JP5420017B2 - Power storage device - Google Patents

Description

  The present invention relates to an electricity storage device having high output, high capacity, and excellent repeatability.

In recent years, with the widespread use of hybrid vehicles that can be driven by both gasoline and electricity, uninterruptible power supplies, mobile communication devices, portable electronic devices, and other devices that require a power source, charging and discharging can be used as the power source. The demand for higher performance of possible power storage devices has become very large. Specifically, high performance is required in characteristics such as output, capacity, and repetition life.
In order to realize an electricity storage device having such characteristics, studies have been made on using an organic compound as an electrode active material. Recently, an organic compound having a π-electron conjugated cloud and a reaction mechanism thereof have been clarified by the present inventors as a new active material that can be expected to be charged and discharged at high speed (for example, Patent Documents 1 and 2). reference).

As the electrode active material, an organic compound having a π electron conjugated cloud can be used from a low molecular compound to a high molecular compound. Since polymer compounds are less soluble in electrolytes than low molecular weight compounds, elution of active materials into electrolytes is suppressed when polymer compounds are used as electrode active materials. It is disclosed that the stability of characteristics is further enhanced.
Specifically, it is disclosed that a polymer compound having a plurality of organic compound sites having a π-electron conjugated cloud can be used as the polymer compound active material. For example, a polymer active material obtained by bonding an organic compound moiety having a π electron conjugated cloud to a compound having a polyacetylene or polymethyl methacrylate chain as a main chain is disclosed.

  In addition, it is disclosed that an electrolyte solution composed of a solvent and an electrolyte salt dissolved therein is used as an electrolyte for constituting an electricity storage device using the organic compound having the π-electron conjugated cloud as an active material. Specifically, it is disclosed that organic solvents such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone, tetrahydrofuran, dioxolane, sulfolane, dimethylformamide are preferably used as the solvent. Yes.

  As described above, in order to obtain an electricity storage device having excellent characteristics such as output, capacity, and repetition life, an organic compound polymer having a π electron conjugated cloud is used as an electrode active material, and various electrolyte salts are used as an electrolyte. It is disclosed that an electrolytic solution obtained by dissolving in a solvent is used.

JP 2004-111374 A JP 2004-342605 A

In an electricity storage device using an organic compound polymer having a π-electron conjugated cloud as an electrode active material, it is known that an electrolyte obtained by dissolving an electrolyte salt in various solvents can be used as an electrolyte. Until now, it has not been clarified at all how the characteristics of the electricity storage device change depending on the solvent.
As a result of the extensive research conducted by the inventors on the electrolyte of an electricity storage device using an organic compound polymer having a π-electron conjugated cloud as an electrode active material, depending on the type of solvent used in the electrolyte, the charge / discharge capacity of the electricity storage device decreases. I found out that sometimes

  The inventors of the present invention have studied in detail the cause of the decrease in charge / discharge capacity of the electricity storage device depending on the type of solvent used in the electrolyte. As a result, the relationship between the relative dielectric constant of the solvent used in the electrolyte and the charge / discharge capacity of the electricity storage device is determined. It became clear that there is a correlation. Specifically, when the relative dielectric constant at 20 ° C. of the solvent used is less than 55, the charge / discharge capacity of the electricity storage device is lower than the design capacity, whereas the relative dielectric constant at 20 ° C. is 55 or more. In the case of 90 or less, it became clear that a high capacity according to the design capacity can be obtained.

That is, an electricity storage device of the present invention includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and an electrolyte including a solvent and an electrolyte salt dissolved in the solvent, and at least of the positive electrode active material and the negative electrode active material on the other hand but, [pi and Nde containing an organic compound polymer having an electron conjugated cloud, relative dielectric constant at 20 ° C. of the solvent is 55 or more and 90 or less, said organic compound polymer, not soluble in said solvent A polymer main chain; and a side chain having an organic compound skeleton having a π electron conjugated cloud bonded to the polymer main chain, and the skeleton of the organic compound having the π electron conjugated cloud is tetrathiaful. Barene skeleton .

  According to the present invention, an electricity storage device having high output, high capacity, and excellent repeatability can be provided. In particular, the problem that the charge / discharge capacity decreases with respect to the design capacity can be solved.

It is a schematic longitudinal cross-sectional view of the coin-type electrical storage device in one embodiment of this invention. It is a schematic sectional drawing of the positive electrode in one embodiment of this invention. It is a schematic sectional drawing of positive electrode active material particle.

