyion complex film and is insolubilized.

  In the preparation of the positive electrode material, an NMP solution containing 2% by weight of PAn and an NMP solution containing 2% by weight of PDBM are added dropwise to an NMP suspension of carbon (ECP600JD, manufactured by Lion) as a conductive additive, and the gel is mixed. A product was obtained. The gel material was kneaded with polytetrafluoroethylene (PTFE) as a binder until it became a bowl shape, and then dried to prepare a positive electrode material. Here, a low concentration product and a high concentration product were produced. That is, in the low concentration product, the mixing ratio of polyion complex (PAn + PDBM): carbon: PTFE was 15:75:10 weight ratio, and in the high concentration product, the mixing ratio was 50:40:10 weight ratio.

An evaluation cell was prepared using each positive electrode material. 2A and 2B are explanatory diagrams of the evaluation cell. FIG. 2A is a cross-sectional view before the evaluation cell 10 is assembled, and FIG. 2B is a cross-sectional view after the evaluation cell 10 is assembled. In assembling the evaluation cell 10, first, lithium metal foil (thickness 0.4 mm, diameter) is formed in the cavity 14 provided in the center of the upper surface of the stainless steel cylindrical base 12 having a thread groove on the outer peripheral surface. 18 mm), a polyethylene separator 18 (microporous polyethylene membrane, manufactured by Tonen Chemical Co., Ltd.), and a positive electrode 20 (the above-described positive electrode material is molded to have a weight of about 4 mg and an electrode area of 1.3 cm ² ). Laminated in order. And after filling 0.3 mL of electrolyte solution of 1M LiPF ₆ using a mixed solution of ethylene carbonate and diethyl carbonate mixed at a volume ratio of 3: 7 as a solvent, an insulating ring 29 made of polypropylene is put, and then A stainless steel cylinder 24 fixed in a liquid-tight manner in a hole of a polypropylene ring 22 was placed on the positive electrode 20, and a stainless steel cup-shaped lid 26 was screwed into the cylindrical base 12. Further, an insulating resin ring 27 made of PTFE is disposed on the cylinder 24, and a pressure bolt 25 having a through hole 25a in a screw groove carved in an inner peripheral surface of an opening 26a provided at the center of the upper surface of the lid 26. The negative electrode 16, the separator 18, and the positive electrode 20 were pressed and adhered. In this way, the evaluation cell 10 was assembled. In addition, since the diameter of the opening 26a provided in the upper surface center of the lid | cover 26 is larger than the diameter of the cylinder 24, the lid | cover 26 and the cylinder 24 are a non-contact state. In addition, since the packing 28 is disposed around the cavity 14, the electrolyte injected into the cavity 14 does not leak to the outside. In this evaluation cell 10, the lid 26, the pressure bolt 25, and the cylindrical base 12 are integrated with the negative electrode 16, so that the whole becomes the negative electrode side, and the column 24 is integrated with the positive electrode 20 and insulated from the negative electrode 16. Therefore, it becomes the positive electrode side. In addition, the evaluation cell 10 produced using the low concentration product as the positive electrode material is Example 1, and the evaluation cell 10 produced using the high concentration product as the positive electrode material is Example 2.

  The charge / discharge characteristics of the evaluation cell 10 of Examples 1 and 2 were evaluated using HJ1001SM8A manufactured by Hokuto Denko Corporation. Specifically, the charge / discharge behavior (cycle characteristics, rate characteristics) was evaluated in the voltage range of 2-4V. Regarding the cycle characteristics, Example 1 was used, and charging / discharging was performed repeatedly at a constant current of 0.5 mA (corresponding to 3C). Regarding the rate characteristics (capacity change at the time of current change), Example 2 was used, the current was sequentially increased, charge / discharge was performed 10 times at each current value, and the capacity was measured. The capacity per active material was determined by subtracting the carbon capacitor capacity from the obtained capacity.

[Comparative Examples 1 and 2]
In Comparative Example 1, PDBM was used alone as the positive electrode active material, and in Comparative Example 2, PAn was used alone as the positive electrode active material. Further, in both Comparative Examples 1 and 2, positive electrode materials were prepared at a mixing ratio of positive electrode active material: carbon: PTFE of 50:40:10 (weight ratio). And the cell was produced similarly to Example 1 and charge / discharge behavior was evaluated.

