JPWO2019172119A1 - Power storage device - Google Patents

Abstract

The present disclosure provides a power storage device (1) having high flame retardancy. The power storage device (1) comes into contact with the positive electrode (10) including the positive electrode active material, the negative electrode (20) containing the negative electrode active material, the electrolytic solution (40) containing alkali metal ions, and the electrolytic solution inside. It has a sealed body (50) that seals the electrolytic solution (40) inside. At least one of the positive electrode active material and the negative electrode active material can occlude and release alkali metal ions. The power storage device (1) further includes a fire extinguishing agent that exhibits a flame-retardant function in the internal space of the sealed body (50). The fire extinguishing agent has a RED value greater than 1 based on the Hansen solubility parameter for the electrolytic solution (40).

Description

The present disclosure relates to a power storage device.

Power storage devices equipped with active materials capable of occluding and releasing alkali metal ions are widely used because they exhibit excellent characteristics such as high operating voltage and excellent energy density. In order to improve the safety of the power storage device, studies have been repeated and many safety tests have been conducted. Examples of the safety test include a nail piercing test and a crushing test simulating an internal short circuit of the power storage device, and a heating test simulating that the power storage device is heated from the outside.

A technique for preventing the power storage device from igniting when the power storage device is internally short-circuited or heated has been proposed. For example, Japanese Patent Application Laid-Open No. 2013-541131 discloses a technique for extinguishing an ignited power storage device by arranging a fire extinguishing agent around the power storage device.

However, even if the technique described in Japanese Patent Application Laid-Open No. 2013-541131 is used, there is a possibility that the ignited power storage device cannot be easily extinguished. For example, the high temperature power storage device ignites and the temperature of the power storage device further rises. Therefore, the organic solvent contained in the power storage device is vaporized and diffuses to the surroundings. When this vaporized organic solvent ignites, a plurality of power storage devices can ignite in a chain. If the power storage devices ignite in a chained manner in this way, the fire may not be easily extinguished by the technique described in Japanese Patent Application Laid-Open No. 2013-541131. Therefore, there is a demand for highly flame-retardant power storage devices.

One feature of the present disclosure is a power storage device having a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, an electrolytic solution, a sealed body, and a fire extinguishing agent. The electrolytic solution comes into contact with the positive electrode and the negative electrode and contains alkali metal ions. The sealed body comes into contact with the electrolytic solution on the inside and seals the electrolytic 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 arranged in the internal space of the sealed body and exhibits a flame retardant function. The fire extinguishing agent has a RED value greater than 1 based on the Hansen solubility parameter for the electrolytic solution.

According to the above characteristics, in the power storage device, a fire extinguishing agent is provided in the internal space of the sealed body. Therefore, since the flame-retardant function of the fire extinguishing agent to make the power storage device flame-retardant can be exerted not from the outside of the sealed body but from the inside, the fire extinguishing agent can surely enhance the flame-retardant property of the power storage device.

Further, since the RED value of the fire extinguishing agent based on the Hansen solubility parameter in the electrolytic solution is larger than 1, the amount of the fire extinguishing agent dissolved in the electrolytic solution is negligibly small. Therefore, the fire extinguishing agent is stable in the power storage device. Therefore, the fire extinguishing agent stably increases the flame retardancy of the power storage device over time, and does not significantly affect the charging / discharging process of the power storage device.

Another feature of the present disclosure is that the electrolyte comprises an organic solvent and an imide-based lithium salt. The positive electrode has a current collecting foil. The positive electrode active material is held in the current collector foil via 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 its capacity even in the environment of 85 ° C. required for installation in the passenger compartment of an 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 extinguishing agent can effectively enhance the flame retardancy of the power storage device.

Another feature of the present disclosure is a lithium ion capacitor. In the pre-doping step generally included in the method for manufacturing a lithium ion capacitor, a single lithium metal is used. Since elemental lithium ions cause ignition, a predoping process is performed so that no elemental 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 placed in the internal space of the sealed body exerts a flame-retardant function to prevent ignition of the lithium-ion capacitor. Further, it is not necessary to spend time in the pre-doping step so that metallic lithium does not precipitate as in the conventional case, and the time in the pre-doping step can be shortened.

It is an exploded perspective view of the power storage device of 1st Embodiment. It is a perspective view of the power storage device of 1st Embodiment. It is a schematic diagram of the cross section of line III-III in the power storage device of FIG. It is a figure explaining the example of the appearance of the positive electrode plate in 1st Embodiment. FIG. 5 is a sectional view taken along line VV of the positive electrode plate of FIG. It is a figure explaining the example of the appearance of the negative electrode plate in 1st Embodiment. FIG. 6 is a sectional view taken along line VII-VII of the negative electrode plate of FIG. It is a figure explaining an example of the appearance of the separator provided with a fire extinguishing agent in the 1st Embodiment. FIG. 5 is a sectional view taken along line IX-IX of the separator of FIG. It is a figure explaining the appearance of another example of a separator provided with a fire extinguishing agent in the first embodiment. In the first embodiment, it is a figure explaining the positional relationship between the positive electrode plate of a positive electrode, the negative electrode plate of a negative electrode, a separator, an electrolytic solution, and a fire extinguishing agent. In the first embodiment, it is an example of a flowchart showing a manufacturing process of a power storage device. It is a figure explaining the positive electrode plate production and the roll press processing for producing the negative electrode plate in the manufacturing process of the power storage device of the first embodiment. It is a figure explaining the example of the appearance of the electrode plate for predoping in the manufacturing process of the power storage device of 1st Embodiment. FIG. 4 is a cross-sectional view taken along the line XV-XV of the pre-doped electrode plate of FIG. It is a figure explaining the roll press processing for producing the electrode for predoping in the manufacturing process of the power storage device of 1st Embodiment. It is a figure explaining the state which performs predoping in the manufacturing process of the power storage device of 1st Embodiment. It is an exploded perspective view of the power storage device of the second embodiment. It is a schematic cross-sectional view of the power storage device of the 2nd Embodiment. In the second embodiment, it is a figure explaining the positional relationship of a positive electrode plate, a negative electrode plate, a separator, an electrolytic solution, and a fire extinguishing agent. It is a schematic cross-sectional view of the power storage device of the 3rd Embodiment. It is a figure explaining the test method of the flame retardant function of a fire extinguishing agent.

[First Embodiment]
Hereinafter, the first embodiment will be described with reference to FIGS. 1 to 17. The power 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-shaped positive electrode plates 11 and a plurality of plate-shaped negative electrode plates 21. The plurality of plate-shaped positive electrode plates 11 and the plurality of plate-shaped negative electrode plates 21 are alternately laminated. Each positive electrode plate 11 includes an electrode terminal connecting portion 12b that projects in one direction. Each negative electrode plate 21 also includes an electrode terminal connecting portion 22b that projects in the same direction as the electrode terminal connecting portion 12b of the positive electrode plate 11 projects. As shown in FIG. 1, the direction in which the electrode terminal connection portion 12b of the positive electrode plate 11 protrudes is the X-axis direction, the stacking direction is the Z-axis direction, and the X-axis and the direction orthogonal to the Z-axis are the Y-axis directions. To do. These X-axis, Y-axis, and Z-axis are orthogonal to each other. In all the figures in which the X-axis, Y-axis, and Z-axis are described, these axial directions indicate the same direction, and in the following description, the description regarding the direction may be based on these axial directions. In the present embodiment and the embodiments described below, the illustration and detailed description of incidental configurations will be 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 electrode plates 11, a plurality of negative electrode plates 21, a plurality of separators 30, an electrolytic solution 40, and a laminating member 50. Here, as shown in FIG. 1, the positive electrode plate 11 and the negative electrode plate 21 are alternately laminated, and the separator 30 is sandwiched between the positive electrode plate 11 and the negative electrode plate 21, respectively. The electrolytic solution 40 is wrapped in two laminated members 50 (sealed body) together with a part of the plurality of positive electrode plates 11, a part of the plurality of negative electrode plates 21, and a plurality of separators 30 laminated in this way. Is sealed in the lithium ion capacitor 1. The electrolytic solution 40 is in contact with the inside of the positive electrode plate 11, the negative electrode plate 21, and the laminating member 50. Although the 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 retardancy of the lithium ion capacitor 1. The lithium ion capacitor 1 may further have separators 30 in the uppermost layer and the lowermost layer in the Z-axis direction, and may be arranged so that each negative electrode plate 21 is sandwiched between the separators 30.