Embodiment 1
The best mode for carrying out the present invention will be described below with reference to the drawings.
The electricity storage device in Embodiment 1 includes a polymer having a molecular structure represented by the following formula (1) (hereinafter represented by poly-TTF) as an organic compound polymer having a π-electron conjugated cloud of a positive electrode active material. A positive electrode is provided. In this electricity storage device, 1 mol concentration of lithium hexafluorophosphate is dissolved in a negative electrode containing metallic lithium as a negative electrode active material, and a solvent in which propylene carbonate and ethylene carbonate are mixed at a volume ratio of 1: 1 as an electrolyte. An electrolyte solution is used. The dielectric constant of the electrolyte solvent at 20 ° C. is 78. The charge / discharge conditions of the electricity storage device are a constant current charge / discharge, a charge upper limit voltage of 4.0V, and a discharge lower limit voltage of 3.0V.

  FIG. 1 is a schematic longitudinal sectional view schematically showing an electricity storage device of the present invention. Reference numeral 11 denotes a stainless steel case that also serves as a positive electrode terminal, in which a positive electrode current collector plate 12, a positive electrode 13, and a separator 14 are accommodated. Reference numeral 15 denotes a stainless steel sealing plate that also serves as a negative electrode terminal. In this sealing plate, a negative electrode 16, a negative electrode current collector plate 17, and a spacer 19 are arranged. Reference numeral 18 denotes a gasket attached to the peripheral edge of the sealing plate 15. The case 11 and the sealing plate 15 are combined, and the peripheral portion of the case 11 is caulked to the peripheral portion side of the sealing plate 15 via the gasket 18 to complete the sealed electricity storage device as illustrated.

  In the following, the reaction mechanism of the organic compound polymer, which is the positive electrode active material, first, then the relationship between the relative dielectric constant of the solvent used for the electrolyte of the electricity storage device and the capacity characteristics of the electricity storage device, as a result of detailed studies Will be described in order.

First, the reaction mechanism of poly-TTF which is a positive electrode active material is demonstrated.
As shown in the formula (1), poly-TTF, which is one of the polymer active materials, has tetrathiafulvalene, which is a reaction site having a π-electron conjugated cloud, as a side chain and a polymer main chain. It has a molecular structure linked through an ester bond. Tetrathiafulvalene, which is a reactive site, is dissolved depending on the solvent used when a single molecule is used as an active material. For this reason, there are restrictions on the type of solvent that can be used as the electrolyte or the device configuration of the electricity storage device. In contrast, poly-TTF has a large molecular weight and is bonded to a polyethylene polymer chain that is insoluble in many solvents, so that its solubility in solvents is greatly reduced, and it can be used as a solvent type or power storage. It is an active material that is expected to have few restrictions on the device configuration of the device.

  The polymer active material represented by the formula (1) is in an electrically neutral state, that is, a discharge state having no charge. When this polymer active material is charged, tetrathiafulvalene enters an oxidized state and emits electrons, as shown in the formula (2), and becomes positively charged.

  Therefore, the electrolyte anion having a negative charge is coordinated to tetrathiafulvalene and becomes a charged state. Tetrathiafulvalene in a charged state becomes electrically neutral by receiving electrons and releases an electrolyte anion to a discharged state. As described above, the polymer active material can operate as an electricity storage device active material by reversibly repeating a charged state as shown in Equation (2) and a discharged state as shown in Equation (1).

  As an example of the positive electrode structure, FIG. 2 is an enlarged schematic sectional view schematically showing the positive electrode 13, and FIG. 3 is an enlarged schematic view of the positive electrode active material contained in the positive electrode 13. A schematic sectional view is shown respectively. In FIG. 2, 12 is a positive electrode current collector, and a positive electrode 13 is formed on the current collector. The positive electrode 13 further includes positive electrode active material particles 21 and a conductive agent part 22 inside. The polymer active material contained in the positive electrode 13 may exist as a particle state as indicated by 21 in FIG. The electrically conductive agent part 22 is formed from what mixed the electronic conductive particle like carbon black with the binder as needed, for example. The conductive agent portion 22 is porous as necessary, and can impregnate and hold the electrolyte solution therein.

