WO2019172119A1 - Electricity storage device - Google Patents

Abstract

The present disclosure provides an electricity storage device (1) which has high flame retardancy. This electricity storage device (1) comprises: a positive electrode (10) that is provided with a positive electrode active material; a negative electrode (20) that is provided with a negative electrode active material; an electrolyte solution (40) that contains alkali metal ions; and a hermetic sealing body (50) which is internally in contact with the electrolyte solution, and in which the electrolyte solution (40) is hermetically sealed. At least one of the positive electrode active material and the negative electrode active material is capable of absorbing and desorbing the alkali metal ions. This electricity storage device (1) is additionally provided with an extinguishing agent in the internal space of the hermetic sealing body (50), said extinguishing agent exhibiting a flameproofing function. The extinguishing agent has an RED value of more than 1 on the basis of the Hansen solubility parameter with respect to the electrolyte solution (40).

Description

Electricity storage device

This disclosure relates to an electricity storage device.

An electricity storage device including an active material capable of occluding and releasing alkali metal ions is widely used because it exhibits excellent characteristics such as high operating voltage and excellent energy density. And in order to improve the safety | security of an electrical storage device, examination is repeated and many safety tests are done. Examples of the safety test include a nail penetration test and a crushing test that simulate an internal short circuit of the power storage device, and a heating test that simulates that the power storage device is heated from the outside.

A technology has been proposed for preventing an electricity storage device from igniting when the electricity storage device has an internal short circuit or is heated. For example, JP 2013-541131A discloses a technique for extinguishing a fired power storage device by disposing a fire extinguishing agent around the power storage device.

However, there is a possibility that the fired power storage device cannot be easily extinguished even by using the technology described in Japanese Patent Publication No. 2013-541131. For example, a high-temperature power storage device ignites and the temperature of the power storage device further increases. For this reason, the organic solvent of the electricity storage device is vaporized and diffused to the surroundings. When ignited by the vaporized organic solvent, a plurality of power storage devices can ignite in a chain. If the power storage devices are ignited in this way, there is a possibility that the technology described in Japanese Patent Publication No. 2013-541131 cannot be easily extinguished. Therefore, there is a demand for highly flame retardant power storage devices.

One feature of the present disclosure is an electricity storage device including a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, an electrolytic solution, a sealing body, and a fire extinguishing agent. The electrolytic solution contacts the positive electrode and the negative electrode and contains alkali metal ions. A sealing body contacts electrolyte solution inside, and seals electrolyte solution. At least one of the positive electrode active material and the negative electrode active material can occlude and release alkali metal ions. The fire extinguishing agent is disposed in the internal space of the sealed body and exhibits a flame retarding function. The fire extinguisher has a RED value greater than 1 based on the Hansen solubility parameter for the electrolyte.

According to the above characteristics, the electricity storage device is provided with a fire extinguishing agent in the internal space of the sealed body. Therefore, the fire-extinguishing function of the fire extinguishing agent to make the electricity storage device flame retardant can be exhibited not from the outside of the sealed body but from the inside.

Moreover, since the RED value based on the Hansen solubility parameter with respect to the electrolyte is larger than 1, the amount of the fire extinguisher dissolved in the electrolyte is negligibly small. Therefore, the fire extinguisher is stable in the electricity storage device. Accordingly, the fire extinguisher stably increases the flame retardance of the electricity storage device over time and does not significantly affect the charge / discharge process of the electricity storage device.

Another feature of the present disclosure is that the electrolytic solution includes an organic solvent and an imide-based lithium salt. The positive electrode has a current collector foil. The positive electrode active material is held on the current collector foil through a binder containing a polymer having a RED value greater than 1 based on the Hansen solubility parameter for the electrolytic solution. Therefore, the binder is stable against the electrolytic solution even in a high temperature environment. Therefore, the power storage device can maintain the capacity even in an environment of 85 ° C. required for installation in the vehicle interior of the automobile, and the increase in internal resistance is small.

Another feature of the present disclosure is that an enclosure provided so as to surround the positive electrode and the negative electrode is provided inside the sealed body. The fire extinguishing agent is provided on the enclosure. Therefore, the fire extinguisher can effectively enhance the flame retardancy of the electricity storage device.

Another feature of the present disclosure is a lithium ion capacitor. In general, a single lithium metal is used in a pre-doping process included in a method of manufacturing a lithium ion capacitor. Since single lithium ions cause ignition, a pre-doping process is performed so that no single lithium metal remains in the lithium ion capacitor. In the unlikely event that a single lithium metal remains in the lithium ion capacitor, the fire extinguishing agent disposed in the internal space of the sealed body exerts a flame retarding function, thereby preventing the ignition of the lithium ion capacitor. Moreover, it is not necessary to spend time in the pre-doping process so that metallic lithium does not precipitate as in the prior art, and the time of the pre-doping process can be shortened.

It is a disassembled perspective view of the electrical storage device of 1st Embodiment. It is a perspective view of the electrical storage device of a 1st embodiment. FIG. 3 is a schematic diagram of a cross section taken along line III-III in the electricity storage device of FIG. 2. In 1st Embodiment, it is a figure explaining the example of the external appearance of a positive electrode plate. FIG. 5 is a cross-sectional view taken along line VV in the positive electrode plate of FIG. 4. In 1st Embodiment, it is a figure explaining the example of the external appearance of a negative electrode plate. FIG. 7 is a sectional view taken along line VII-VII in the negative electrode plate of FIG. In 1st Embodiment, it is a figure explaining the example of the external appearance of a separator provided with a fire extinguisher. FIG. 9 is a sectional view taken along line IX-IX in the separator of FIG. In 1st Embodiment, it is a figure explaining the external appearance of the other example of a separator provided with a fire extinguisher. In 1st Embodiment, it is a figure explaining the positional relationship of the positive electrode plate of a positive electrode, the negative electrode plate of a negative electrode, a separator, electrolyte solution, and a fire extinguishing agent. In 1st Embodiment, it is an example of the flowchart which shows the manufacture process of an electrical storage device. It is a figure explaining the roll press process for positive electrode plate preparation and negative electrode plate preparation in the manufacture process of the electrical storage device of 1st Embodiment. It is a figure explaining the example of the external appearance of the electrode plate for pre dope in the manufacture process of the electrical storage device of 1st Embodiment. FIG. 15 is a sectional view taken along the line XV-XV in the pre-doping electrode plate of FIG. 14. It is a figure explaining the roll press process for electrode preparation for pre dope in the manufacture process of the electrical storage device of 1st Embodiment. It is a figure explaining the state which performs pre dope in the manufacture process of the electrical storage device of 1st Embodiment. It is a disassembled perspective view of the electrical storage device of 2nd Embodiment. It is typical sectional drawing of the electrical storage device of 2nd Embodiment. In 2nd Embodiment, it is a figure explaining the positional relationship of a positive electrode plate, a negative electrode plate, a separator, electrolyte solution, and a fire extinguisher. It is typical sectional drawing of the electrical storage device of 3rd Embodiment. It is a figure explaining the test method of the flame-retardant function of a fire extinguisher.

[First Embodiment]
Hereinafter, the first embodiment will be described with reference to FIGS. The electricity storage device in the first embodiment is a lithium ion capacitor 1. As shown in the exploded perspective view of FIG. 1, the lithium ion capacitor 1 includes a plurality of plate-like positive electrode plates 11 and a plurality of plate-like negative electrode plates 21. The plurality of plate-like positive electrode plates 11 and the plurality of plate-like negative electrode plates 21 are alternately stacked. Each positive electrode plate 11 includes an electrode terminal connection portion 12b protruding in one direction. Each negative electrode plate 21 also includes an electrode terminal connection portion 22b that protrudes in the same direction as the direction in which the electrode terminal connection portion 12b of the positive electrode plate 11 protrudes. As shown in FIG. 1, the direction in which the electrode terminal connecting portion 12b of the positive electrode plate 11 projects is the X-axis direction, the stacked direction is the Z-axis direction, and the direction perpendicular to the X-axis and the Z-axis is the Y-axis direction. To do. These X axis, Y axis, and Z axis are orthogonal to each other. In all of the drawings in which the X axis, the Y axis, and the Z axis are described, these axial directions indicate the same direction, and in the following description, descriptions regarding directions may be based on these axial directions. It should be noted that in the present embodiment and the embodiments described below, the illustration and detailed description of the incidental configuration are omitted.

<1. Overall structure of lithium ion capacitor 1 (FIGS. 1 to 3)>
As shown in FIG. 1, the lithium ion capacitor 1 includes a plurality of positive plates 11, a plurality of negative plates 21, a plurality of separators 30, an electrolytic solution 40, and a laminate member 50. Here, as shown in FIG. 1, the positive plates 11 and the negative plates 21 are alternately stacked, and the separators 30 are sandwiched between the positive plates 11 and the negative plates 21. The electrolyte solution 40 is encased in two laminate members 50 (sealing bodies) together with a part of the plurality of positive electrode plates 11, a part of the plurality of negative electrode plates 21, and the plurality of separators 30 laminated in this manner. The lithium ion capacitor 1 is sealed. The electrolytic solution 40 is in contact with the inside of the positive electrode plate 11, the negative electrode plate 21, and the laminate member 50. Although details will be described later, the separator 30 includes a fire extinguishing agent 32 (see FIG. 3), and the fire extinguishing agent 32 improves the flame retardance of the lithium ion capacitor 1. The lithium ion capacitor 1 may further include separators 30 in the uppermost layer and the lowermost layer in the Z-axis direction, and the negative electrode plates 21 may be disposed so as to be sandwiched between the separators 30.