The electrode terminal connection portions 12b of the plurality of positive electrode plates 11 project in the same direction and conduct with the positive electrode terminals 14. The conductor members on the positive electrode side, such as the positive electrode terminal 14 and the plurality of positive electrode plates 11 connected to the positive electrode terminal 14, are collectively referred to as the positive electrode 10. The electrode terminal connection portions 22b of the plurality of negative electrode plates 21 and the negative electrode terminals 24 are conductive. The conductor members on the negative electrode side, such as the negative electrode terminal 24 and the plurality of negative electrode plates 21 connected to the negative electrode terminal 24, are collectively referred to as the negative electrode 20. The lithium ion capacitor 1 has the above-described configuration inside, and its appearance is shown in FIG. The III-III cross section of the lithium ion capacitor 1 shown in FIG. 2 is schematically shown in FIG. In FIG. 3, a space is provided between each member in the lithium ion capacitor 1 for the sake of clarity. However, in reality, the positive electrode plate 11, the negative electrode plate 21, and the separator 30 are laminated with almost no gap.

<2. About 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)>
As the positive electrode plate 11, a conventional positive electrode plate of a lithium ion capacitor can be used. That is, the positive electrode plate 11 includes a thin plate-shaped current collector 12 and a positive electrode active material layer 13 coated on the current collector 12. As shown in FIG. 4, in the current collector 12, the rectangular current collector 12a and the electrode terminal connection portion 12b protruding from one end of the current collector 12a (the left end of the upper side in the example of FIG. 4) are integrally formed. It 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. Then, the width of the electrode terminal connecting portion 12b shown in FIGS. 1 and 4 in the Y-axis direction can be appropriately changed. The width may be the same as that of the current collector 12a, for example. Further, the positive electrode active material layer 13 is coated on both surfaces of the current collector 12a, but the coated surface may be either one surface. Here, since the current collector 12a is formed with a plurality of holes 12c, the 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 is a collection of a positive electrode active material having a large specific surface area and high conductivity, a conductive auxiliary agent for increasing the electrical conductivity of the positive electrode active material layer 13, and binding of the positive electrode active material and the positive electrode active material. Includes a binder that binds the current collecting unit 12a of the electric body 12 to the current collecting unit 12a. The positive electrode active material layer 13 may further contain other components such as a thickener. As the positive electrode active material, for example, activated carbon, carbon nanotubes, polyacene and the like can be used. As the conductive auxiliary agent, for example, Ketjen black, acetylene black, fine particles of graphite, and fine fibers of graphite can be used. As the thickener, for example, carboxylmethyl cellulose [CMC] can be used.

Binders are used to bind the materials that make up the positive electrode. The binder is mainly composed of a polymer, which 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) of more than 1 based on the Hansen solubility parameter (HSP) with respect to the electrolytic solution 40. A polymer having a RED value greater than 1 with respect to the electrolytic solution 40 does not dissolve in the electrolytic solution 40, so that the rate of increase in internal resistance is small even when the lithium ion capacitor 1 is used for a long time in a high temperature environment. Examples of such a polymer include polyacrylic acid. The term "polyacrylic acid" as used herein is a broad concept including not only unneutralized polyacrylic acid but also neutralized salts of polyacrylic acid and crosslinked ones. Polyacrylic acid may be used alone or in combination of two or more. Water or an organic solvent can be used as the solvent for dissolving the polymer. An aqueous binder that uses water as a solvent is preferable because it can reduce the environmental load in the manufacturing process. Polyacrylic acid is also suitable in that it can form 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 based on the positive electrode active material. If 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, it may cause an increase in the internal resistance of the lithium ion capacitor 1.

<2-2. Structure of the negative electrode plate 21 (FIGS. 1, FIG. 3, FIG. 6, FIG. 7)>
As the negative electrode plate 21, a conventional negative electrode plate of a lithium ion capacitor can be used. The negative electrode plate 21 has roughly the same structure as the positive electrode plate 11 described above. That is, the negative electrode plate 21 includes a thin plate-shaped 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 ion Li +.} Then, as will be described later, the negative electrode active material is adsorbed (so-called pre-doped) ^{with lithium ions Li + during production.}

As shown in FIG. 6, the current collector 22 has a rectangular current collector 22a and an electrode terminal connection 22b protruding outward from one end of the current collector 22a (in the example of FIG. 6, the right end of the upper side). It is formed integrally. 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. Further, the negative electrode active material layer 23 is coated on both surfaces of the current collector 22a, but the coated surface may be either one surface. Here, similarly to the positive electrode plate 11 described above, since the current collector 22a has a plurality of holes 22c formed, the cations and anions of the electrolytic solution 40 can pass through the current collector 22a. Further, 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 apart from each other in the Z-axis direction. Therefore, it is possible to prevent the electrode terminal connecting portion 12b and the electrode terminal connecting portion 22b from coming into contact with each other. Here, the width of the electrode terminal connecting portion 22b shown in FIGS. 1 and 6 in the Y-axis direction can be appropriately changed, and may be the same width as, for example, 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 as in 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 absorbing and removing lithium ion Li +} , a binder for binding the negative electrode active material, and a binder for binding the negative electrode active material and the current collecting portion 22a of the current collector 22. .. The negative electrode active material layer 23 may contain other components such as a conductive auxiliary agent for enhancing the electrical conductivity of the negative electrode active material layer 23 and a thickener. As the negative electrode active material, for example, graphite can be used. As the conductive auxiliary agent, the binder, and the thickener, the same substances as those of the positive electrode plate 11 described above can be used. That is, for example, Ketjen black, acetylene black, graphite fine particles, and graphite fine fibers can be used as the conductive auxiliary agent. As the binder, for example, polyvinylidene fluoride, styrene-butadiene rubber [SBR], or polyacrylic acid can be used. As the thickener, for example, carboxylmethyl cellulose [CMC] can be used.

<2-3. Structure of separator 30 (FIGS. 1, 3, 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 is set (see FIGS. 1, 4, and 6). As shown in FIG. 9, the separator 30 is a porous sheet-like separator sheet 31 for separating between the positive electrode plate 11 and the negative electrode plate 21, and a fire extinguishing agent 32 coated on both sides of the separator sheet 31. And have. The separator 30 is configured so that the cations and anions of the electrolytic solution 40 can permeate.