  As shown in FIG. 3, the positive electrode active material particle 21 includes a surface layer portion 31 and a center portion 32. Since the electrolyte solution is mainly impregnated and held inside the porous conductive agent part, it is the surface layer part 31 that allows the active material particles to come into contact with the electrolyte solution. Therefore, when the positive electrode is charged, first, the surface layer portion 31 of the positive electrode active material is oxidized and positively charged, and the electrolyte anion transferred from the electrolyte solution is coordinated to the active material, and the active material is charged. It becomes a state. As the charging reaction proceeds, the portion occupied by the charging active material gradually increases from the surface layer portion toward the center portion. That is, as the electrolyte anion passes from the electrolyte solution to the inside of the active material particles through the surface layer portion and moves toward the center portion, the charging reaction proceeds to the inside of the active material particles.

Next, the relationship between the relative dielectric constant of the solvent used for the electrolyte of the electricity storage device and the electricity storage device characteristics will be described.
In order for the charging reaction to proceed completely to the center of the active material particle, the electrolyte anion can move inside the active material particle, and it can contribute to charge / discharge completely to the inside of the active material particle. It is indispensable to obtain. In order to allow electrolyte anions to move inside the active material particles, it is considered that a solvent that dissolves an electrolyte salt that is an electrolyte plays a very important role.

  As the molecular structure of the active material at the time of charging, the expression (2) shows that the electrolyte anion is coordinated to the positively charged active material. At this time, it is considered that a Coulomb attractive force acts between the positively charged active material and the electrolyte anion having a negative charge. When this binding force is strong, it is considered that the electrolyte anion is strongly trapped in the active material molecule. Therefore, when the surface layer portion of the active material particle is charged, the electrolyte anion is trapped in the surface layer portion of the active material particle, passes through the active material surface layer portion from the electrolyte solution, and enters the active material center portion. Becomes impossible. In this case, the active material particles cannot react to the inside of the particles, and only a capacity smaller than the designed capacity can be used, resulting in a decrease in capacity.

  In order to solve such a problem that the capacity decreases, in the present invention, a solvent having a high relative dielectric constant is used as a solvent for the electrolyte. The molecular structure of the charge active material in the case of using a solvent having a high dielectric constant, that is, a solvent in which propylene carbonate (PC) and ethylene carbonate (EC) are mixed at a volume ratio of 1: 1 in this embodiment is schematically shown. It shows in Formula (3).

  It is considered that the solvent having a high relative dielectric constant solvates with the charged and positively charged tetrathiafulvalene part and alleviates the electrostatic attractive force between the active material and the electrolyte anion. As a result, the electrolyte anion is not strongly trapped by the charged active material, and can move inside the charged active material. Therefore, even when the surface layer portion of the active material particles is charged, the electrolyte anion is not trapped in the surface layer portion of the active material particles, and passes through the active material surface layer portion from the electrolyte solution and enters the active material center portion. Thus, it is considered that the active material particles can be used for charging and discharging up to the inside of the particles.

  In general, in a solvent in which a salt composed of an anion and a cation is dissolved, in order to dissociate the salt and enable each ion to move independently, a solvent having a high relative dielectric constant is effective. Are known. The cause is known to be that a solvent having a high relative dielectric constant preferentially solvates the cation of the salt and relaxes the electrostatic attractive force between the anion and the cation. Also in the polymer active material in the present embodiment, a solvent having a high relative dielectric constant is preferentially solvated with a cation that is a reaction site of the charged active material, and the anion-cation space is the same. It is estimated that the electrostatic attraction of the

Due to the mechanism described above, it is considered effective that the relative dielectric constant of the solvent used in the electrolyte is a certain value or more. Further, as a result of detailed studies, it has been found that it is effective that there is a threshold value as the relative dielectric constant of the solvent and the relative dielectric constant at 20 ° C. is 55 or more and 90 or less. That is, in an electricity storage device using an organic compound polymer having a π-electron conjugated cloud as an active material, when the relative permittivity at 20 ° C. of the electrolyte solvent is 0 or more and less than 55, all of the active material particles are used for charging and discharging. Therefore, when the relative dielectric constant at 20 ° C. is 55 or more and 90 or less, the entire capacity of the active material particles can be used for charging / discharging. Thus, an electricity storage device with a high capacity as designed can be obtained.
Furthermore, when the relative dielectric constant increases, the viscosity of the solvent increases and the conductivity of the electrolytic solution may decrease, or the wettability of the separator or electrode plate to the solvent may decrease. . For these reasons, the relative dielectric constant of the solvent at 20 ° C. is preferably 55 to 65.