The electrode terminal connection portions 12 b of the plurality of positive electrode plates 11 protrude in the same direction and are electrically connected to the positive electrode terminal 14. The positive electrode side conductor members such as the positive electrode terminal 14 and the plurality of positive electrode plates 11 connected thereto are collectively referred to as a positive electrode 10. The electrode terminal connection portions 22b of the plurality of negative electrode plates 21 and the negative electrode terminals 24 are electrically connected. Conductive members on the negative electrode side such as the negative electrode terminal 24 and the plurality of negative electrode plates 21 connected thereto are collectively referred to as the negative electrode 20. The lithium ion capacitor 1 has the above-described configuration inside, and its external appearance is shown in FIG. FIG. 3 schematically shows a III-III cross section of the lithium ion capacitor 1 shown in FIG. In FIG. 3, for easy understanding, the members in the lithium ion capacitor 1 are illustrated with a space therebetween. However, in practice, the positive electrode plate 11, the negative electrode plate 21, and the separator 30 are stacked with almost no gap.

<2. Each part of the lithium ion capacitor 1 (FIGS. 1, 3 to 10)>
<2-1. Structure of the positive electrode plate 11 (FIGS. 1, 3 to 5)>
The positive electrode plate 11 can be a positive electrode plate of a conventional lithium ion capacitor. That is, the positive electrode plate 11 includes a thin plate-like current collector 12 and a positive electrode active material layer 13 coated on the current collector 12. As shown in FIG. 4, the current collector 12 includes a rectangular current collector 12 a and an electrode terminal connection portion 12 b protruding from one end of the current collector 12 a (the left end of the upper side in the example of FIG. 4). Is formed. The current collector 12a is a metal foil having a plurality of holes 12c penetrating in the Z-axis direction. The electrode terminal connecting portion 12b may or may not have a plurality of holes similar to the holes 12c of the current collecting portion 12a. And the width | variety of the Y-axis direction of the electrode terminal connection part 12b shown to FIG. 1 and FIG. 4 can be changed suitably. The width may be, for example, the same width as the current collector 12a. Moreover, although the positive electrode active material layer 13 is coated on both surfaces of the current collection part 12a, the coated surface may be either one surface. Here, since the current collector 12a has a plurality of holes 12c, cations and anions of the electrolytic solution 40 can pass through the current collector 12a.

As the current collector 12, for example, a metal foil made of aluminum, stainless steel, copper, or nickel can be used. The positive electrode active material layer 13 includes a positive electrode active material having a large specific surface area and high conductivity, a conductive auxiliary agent for increasing the electric conductivity of the positive electrode active material layer 13, binding of the positive electrode active material, and collection of the positive electrode active material. And a binder that binds the current collector 12a of the electric body 12. The positive electrode active material layer 13 may further include other components such as a thickener. As the positive electrode active material, for example, activated carbon, carbon nanotube, polyacene, or the like can be used. As the conductive auxiliary agent, for example, ketjen black, acetylene black, graphite fine particles, and graphite fine fibers can be used. As the thickener, for example, carboxymethyl cellulose [CMC] can be used.

The binder is used to bind the material constituting the positive electrode. The binder is mainly composed of a polymer that is an adhesive component. The polymer is selected from polyvinylidene fluoride, styrene-butadiene rubber [SBR], polyacrylic acid, and the like. The polymer preferably has a RED value (relative energy difference) based on a Hansen solubility parameter (HSP) in the electrolytic solution 40 of greater than 1. A polymer having a RED value larger than 1 with respect to the electrolytic solution 40 does not dissolve in the electrolytic solution 40, and therefore the increase rate of the internal resistance is small even when the lithium ion capacitor 1 is used in a high temperature environment for a long time. An example of such a polymer is polyacrylic acid. The polyacrylic acid here is a broad concept including not only unneutralized polyacrylic acid but also neutralized polyacrylic acid salts and cross-linked ones. Polyacrylic acid may be used alone or in combination of two or more. As a solvent for dissolving the polymer, water or an organic solvent can be used. An aqueous binder using water as a solvent is preferable because it can reduce the environmental burden in the manufacturing process. Polyacrylic acid is also suitable in that it can constitute an aqueous binder using water as a solvent. A detailed description of the RED value based on the Hansen solubility parameter will be described later.

The binder is preferably added in an amount of 1 to 10% by mass with respect to the positive electrode active material. When the binder is less than 1% by mass, the binding force tends to be insufficient. On the other hand, if the binder exceeds 10% by mass, the internal resistance of the lithium ion capacitor 1 may increase.

<2-2. Structure of Negative Electrode Plate 21 (FIGS. 1, 3, 6, and 7)>
The negative electrode plate 21 can be a negative electrode plate of a conventional lithium ion capacitor. The negative electrode plate 21 roughly has the same structure as the positive electrode plate 11 described above. That is, the negative electrode plate 21 includes a thin plate-like current collector 22 and a negative electrode active material layer 23. The negative electrode active material layer 23 includes a negative electrode active material capable of occluding and releasing lithium ions Li ⁺ . As will be described later, the negative electrode active material is adsorbed with lithium ions Li ⁺ during manufacturing (so-called pre-doped).

As shown in FIG. 6, the current collector 22 includes a rectangular current collector 22 a and an electrode terminal connection 22 b that protrudes outward from one end of the current collector 22 a (the right end of the upper side in the example of FIG. 6). It is integrally formed. The current collector 22a is a metal foil having a plurality of holes 22c penetrating in the Z-axis direction (see FIG. 7). The electrode terminal connecting portion 22b may or may not have a plurality of holes similar to the holes 22c of the current collecting portion 22a. Moreover, although the negative electrode active material layer 23 is coated on both surfaces of the current collection part 22a, the coated surface may be either one surface. Here, like the positive electrode plate 11 described above, the current collector 22a is formed with a plurality of holes 22c, so that cations and anions of the electrolytic solution 40 can pass through the current collector 22a. As shown in FIG. 1, the electrode terminal connecting portion 12b of the positive electrode plate 11 and the electrode terminal connecting portion 22b of the negative electrode plate 21 are provided at positions spaced from each other in the Z-axis direction. Therefore, it can prevent that the electrode terminal connection part 12b and the electrode terminal connection part 22b contact each other. Here, the width in the Y-axis direction of the electrode terminal connecting portion 22b shown in FIGS. 1 and 6 can be changed as appropriate, and may be, for example, the same width as the current collecting portion 22a.

As the current collector 22, for example, a metal foil made of aluminum, stainless steel, or copper can be used in the same manner as the current collector 12 of the positive electrode plate 11. The negative electrode active material layer 23 includes a negative electrode active material capable of adsorbing and desorbing lithium ions Li ⁺ and a binder for binding the negative electrode active material and binding the negative electrode active material and the current collector 22 a of the current collector 22. . The negative electrode active material layer 23 may include other components such as a conductive additive and a thickener for increasing the electrical conductivity of the negative electrode active material layer 23. For example, graphite can be used as the negative electrode active material. The same material as the positive electrode plate 11 described above can be used as the conductive additive, binder, and thickener. That is, for example, ketjen black, acetylene black, graphite fine particles, and graphite fine fibers can be used as the conductive assistant. As the binder, for example, polyvinylidene fluoride, styrene-butadiene rubber [SBR], or polyacrylic acid can be used. As the thickener, for example, carboxymethyl cellulose [CMC] can be used.

<2-3. Structure of Separator 30 (FIGS. 1, 3, and 8 to 10)>
The separator 30 has a plate shape (see FIGS. 1 and 8). The vertical and horizontal lengths of the separator 30 are longer than the vertical and horizontal lengths of the current collector 12a of the current collector 12 of the positive electrode plate 11 and the vertical and horizontal lengths of the current collector 22a of the current collector 22 of the negative electrode plate 21. It has been set (see FIGS. 1, 4 and 6). As shown in FIG. 9, the separator 30 includes a porous sheet-like separator sheet 31 for separating the positive electrode plate 11 and the negative electrode plate 21, and a fire extinguishing agent 32 coated on both surfaces of the separator sheet 31. And have. The separator 30 is configured to allow the cation and anion of the electrolytic solution 40 to pass therethrough.

The fire extinguishing agent 32 only needs to be coated on the separator sheet 31. That is, the fire extinguishing agent 32 may be applied on one side of the separator sheet 31 or may be partially applied on the separator sheet 31. For example, as shown in FIG. 10, a fire extinguishing agent 32 may be applied on the outer side excluding the center of the separator sheet 31. The fire extinguishing agent 32 may be applied to a part of the outer side of the separator sheet 31. The fire extinguishing agent 32 may be applied to the separator sheet 31 in a plurality of strips or dots.

The separator sheet 31 may be a conventional lithium ion capacitor separator. As the separator sheet 31, for example, papermaking such as viscose rayon or natural cellulose, non-woven fabric such as polyethylene or polypropylene can be used.

The fire extinguishing agent 32 exhibits a flame retarding function and has a RED value greater than 1 based on the Hansen solubility parameter (HSP) for the electrolytic solution 40. The Hansen solubility parameter was published by Charles M Hansen and is known as a solubility index indicating how much a certain substance is dissolved in a certain substance. For example, water and oil generally do not melt together because the “properties” of water and oil are different. As the “property” of the substance relating to the solubility, in the Hansen solubility parameter, three items of the dispersion term D, the polar term P, and the hydrogen bond term H are expressed numerically for each substance. Here, the dispersion term D is a value representing the magnitude of Van der Waals force. The polar term P is a value representing the magnitude of the dipole moment. The hydrogen bond term H is a value representing the size of the hydrogen bond. The basic idea is explained below. For this reason, explanation of handling the hydrogen bond term H divided into donor and acceptor properties is omitted.

Hansen solubility parameters (D, P, H) are plotted in a three-dimensional orthogonal coordinate system (Hansen space, HSP space) in order to study solubility. For example, the Hansen solubility parameter for each of the solution A and the solid B can be plotted on two coordinates (coordinate A and coordinate B) corresponding to the solution A and the solid B, respectively, in the Hansen space. And, the shorter the distance Ra (HSP distance, Ra) between the coordinates A and B, the solutions A and the solids B have the above-mentioned “properties”, so the solid B is more likely to dissolve in the solution A. it can. On the contrary, it can be considered that the longer the distance Ra is, the more difficult the solution A and the solid B are dissolved in the solution A because the solution A and the solid B have “properties” that are not similar to each other.