[Evaluation results]
FIG. 3 is a graph showing the results of the cycle characteristics of Example 1 and Comparative Example 1. As apparent from FIG. 3, in Comparative Example 1, the capacity decreased to nearly 40% of the initial value in only 100 cycles. When the decomposition was investigated, elution of PDBM, which is the positive electrode active material, was detected, and as a result, it was found that the capacity was reduced. On the other hand, in Example 1, the capacity close to 90% of the initial value was maintained even after 500 cycles even after the high rate charge / discharge of 3C. These values were higher than those of Non-Patent Document 2 and were equivalent to Non-Patent Document 1.

  FIG. 4 is a graph showing a change in capacity per weight of the positive electrode active material when the current value is changed. As is clear from FIG. 4, in Example 2, the maximum capacity (before the cycle test) was 200 mAh / g, and not only a high value was obtained as compared with Comparative Examples 1 and 2, but also Non-Patent Document 1, Even when the value of 2 was 77,150 mAh / g, a high value was obtained. In the case of a low current (up to 2 mA), the capacity of 1.5 to 8 times that of Comparative Examples 1 and 2 was obtained in Example 2. Further, in the case of a high current (10 mA), the capacity was not obtained in Comparative Example 2, and the capacity was also reduced to about 10 mAh / g in Comparative Example 1, whereas in Example 2, a large current (5.2 A / g) was obtained. Despite the weight of the active material (corresponding to 25C), the capacity of 50 mAh / g was maintained.

FIG. 5 is a graph showing the relationship between the current and the discharge capacity per active material in the low-concentration product of Example 1. As apparent from FIG. 5, in the low concentration product of Example 1, the capacity per active material weight at 20 mA (17 mA / cm ² ) was 74 mAh / g. In Non-Patent Document 1, where high output is said to be possible, it is clear that Example 1 has a high capacity and high output because it is only 70 mAh / g at 1.0 mA / cm ² .

[Examples 3-5, Comparative Examples 3-5]
The weight ratio of PAn and PDBM was 1: 2, 1: 1, 2: 1, and a positive electrode material having an active material concentration of 50 wt% was prepared in the same manner as in the high concentration product of Example 2 to prepare an evaluation cell. These evaluation cells are referred to as Example 3 (weight ratio 1: 2), Example 4 (weight ratio 1: 1), and Example 5 (weight ratio 2: 1). On the other hand, the weight ratio of PAn and PDBM was set to 1: 0, 0: 1, 0: 0, and a positive electrode material having an active material concentration of 50 wt% was prepared in the same manner as the high concentration product of Example 2 to prepare an evaluation cell. These evaluation cells are referred to as Comparative Example 3 (weight ratio 1: 0), Comparative Example 4 (weight ratio 0: 1), and Comparative Example 5 (weight ratio 0: 0). The results of evaluating the characteristics of these evaluation cells are shown in Table 1. Each of Examples 4 to 6 has a very large capacity as compared with Comparative Examples 3 to 5. From this result, it can be said that the weight ratio of PAn and PDBM may not be 1: 1.

[ Reference Example 1 ]
Sulfonated polyaniline (SPAn) obtained by sulfonating PAn with fuming sulfuric acid was synthesized according to Magazine Polymer (Vol. 33, 4410 (1992)). This SPAn functions as a substance having a polarity opposite to that of Example 1, that is, an anionic substance. On the other hand, as a compound that functions as a cationic substance, a 4-amino-2,2,6,6-tetramethylpiperidinyloxy radical (TEMPO amine, manufactured by Tokyo Chemical Industry Co., Ltd.) that becomes an oxoammonium ion structure upon oxidation. Was used. SPAn is insoluble in water, but by reacting with TEMPO amine, it was dissolved in water and became a deep blue liquid. From this it is clear that both form a polyion complex. In Example 2, an active material concentration of 50 wt% was obtained in the same manner as in Example 2 except that an aqueous solution in which SPAn and TEMPO amine were mixed at a weight ratio of 1: 1 was used instead of the gel material of PAn and PDBM. A positive electrode material was prepared. The positive electrode material was sufficiently dried so that no moisture remained. Using such a positive electrode material, an evaluation cell ( Reference Example 1 ) was produced in the same manner as in Example 2, and the rate characteristics were evaluated. The result is shown in FIG.