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

As the separator sheet 31, a conventional lithium ion capacitor separator can be used. 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 retardant function and has a RED value of more than 1 based on the Hansen solubility parameter (HSP) for the electrolytic solution 40. The Hansen solubility parameter, published by Charles M Hansen, is known as an indicator of the solubility of a substance in a substance. For example, water and oil generally do not dissolve, because the "property" of water and oil is different. As the "property" of the substance related to this solubility, in the Hansen solubility parameter, three items of dispersion term D, polarity term P, and hydrogen bond term H are numerically represented for each substance. Here, the dispersion term D is a value representing the magnitude of the van der Waals force. The polarity 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. Therefore, the description of treating the hydrogen bond term H by dividing it into a donor property and an acceptor property will be omitted.

The Hansen solubility parameter (D, P, H) is plotted in a three-dimensional Cartesian coordinate system (Hansen space, HSP space) to examine the solubility. For example, the Hansen solubility parameters of solution A and solid B, respectively, can be plotted in the Hansen space at two coordinates (coordinate A, coordinate B) corresponding to solution A and solid B, respectively. Then, it can be considered that the shorter the distance Ra (HSP distance, Ra) between the coordinates A and the coordinates B, the easier it is for the solid B to dissolve in the solution A because the solution A and the solid B have the above-mentioned "property" similar to each other. it can. On the contrary, the longer the distance Ra, the more difficult it is to dissolve the solid B in the solution A because the solution A and the solid B have “property” that are not similar to each other.

Further, the interaction radius R0 is defined as the distance Ra that is the boundary between the soluble substance and the insoluble substance with respect to the solution A. 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 is not dissolved in the solution A. Further, the value obtained by dividing the distance Ra by the interaction radius R0 is defined as the 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 is not dissolved in the solution A. In this way, it can be determined whether or not the solid B is soluble in the solution A based on the RED values for 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 fire extinguishing agent 32. Since the RED value of the fire extinguishing agent 32 based on the Hansen solubility parameter for the electrolytic solution 40 is larger than 1, it can be considered that the fire extinguishing agent 32 does not dissolve in the electrolytic solution 40. On the contrary, it can be considered that the fire extinguishing agent having a poor solubility in the electrolytic solution 40 also has a RED value larger than 1 based on the Hansen solubility parameter.

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

As the fire extinguishing agent 32, among known fire extinguishing agents, a fire extinguishing agent that exhibits a flame retardant function and has a RED value greater than 1 based on the Hansen solubility parameter for the electrolytic solution 40 can be used. As such a fire extinguishing agent 32, for example, a fire extinguishing agent containing a fuel component A, an oxidizing agent component B, and an organic salt component C, which will be described below, can be used. This fire extinguishing agent contains 15 to 50 parts by mass of fuel component A, 85 to 50 parts by mass of oxidant component B, and 7 to 50 parts by mass of organic salt component C with respect to a total of 100 parts by mass of fuel component A and oxidant component B. Contains 1000 parts by mass.

When this fire extinguishing agent is heated, the fuel component A and the oxidant component B burn to generate an aerosol containing potassium radicals from the organic salt component C. The potassium radical contained in this aerosol has a fire extinguishing action and a flame retardant function of suppressing ignition. Here, the flame-retardant function of this fire extinguishing agent is a function of immediately generating potassium radicals when they start to ignite, and suppressing 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 compositions of the fuel component A, the oxidant component B, and the organic salt component C. In addition, this fire extinguishing agent can generate potassium radicals having a fire extinguishing action and a flame-retardant function of suppressing ignition, but the generated radicals are radicals having a fire-extinguishing action or a flame-retardant function other than potassium radicals. May be. That is, the fire extinguishing agent may be a fire extinguishing agent that generates radicals having a fire extinguishing action or a flame retardant function other than potassium radicals. Further, the fire extinguishing agent may have a flame retardant function to prevent ignition as described above, and radicals that stop the chain reaction of combustion that occurs when ignition such as a thermal decomposition reaction or an oxidation reaction is stopped by a radical trap. It does not have to generate the containing aerosol. For example, the fire extinguishing agent may have a flame retardant function of stopping the chain reaction of combustion by generating an inert gas such as nitrogen, argon or carbon dioxide. It is also possible to use a storage alloy or the like that can store the inert gas in advance and release it at a predetermined temperature. Fire extinguishing agents other than halogen and phosphorus flame retardants are preferable because they are highly safe for the environment. Further, if the above configuration is configured to release an inert gas other than carbon dioxide, the safety for humans can be enhanced.

Fuel component A is dicyandiamide, nitroguanidine, guanidine nitrate, urea, melamine, melamine cyanurate, avicell, guagam, sodium carboxylmethylcellulose, potassium carboxylmethylcellulose, ammonium carboxylmethylcellulose, nitrocellulose, aluminum, boron, magnesium, magnalium, zirconium, Titanium, titanium hydride, tungsten, silicon, etc. As the fuel component A, only one type may be used, or two or more types may be mixed.

Examples of the oxidizing agent component B include an inorganic oxidizing agent and the like. Inorganic oxidants include potassium nitrate, sodium nitrate, strontium nitrate, ammonium perchlorate, potassium perchlorate, basic copper nitrate, copper (I) oxide, copper (II) oxide, iron (II) oxide, and iron (III) oxide. ), Molybdenum trioxide, etc. As the oxidizing agent component B, only one kind may be used, or two or more kinds may be mixed.

Examples of the organic salt component C include an organic carboxylic acid potassium salt and the like. Potassium organic carboxylates include potassium acetate, potassium propionate, monopotassium citrate, dipotassium citrate, tripotassium citrate, monopotassium ethylenediamine tetraacetate, dipotassium dihydrogen tetraacetate ethylenediamine, and monohydrogen tetraacetate ethylenediamine. Tripotassium, tetrapotassium ethylenediamine tetraacetate, potassium hydrogen phthalate, dipotassium phthalate, potassium hydrogen oxalate, dipotassium oxalate and the like. As the organic salt component C, only one kind may be used, or two or more kinds may be mixed.

<2-4. Composition of electrolyte 40>
As the electrolytic solution 40, a conventional electrolytic solution of a lithium ion capacitor can be used. That is, the electrolytic solution 40 contains an organic solvent (non-aqueous solvent) and an electrolyte. Additives may be added to the electrolytic solution 40 as appropriate. Examples of the additive include vinylene carbonate [VC].

As organic solvents, carbonate-based organic solvents, nitrile-based organic solvents, lactone-based organic solvents, ether-based organic solvents, alcohol-based organic solvents, ester-based organic solvents, amide-based organic solvents, sulfone-based organic solvents, ketone-based organic solvents, fragrances. A group organic solvent can be exemplified. Only one type of solvent may be used, or two or more types may be mixed. The organic solvent preferably has a heat resistance of 85 ° C. or higher.

As carbonate-based organic solvents, cyclic carbonates such as ethylene carbonate [EC], propylene carbonate [PC] and fluoroethylene carbonate [FEC], chains such as ethyl methyl carbonate [EMC], diethyl carbonate [DEC] and dimethyl carbonate [DMC]. A state carbonate can be exemplified.

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 inferior heat resistance. That is, when dimethyl carbonate (DMC) is contained in the organic solvent, dimethyl carbonate (DMC) is thermally decomposed into diethyl carbonate (DEC), and the decomposition by-product at that time causes an increase in internal resistance and deterioration of heat resistance. (Note that this speculation does not limit the technology of this 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 in the range of, for example, EMC: DEC = 2: 1 to 1: 2.

Although various cyclic carbonates can be used as the cyclic carbonate, it is preferable to use ethylene carbonate (EC) having a solid electrolytic solution phase-to-phase (SEI) film forming ability from the viewpoint of improving the oxidation resistance of the electrolytic solution. When ethylene carbonate (EC) and another cyclic carbonate (for example, PC) are mixed and used as the cyclic carbonate, it is preferable that ethylene carbonate (EC) is contained in a larger amount than the other cyclic carbonate (for example, PC). .. When a relatively large amount of ethylene carbonate (EC) is contained in this way, ethylene carbonate (EC) is reduced and decomposed, and an SEI film is formed on the surface of the negative electrode. As a result, the electrolytic solution is not directly exposed to the potential of lithium (Li).