Further, a distance Ra that becomes a boundary between a substance that dissolves and a substance that does not dissolve in the solution A is defined as an interaction radius R0. Therefore, for the solution A and the solid B, when the distance Ra is smaller than the interaction radius R0 (Ra <R0), it can be considered that the solid B is dissolved in the solution A. On the other hand, when this Ra is larger than the interaction radius R0 (R0 <Ra), it can be considered that the solid B does not dissolve in the solution A. Further, a value obtained by dividing the distance Ra by the interaction radius R0 is defined as a RED value (= Ra / Ro). Then, when the RED value is smaller than 1 (RED = Ra / Ro <1), Ra <R0 and it can be considered that the solid B is dissolved in the solution A. On the other hand, when the RED value is larger than 1 (RED = Ra / Ro> 1), R0 <Ra, and it can be considered that the solid B does not dissolve in the solution A. In this way, it can be determined whether or not the solid B is dissolved in the solution A based on the RED values relating to the solution A and the solid B.

Here, in the present embodiment, the solution A corresponds to the electrolytic solution 40 and the solid B corresponds to the extinguishing agent 32. Since the RED value based on the Hansen solubility parameter with respect to the electrolytic solution 40 is greater than 1, the fire extinguisher 32 can be regarded as not dissolving in the electrolytic solution 40. Conversely, a fire extinguisher that is sparingly soluble in the electrolytic solution 40 can also be considered to have a RED value greater than 1 based on the Hansen solubility parameter.

The Hansen solubility parameter and the interaction radius R0 can be calculated using the chemical structure and composition ratio of the components and experimental results. In that case, it can be obtained using software HSPiP developed by Hansen et al. (Hansen Solubility Parameters in Practice: Windows [registered trademark] software for efficiently handling HSP). The software HSPiP is available as of March 5, 2018 from http://www.hansen-solubility.com/. Also, the Hansen solubility parameters (D, P, H) can be calculated for a mixed solvent in which a plurality of solvents are mixed.

As the fire extinguisher 32, a fire extinguisher that exhibits a flame retarding function and has a RED value greater than 1 based on the Hansen solubility parameter with respect to the electrolyte 40 can be used among known fire extinguishers. As such a fire extinguisher 32, the fire extinguisher containing the fuel component A, the oxidizing agent component B, and the organic salt component C which are demonstrated below can be used, for example. This fire extinguisher is 15 to 50 parts by mass of fuel component A, 85 to 50 parts by mass of oxidant component B, and 7 to 7 parts of organic salt component C with respect to 100 parts by mass of fuel component A and oxidant component B in total. It contains 1000 parts by mass.

When this fire extinguisher is heated, the fuel component A and the oxidant component B are combusted, so that an aerosol containing potassium radicals can be generated from the organic salt component C. The potassium radical contained in this aerosol has a fire extinguishing action and a flame retarding function that suppresses ignition. Here, the flame-retarding function of this fire extinguishing agent is a function that immediately generates potassium radicals when starting to ignite, and suppresses ignition by the fire extinguishing action of the potassium radicals. The temperature at which the fuel component A and the oxidant component B burn can be set by appropriately changing the composition of the fuel component A, the oxidant component B, and the organic salt component C. In addition, this fire extinguisher can generate a potassium radical having a fire extinguishing action and a flame retarding function to suppress ignition, but the generated radical is a radical having a fire extinguishing action or a flame retarding function other than the potassium radical. It may be. That is, the fire extinguishing agent may be a fire extinguishing agent that generates a radical having a fire extinguishing action or a flame retarding function other than the potassium radical. In addition, the extinguishing agent only needs to have a flame-retarding function to prevent ignition as described above, and a radical that stops a chain reaction of combustion that occurs when a pyrolysis reaction, an oxidation reaction, or the like is ignited by a radical trap. It does not have to generate an aerosol. For example, the fire extinguishing agent may have a flame retarding function that stops the chain reaction of combustion by generating an inert gas such as nitrogen, argon, or carbon dioxide. It is also possible to use an occlusion alloy that occludes an inert gas in advance and can be released at a predetermined temperature. Extinguishing agents other than halogen and phosphorus-based flame retardants are preferable in terms of increasing safety to the environment. Moreover, if it is set as the structure which discharge | releases inert gas other than a carbon dioxide with said structure, the safety | security with respect to a person can also be improved.

Fuel component A includes dicyandiamide, nitroguanidine, guanidine nitrate, urea, melamine, melamine cyanurate, Avicel, guar gum, sodium carboxymethylcellulose, carboxymethylcellulose potassium, carboxymethylcellulose ammonium, nitrocellulose, aluminum, boron, magnesium, magnalium, zirconium, Titanium, titanium hydride, tungsten, silicon and the like. The fuel component A may be used alone or in combination of two or more.

Examples of the oxidizing agent component B include inorganic oxidizing agents. Inorganic oxidizers include potassium nitrate, sodium nitrate, strontium nitrate, ammonium perchlorate, potassium perchlorate, basic copper nitrate, copper (I) oxide, copper (II) oxide, iron (II) oxide, iron oxide (III ), Molybdenum trioxide and the like. Only 1 type may be used for the oxidizing agent component B, and 2 or more types may be mixed.

Examples of the organic salt component C include organic carboxylic acid potassium salts. Organic carboxylic acid potassium salt is potassium acetate, potassium propionate, monopotassium citrate, dipotassium citrate, tripotassium citrate, ethylenediaminetetraacetic acid monopotassium dihydrogen, ethylenediaminetetraacetic acid dipotassium dihydrogen, ethylenediaminetetraacetic acid monohydrogen Examples include tripotassium, tetrapotassium ethylenediaminetetraacetate, potassium hydrogen phthalate, dipotassium phthalate, potassium hydrogen oxalate, and dipotassium oxalate. Only 1 type may be used for the organic salt component C, and 2 or more types may be mixed.

<2-4. Composition of Electrolytic Solution 40>
As the electrolytic solution 40, a conventional lithium ion capacitor electrolytic solution can be used. That is, the electrolytic solution 40 includes an organic solvent (nonaqueous solvent) and an electrolyte. You may add an additive to the electrolyte solution 40 suitably. Examples of the additive include vinylene carbonate [VC].

As organic solvents, carbonate organic solvents, nitrile organic solvents, lactone organic solvents, ether organic solvents, alcohol organic solvents, ester organic solvents, amide organic solvents, sulfone organic solvents, ketone organic solvents, aromatic A group organic solvent can be exemplified. Only 1 type may be used for a solvent and 2 or more types may be mixed. The organic solvent preferably has a heat resistance of 85 ° C. or higher.

Examples of carbonate-based organic solvents include cyclic carbonates such as ethylene carbonate [EC], propylene carbonate [PC], and fluoroethylene carbonate [FEC], and chains such as ethyl methyl carbonate [EMC], diethyl carbonate [DEC], and dimethyl carbonate [DMC]. Examples of the carbonates.

Here, various chain carbonates can be used as the chain carbonate, but from the viewpoint of improving the heat resistance of the electrolytic solution, it is preferable not to use dimethyl carbonate (DMC) having a low boiling point and poor heat resistance. That is, when dimethyl carbonate (DMC) is contained in an organic solvent, dimethyl carbonate (DMC) is thermally decomposed into diethyl carbonate (DEC), and decomposition by-products at this time cause an increase in internal resistance and a deterioration in heat resistance. (Note that this inference does not limit the technology of the present disclosure). Considering the use of a lithium ion capacitor in a high temperature environment, it is possible to use ethyl methyl carbonate (EMC) having a relatively high boiling point and low viscosity or diethyl carbonate (DEC) having a higher boiling point as the chain carbonate. preferable. From the viewpoint of improving heat resistance, it is more preferable to use a mixture of ethyl methyl carbonate (EMC) and diethyl carbonate (DEC). The ratio of ethyl methyl carbonate (EMC) to diethyl carbonate (DEC) in the organic solvent is not particularly limited, but can be set, for example, in the range of EMC: DEC = 2: 1 to 1: 2.

Various cyclic carbonates can be used as the cyclic carbonate. From the viewpoint of improving the oxidation resistance of the electrolytic solution, it is preferable to use ethylene carbonate (EC) having a solid electrolyte phase (SEI) film forming ability. And as a cyclic carbonate, when mixing and using ethylene carbonate (EC) and another cyclic carbonate (for example, PC), it is preferable to contain ethylene carbonate (EC) more than other cyclic carbonates (for example, PC). . When ethylene carbonate (EC) is relatively contained in this manner, ethylene carbonate (EC) is reduced and decomposed, and an SEI film is generated on the negative electrode surface. Thereby, the electrolytic solution is not directly exposed to the potential of lithium (Li).

Examples of nitrile organic solvents include acetonitrile, acrylonitrile, adiponitrile, valeronitrile, and isobutyronitrile. Examples of the lactone organic solvent include γ-butyrolactone and γ-valerolactone. Examples of ether organic solvents include cyclic ethers such as tetrahydrofuran and dioxane, and chain ethers such as 1,2-dimethoxyethane, dimethyl ether, and triglyme. Examples of the alcohol organic solvent include ethyl alcohol and ethylene glycol. Examples of the ester organic solvent include phosphate esters such as methyl acetate, propyl acetate and trimethyl phosphate, sulfate esters such as dimethyl sulfate, and sulfite esters such as dimethyl sulfite. Examples of the amide organic solvent include N-methyl-2-pyrrolidone and ethylenediamine. Examples of the sulfone-based organic solvent include chain sulfones such as dimethyl sulfone and cyclic sulfones such as 3-sulfolene. Examples of the ketone organic solvent include methyl ethyl ketone, and toluene as the aromatic organic solvent. The above-mentioned various organic solvents excluding the carbonate-based organic solvent are preferably used by mixing cyclic carbonates, and particularly preferably used by mixing with ethylene carbonate [EC] capable of forming a protective film.