Examples of the organic polymer active material that can be used as the active material in the electricity storage device of the present invention include organic compounds having a π-electron conjugated cloud. The organic polymer active material to be used is not particularly limited as long as it is a polymer, but those having an average molecular weight of 10,000 or more can be suitably used. This is because the solubility of the active material molecules in the solvent is greatly reduced, and it is expected that there are few restrictions on the type of solvent that can be used for the electrolyte or the device configuration of the electricity storage device.
In addition, the organic compound active material having a π-electron conjugated cloud is not necessarily a high molecular weight material, and a low molecular weight material having a molecular weight of less than 10,000 can be used as the active material. However, since the solubility in the electrolyte solvent is different from that of the polymer, the solvent type that can be used as the electrolyte must be designed in consideration of the solubility in addition to the above reasons. It is considered that the optimum value of the electrolyte solvent to be used is different. Therefore, it is excluded from the target of active materials that can be used in the electricity storage device of the present invention.

  Examples of the organic compound polymer having a π electron conjugated cloud include an organic compound polymer having a structure represented by the following general formula (4) or (5).

(In the formula (4), X is a sulfur atom or an oxygen atom, and R ^{1 to} R ⁴ are each independently a chain aliphatic group, a cyclic aliphatic group, a hydrogen atom, a hydroxyl group, a cyano group, an amino group. , A nitro group or a nitroso group, wherein R ⁵ and R ⁶ are each independently a hydrogen atom, a chain aliphatic group, or a cyclic aliphatic group, and the aliphatic group is an oxygen atom, a nitrogen atom, a sulfur atom And at least one selected from the group consisting of a silicon atom, a phosphorus atom, a boron atom and a halogen atom.

(In the formula (5), X is a nitrogen atom, and R ^{1 to} R ⁴ are each independently a chain aliphatic group, cyclic aliphatic group, hydrogen atom, hydroxyl group, cyano group, amino group, nitro group. Or a nitroso group, wherein R ⁵ and R ⁶ are each independently a hydrogen atom, a chain aliphatic group, or a cyclic aliphatic group, and the aliphatic group is an oxygen atom, a nitrogen atom, a sulfur atom, or a silicon atom. , At least one selected from the group consisting of a phosphorus atom, a boron atom, and a halogen atom.

  Another example of the π-electron compound is an organic compound polymer having a structure represented by the following general formula (6).

(In the formula (6), X ^{1 to} X ⁴ are each independently a sulfur atom, oxygen atom, selenium atom, or tellurium atom, and R ^{1 to} R ² are each independently a chain aliphatic group or a cyclic aliphatic group. And the aliphatic group may 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.)

  The organic compound polymer that is an active material may be a polymer in which organic compounds having a π-electron conjugated cloud that is a reaction site of the structure of the above general formulas (4) to (6) are bonded together, Alternatively, a polymer formed by binding an organic compound molecule having a π electron conjugated cloud as a reaction site as described above as a side chain to a polymer main chain insoluble in an electrolyte solvent as a non-reaction site. Also good.

In the case of the latter polymer active material, the polymer main chain used as the polymer main chain insoluble in the electrolyte solvent can be used without any limitation. Specifically, for example, hydrocarbon polymers such as polyethylene, polypropylene, polyacetylene, polymethyl methacrylate, polystyrene, polyurethane, polyacrylonitrile, polymethylpentene, polyether ether ketone, polyether sulfone, or halogenated polymers thereof. To various polymer main chains.
For example, specific examples of the organic polymer having reaction sites having the structures of the general formulas (4) and (5) include compounds represented by the following chemical formulas (7) and (8).

  For example, as an example of the organic polymer having a reaction site having the structure of the general formula (6), compounds represented by the following chemical formulas (9) to (15) can be given as specific examples.

  Moreover, when producing the electrode containing these active materials, you may use a electrically conductive agent in order to provide electronic conductivity. Specifically, a carbon material such as carbon black, graphite, and acetylene black, a conductive polymer such as polyaniline, polypyrrole, or polythiophene, and an active material may be mixed to form an electrode. Further, as the ion conductive auxiliary agent, a solid electrolyte made of polyethylene oxide or the like, or a gel electrolyte made of polymethyl methacrylate or the like may be included in the positive electrode. Furthermore, in order to improve the binding property of the active material, binders such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, polyethylene, polyimide, polyacrylic acid, etc. May be included in the positive electrode. As the current collector, a metal foil, a metal mesh, a resin film containing a conductive filler, or the like is used as in a general battery.