Further, examples of the nitrile-based organic solvent include acetonitrile, acrylonitrile, adiponitrile, valeronitrile, and isobutyronitril. Further, as the lactone-based organic solvent, γ-butyrolactone and γ-valerolactone can be exemplified. Examples of the ether-based organic solvent include cyclic ethers such as tetrahydrofuran and dioxane, and chain ethers such as 1,2-dimethoxyethane, dimethyl ether and triglime. Further, as the alcohol-based organic solvent, ethyl alcohol and ethylene glycol can be exemplified. Examples of the ester-based 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 sulfate. Examples of the amide-based 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. Methyl ethyl ketone can be exemplified as the ketone-based organic solvent, and toluene can be exemplified as the aromatic organic solvent. The various organic solvents other than the carbonate-based organic solvent are preferably mixed with a cyclic carbonate, and particularly preferably mixed with an ethylene carbonate [EC] capable of forming a protective film.

As the electrolyte, a lithium salt of a cation (cation) Li ion and an anion (anion) is used. 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] can be used. it can. Only one of these lithium salts may be used, or two or more of these lithium salts may be used. In particular, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, lithium bis (pentafluoroethane sulfonyl) imide lithium salt such as imide (-SO 2 _-N-SO 2 _- lithium having the partial structure 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 the appropriate viscosity of the electrolytic solution 40 and the ionic 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 the decrease in the concentration of the ions in which the electrolyte is dissociated, which is not preferable. Further, if the concentration of the electrolyte is larger than 10.0 mol / L, the ionic conductivity of the electrolytic solution 40 is too low due to the increase in the viscosity of the electrolytic solution 40, which is not preferable.

<2-5. Structure of laminated member 50 (FIGS. 1 and 3)>
As shown in FIG. 3, the laminated member 50 includes a core material sheet 51, an outer sheet 52, and an inner sheet 53. Then, the outer sheet 52 is adhered to the outer surface of the core material sheet 51, and the inner sheet 53 is adhered 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. About 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 also has 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 collecting portion 12a of the positive electrode plate 11 and the current collecting portion 22a of the negative electrode plate 21. Further, the separator 30 is also configured so that the anions and cations of the electrolytic solution 40 can permeate. FIG. 11 schematically shows the positional relationship between 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 fire extinguishing agent 32 of the lithium ion capacitor 1. As shown in FIG. 11, the positive electrode plate 11 and the negative electrode plate 21 sandwich a separator 30 provided with a fire extinguishing agent 32 in between. In the lithium ion capacitor 1, an electric double layer is formed on the surface of the positive electrode plate 11 by the positive electrode active material and the anion of the electrolyte, and the negative electrode plate 21 is filled by adsorbing and desorbing ^{lithium ion Li + on the negative electrode active material.} Discharge. Further, as will be described later, at the time of manufacturing the lithium ion capacitor 1, lithium ion Li ⁺ is adsorbed on the negative electrode active material of the negative electrode plate 21 (predoping). 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 becomes large, 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 has a large capacity and a high output.

<4. About the effect of fire extinguishing agent>
Generally, in the process of pre-doping during manufacturing, lithium ion Li ⁺ is adsorbed in advance on the negative electrode active material of the negative electrode plate 21. The source of this lithium ion Li ⁺ is a lithium metal that is arranged in the internal space where the electrolytic solution of the lithium ion capacitor exists ^{and is converted into 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 It is a chemical method to make lithium ion Li ^+.

Regardless of which of these methods is used, a simple substance lithium metal is used in the pre-doping step generally included in the method for manufacturing a lithium ion capacitor. Then, usually, a pre-doping step is performed so that a single lithium metal does not remain 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 ignite. .. Even in such a case, in the lithium ion capacitor 1 of the present embodiment, since the fire extinguishing agent 32 exhibiting the flame retardant function is provided in the internal space of the laminated member 50 (sealed body), ignition can be prevented. .. Further, it is not necessary to spend time in the pre-doping step so that metallic lithium does not precipitate as in the conventional case, and the time in the pre-doping step can be shortened.

In the lithium ion capacitor 1 (storage device), a fire extinguishing agent 32 is provided in the internal space of the laminated member 50 (sealed body). Therefore, the flame-retardant function of the fire extinguishing agent 32 to make the lithium ion capacitor 1 (storage device) flame-retardant can be exhibited not from the outside of the laminated member 50 (sealed body) but from the inside. Therefore, the fire extinguishing agent 32 can surely enhance the flame retardancy of the lithium ion capacitor 1 (storage device).

Further, 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 (storage device). Can be enhanced.

Further, since the fire extinguishing agent 32 has a RED value larger than 1 based on the Hansen solubility parameter for the electrolytic solution 40, the amount of the fire extinguishing agent 32 dissolved in the electrolytic solution 40 is negligibly small. Therefore, the fire extinguishing agent 32 can be considered to be stable. Therefore, the fire extinguishing agent 32 stably enhances the flame retardancy of the lithium ion capacitor 1 (storage device) over time, and does not significantly affect the charging / discharging process of the lithium ion capacitor 1 (storage device).

<5. About the manufacturing method of the lithium ion capacitor 1 (FIGS. 12 to 17)>
The manufacturing method of the lithium ion capacitor 1 of this embodiment will be described. As described above, the ^{predoping method for adsorbing lithium ion 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 convert the lithium metal into lithium ion Li ⁺ . The chemical method dissolves the lithium metal in the electrolyte. In the following, first, the case where the predoping is performed by the chemical method will be described, and then the case where the predoping is performed by the electrochemical method will be described. The lithium ion capacitor 1 can be manufactured as shown in FIG.

In the production of the lithium ion capacitor 1, first, the positive electrode plate 11 and the negative electrode plate 21 are produced (S1). The order of producing the positive electrode plate 11 and the negative electrode plate 21 may be either first or in parallel.

A method for producing the positive electrode plate 11 will be described. The positive electrode plate 11 includes a metal thin plate-shaped current collector 12 in which a plurality of holes 12c are formed, and a positive electrode active material layer 13 coated on both sides or one side of the current collector 12. First, the material for the positive electrode active material layer 13 is prepared. That is, a slurry prepared by mixing the above-mentioned positive electrode active material, a conductive auxiliary agent, a binder, a solvent such as water or an organic solvent, and, if necessary, a component such as a thickener, using a mixer. To do. Then, this slurry is applied to one side or both sides of a thin metal plate having a plurality of holes formed as a material of the current collector 12. The slurry is then dried to remove solvent and pressed to make the thickness uniform (see FIG. 13). When the slurry is applied to the thin metal plate, it may be applied on one side at a time, or on both sides at the same time.

As the coating method, for example, a gravure coating method, a bar coating method, a spray coating method, a spin coating method, an air knife coating method, a roll coating method, a blade coating method, a gate roll coating method, a die coating method and the like can be used. it can. Among these, the blade coating method and the die coating method are preferable. Further, as a drying method, for example, a method of heat drying in a hot air drying furnace or the like can be used. For the press, for example, a roll press machine can be used.