The electrolyte uses a lithium salt of Li ions, which are cations (cations), and anions (anions). Examples of the electrolyte include lithium perchlorate [LiClO ₄ ], lithium hexafluorophosphate [LiPF ₆ ], lithium tetrafluoroborate [LiBF ₄ ], lithium bis (fluorosulfonyl) imide [LiN (FSO ₂ ) ₂ , LiFSI. ], Lithium bis (trifluoromethanesulfonyl) imide [LiN (SO ₂ CF ₃ ) ₂ , LiTFSI], lithium bis (pentafluoroethanesulfonyl) imide [LiN (SO ₂ CF ₂ CF ₃ ) ₂ , LiBETI] it can. These lithium salts may be used alone or in combination of two or more. In particular, lithium having a partial structure of an imide-based lithium salt (—SO ₂ —N—SO ₂ —) such as lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, and lithium bis (pentafluoroethanesulfonyl) imide Salt) is preferable because it has a heat resistance of 85 ° C. or higher.

The concentration of the electrolyte in the electrolytic solution 40 is preferably 0.5 to 10.0 mol / L. From the viewpoint of an appropriate viscosity of the electrolytic solution 40 and ion conductivity, the concentration of the electrolyte in the electrolytic solution 40 is more preferably 0.5 to 2.0 mol / L. When the concentration of the electrolyte is less than 0.5 mol / L, the ionic conductivity of the electrolytic solution 40 is too low due to a decrease in the concentration of ions from which the electrolyte is dissociated. Moreover, it is not preferable that the concentration of the electrolyte is higher than 10.0 mol / L because the ionic conductivity of the electrolytic solution 40 is too low due to an increase in the viscosity of the electrolytic solution 40.

<2-5. Structure of Laminate Member 50 (FIGS. 1 and 3)>
As shown in FIG. 3, the laminate member 50 includes a core material sheet 51, an outer sheet 52, and an inner sheet 53. The outer sheet 52 is bonded to the outer surface of the core material sheet 51, and the inner sheet 53 is bonded to the inner surface of the core material sheet 51. For example, the core material sheet 51 is an aluminum foil. The outer sheet 52 is a resin sheet such as a nylon pet film. The inner sheet 53 is a resin sheet such as polypropylene.

<3. Regarding the charging / discharging process of the lithium ion capacitor 1 (FIGS. 3 and 11)>
As described above, the current collector 12a of the current collector 12 of the positive electrode plate 11 includes a plurality of holes 12c penetrating in the Z direction. The current collector 22a of the current collector 22 of the negative electrode plate 21 is also provided with a plurality of holes 22c penetrating in the Z direction. Therefore, the anions and cations of the electrolytic solution 40 can pass through the current collector 12 a of the positive electrode plate 11 and the current collector 22 a of the negative electrode plate 21. The separator 30 is also configured to allow the anion and cation of the electrolytic solution 40 to pass therethrough. The positional relationship among the positive electrode plate 11 of the positive electrode 10, the negative electrode plate 21 of the negative electrode 20, the separator 30, the electrolytic solution 40, and the extinguishing agent 32 of the lithium ion capacitor 1 is schematically shown in FIG. As shown in FIG. 11, the positive electrode plate 11 and the negative electrode plate 21 sandwich a separator 30 having a fire extinguishing agent 32 therebetween. The lithium ion capacitor 1 is formed by forming an electric double layer with the positive electrode active material and the anion of the electrolyte on the surface of the positive electrode plate 11 and adsorbing and desorbing lithium ions Li ⁺ on the negative electrode active material with the negative electrode plate 21. Discharge. Further, as will be described later, when the lithium ion capacitor 1 is manufactured, lithium ion Li ⁺ is adsorbed on the negative electrode active material of the negative electrode plate 21 (pre-doping). Since the lithium ion Li ⁺ is adsorbed on the negative electrode active material, the potential difference between the positive electrode plate 11 and the negative electrode plate 21 is increased, and the energy density of the electric double layer formed on the positive electrode plate 11 can be increased. . As a result, the lithium ion capacitor 1 is increased in capacity and output.

<4. About the effects of fire extinguishing agents>
Generally, in the pre-doping process at the time of manufacture, lithium ions Li ⁺ are adsorbed in advance on the negative electrode active material of the negative electrode plate 21. The lithium ion Li ⁺ supply source is lithium metal that is disposed in the internal space where the electrolyte solution of the lithium ion capacitor is present and is converted to Li ⁺ . How to lithium metal to the lithium ion Li ⁺ is generally dissolved electrochemical method for the lithium metal to the lithium ion Li ⁺ by applying a voltage to the lithium metal and the negative electrode plate 21, the lithium metal to the electrolyte And a chemical method for producing lithium ion Li ⁺ .

In any of these methods, a single lithium metal is generally used in the pre-doping step included in the method of manufacturing a lithium ion capacitor. In general, a pre-doping process is performed so that no single lithium metal remains in the lithium ion capacitor. However, in the unlikely event that a single lithium metal remains in the lithium ion capacitor, an internal short circuit occurs in the lithium ion capacitor, or the lithium ion capacitor is heated, the lithium ion capacitor may be ignited. . Also in such a case, the lithium ion capacitor 1 of the present embodiment can prevent ignition because the extinguishing agent 32 that exhibits the flame retarding function is provided in the internal space of the laminate member 50 (sealing body). . Moreover, it is not necessary to spend time in the pre-doping process so that metallic lithium does not precipitate as in the prior art, and the time of the pre-doping process can be shortened.

In the lithium ion capacitor 1 (power storage device), the fire extinguishing agent 32 is provided in the internal space of the laminate member 50 (sealing body). Therefore, the flame retarding function of the fire extinguishing agent 32 to make the lithium ion capacitor 1 (electric storage device) flame retardant can be exhibited not from the outside of the laminate member 50 (sealing body) but from the inside. Therefore, the fire extinguisher 32 can improve the flame retardance of the lithium ion capacitor 1 (electric storage device) with certainty.

The fire extinguishing agent 32 is provided on the separator 30 that separates the positive electrode plate 11 (positive electrode) and the negative electrode plate 21 (negative electrode). Therefore, ignition due to a short circuit between the positive electrode plate 11 (positive electrode) and the negative electrode plate 21 (negative electrode) can be reliably suppressed, and the fire extinguishing agent 32 more effectively reduces the flame retardancy of the lithium ion capacitor 1 (electric storage device). Can increase.

Further, the extinguishing agent 32 has a RED value based on the Hansen solubility parameter with respect to the electrolytic solution 40 larger than 1, so that the amount of the extinguishing agent 32 dissolved in the electrolytic solution 40 is negligibly small. Therefore, it can be considered that the extinguishing agent 32 is stable. Therefore, the fire extinguishing agent 32 stably increases the flame retardance of the lithium ion capacitor 1 (power storage device) over time, and does not significantly affect the charge / discharge process of the lithium ion capacitor 1 (power storage device).

<5. Manufacturing Method for Lithium Ion Capacitor 1 (FIGS. 12 to 17)>
A method for manufacturing the lithium ion capacitor 1 of the present embodiment will be described. As described above, the pre-doping method for adsorbing lithium ions Li ⁺ on the negative electrode active material layer 23 of the negative electrode plate 21 is generally selected from an electrochemical method and a chemical method. In the electrochemical method, a voltage is applied to the lithium metal and the negative electrode plate 21 to change the lithium metal to lithium ion Li ⁺ . The chemical method dissolves lithium metal in the electrolyte. Below, it demonstrates as what performs pre dope with a chemical method first, and demonstrates the case where pre dope is performed with an electrochemical method after that. The lithium ion capacitor 1 can be manufactured as shown in FIG.

In the manufacture of the lithium ion capacitor 1, first, the positive electrode plate 11 and the negative electrode plate 21 are prepared (S1). Either the positive electrode plate 11 or the negative electrode plate 21 may be produced in parallel or in any order.

A method for producing the positive electrode plate 11 will be described. The positive electrode plate 11 includes a thin metal plate-like current collector 12 in which a plurality of holes 12 c are formed, and a positive electrode active material layer 13 coated on both surfaces or one surface of the current collector 12. First, a material for the positive electrode active material layer 13 is prepared. That is, the slurry which mixed the positive electrode active material mentioned above, a conductive support agent, a binder, solvents, such as water and an organic solvent, and components, such as a thickener as needed, is prepared. To do. Then, this slurry is applied to one side or both sides of a thin metal plate in which a plurality of holes as materials for the current collector 12 are formed. Next, the slurry is dried to remove the solvent from the slurry, and pressed to make the thickness uniform (see FIG. 13). When applying a slurry to a metal thin plate, you may apply one side at a time, and may apply both surfaces simultaneously.

Examples of the coating method include gravure coating, bar coating, spray coating, spin coating, air knife coating, roll coating, blade coating, gate roll coating, and die coating. it can. Among these, the blade coating method and the die coating method are preferable. Moreover, as a drying method, the method of heat-drying with a hot air drying furnace etc. can be used, for example. For the press, for example, a roll press machine can be used.

Moreover, the positive electrode plate 11 may be created as follows. The metal thin plate used as the material of the current collector 12 to which the slurry is applied is a metal thin plate having a plurality of holes wound in a roll shape, and the slurry is applied to the metal thin plate. Then, the metal thin plate coated with the slurry is dried and pressed, and after the pressing, it is cut into the size of the positive electrode plate 11 (see FIG. 4), and further coated on the portion (see FIG. 4) that becomes the electrode terminal connection portion 12b. The positive electrode active material layer may be peeled off. Further, the metal thin plate to which the slurry is applied is a metal thin plate having a plurality of holes wound in a roll shape, and the slurry is applied to a portion to be the current collecting portion 12a on the metal thin plate, where the electrode terminal connection portion The portion to be 12b is not coated with slurry, and may be cut into the size of the positive electrode plate 11 (see FIG. 4) before or after pressing. Moreover, you may cut | divide the metal thin plate which applies a slurry into the magnitude | size of the positive electrode plate 11, before applying a slurry.