Next, an electrolyte that can be used in the electricity storage device of the present invention will be described. The electrolyte of the present invention can be obtained by dissolving a salt composed of an anion and a cation in a solvent.
As the salt, a salt composed of the following anions and cations can be used. The anion species include halide anions, perchlorate anions, trifluoromethanesulfonate anions, tetrafluoroborate anions, hexafluorophosphate anions, trifluoromethanesulfonate anions, nonafluoro-1-butanesulfonate anions, bis ( Examples thereof include a trifluoromethanesulfonyl) imide anion and a bis (perfluoroethylsulfonyl) imide anion. Examples of the cation species include alkali metal cations such as lithium, sodium and potassium, alkaline earth metal cations such as magnesium, quaternary ammonium cations such as tetraethylammonium and 1,3-ethylmethylimidazolium.

  As the cation species, a quaternary ammonium cation or a lithium cation can be preferably used. The reason is as follows. That is, since the quaternary ammonium cation has a high ion mobility and can obtain an electrolytic solution with high conductivity, and a negative electrode having an electric double layer capacity such as activated carbon having a high reaction rate can be used as a counter electrode. A high output power storage device can be obtained. The lithium cation can use a negative electrode capable of inserting and extracting lithium with a low reaction potential and a high capacity density as a counter electrode, so that an electricity storage device with high voltage and high energy density can be obtained.

As a solvent that can be used in the electricity storage device of the present invention, a solvent that can be used for a nonaqueous secondary battery or a nonaqueous electric double layer capacitor can be used as long as the relative dielectric constant is 55 or more and 90 or less. It is.
Specifically, a solvent containing a cyclic carbonate can be suitably used. This is because cyclic carbonates have a very high dielectric constant, as represented by 90 of ethylene carbonate and 65 of propylene carbonate. Therefore, by containing these solvents as components, the ratio at 20 ° C. This is because a solvent having a dielectric constant of 55 or more and 90 or less can be easily obtained. Of the cyclic carbonates, propylene carbonate is preferred. This is because the freezing point is −49 ° C., which is lower than that of ethylene carbonate, and the electricity storage device can be operated even at a low temperature.

  Moreover, the solvent containing cyclic ester can also be used suitably. This is because the cyclic ester has a very high relative dielectric constant as represented by 42 of γ-butyrolactone, and therefore by containing these solvents as components, the relative dielectric constant at 20 ° C. is 55 or more and 90 This is because the following solvent can be easily obtained. γ-Butyrolactone alone does not fall within the range of a relative dielectric constant of 55 or more and 90 or less at 20 ° C., but it may be used alone by increasing the relative dielectric constant by derivatization. It may be mixed with other solvents such as cyclic carbonates and used as a solvent having a relative dielectric constant of 55 to 90 at 20 ° C.

Further, the solvent may be used alone or in combination with a plurality of solvents. Examples of other solvents that can be used include chain carbonate esters, chain esters, cyclic ethers, and the like. Specifically, non-aqueous solvents such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, tetrahydrofuran, dioxolane, sulfolane, dimethylformamide, acetonitrile, dimethyl sulfoxide and the like are used.
The electrolyte using these solvents can be used by impregnating at least the inside of the positive electrode, but a solid electrolyte or a gel electrolyte may be further used as necessary.

The negative electrode active material in the electricity storage device of the present invention is not particularly limited, and includes carbon materials such as graphite and amorphous carbon, lithium metal, lithium-containing composite nitride, lithium-containing titanium oxide, silicon, and silicon. Alloys, silicon oxide, tin, tin-containing alloys, and materials that can reversibly store and release lithium, such as tin oxide, or carbon materials with electric double layer capacity, such as activated carbon, π-electron conjugation An organic compound material having a cloud can be used. These negative electrode materials may be used alone or in combination with a plurality of negative electrode materials.
In this embodiment, an example in which an organic compound polymer having a π-electron conjugated cloud is used as a positive electrode active material and metal lithium is used for a negative electrode is shown. However, the device configuration is not limited to this, and a π-electron conjugated cloud is included. An organic compound may be used as the negative electrode active material, or an organic compound that can be oxidized and reduced together with the positive and negative electrode active materials may be used as the active material.