Further, the positive electrode plate 11 may be created as follows. The metal thin plate used as the material of the current collector 12 for applying the slurry 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 thin metal plate coated with the slurry is dried and pressed, and after pressing, it is cut into the size of the positive electrode plate 11 (see FIG. 4), and further coated on the portion to be the electrode terminal connection portion 12b (see FIG. 4). The positive electrode active material layer that has been formed 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 the portion of the metal thin plate to be the current collecting portion 12a, where the electrode terminal connection portion is formed. The portion to be 12b may not be coated with the slurry, and may be cut into the size of the positive electrode plate 11 (see FIG. 4) before or after pressing. Further, the thin metal plate to which the slurry is applied may be cut into the size of the positive electrode plate 11 before the slurry is applied.

As described above, the negative electrode plate 21 has roughly 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 described above, a binder, a solvent such as water or an organic solvent, and, if necessary, a component such as a conductive auxiliary agent or a thickener. To prepare a mixed slurry using a mixer. Then, this slurry is applied to one side or both sides of a thin metal plate having a plurality of holes formed as a material for the current collector 22. The slurry is then dried to remove solvent and pressed to make the thickness uniform (see FIG. 13). When the slurry is applied to the thin metal plate, it may be applied on one side at a time, or on both sides at the same time.

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

Next, the lithium metal used for predoping is processed into a predetermined shape (S3). Here, as an example, a pre-doped negative electrode plate 21p is created. To prepare the negative electrode plate 21p for pre-doping, a lithium metal foil LiS1 having a predetermined shape is placed on the negative electrode active material layer 23 of the negative electrode plate 21 (see FIGS. 14 and 15), and the negative electrode active material of the negative electrode plate 21 is further pressed. The layer 23 and the lithium metal foil LiS1 are crimped (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 this S3, one negative electrode plate 21 is used, but since this S3 can be performed after creating one negative electrode plate 21 in S1, S1 and this S3 can also be performed in parallel. .. Further, after the one negative electrode plate 21 is produced in S1, S1, S2, and S3 can be performed in parallel, and the order in which S1, S2, and S3 are performed can be appropriately changed.

Next, a laminated body is prepared 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 a positive electrode terminal 14 and a negative electrode terminal 24 are assembled (S4). First, as shown in FIG. 17, the plurality of positive electrode plates 11 and the plurality of negative electrode plates 21 are alternately laminated, and the separator 30 is sandwiched between the positive electrode plate 11 and the negative electrode plate 21, respectively. , The pre-doped negative electrode plate 21p, the positive electrode plate 11, the negative electrode plate 21, and the separator 30 are laminated. Here, the pre-doped negative electrode plate 21p is laminated on the uppermost layer in the Z-axis direction. Next, the positive electrode terminals 14 are assembled to the plurality of positive electrode plates 11, and the negative electrode terminals 24 are further assembled to the pre-doped negative electrode plates 21p and the plurality of negative electrode plates 21 to create a laminate. The separator 30 may be further arranged on the uppermost layer in the Z-axis direction of the laminated body, or the separator 30 may be further arranged on the lowermost layer in the Z-axis direction of the laminated body. In the above, it has been described that the positive electrode terminal 14 and the negative electrode terminal 24 are assembled after laminating the pre-doped negative electrode plate 21p, the positive electrode plate 11, the negative electrode plate 21, and the separator 30. The order of assembly and assembly may be changed as appropriate. For example, the positive electrode terminal 14 and the positive electrode plate 11 may be connected and the negative electrode terminal 24 and the negative electrode plate 21 may be connected in parallel with the lamination. Further, S3 for processing the lithium metal used for predoping into a predetermined shape is simply a step of preparing the lithium metal leaf LiS1, and instead of arranging the predoping negative electrode plate 21p on the laminate prepared in the step of S4, the lithium metal foil LiS1 and one negative electrode plate 21 may be arranged.

Next, the above-mentioned 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 portion excluding a part of the laminate member 50 is welded. To do.

Next, pre-doping is performed to adsorb the ^{lithium ion Li +} on the negative electrode active material layer 23 (S6). First, the electrolytic solution 40 prepared in advance is injected into the internal space of the laminating member 50. Then, the laminating member 50 is sealed, and the electrolytic solution 40 is sealed. As a result, the lithium metal leaf LiS1 on the pre-doped 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 laminating member 50. ^{The lithium ion Li +} in the electrolytic solution 40 is adsorbed on the negative electrode active material layer 23, and the lithium metal leaf LiS1 becomes lithium ion Li ⁺ and dissolves in the electrolytic solution 40. As described above, the current collector 12a of the current collector 12 of the positive electrode plate 11 has a plurality of holes 12c, and the current collector 22a of the current collector 22 of the negative electrode plate 21 has a plurality of holes 22c. Therefore, the lithium ion Li ⁺ in the electrolytic solution 40 can permeate the positive electrode plate 11 and the negative electrode plate 21. Further, the separator 30 is also configured so that ^{the lithium ion Li + in the electrolytic solution 40 can permeate. Therefore, lithium ion Li +} can be adsorbed on the negative electrode active material layer 23 of all the negative electrode plates 21. Here, in order to facilitate the dissolution of the lithium metal leaf LiS1 in the electrolytic solution 40, the lithium metal leaf LiS1 may be heated together with the electrolytic solution 40. Even if the lithium metal becomes liable to ignite due to heating, the ignition of the lithium metal is suppressed because the fire extinguishing agent 32 is contained in the internal space of the laminating member 50 together with the lithium metal.

Next, charging / discharging 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 laminated member 50 with an external electric circuit. Generally, gas is generated in this charge / discharge process.

Next, the gas is discharged to the outside of the laminating 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 gas existing in the internal space of the laminating member 50 before charging / discharging.

Finally, the internal space of the laminated member 50 is sealed (S9). This completes the production of the lithium ion capacitor 1. Here, other steps may be included if necessary. For example, the time when the lithium ion capacitor 1 is inspected and the inspection is completed can be the time when the production of the lithium ion capacitor 1 is completed.

<6. About another example of the manufacturing method of the lithium ion capacitor 1>
In the above production method, as described above, predoping was performed by a chemical method in which lithium metal is dissolved in an electrolytic solution to form lithium ions Li ^+. On the other hand, a method for manufacturing the lithium ion capacitor 1 when the 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 pre-doping negative electrode plate 21p was prepared by crimping the lithium metal leaf LiS1 onto the negative electrode active material layer 23 of the negative electrode plate 21. In this method, instead, a pre-doped electrode (not shown) in which an electrode terminal (not shown) and a lithium metal foil (not shown) are attached to a metal foil (for example, copper foil, not shown) is created. Then, in the step (S4) of creating the laminate, the pre-doped electrode, the plurality of positive electrode plates 11, the plurality of negative electrode plates 21, the plurality of separators 30 are laminated, and the positive electrode terminal 14 and the negative electrode terminal 24 are assembled. I do. In this lamination, for example, the predoping electrode is placed in the uppermost layer in the Z-axis direction, and the separator 30 is sandwiched between the predoping electrode and the negative electrode plate 21. Then, in the step (S5) of including the laminate in the laminate member 50, a part of the positive electrode terminal 14, a part of the negative electrode terminal 24, and a part of the electrode terminals of the predoping electrode are outside the laminate member 50. The laminate is included in the laminate member 50 so as to be exposed to the surface. Then, in the above-mentioned step of performing predoping (S6), after sealing the electrolytic solution 40 as described above, a voltage is applied between the predoping electrode and the plurality of negative electrode plates 21 (that is, one negative electrode 20). The lithium metal is ^{converted to lithium ion Li +} and pre-doped. Further, S1, S2, S7, S8, and S9 are performed as described above.