As described above, the negative electrode plate 21 roughly has the same structure as the positive electrode plate 11. The major difference between the negative electrode plate 21 and the positive electrode plate 11 is that the material of the negative electrode active material of the negative electrode active material layer 23 is different from the material of the positive electrode active material of the positive electrode active material layer 13. Therefore, the negative electrode plate 21 can be manufactured in the same manner as the positive electrode plate 11. That is, first, the negative electrode active material, which is the material of the negative electrode active material layer 23, a binder, a solvent such as water or an organic solvent, and components such as a conductive additive or a thickener as necessary. Is prepared using a mixer. Then, this slurry is applied to one side or both sides of a thin metal plate in which a plurality of holes serving as the material of the current collector 22 are formed. Next, the slurry is dried to remove the solvent from the slurry, and pressed to make the thickness uniform (see FIG. 13). When applying a slurry to a metal thin plate, you may apply one side at a time, and may apply both surfaces simultaneously.

Next, the extinguishing agent 32 is processed into a predetermined shape (S2). The extinguishing agent 32 is applied on the separator sheet 31 (see FIGS. 3 and 9). Moreover, you may press (refer FIG. 13) in order to make thickness uniform. This coating can be performed in the same manner as the method of applying the positive electrode active material layer 13 to the current collector 12 of the positive electrode plate 11 described above. When the fire extinguishing agent 32 is applied to both surfaces of the separator sheet 31, the coating may be performed on each side or simultaneously on both sides. Further, the pressing can be performed in the same manner as the pressing of the positive electrode plate 11 described above.

Next, lithium metal used for pre-doping is processed into a predetermined shape (S3). Here, the negative electrode plate 21p for pre dope is produced as the example. The pre-doping negative electrode plate 21p is prepared by placing a lithium metal foil LiS1 having a predetermined shape on the negative electrode active material layer 23 of the negative electrode plate 21 (see FIGS. 14 and 15), and further pressing the negative electrode active material of the negative electrode plate 21. The layer 23 and the lithium metal foil LiS1 are pressure-bonded (see FIG. 16). Here, for the press, for example, a roll press machine may be used. Further, powdered lithium metal may be used instead of the lithium metal foil LiS1. Further, in S3, one negative electrode plate 21 is used. However, since S3 can be performed after one negative electrode plate 21 is formed in S1, S1 and S3 can be performed in parallel. . Further, if one negative electrode plate 21 is created in S1, S1, S2, and S3 can be performed in parallel, and the order in which S1, S2, and S3 are performed can be changed as appropriate.

Next, a laminate in which lithium metal, a plurality of positive electrode plates 11, a plurality of negative electrode plates 21, and a plurality of separators 30 are laminated, and the positive electrode terminal 14 and the negative electrode terminal 24 are assembled is prepared (S4). First, as shown in FIG. 17, the plurality of positive plates 11 and the plurality of negative plates 21 are alternately stacked, and the separators 30 are sandwiched between the positive plates 11 and the negative plates 21. The negative electrode plate 21p for pre-doping, the positive electrode plate 11, the negative electrode plate 21, and the separator 30 are laminated. Here, the pre-doping negative electrode plate 21p is laminated on the uppermost layer in the Z-axis direction. Next, the positive electrode terminal 14 is assembled to the plurality of positive electrode plates 11, and the negative electrode terminal 24 is assembled to the pre-doping negative electrode plate 21 p and the plurality of negative electrode plates 21 to form a laminate. In addition, the separator 30 may be further arranged in the uppermost layer in the Z-axis direction of the laminated body, and the separator 30 may be further arranged in the lowermost layer in the Z-axis direction of the laminated body. In the above description, the negative electrode plate 21p for pre-doping, the positive electrode plate 11, the negative electrode plate 21, and the separator 30 are stacked, and then the positive electrode terminal 14 and the negative electrode terminal 24 are assembled. The order of assembly and assembly may be changed as appropriate. For example, the connection between the positive electrode terminal 14 and the positive electrode plate 11 and the connection between the negative electrode terminal 24 and the negative electrode plate 21 may be performed in parallel with the lamination. Further, S3 for processing the lithium metal used for pre-doping into a predetermined shape is simply a step of preparing lithium metal foil LiS1, and lithium metal foil is used instead of disposing the negative electrode plate 21p for pre-doping in the laminate produced in step S4. LiS1 and one negative electrode plate 21 may be disposed.

Next, the above laminate is included in the laminate member 50 (S5). First, the laminate is included in the laminate member 50 so that a part of the positive electrode terminal 14 and a part of the negative electrode terminal 24 are exposed to the outside of the laminate member 50, and the peripheral part excluding a part of the laminate member 50 is welded. To do.

Next, pre-doping is performed to adsorb lithium ion Li ⁺ on the negative electrode active material layer 23 (S6). First, the electrolyte solution 40 prepared in advance is injected into the internal space of the laminate member 50. Then, the laminate member 50 is sealed, and the electrolytic solution 40 is sealed. Thereby, the lithium metal foil LiS1 on the pre-doping negative electrode plate 21p, the negative electrode active material layers 23 of the plurality of negative electrode plates 21, and the electrolytic solution 40 are sealed in the internal space of the laminate member 50. Lithium ion Li ⁺ in the electrolytic solution 40 is adsorbed by the negative electrode active material layer 23, and the lithium metal foil LiS 1 is dissolved in the electrolytic solution 40 as lithium ion Li ⁺ . As described above, the current collector 12a of the current collector 12 of the positive electrode plate 11 includes a plurality of holes 12c, and the current collector 22a of the current collector 22 of the negative electrode plate 21 includes a plurality of holes 22c. Therefore, lithium ions Li ⁺ in the electrolytic solution 40 can pass through the positive electrode plate 11 and the negative electrode plate 21. Further, the separator 30 is also configured so that lithium ions Li ⁺ in the electrolytic solution 40 can pass therethrough. For this reason, lithium ion Li ⁺ can be adsorbed to the negative electrode active material layers 23 of all the negative electrode plates 21. Here, the lithium metal foil LiS1 may be heated together with the electrolytic solution 40 in order to easily dissolve the lithium metallic foil LiS1 in the electrolytic solution 40. Even if the lithium metal is easily ignited by heating, the fire extinguishing agent 32 is included in the internal space of the laminate member 50 together with the lithium metal, so that the ignition of the lithium metal can be suppressed.

Next, charge / discharge and aging are performed (S7). Charging / discharging and aging are performed by connecting the positive electrode terminal 14 and the negative electrode terminal 24 exposed to the outside from the laminate member 50 to an external electric circuit. In general, gas is generated during the charge / discharge process.

Next, the gas is discharged to the outside of the laminate member 50 (S8). First, the sealed laminate member 50 is opened, and the gas generated by charging / discharging is discharged to the outside of the laminate member 50. The gas to be discharged may include a gas present in the internal space of the laminate member 50 before charging / discharging.

Finally, the internal space of the laminate member 50 is sealed (S9). Thereby, manufacture of the lithium ion capacitor 1 is completed. Here, you may include another process as needed. For example, the time when the lithium ion capacitor 1 is inspected and the inspection is completed can be set as the time when the manufacture of the lithium ion capacitor 1 is completed.

<6. Other Examples of Manufacturing Method of Lithium Ion Capacitor 1>
In the above manufacturing method, as described above, pre-doping was performed by a chemical method in which lithium metal was dissolved in an electrolytic solution to form lithium ion Li ⁺ . On the other hand, the manufacturing method of the lithium ion capacitor 1 when pre-doping is performed by an electrochemical method will be described below. This manufacturing method is substantially the same as the method including S1 to S9 described above (see FIG. 12) except for the points described below. That is, in the step (S3) of processing the lithium metal used for the pre-doping described above into a predetermined shape, a negative electrode plate 21p for pre-doping in which the lithium metal foil LiS1 was pressure-bonded on the negative electrode active material layer 23 of the negative electrode plate 21 was created. In this method, instead, a pre-doping electrode (not shown) in which an electrode terminal (not shown) and a lithium metal foil (not shown) are assembled on a metal foil (for example, copper foil, not shown) is created. In the step of creating a laminate (S4), this pre-doping electrode, a plurality of positive plates 11, a plurality of negative plates 21, a plurality of separators 30 are stacked, and the positive terminals 14 and negative terminals 24 are assembled. I do. In this stacking, for example, the pre-doping electrode is placed in the uppermost layer in the Z-axis direction, and includes including the separator 30 between the pre-doping electrode and the negative electrode plate 21. In the step of enclosing the laminate in the laminate member 50 (S5), a part of the positive electrode terminal 14, a part of the negative electrode terminal 24, and a part of the electrode terminal of the pre-doping electrode are external to the laminate member 50. The laminate is included in the laminate member 50 so as to be exposed to the surface. In the pre-doping step (S6) described above, after the electrolyte solution 40 is sealed as described above, a voltage is applied between the pre-doping electrode and the plurality of negative electrode plates 21 (that is, one negative electrode 20). Then, lithium metal is changed to lithium ion Li ⁺ and pre-doping is performed. Further, S1, S2, S7, S8, and S9 are performed as described above.