  The present invention includes an organic compound polymer having a π-electron conjugated cloud in at least one of a positive electrode active material and a negative electrode active material, and by using a solvent having a relative dielectric constant of 55 to 90 at 20 ° C. as an electrolyte solvent, An electricity storage device having high output, high capacity, and excellent repetitive characteristics can be provided. In particular, the problem that the charge / discharge capacity decreases with respect to the design capacity can be solved.

Although the electrical storage device of this invention is demonstrated in detail with an Example below, this invention is not limited to these Examples.
Example 1
The positive electrode was produced as follows. As an active material, poly-TTF, which is a polymer having a molecular structure represented by the chemical formula (1), was used as an organic compound polymer having a π-conjugated electron cloud. Poly-TTF was synthesized by reacting polyvinyl alcohol and a tetrathiafulvalene carboxyl derivative by dehydration condensation. The poly-TTF used had an average molecular weight of about 50,000 and a theoretical maximum capacity of 190 mAh / g. The poly-TTF was used after being pulverized in a mortar. The particle diameter of the π-conjugated polymer active material after mortar grinding was about 10 μm. As an active material, 37.5 mg of poly-TTF and 100 mg of acetylene black as a conductive agent were uniformly mixed, and further 25 mg of polytetrafluoroethylene as a binder was added and mixed to obtain a positive electrode mixture. This positive electrode mixture was pressure-bonded onto an aluminum wire mesh, vacuum-dried, and then punched and cut into a disk shape having a diameter of 13.5 mm to obtain a positive electrode plate. The coating weight of the positive electrode active material was 1.7 mg / cm ² per electrode plate unit area.

As the negative electrode active material, metallic lithium (thickness: 300 μm) was punched into a disk shape having a diameter of 15 mm and attached to a disk-shaped stainless steel current collector plate having a diameter of 15 mm to produce a negative electrode.
For the electrolyte, an electrolytic solution obtained by dissolving 1 mol / L lithium hexafluorophosphate in a solvent in which ethylene carbonate (EC) and propylene carbonate (PC) are mixed at a volume ratio of 1: 1 as a solvent is used. Using. The relative permittivity of the solvent used at 20 ° C. is 78. The relative dielectric constant of the solvent was measured by a capacitance method.
The electrolytic solution was impregnated in a separator composed of a positive electrode, a negative electrode, and a porous polyethylene sheet having a thickness of 20 μm.
The positive electrode, the negative electrode, and the separator were sandwiched between a coin-type battery case as shown in FIG. 1 and a sealing plate equipped with a gasket, and caulked and sealed with a press to obtain a coin-type electricity storage device.

Example 2
The electricity storage device of Example 2 has the same configuration as that of Example 1 except for the electrolytic solution. The electrolytic solution is obtained by dissolving 1 mol / L of lithium hexafluorophosphate in PC. The solvent used had a relative dielectric constant of 65 at 20 ° C.

Example 3
The electricity storage device of Example 3 has the same configuration as that of Example 1 except for the electrolytic solution. The electrolytic solution used was a solution in which lithium hexafluorophosphate having a concentration of 1 mol / L was dissolved in a solvent in which PC and diethyl carbonate (DEC) were mixed at a volume ratio of 12: 1. The solvent used has a relative dielectric constant of 60 at 20 ° C.

Example 4
The electricity storage device of Example 4 has the same configuration as that of Example 1 except for the electrolytic solution. As the electrolytic solution, a solution in which 1 mol / L of lithium hexafluorophosphate was dissolved in a solvent in which PC and DEC were mixed at a volume ratio of 5: 1 was used. The solvent used had a relative dielectric constant of 55 at 20 ° C.

<< Comparative Example 1 >>
The electricity storage device of Comparative Example 1 has the same configuration as that of Example 1 except for the electrolytic solution. As the electrolytic solution, a solution in which lithium hexafluorophosphate having a concentration of 1 mol / L was dissolved in a solvent in which PC and DEC were mixed at a volume ratio of 3.2: 1 was used. The relative permittivity of the solvent used at 20 ° C. is 50.