Therefore, the production method including S1 to S9 described above using FIG. 12 includes a production method in which predoping is performed by a chemical method and a production method in which predoping is performed by an electrochemical method. Further, in this manufacturing method, the fire extinguishing agent 32 is housed together with the lithium metal leaf LiS1 in the internal space of the laminating member 50 in the step (S5) of encapsulating the laminated body in the laminating member 50 before pre-doping. Therefore, after the encapsulation step (S5), the fire extinguishing agent 32 is housed together with the lithium metal leaf LiS1 in the internal space of the laminating member 50. Therefore, in this manufacturing method (S1 to S9), since the lithium ion capacitor being manufactured has high flame retardancy in the steps after the inclusion step (S5), the lithium ion capacitor 1 can be manufactured more safely. It has become.

[Second Embodiment]
Subsequently, the power storage device of the second embodiment will be described with reference to FIGS. 18 to 20. The power 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 the lithium ion capacitor 1 according to the first embodiment, the same reference numerals are given to the configurations and the description thereof will be omitted.

<1. Structure of Lithium Ion Capacitor 2 (FIGS. 18 and 19)>
In the first embodiment described above, the fire extinguishing agent 32 was provided on the separator sheet 31. However, the fire extinguishing agent may be provided in the internal space of the laminated member 50 (sealed body). The lithium ion capacitor 2 of the present embodiment has two plate-shaped fire extinguishing agents 60 formed by solidifying a fire extinguishing agent having the same components as the fire extinguishing agent 32 of the first embodiment into a plate shape (see FIG. 18). ). The lithium ion capacitor 2 has a separator 130 corresponding to the separator sheet 31 of the first embodiment (see FIG. 19). In the lithium ion capacitor 2, a plurality of laminated positive electrode plates 11, a plurality of negative electrode plates 21, and a plurality of separators 130 are provided between the two plate-shaped fire extinguishing agents 60 (see FIGS. 18 and 19). In FIG. 19, which shows a schematic cross section of the lithium ion capacitor 2 of the present embodiment, a space is provided between each member in the lithium ion capacitor 2 for easy understanding. However, in reality, the positive electrode plate 11, the negative electrode plate 21, and the separator 130 are laminated with almost no gap. Further, the number of the plate-shaped fire extinguishing agent 60 is not limited to two, and may be three or more. Further, one plate-shaped fire extinguishing agent 60 may be a stack of a plurality of plate-shaped fire extinguishing agents.

<2. About the charge / discharge 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 for 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. FIG. 20 schematically shows the positional relationship between 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 fire extinguishing agent (plate-shaped fire extinguishing agent 60) of the lithium ion capacitor 2. 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. Similar 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 anions of the electrolytic solution 40, and in the negative electrode plate 21, lithium is used as the negative electrode active material. Charging and discharging is performed by desorbing and desorbing ion Li ^+.

<3. About the effect of the fire extinguishing agent of the lithium ion capacitor 2 (FIGS. 18 to 20)>
In the lithium ion capacitor 2 of the present embodiment, similarly to the lithium ion capacitor 1 of the first embodiment described above, the plate-shaped fire extinguishing agent 60 (fire extinguishing agent) charges and discharges the lithium ion capacitor 2 (storage device). Highly flame-retardant without significantly affecting the process. Here, the plate-shaped fire extinguishing agent 60 (fire extinguishing agent) is configured as a single plate-shaped component. Therefore, the amount of the fire extinguishing agent provided in the lithium ion capacitor 2 (storage device) can be easily adjusted.

<4. About the 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 including S1 to S9 of the first embodiment described above (see FIG. 12). .. As described above, the lithium ion capacitor 2 (see FIG. 19) is different from the lithium ion capacitor 1 (see FIG. 3) of the first embodiment in that the separator 130 and the plate-shaped fire extinguishing agent 60 are provided. Therefore, the method for manufacturing the lithium ion capacitor 2 of the present embodiment includes S2, which is a step of processing the fire extinguishing agent, among the manufacturing methods (see FIG. 12) including S1 to S9 of the first embodiment described above. The separator 130 and S4, which is a step in which the fire extinguishing agent is arranged, will be described.

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

Therefore, the method for manufacturing the lithium ion capacitor 2 (S1 to S9) enhances the flame retardancy of the lithium ion capacitor (storage device) being manufactured in the steps after the step (S5) in which the laminate is included in the laminated member 50. be able to. That is, the lithium ion capacitor 2 (storage device) can be manufactured more safely.

[Third Embodiment]
The power storage device of the third embodiment will be described with reference to FIG. The power storage device of the third embodiment is a lithium ion capacitor 3. 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 numerals are given to the configurations and the description thereof will be omitted.

<1. Structure of Lithium Ion Capacitor 3 (Fig. 21)>
In the first embodiment, the fire extinguishing agent 32 was provided on the separator 30. However, the fire extinguishing agent may be provided in the internal space of the laminated member 50 (sealed 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). Further, the lithium ion capacitor 3 has a plurality of laminated positive electrode plates 11 of the positive electrode 10, a plurality of negative electrode plates 21 of the negative electrode 20, and a surrounding body 70 surrounding the outer periphery of the plurality of separators 130. More specifically, the surrounding body 70 surrounds the periphery of the laminated body having the plurality of laminated positive electrode plates 11, the plurality of negative electrode plates 21, and the plurality of separators 130, and the uppermost layer of the laminated body in the Z-axis direction. The bottom layer is the negative electrode plate 21. In addition, in FIG. 21, for the sake of clarity, it is shown with a space between each member in the lithium ion capacitor 3. However, in reality, the positive electrode plate 11, the negative electrode plate 21, and the separator 130 are laminated with almost no gap.

The surrounding body 70 is composed of a surrounding body core material 71 and a fire extinguishing agent 72 coated on both sides thereof. The enclosure 70 has the same configuration as the separator 30 of the first embodiment (see FIGS. 8 and 9). That is, the surrounding body core material 71 corresponds to a lengthened separator sheet 31 of the first embodiment. As the fire extinguishing agent 72 (not shown) coated on the surrounding body core material 71, the same component as the fire extinguishing agent 32 of the first embodiment can be used. As the enclosure core material 71, the same material as the separator of the conventional lithium ion capacitor can be used as in the separator sheet 31. For example, the enclosure core material 71 is made of papermaking such as viscose rayon or natural cellulose, or non-woven fabric such as polyethylene or polypropylene.

Here, the fire extinguishing agent 72 may be coated on the surrounding body core material 71. The fire extinguishing agent 72 may be coated on one side of the surrounding body core material 71, similarly to the fire extinguishing agent 32 coated on the separator sheet 31 of the first embodiment, and may be applied to the surrounding body core material 71. It may be partially coated. For example, similarly to the separator 30 of FIG. 10, the fire extinguishing agent 72 may be applied to the outside of the enclosure core material 71 except for the center. Further, the fire extinguishing agent 72 may be applied to a part of the outside of the surrounding body core material 71. The fire extinguishing agent 72 may be applied on the surrounding body core material 71 in a plurality of strips or dots.