[Comparative Examples 6 and 7]
A positive electrode material having an active material concentration of 50 wt% was prepared in the same manner as in Example 2 except that TEMPO amine was used in place of the gel material of PAn and PDBM in Example 2. In the same manner as in Example 2, an evaluation cell (Comparative Example 6) was produced. In addition, a positive electrode material having an active material concentration of 50 wt% was prepared in the same manner as in Example 2 except that SPAn was used instead of the gel material of PAn and PDBM in Example 2, and this positive electrode material was used. An evaluation cell (Comparative Example 7) was produced in the same manner as in Example 2. The rate characteristics of these evaluation cells of Comparative Examples 6 and 7 were also evaluated. The result is shown in FIG.

[Evaluation results]
As is clear from FIG. 6, in Reference Example 1 , the capacity was higher in the entire current region than in Comparative Examples 6 and 7. From this result, it can be seen that a good effect can be obtained even when a polyion complex using an anionic conductive polymer is used as the positive electrode active material.

[ Reference Example 2 ]
As a compound that functions as an anionic substance, 4-carboxyl-2,2,6,6-tetramethylpiperidinyloxy radical having a carboxyl group bonded to the 4-position of TEMPO (TEMPO acid, manufactured by Tokyo Chemical Industry Co., Ltd.) PAn was used as a compound that functions as a cationic substance. In Example 2, a positive electrode material having an active material concentration of 50 wt% was prepared in the same manner as in Example 2 except that TEMPO acid and an NMP solution of PAn were used instead of the NMP solution of PAn and PDBM. Using such a positive electrode material, an evaluation cell ( Reference Example 2 ) was produced in the same manner as in Example 2, and the rate characteristics were evaluated. The result is shown in FIG.

[Comparative Examples 8 and 9]
A positive electrode material was prepared in the same manner as in Reference Example 2 except that TEMPO having no anionic property was used instead of TEMPO acid in Reference Example 2, and an evaluation cell (Comparative Example 8) was prepared. Further, except that in Reference Example 2 using only PAn, a positive electrode material was prepared in the same manner as in Reference Example 2, was produced evaluation cell (Comparative Example 9). The rate characteristics of these evaluation cells of Comparative Examples 8 and 9 were also evaluated. The result is shown in FIG.

[Evaluation results]
As is clear from FIG. 7, in Reference Example 2 , the capacity was higher in the entire current region than in Comparative Examples 8 and 9. From this result, it can be seen that even when a polyion complex composed of a combination of a cationic conductive polymer and an anionic organic compound is used as the positive electrode active material, a good effect can be obtained.

  The electricity storage device of the present invention can be used mainly in the electrochemical industry. For example, it can be used for power sources of hybrid vehicles and electric vehicles, power sources for consumer electronics such as mobile phones and personal computers, and load leveling (load leveling). It can be used for electrochemical devices.

It is a graph of the absorption spectrum of a polyion complex. 2 is a cross-sectional view for explaining an evaluation cell 10. FIG. 6 is a graph showing a change in capacity with respect to the number of cycles in Example 1 and Comparative Example 1. It is a graph showing the discharge capacity with respect to the electric current of Example 2 and Comparative Examples 1 and 2. FIG. It is a graph showing the relationship between the electric current of Example 1, and the discharge capacity per active material. 6 is a graph showing discharge capacity with respect to current in Reference Example 1 and Comparative Examples 6 and 7. It is a graph showing the discharge capacity with respect to the electric current of the reference example 2 and the comparative examples 8 and 9. FIG.

Explanation of symbols

10 Evaluation Cell, 12 Cylindrical Base, 14 Cavity, 16 Negative Electrode, 18 Separator, 20 Positive Electrode, 22 Ring, 24 Column, 25 Pressure Bolt, 25a Through Hole, 26 Lid, 26a Opening, 27 Insulating Resin Ring, 28 Packing, 29 Insulation ring.

Claims (2)

Both are storage devices using a polyion complex composed of a cationic organic compound having redox properties and an anionic organic compound as an electrode active material,
The cationic organic compound is a conductive polymer compound composed of polyanilines, polypyrroles or polythiophenes,
The anionic organic compound is a benzoquinone polymer or dihydrobenzoquinone polymer having a phenolic hydroxyl group (however, excluding a coordination polymer complex) .
Power storage device. A lithium secondary battery using the polyion complex as a positive electrode active material and a material capable of occluding and releasing lithium ions as a negative electrode active material,
The electricity storage device according to claim 1.