Therefore, the manufacturing method including S1 to S9 described above with reference to FIG. 12 includes a manufacturing method in which pre-doping is performed by a chemical method and a manufacturing method in which pre-doping is performed by an electrochemical method. Further, in this manufacturing method, the fire extinguishing agent 32 is accommodated together with the lithium metal foil LiS1 in the internal space of the laminate member 50 in the step (S5) of including the laminate in the laminate member 50 before pre-doping. For this reason, after this enclosing step (S5), the fire extinguishing agent 32 is accommodated in the internal space of the laminate member 50 together with the lithium metal foil LiS1. Therefore, this manufacturing method (S1 to S9) is a manufacturing method that can manufacture the lithium ion capacitor 1 more safely because the flame retardance of the lithium ion capacitor being manufactured is high in the steps after the enclosing step (S5). It has become.

[Second Embodiment]
Next, an electricity storage device according to the second embodiment will be described with reference to FIGS. The electricity storage device according to the second embodiment is a lithium ion capacitor 2. When the lithium ion capacitor 2 has substantially the same configuration as that of the lithium ion capacitor 1 according to the first embodiment, the same reference numeral is given to the configuration and description thereof is omitted.

<1. Structure of Lithium Ion Capacitor 2 (FIGS. 18 and 19)>
In the first embodiment described above, the fire extinguishing agent 32 is provided on the separator sheet 31. However, the fire extinguishing agent should just be provided in the internal space of the laminate member 50 (sealing body). The lithium ion capacitor 2 of the present embodiment has two plate-like extinguishing agents 60 formed by hardening the extinguishing agent having the same component as the extinguishing agent 32 of the first embodiment into a plate shape (see FIG. 18). ). And the lithium ion capacitor 2 has the separator 130 equivalent to the separator sheet 31 of 1st Embodiment (refer FIG. 19). In the lithium ion capacitor 2, a plurality of stacked positive electrode plates 11, a plurality of negative electrode plates 21, and a plurality of separators 130 are provided between two plate-like extinguishing agents 60 (see FIGS. 18 and 19). Note that, in FIG. 19 showing a schematic cross section of the lithium ion capacitor 2 of the present embodiment, the members in the lithium ion capacitor 2 are illustrated with a space therebetween for the sake of clarity. However, in practice, the positive electrode plate 11, the negative electrode plate 21, and the separator 130 are stacked with almost no gap. Moreover, the number of the plate-shaped fire extinguishing agents 60 is not limited to two, and may be three or more. Moreover, it is good also as what laminated | stacked the several plate-shaped fire extinguishing agent for one plate-shaped fire extinguishing agent 60. FIG.

<2. Regarding the charging / discharging process of the lithium ion capacitor 2 (FIGS. 19 and 20)>
The configuration of the positive electrode 10 and the negative electrode 20 is the same in the lithium ion capacitor 2 (see FIG. 19) of the present embodiment and the lithium ion capacitor 1 (see FIG. 3) of the first embodiment. The positional relationship among the positive electrode plate 11 of the positive electrode 10, the negative electrode plate 21 of the negative electrode 20, the separator 130, the electrolytic solution 40, and the extinguishing agent (plate-shaped extinguishing agent 60) of the lithium ion capacitor 2 is schematically shown in FIG. 20. It was shown to. As shown in FIG. 20, the positive electrode plate 11 and the negative electrode plate 21 are arranged with the separator 130 interposed therebetween. Similarly to the lithium ion capacitor 1, the lithium ion capacitor 2 forms an electric double layer on the surface of the positive electrode plate 11 with the positive electrode active material and the anion of the electrolytic solution 40, and the negative electrode plate 21 uses lithium as the negative electrode active material. Charge and discharge are performed by adsorbing and desorbing ions Li ⁺ .

<3. Effect of fire extinguishing agent for lithium ion capacitor 2 (FIGS. 18 to 20)>
In the lithium ion capacitor 2 of the present embodiment, the plate-like extinguishing agent 60 (extinguishing agent) is used for charging / discharging of the lithium ion capacitor 2 (electric storage device), similarly to the lithium ion capacitor 1 of the first embodiment described above. High flame retardancy without significant impact on the process. Here, the plate-like extinguishing agent 60 (extinguishing agent) is configured as a single plate-like component. For this reason, the quantity of the extinguishing agent provided in the lithium ion capacitor 2 (electric storage device) can be easily adjusted.

<4. About manufacturing method of lithium ion capacitor 2>
Although the details will be described below, the lithium ion capacitor 2 of the present embodiment can be manufactured by substantially the same manufacturing method as the manufacturing method (see FIG. 12) including S1 to S9 of the first embodiment described above. . As described above, the lithium ion capacitor 2 (see FIG. 19) differs from the lithium ion capacitor 1 (see FIG. 3) of the first embodiment in that the separator 130 and the plate-like fire extinguishing agent 60 are provided. Therefore, the manufacturing method of the lithium ion capacitor 2 of the present embodiment includes S2 which is a process of extinguishing agent in the manufacturing method including S1 to S9 of the first embodiment (see FIG. 12), S4 which is a process by which the separator 130 and a fire extinguisher are arrange | positioned is demonstrated.

The step (S2) of processing the fire extinguisher into a predetermined shape in the present embodiment is a step of creating a plate fire extinguisher 60 in which the fire extinguisher is formed into a plate shape by press molding or the like. Further, the step (S4) of creating a laminate in which the lithium metal, the plurality of positive plates, the plurality of negative plates, and the plurality of separators in the present embodiment are laminated and the positive terminal and the negative terminal are assembled, A separator 130 is laminated instead of the separator 30, and two plate-like fire extinguishing agents 60 are also added to the laminated body. Note that the difference between the lithium ion capacitor 2 of the present embodiment and the lithium ion capacitor 1 of the first embodiment is due to the form of the extinguishing agent and the separator, and is not related to the lithium metal used for pre-doping. . Therefore, the difference between the case where pre-doping is performed by a chemical method and the case where pre-doping is performed electrochemically is the same as in the case of the first embodiment.

Therefore, in the manufacturing method (S1 to S9) of the lithium ion capacitor 2, the flame retardance of the lithium ion capacitor (power storage device) being manufactured is increased in the steps after the step (S5) of enclosing the laminate in the laminate member 50. be able to. That is, the lithium ion capacitor 2 (power storage device) can be manufactured more safely.

[Third Embodiment]
The electrical storage device of 3rd Embodiment is demonstrated using FIG. The electricity storage device of the third embodiment is a lithium ion capacitor 3. In addition, when the lithium ion capacitor 3 has substantially the same configuration as the lithium ion capacitor 1 according to the first embodiment, the same reference numeral is given to the configuration and the description is omitted.

<1. Structure of lithium ion capacitor 3 (FIG. 21)>
In the first embodiment, the fire extinguishing agent 32 is provided in the separator 30. However, the fire extinguishing agent should just be provided in the internal space of the laminate member 50 (sealing body). A schematic cross section of the lithium ion capacitor 3 of the present embodiment is shown in FIG. The lithium ion capacitor 3 of the present embodiment has a separator 130 corresponding to the separator sheet 31 of the first embodiment (see FIG. 21). In addition, the lithium ion capacitor 3 includes a surrounding body 70 that surrounds the outer periphery of the plurality of positive plates 11 of the positive electrode 10, the plurality of negative plates 21 of the negative electrode 20, and the plurality of separators 130. More specifically, the surrounding body 70 surrounds the periphery of the multilayer body including the plurality of stacked positive electrode plates 11, the plurality of negative electrode plates 21, and the plurality of separators 130, and the uppermost layer in the Z-axis direction of the multilayer body. The lowest layer is the negative electrode plate 21. In FIG. 21, for easy understanding, the members in the lithium ion capacitor 3 are illustrated with an interval. However, in practice, the positive electrode plate 11, the negative electrode plate 21, and the separator 130 are stacked with almost no gap.

The enclosure 70 includes an enclosure core 71 and a fire extinguishing agent 72 coated on both sides thereof. The enclosure 70 has the same configuration as that of the separator 30 of the first embodiment (see FIGS. 8 and 9). That is, the envelope core 71 corresponds to a lengthened separator sheet 31 of the first embodiment. As the extinguishing agent 72 (not shown) applied to the envelope core 71, the same component as the extinguishing agent 32 of the first embodiment can be used. The envelope core 71 can be the same as the separator of the conventional lithium ion capacitor, similarly to the separator sheet 31. For example, the envelope core 71 is made of paper such as viscose rayon or natural cellulose, or a nonwoven fabric such as polyethylene or polypropylene.

Here, the fire extinguishing agent 72 may be coated on the envelope core 71. The fire extinguishing agent 72 may be applied to one side of the envelope core material 71 in the same manner as the extinguishing agent 32 applied on the separator sheet 31 of the first embodiment. It may be partially coated. For example, as in the separator 30 of FIG. 10, the fire extinguishing agent 72 may be applied to the outside except the center of the envelope core 71. The fire extinguishing agent 72 may be applied to a part of the outer side of the envelope core 71. The fire extinguishing agent 72 may be coated on the envelope core 71 in a plurality of strips or dots.

<2. Regarding the charging / discharging process of the lithium ion capacitor 3 (FIGS. 20 and 21)>
The configurations of the positive electrode 10 and the negative electrode 20 are the same in the lithium ion capacitor 3 (see FIG. 21) of the present embodiment and the lithium ion capacitor 1 (see FIG. 3) of the first embodiment. Further, the separator 130 of the lithium ion capacitor 3 is the same as the separator sheet 31 of the first embodiment. The positional relationship among the positive electrode plate 11 of the positive electrode 10, the negative electrode plate 21 of the negative electrode 20, the separator 130, and the electrolytic solution 40 of the lithium ion capacitor 3 is schematically the positional relationship according to the second embodiment. The same applies (see FIG. 20). The positive electrode plate 11 and the negative electrode plate 21 are disposed so as to sandwich the separator 130 therebetween. The lithium ion capacitor 3 forms an electric double layer on the surface of the positive electrode plate 11 with the positive electrode active material and the anion of the electrolytic solution 40, and the negative electrode plate 21 adsorbs and desorbs lithium ions Li ⁺ on the negative electrode active material. Charge and discharge with.