<2. About the charging / discharging process of the lithium ion capacitor 3 (FIGS. 20 and 21)>
The configuration of the positive electrode 10 and the negative electrode 20 is the same for 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 between 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 is true (see FIG. 20). The positive electrode plate 11 and the negative electrode plate 21 are arranged so as to sandwich the separator 130 in between. In the lithium ion capacitor 3, an electric double layer is formed on the surface of the positive electrode plate 11 by the positive electrode active material and the anion of the electrolytic solution 40, and the negative electrode plate 21 absorbs and desorbs lithium ion 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)>
Similar to the lithium ion capacitor 1 of the first embodiment, the lithium ion capacitor 3 has high flame retardancy without the fire extinguishing agent 72 having a great influence on the charging / discharging process of the lithium ion capacitor 3 (storage device). Has. Here, the fire extinguishing agent 72 of the lithium ion capacitor 3 is provided in the surrounding body 70 provided in the internal space of the laminated member 50 (sealed body), and the surrounding body 70 is the positive electrode plate 11 and the negative electrode 20 of the positive electrode 10. It is arranged so as to surround the negative electrode plate 21. Therefore, the fire extinguishing agent 72 can effectively enhance the flame retardancy of the lithium ion capacitor 3 (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 including S1 to S9 of the first embodiment (see FIG. 12). The lithium ion capacitor 3 (see FIG. 21) differs from the lithium ion capacitor 1 (see FIG. 3) of the first embodiment in that the separator 130 and the enclosure 70 including the fire extinguishing agent 72 are provided. Therefore, the method for manufacturing the lithium ion capacitor 3 of the present embodiment includes S2, which is a step of processing the fire extinguishing agent, among the manufacturing methods (see FIG. 12) including S1 to S9 of the first embodiment described above. The separator 130 and S4, which is a step in which the fire extinguishing agent is arranged, will be described.

In the step (S2) of processing the fire extinguishing agent into a predetermined shape, the enclosure 70 is created in the same manner as in the method of 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 surrounding body 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.

Further, in 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 terminal and the negative electrode terminal are assembled, the step (S4) is instead of the separator 30 to be assembled. Including a step of laminating the separator 130 on the laminated body and winding the surrounding body 70 around the laminated body. 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 fire extinguishing agent and the separator, and is not related to the lithium metal used for predoping. .. Therefore, the difference between the case where the pre-doping is performed by the chemical method and the case where the pre-doping is performed electrochemically is considered in the same manner as in the methods S1 to S9 for manufacturing the lithium ion capacitor 1 of the first embodiment described above. be able to. That is, the lithium metal foil used for pre-doping is surrounded by the enclosure 70 like the positive electrode plate 11 and the negative electrode plate 21.

Therefore, in this manufacturing method (S1 to S9), the flame retardancy of the lithium ion capacitor 3 (storage device) being manufactured is high in the steps after the step (S5) in which the laminate is included in the laminated member 50. Therefore, the lithium ion capacitor 3 (storage device) can be manufactured more safely.

[Other embodiments]
The power 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, the power storage device of the above embodiment is a lithium ion capacitor, but the technique of the present disclosure can be applied to various power storage devices using a material capable of storing and releasing 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 power storage device using these alkali metals is provided with a carbon material for the negative electrode, an alkali metal oxide or the like for the positive electrode so that the standard electrode potential difference becomes relatively large. Specific examples thereof include various power storage devices such as a lithium ion secondary battery, a lithium polymer secondary battery, a sodium ion secondary battery, a potassium ion secondary battery, and an all-solid-state battery. Even in a secondary battery that uses an alkali metal other than a lithium ion capacitor, dendrites of the alkali metal are generated due to long-term use or the like, which causes short-circuit ignition. Therefore, the technique of the present disclosure can suppress ignition of various power storage devices using alkali metal ions and keep them safe.

Further, the fire extinguishing agent can be a powdered fire extinguishing agent instead of the fire extinguishing agent 32, the plate-shaped fire extinguishing agent 60, and the fire extinguishing agent 72 of the above-described embodiment, and can be dispersed in the electrolytic solution 40. Further, in the lithium ion capacitor 1 of the first embodiment, the plate-shaped fire extinguishing agent 60 of the second embodiment and the enclosure 70 or the enclosure core material 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 enclosure 70 or the enclosure core material of the third embodiment may be used. 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-shaped fire extinguishing agent 60 of the second embodiment is added. Is also good. Further, in the first to third embodiments, the lithium ion capacitors 1 to 3 are laminated cells in which the positive electrode plate 11, the negative electrode plate 21, and the separator 30 are laminated, but the long positive electrode and the long negative electrode And, it can be made into a winding type cell in which a long separator is wound.

[Example]
Hereinafter, the techniques of the present disclosure will be described in more detail with reference to examples, but the techniques of the present disclosure are not limited to the scope of these examples.

<Test of flame-retardant function of fire extinguishing agent (Fig. 22)>
A plate-shaped fire extinguishing agent 103 is obtained by mixing 15% by mass of dicyandiamide as a fuel component A, 77% by mass of potassium nitrate as an oxidizing agent component B, and 8% by mass of potassium acetate as an organic salt component C, forming it into a plate shape, and then naturally drying it. Obtained. In the following, the effect of the fire extinguishing agent will be investigated by comparing the case where the lithium metal leaf is heated in the air collecting bottle 101 and the case where the plate-shaped fire extinguishing agent 103 and the lithium metal leaf 102 are heated in the air collecting bottle 101. It was. It is known that the spontaneous combustion temperature (ignition point) of lithium metal is about 180 ° C.

When the plate-shaped fire extinguishing agent 103 and the lithium metal leaf 102 were heated in the air collecting bottle 101, they were heated as shown in FIG. That is, the air collecting bottle 101 was installed in the heating furnace 100. Then, the plate-shaped fire extinguishing agent 103 compacted into a plate shape and the lithium metal leaf 102 were placed in the air collecting bottle 101. Further, the thermometer 104 was installed so that the temperature measuring unit of the thermometer 104 touched the lithium metal leaf 102 so that the temperature of the lithium metal foil 102 could be measured. Then, the temperature in the heating furnace was raised. As a result, even if the temperature of the lithium metal leaf 102 rose to 280 ° C., the lithium metal leaf 102 did not ignite. It is considered that this is because when the temperature of the plate-shaped fire extinguishing agent 103 becomes 150 ° C. or higher, white smoke (aerosol) containing potassium radicals having a fire extinguishing action is generated, and the ignition of the lithium metal leaf 102 is suppressed by the potassium radicals. ..

Next, when the lithium metal leaf was heated in the air collecting bottle 101, the plate-shaped fire extinguishing agent 103 was removed from the state shown in FIG. 22 described above, and the temperature in the heating furnace 100 was raised. As a result, the lithium metal leaf ignited when the temperature of the lithium metal leaf was 182 ° C. As described above, when the fire extinguishing agent was present around the lithium metal leaf, the fire extinguishing agent suppressed the ignition of the lithium metal leaf.

<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 (sodium neutralized salt of polyacrylic acid) as a binder, 15 parts by mass of acetylene black as a conductive auxiliary agent, and 345 parts by mass of water as a solvent. To prepare a positive electrode slurry A containing a positive electrode active material.

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

Next, an aluminum foil (porous foil) having a thickness of 15 μm was used as the current collector foil, and each of the positive electrode slurry A was applied to the current collector foil and dried to prepare a positive electrode A. The amount of the positive electrode slurry A applied 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 to prepare a slurry for a negative electrode by the following procedure. ..
(1) A pre-slurry was prepared by mixing the material excluding the binder and water with a mixer a.
(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 with a mixer a to prepare a slurry for a negative electrode.