<< Comparative Example 2 >>
The electricity storage device of Comparative Example 2 has the same configuration as that of Example 1 except for the electrolytic solution. As the electrolytic solution, a solution obtained by dissolving 1 mol / L lithium hexafluorophosphate in a solvent in which PC and DEC were mixed at a volume ratio of 1.5: 1 was used. The solvent used has a relative dielectric constant of 40 at 20 ° C.

<< Comparative Example 3 >>
The electricity storage device of Comparative Example 3 has the same configuration as that of Example 1 except for the electrolytic solution. As the electrolytic solution, a solution obtained by dissolving 1 mol / L lithium hexafluorophosphate in a solvent in which PC and DEC were mixed at a volume ratio of 1: 1 was used. The solvent used had a relative dielectric constant of 34 at 20 ° C.

The charge / discharge capacities of the electricity storage devices of Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated as follows.
Under an environment of a temperature of 20 ° C., the battery was charged / discharged at a constant current of 0.1 mA with a charge upper limit voltage of 4.0 V and a discharge lower limit voltage of 3.0 V. After the end of charging, there was no rest time until discharging was started. And the value which divided the charging capacity at the time of the first charging / discharging by the active material weight, ie, the charging capacity per unit weight of an active material, was evaluated as charging / discharging capacity.
The evaluation results are shown in Table 1.

As shown in Table 1, in Examples 1 to 4 where the relative dielectric constant at 20 ° C. of the solvent used in the electrolytic solution is 55 or more and 90 or less, it is 178 mAh / g or more per unit weight of the active material, which is almost the theory of the active material. A high capacity close to the capacity was obtained.
On the other hand, when the relative dielectric constant at 20 ° C. of the solvent used in the electrolyte solution is less than 55 as in Comparative Examples 1 to 3, the capacity is 28 mAh / g or less per unit weight of the active material, which is large compared to the design. There was a decrease that would decrease. This is presumably because the solvation of the solvent to the positively charged active material molecules at the time of charging is insufficient, and only the surface layer portion of the active material particles can contribute to charging and discharging.

  As described above, in an electricity storage device including at least an organic compound polymer having a π-electron conjugated cloud as an active material, by using a solvent having a relative dielectric constant of 55 or more and 90 or less at 20 ° C. as an electrolyte solvent, high output, An electricity storage device having a high capacity and excellent repetitive characteristics can be provided. In particular, the problem of a decrease in charge / discharge capacity with respect to the design capacity can be solved.

  The electricity storage device of the present invention has high output, high capacity, and excellent repeatability. Therefore, it can be used for various portable devices, transportation devices, uninterruptible power supplies, and the like.

DESCRIPTION OF SYMBOLS 11 Case 12 Positive electrode current collector plate 13 Positive electrode 14 Separator 15 Sealing plate 16 Negative electrode 17 Negative electrode current collector plate 18 Gasket 21 Positive electrode active material particle 22 Conductive agent part 31 Surface layer part of positive electrode active material particle 32 Center part of positive electrode active material particle

Claims (8)

A positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and an electrolyte including a solvent and an electrolyte salt dissolved in the solvent,
At least one of the positive electrode active material and the negative electrode active material contains an organic compound polymer having a π electron conjugated cloud,
The relative dielectric constant of the solvent at 20 ° C. is 55 or more and 90 or less,
The organic compound polymer has a polymer main chain insoluble in the solvent, and a side chain having a skeleton of an organic compound bonded to the polymer main chain and having a π-electron conjugated cloud;
The electrical storage device whose skeleton of the organic compound having the π-electron conjugated cloud is a tetrathiafulvalene skeleton.   The electrical storage device according to claim 1, wherein the organic compound polymer has a molecular weight of 10,000 or more.   The electrical storage device according to claim 1, wherein the solvent has a relative dielectric constant at 20 ° C of 55 or more and 65 or less. The organic compound polymer has a structure represented by the following formula (9), (10), (11) , ( 13), (14), or (15). The electricity storage device described in 1.

(In the formula, n represents the number of repeating monomer units.)   The electricity storage device according to claim 1, wherein the solvent contains a cyclic carbonate.   The electricity storage device according to claim 1, wherein the solvent contains a cyclic ester.   The electricity storage device according to claim 1, wherein the electrolyte salt includes an anion and a cation, and the cation includes a quaternary ammonium salt.   The electricity storage device according to claim 1, wherein the electrolyte salt includes an anion and a cation, and the cation is a lithium ion.

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