<3. About the effect of the fire-extinguishing agent of the lithium ion capacitor 3 (FIGS. 12 and 21)>
Like the lithium ion capacitor 1 of the first embodiment, the lithium ion capacitor 3 has high flame resistance without the fire extinguishing agent 72 having a great influence on the charge / discharge process of the lithium ion capacitor 3 (power storage device). Have Here, the fire extinguishing agent 72 of the lithium ion capacitor 3 is provided in an enclosure 70 provided in the internal space of the laminate member 50 (sealing body), and the enclosure 70 includes the positive electrode plate 11 of the positive electrode 10 and the negative electrode 20. It arrange | positions so that the negative electrode plate 21 may be enclosed. Therefore, the fire extinguishing agent 72 can effectively enhance the flame retardance of the lithium ion capacitor 3 (electric storage device).

<4. About the manufacturing method of the lithium ion capacitor 3 (FIG. 21)>
The lithium ion capacitor 3 of the present embodiment can be manufactured by substantially the same manufacturing method as the manufacturing method (see FIG. 12) including S1 to S9 of the first embodiment. The lithium ion capacitor 3 (see FIG. 21) differs from the lithium ion capacitor 1 (see FIG. 3) of the first embodiment in that it includes a separator 130 and an enclosure 70 including a fire extinguishing agent 72. Therefore, the manufacturing method of the lithium ion capacitor 3 of the present embodiment includes S2 which is a process of extinguishing agent in the manufacturing method including S1 to S9 of the first embodiment (see FIG. 12), S4 which is a process by which the separator 130 and a fire extinguisher are arrange | positioned is demonstrated.

In the step (S2) of processing the fire extinguisher into a predetermined shape, the enclosure 70 is created in the same manner as the method for creating the separator 30 of the lithium ion capacitor 1 of the first embodiment. More specifically, the fire extinguishing agent 72 is applied to the envelope core material 71 in the same manner as the method of applying the positive electrode active material layer 13 to the current collector 12 of the positive electrode plate 11 of S1 described above.

The step (S4) of creating a laminate in which lithium metal, a plurality of positive electrode plates, a plurality of negative electrode plates, and a plurality of separators are laminated and the positive electrode terminals and the negative electrode terminals are assembled is replaced with the separator 30 to be assembled. And the step of laminating the separator 130 and winding the envelope 70 around the laminate. Note that the difference between the lithium ion capacitor 3 of the present embodiment and the lithium ion capacitor 1 of the first embodiment is due to the form of the extinguishing agent and the separator, and is not related to the lithium metal used for pre-doping. . Accordingly, the difference between the case where the pre-doping is performed by the chemical method and the case where the pre-doping is performed by the electrochemical method is considered in the same manner as the manufacturing methods S1 to S9 of the lithium ion capacitor 1 of the first embodiment. be able to. That is, the lithium metal foil used for pre-doping is surrounded by the enclosure 70 in the same manner as the positive electrode plate 11 and the negative electrode plate 21.

Therefore, in this manufacturing method (S1 to S9), the lithium ion capacitor 3 (power storage device) being manufactured is highly flame-retardant in the steps after the step (S5) of enclosing the laminate in the laminate member 50. Therefore, the lithium ion capacitor 3 (electric storage device) can be manufactured more safely.

[Other embodiments]
The electricity storage device of the present disclosure is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present disclosure.

For example, although the electricity storage device of the above embodiment is a lithium ion capacitor, the technology of the present disclosure can be applied to various electricity storage devices using materials that can occlude and release alkali metal ions. Examples of the alkali metal include lithium having a standard electrode potential of −3.045V, sodium having a standard electrode potential of −2.714V, potassium having a standard electrode potential of −2.925V, and the like. The electricity storage device using these alkali metals includes a carbon material in the negative electrode and an alkali metal oxide in the positive electrode so that the standard electrode potential difference is relatively large. Specific examples thereof include various power storage devices such as lithium ion secondary batteries, lithium polymer secondary batteries, sodium ion secondary batteries, potassium ion secondary batteries, and all solid state batteries. Even in secondary batteries using alkali metals other than lithium ion capacitors, dendrites of alkali metals are generated due to long-term use and the like, causing short circuit ignition. Therefore, the technology of the present disclosure can suppress ignition of various power storage devices that use alkali metal ions, and can be kept safe.

Further, the extinguishing agent can be dispersed in the electrolyte 40 as a powder extinguishing agent instead of the extinguishing agent 32, the plate-like extinguishing agent 60, and the extinguishing agent 72 of the above-described embodiment. Further, in the lithium ion capacitor 1 of the first embodiment, the plate-shaped fire extinguisher 60 of the second embodiment and the enclosure 70 or the enclosure core 71 of the third embodiment may be added. . Further, in the lithium ion capacitor 2 of the second embodiment, the separator 30 of the first embodiment may be used instead of the separator 130, and the envelope 70 or the envelope core material of the third embodiment. 71 may be added. Further, in the lithium ion capacitor 3 of the third embodiment, the separator 30 of the first embodiment may be used instead of the separator 130, and the plate-like extinguishing agent 60 of the second embodiment is added. Also good. In the first to third embodiments, the lithium ion capacitors 1 to 3 are stacked cells in which the positive electrode plate 11, the negative electrode plate 21, and the separator 30 are stacked, but the long positive electrode and the long negative electrode And it can be set as the wound type cell which wound the long separator.

[Example]
Hereinafter, the technology of the present disclosure will be described more specifically with reference to examples. However, the technology of the present disclosure is not limited to the scope of the examples.

<Test of fire-retardant function of fire extinguishing agent (FIG. 22)>
Mixing 15% by mass of dicyandiamide as the fuel component A, 77% by mass of potassium nitrate as the oxidant component B, and 8% by mass of potassium acetate as the organic salt component C, forming into a plate shape, and then drying naturally, Obtained. Below, the case where the lithium metal foil is heated in the air collection bottle 101 is compared with the case where the plate-shaped fire extinguishing agent 103 and the lithium metal foil 102 are heated in the air collection bottle 101, and the effect of the fire extinguishing agent is examined. It was. In addition, it is known that the spontaneous ignition temperature (ignition point) of lithium metal is about 180 ° C.

When the plate-shaped fire extinguisher 103 and the lithium metal foil 102 were heated in the air collection bottle 101, they were heated as shown in FIG. That is, the air collection bottle 101 was installed in the heating furnace 100. Then, the plate-shaped fire extinguisher 103 pressed into a plate shape and the lithium metal foil 102 were put in the air collection bottle 101. Moreover, the thermometer 104 was installed so that the temperature measurement part of the thermometer 104 might touch the lithium metal foil 102 so that the temperature of the lithium metal foil 102 could be measured. And the temperature in a heating furnace was raised. As a result, even when the temperature of the lithium metal foil 102 rose to 280 ° C., the lithium metal foil 102 did not ignite. This is considered to be because when the temperature of the plate-like fire extinguishing agent 103 is 150 ° C. or higher, white smoke (aerosol) containing potassium radicals having a fire extinguishing action is generated, and ignition of the lithium metal foil 102 is suppressed by the potassium radicals. .

Next, when the lithium metal foil was heated in the air collection bottle 101, the temperature in the heating furnace 100 was increased from the state shown in FIG. As a result, the lithium metal foil ignited when the temperature of the lithium metal foil was 182 ° C. As described above, when a fire extinguishing agent is present around the lithium metal foil, the ignition of the lithium metal foil was suppressed by the fire extinguishing agent.

<Creation of lithium ion capacitor>
[Creation of positive electrode]
First, 88 parts by mass of powdered activated carbon as a positive electrode active material, 6 parts by mass of polyacrylic acid (polyacrylic acid sodium neutralized salt) as a binder, 15 parts by mass of acetylene black as a conductive assistant, and 345 parts by mass of water as a solvent. A positive electrode slurry A containing a positive electrode active material was prepared.

A positive electrode slurry A using polyacrylic acid as a binder was prepared by the following procedure.
(1) A pre-slurry was prepared by mixing all materials and water with a mixer a (Shinky Co., Ltd. Awatori Nertaro ARE-310).
(2) The pre-slurry obtained in (1) was further mixed with a mixer b (Filmix 40-L manufactured by PRIMIX Co., Ltd.) to prepare an intermediate slurry.
(3) The intermediate slurry obtained in (2) was mixed again with the mixer a to prepare a positive electrode slurry A.

Next, an aluminum foil (porous foil) having a thickness of 15 μm was used as the current collector foil, and the positive electrode slurry A was applied to the current collector foil and dried to prepare the positive electrode A. The coating amount of the positive electrode slurry A was adjusted so that the mass of the activated carbon after drying was 3 mg / cm ² . A blade coater or a die coater was used for coating the positive electrode slurry A on the current collector foil.

[Creation of negative electrode]
First, 95 parts by mass of graphite as a negative electrode active material, 1 part by mass of SBR as a binder, 1 part by mass of CMC as a thickener, and 100 parts by mass of water as a solvent were mixed, and a slurry for negative electrode was prepared by the following procedure. .
(1) A material excluding the binder and water were mixed in a mixer a to prepare a pre-slurry.
(2) The pre-slurry obtained in (1) was further mixed with a mixer b to prepare an intermediate slurry.
(3) A binder was added to the intermediate slurry obtained in (2) and mixed by a mixer a to prepare a negative electrode slurry.

Next, a copper foil (porous foil) having a thickness of 10 μm was used as the current collector foil, and the negative electrode slurry was applied to the current collector foil and dried to prepare a negative electrode. The coating amount of the negative electrode slurry was adjusted so that the mass of graphite after drying was 3 mg / cm ² . A blade coater was used for coating the negative electrode slurry on the current collector foil.