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

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

[Creating a siege]
A fire extinguishing agent was prepared by mixing 15% by mass of dicyandiamide as the fuel component A, 77% by mass of potassium nitrate as the oxidizing agent component B, and 8% by mass of potassium acetate as the organic salt component C. When the RED value based on the Hansen solubility parameter of the fire extinguishing agent in the electrolytic solution I was calculated, it was confirmed that it was larger than 1. This fire extinguishing agent was applied to both sides of cellulose having a thickness of 20 μm and air-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 punched out to form a rectangle with a size of 60 mm × 40 mm, and the coating film in the 20 mm × 40 mm region on one end side of the long side is peeled off while leaving the coating film of 40 mm × 40 mm to collect the current. Was installed.
(2) A laminated body was prepared by facing the coating film portions of the positive electrode and the negative electrode with a cellulose separator having a thickness of 20 μm interposed therebetween.
(3) The laminate produced in (2) and the metallic lithium foil for lithium predoping are surrounded by an enclosure, encapsulated in an aluminum laminate foil, an electrolytic solution is injected, and sealed to form the lithium ions of Test Example 1. A capacitor was manufactured.
The lithium ion capacitor of Test Example 2 was prepared by using cellulose having a thickness of 20 μm to which the fire extinguishing agent was not applied as an enclosure in (3) above.

<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 extinguishing agent, it did not ignite even at 210 ° C. On the other hand, the lithium ion capacitor of Test Example 2 did not have a fire extinguishing agent, so it ignited at 183 ° C.

<Internal resistance>
The lithium ion capacitor was pre-doped, charged / discharged, and aged. Then, at room temperature (25 ° C.), the internal resistance of the lithium ion capacitor was measured with a cutoff 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%. No significant difference was found in the internal resistance between Test Example 1 and Test Example 2, and the fire extinguishing agent did not deteriorate the performance of the capacitor.

<Nail piercing test>
A nail was pierced into the lithium ion capacitor, the presence or absence of ignition, etc. was observed, and the surface temperature was measured. A 3 mm diameter nail was pierced into the lithium ion capacitor at a speed of 80 mm / sec. The position where the nail is pierced is the position where the 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 10 mm from the position where the nail was stabbed to the side opposite to the current collecting tab side was measured for 1 hour from the time when the nail was stabbed.

As a result of the nail piercing 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 pierced. The lithium-ion capacitor of Test Example 1 was able to fully exhibit its flame-retardant function by containing a fire extinguishing agent. Since Test Example 1 did not ignite even at a surface temperature of 146 ° C, it was put into a nail piercing test or crushing test (automobile accident, etc.) with the lithium ion capacitor operating normally in a high temperature environment of 85 ° C or higher. Even if I encountered it, I was able to confirm that it could be kept safe without catching fire.

<Creation of other lithium-ion capacitors>
In order to investigate the high temperature durability of lithium ion capacitors, a plurality of lithium ion capacitors with different binders and electrolytes were prepared by the following procedure. Since the basic preparation method is the same as that of Test Example 1, only the differences are shown below.

[Creation of positive electrode]
Slurries B and C for positive electrodes containing a positive electrode active material were prepared with the compositions shown in Table 1 below. Carboxymethyl cellulose [CMC] was used as the thickener. “SBR” in Table 1 indicates styrene-butadiene rubber, “parts” indicates parts by mass, and “%” indicates mass%.

Slurries B and C for positive electrodes using acrylic acid ester or SBR as a binder were prepared by the following procedure.
(1) A pre-slurry was prepared by mixing the material excluding the binder and water with a mixer a.
(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 with a mixer a to prepare a slurry B or C for a positive electrode.

Next, each of the positive electrode slurry B was applied to the current collector foil and dried to prepare a positive electrode B. The current collector foil is an aluminum foil (porous foil) having a thickness of 15 μm. The amount of the positive electrode slurry B applied 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 on the current collector foil. Similarly, the positive electrode C was prepared using the positive electrode slurry C.

[Preparation of electrolyte]
Lithium hexafluorophosphate (LiPF6) was added to a mixed solvent of 30 vol% ethylene carbonate (EC), 30 vol% dimethyl carbonate (DMC) and 40 vol% ethyl methyl carbonate (EMC) to prepare an electrolytic solution P. Lithium bis (fluorosulfonylimide) (LiFSI) 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%. ) Was added at 1 mol / L to prepare an electrolytic solution I2.

[Assembly of Lithium Ion Capacitor]
A lithium ion capacitor was prepared by combining the positive electrode and the electrolytic solution shown in Table 2. Table 2 also shows the RED value of the polymer constituting the binder with respect to the electrolytic solution in each combination. The lithium ion capacitors of Test Examples 3 to 6 include an enclosure coated with a fire extinguishing agent.

[Measurement of initial performance]
Lithium predoping, charging / discharging, and aging of the lithium ion capacitors of Test Examples 1 and 3 to 6 were performed. Then, at room temperature (25 ° C.), the internal resistance and discharge capacity of each lithium ion capacitor were measured with a cutoff voltage of 2.2 to 3.8 V and a measurement current of 10 C, and the result was used as the 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. in a state where an external power source was connected and the voltage was maintained at 3.8 V. The leaving time corresponds to an 85 ° C., 3.8 V float time. After a lapse of a predetermined time, the lithium ion capacitor was taken out from the constant temperature bath, returned to room temperature, and then the internal resistance and the discharge capacity were measured under the same conditions as the above initial performance measurement, and the capacity retention rate (initial discharge capacity was set to 100%). The percentage of the discharge capacity at that 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 halved in a short time in Test Example 6 using an electrolytic solution containing lithium fluoride phosphate which is not an imide-based lithium salt as an electrolyte. On the other hand, in Test Examples 1 and 3 to 5 in which an electrolytic solution containing an imide-based lithium salt was used as the electrolyte, the capacity retention rate was kept high for a long time. However, it was clarified that even when an electrolytic solution containing an imide-based lithium salt was used as the electrolyte, there was a difference in the internal resistance increase rate depending on the composition of the binder of the positive electrode. Therefore, when the RED values (see Table 2) of the polymer constituting the binder of the positive electrode with respect to the electrolytic solution were compared, in Test Example 4 using an acrylic acid 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. On the other hand, in Test Examples 1 and 3, an electrolytic solution containing an imide-based lithium salt is used as the electrolyte, and polyacrylic acid having a RED value greater than 1 with respect to the electrolytic solution is used as the polymer constituting the binder of the positive electrode. .. In this case, it is clear that the polymer constituting the binder of the positive electrode is difficult to dissolve in the electrolytic solution, 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 suppressed to a small value. became.

Claims (4)

Positive electrode with positive electrode active material and positive electrode
Negative electrode with negative electrode active material and
An electrolytic solution that comes into contact with the positive electrode and the negative electrode and contains alkali metal ions,
A sealed body that comes into contact with the electrolytic solution inside and seals the electrolytic solution,
Have,
At least one of the positive electrode active material and the negative electrode active material is a power storage device capable of occluding and releasing the alkali metal ions.
A fire extinguishing agent that exerts a flame-retardant function is provided in the internal space of the sealed body.
The fire extinguishing agent is a power storage device having a RED value greater than 1 based on the Hansen solubility parameter for the electrolytic solution. The power storage device according to claim 1.
The electrolytic solution contains an organic solvent and an imide-based lithium salt, and contains an organic solvent and an imide-based lithium salt.
The positive electrode has a current collecting foil and
The positive electrode active material is a power storage device held in the current collector foil via a binder containing a polymer having a RED value greater than 1 based on the Hansen solubility parameter for the electrolytic solution. The power storage device according to claim 1 or 2.
Inside the sealed body, a surrounding body provided so as to surround the positive electrode and the negative electrode is provided.
The fire extinguishing agent is a power storage device provided on the enclosure. The power storage device according to any one of claims 1 to 3.
A power storage device that is a lithium-ion capacitor.

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