[Preparation of electrolyte]
As a solvent, a mixed solvent of 30% by volume of ethylene carbonate (EC), 30% by volume of dimethyl carbonate (DMC) and 40% by volume of ethyl methyl carbonate (EMC) was used. 1 mol / L of lithium bis (fluorosulfonylimide) (LiFSI) was added to the mixed solvent to prepare an electrolytic solution I.

[Creating an enclosure]
A fire extinguisher was prepared by mixing 15% by mass of dicyandiamide as fuel component A, 77% by mass of potassium nitrate as oxidant component B, and 8% by mass of potassium acetate as organic salt component C. When the RED value based on the Hansen solubility parameter for the electrolyte solution I of the fire extinguisher was calculated, it was confirmed that the value was larger than 1. This fire extinguisher was applied on both sides of cellulose having a thickness of 20 μm, and naturally dried to form an enclosure.

[Assembly of lithium ion capacitor]
The lithium ion capacitors of Test Examples 1 and 2 were produced by the following procedure.
(1) The positive electrode and the negative electrode are each punched out into a rectangle of 60 mm × 40 mm, and the current collecting tab is formed by stripping off the 20 mm × 40 mm region of the coating on the long side, leaving the 40 mm × 40 mm coating film. Attached.
(2) A laminate was prepared by making the coating portions of the positive electrode and the negative electrode face each other with a cellulose separator having a thickness of 20 μm interposed therebetween.
(3) The laminate prepared in (2) and the lithium metal foil for lithium pre-doping are surrounded by an enclosure, enclosed in an aluminum laminate foil, injected with an electrolytic solution, sealed, and the lithium ion of Test Example 1 A capacitor was produced.
In addition, the lithium ion capacitor of Test Example 2 was prepared using cellulose having a thickness of 20 μm to which the fire extinguishing agent was not applied in (3) as an enclosure.

<Heating test>
The lithium ion capacitor was heated in a heating furnace. As a result, since the lithium ion capacitor of Test Example 1 was provided with a fire extinguisher, it did not ignite even at 210 ° C. On the other hand, the lithium ion capacitor of Test Example 2 ignited at 183 ° C. because it did not include a fire extinguishing agent.

<Internal resistance>
The lithium ion capacitor was pre-doped, charged / discharged, and aged. Thereafter, the internal resistance of the lithium ion capacitor was measured at room temperature (25 ° C.) with a cut-off voltage of 2.2 to 3.8 V and a measurement current of 10 C, and the internal resistance ratio was determined. The internal resistance ratio was 98.1% in Test Example 1, assuming that Test Example 2 was 100%. There was no significant difference in internal resistance between Test Example 1 and Test Example 2, and the fire extinguishing agent did not deteriorate the performance of the capacitor.

<Nail penetration test>
A nail was pierced into the lithium ion capacitor, the presence or absence of ignition was observed, and the surface temperature was measured. A 3 mm diameter nail was inserted into the lithium ion capacitor at a speed of 80 mm / sec. The position where the nail is pierced is a position where two diagonal lines intersect on a surface having a large area parallel to the height direction of the lithium ion capacitor. The temperature at a position of 10 mm from the position where the nail was pierced to the side opposite to the current collecting tab side was measured for 1 hour from the time when the nail was pierced.

As a result of the nail penetration test, Test Example 1 had a maximum surface temperature of 146 ° C. and did not ignite. In Test Example 2, the maximum surface temperature was 332 ° C., and the lithium ion capacitor exploded immediately after the nail was stabbed. The lithium ion capacitor of Test Example 1 was able to sufficiently exhibit the flame retarding function by including a fire extinguisher. Since Test Example 1 did not ignite even at a surface temperature of 146 ° C, it was put into a nail penetration test or a crush test (such as an automobile accident) with the lithium ion capacitor operating normally in a high-temperature environment of 85 ° C or higher. Even if it was encountered, it was confirmed that it could remain safe without igniting.

<Creation of other lithium ion capacitors>
In order to investigate the high temperature durability of the lithium ion capacitor, a plurality of lithium ion capacitors with different binders and electrolytes were prepared by the following procedure. In addition, since the basic preparation method is the same as the said Test example 1, only a different point is shown below.

[Creation of positive electrode]
Positive electrode slurries B and C containing a positive electrode active material having the composition shown in Table 1 below were prepared. Carboxymethylcellulose [CMC] was used as a thickener. In Table 1, “SBR” indicates styrene-butadiene rubber, “part” indicates part by mass, and “%” indicates mass%.

The positive electrode slurries B and C using acrylic ester or SBR as a binder were prepared by the following procedure.
(1) A material excluding the binder and water were mixed in a mixer a to prepare a pre-slurry.
(2) The pre-slurry obtained in (1) was further mixed with a mixer b to prepare an intermediate slurry.
(3) A binder was added to the intermediate slurry obtained in (2) and mixed by a mixer a to prepare positive electrode slurry B or C.

Next, each positive electrode slurry B was applied to a current collector foil and dried to prepare positive electrode B. The current collector foil is an aluminum foil (porous foil) having a thickness of 15 μm. The coating amount of the positive electrode slurry B was adjusted so that the mass of the activated carbon after drying was 3 mg / cm ² . A blade coater or a die coater was used for coating the positive electrode slurry B onto the current collector foil. Similarly, a positive electrode C was prepared using the positive electrode slurry C.

[Preparation of electrolyte]
An electrolyte solution P was prepared by adding lithium hexafluorophosphate (LiPF6) to a mixed solvent of ethylene carbonate (EC) 30 vol%, dimethyl carbonate (DMC) 30 vol%, and ethyl methyl carbonate (EMC) 40 vol%. In a mixed solvent of ethylene carbonate (EC) 30 vol%, ethyl methyl carbonate (EMC) 46.7 vol%, diethyl carbonate (DEC) 23.3 vol%, propylene carbonate (PC) 10 vol%, lithium bis (fluorosulfonylimide) (LiFSI) ) Was added at 1 mol / L to prepare an electrolytic solution I2.

[Assembly of lithium ion capacitor]
Lithium ion capacitors were produced with combinations of positive electrodes and electrolytes shown in Table 2. Table 2 also shows the RED value for the electrolyte solution of the polymer constituting the binder in each combination. Note that the lithium ion capacitors of Test Examples 3 to 6 include an enclosure coated with a fire extinguishing agent.

[Measurement of initial performance]
The lithium ion capacitors of Test Examples 1 and 3 to 6 were subjected to lithium pre-doping, charge / discharge, and aging. Thereafter, the internal resistance and discharge capacity of each lithium ion capacitor were measured at room temperature (25 ° C.) with a cut-off voltage of 2.2 to 3.8 V and a measurement current of 10 C, and the results were used as initial performance.

[Durability test (85 ° C float test)]
The lithium ion capacitors of Test Examples 1 and 3 to 6 were left in a constant temperature bath at 85 ° C. with an external power supply connected and the voltage maintained at 3.8V. The standing time corresponds to 85 ° C. and 3.8 V float time. After the elapse of a predetermined time, the lithium ion capacitor is taken out of the thermostatic chamber, returned to room temperature, and then measured for internal resistance and discharge capacity under the same conditions as those for the initial performance measurement. The capacity retention rate (initial discharge capacity is 100%) The percentage of discharge capacity at the time) and the internal resistance increase rate (internal resistance increase rate from the initial performance) were calculated. The results are shown in Table 3.

As shown in Table 3, when left in a high temperature environment of 85 ° C., the capacity retention rate is reduced to half in a short time in Test Example 6 using an electrolytic solution containing lithium fluorophosphate that is not an imide lithium salt as an electrolyte. On the other hand, in Test Examples 1 and 3 to 5 using an electrolytic solution containing an imide lithium salt as the electrolyte, the capacity retention rate was kept high for a long time. However, even when an electrolytic solution containing an imide-based lithium salt is used as the electrolyte, it has become clear that there is a difference in the rate of increase in internal resistance depending on the configuration of the binder of the positive electrode. Therefore, when comparing the RED value (see Table 2) with respect to the electrolyte of the polymer constituting the positive electrode binder, in Test Example 4 using an acrylate ester having a RED value of 1 or less and Test Example 5 using SBR, It was found that the rate of increase in internal resistance was high. In contrast, in Test Examples 1 and 3, an electrolytic solution containing an imide-based lithium salt is used as an electrolyte, and polyacrylic acid having a RED value greater than 1 is used as a polymer constituting the positive electrode binder. . In this case, it is clear that the polymer constituting the positive electrode binder is not easily dissolved in the electrolyte, and the capacity retention rate is kept high even when left in a high temperature environment of 85 ° C., and the internal resistance increase rate can be kept small. became.

Claims (4)

1. A positive electrode comprising a positive electrode active material;
   A negative electrode comprising a negative electrode active material;
   An electrolyte solution in contact with the positive electrode and the negative electrode and containing alkali metal ions;
   A sealing body that contacts the electrolyte solution inside and seals the electrolyte solution;
   Have
   At least one of the positive electrode active material and the negative electrode active material is an electricity storage device capable of occluding and releasing the alkali metal ions,
   In the internal space of the sealed body, provided with a fire extinguisher that exhibits a flame-retardant function,
   The fire extinguishing agent is an electricity storage device having a RED value greater than 1 based on a Hansen solubility parameter for the electrolyte.
2. The electricity storage device according to claim 1,
   The electrolytic solution includes an organic solvent and an imide lithium salt,
   The positive electrode has a current collector foil,
   The electricity storage device, wherein the positive electrode active material is held on the current collector foil through a binder including a polymer having a RED value based on a Hansen solubility parameter with respect to the electrolytic solution of greater than 1.
3. The electricity storage device according to claim 1 or 2,
   An enclosure provided so as to surround the positive electrode and the negative electrode is provided inside the sealing body,
   The fire extinguishing agent is an electricity storage device provided on the enclosure.
4. The power storage device according to any one of claims 1 to 3,
   An electricity storage device that is a lithium ion capacitor.

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