CN111095655B - Gel electrolyte, hard gel electrolyte, and electrochemical device - Google Patents

Gel electrolyte, hard gel electrolyte, and electrochemical device Download PDF

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Publication number
CN111095655B
CN111095655B CN201880058761.9A CN201880058761A CN111095655B CN 111095655 B CN111095655 B CN 111095655B CN 201880058761 A CN201880058761 A CN 201880058761A CN 111095655 B CN111095655 B CN 111095655B
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electrolyte
gel
mass
gel electrolyte
solvent
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CN111095655A (en
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齐藤恭辉
奥原淳史
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DKS Co Ltd
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Dai Ichi Kogyo Seiyaku Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/24—Crosslinking, e.g. vulcanising, of macromolecules
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/06—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/06—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
    • H01B1/12—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances organic substances
    • H01B1/122—Ionic conductors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/54—Electrolytes
    • H01G11/56—Solid electrolytes, e.g. gels; Additives therein
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
    • H01G9/20—Light-sensitive devices
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0085—Immobilising or gelification of electrolyte
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/542—Dye sensitized solar cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Abstract

Provided is a gel electrolyte which can achieve high efficiency in the manufacture of an electrochemical device and can achieve good device performance in the obtained electrochemical device. The gel electrolyte is a gel-like body composed of at least a matrix material and an electrolyte solution and contains a crosslinkable reactive group, and the gel electrolyte is cured by subjecting the reactive group to a crosslinking reaction to be used as an electrolyte possessed by an electrochemical device. The electrolyte solution is composed of at least an ionic substance and an electrolyte solution solvent, and the mass of the reactive group contained in the gel-like body is in the range of 0.03 mass% to 6.5 mass% relative to the mass of the electrolyte solution solvent, and the gel-like body in the unreacted state of the reactive group has a shear elastic modulus of 1MPa or more.

Description

Gel electrolyte, hard gel electrolyte, and electrochemical device
Technical Field
The present invention relates to a gel-like body containing a crosslinkable reactive group, and relates to a gel electrolyte that can be used as an electrolyte of an electrochemical device by curing the reactive group through a crosslinking reaction, a hard gel electrolyte (hard gelelectrolyte) obtained by curing the gel electrolyte, and an electrochemical device having the hard gel electrolyte.
Background
As an electrochemical device using an electrochemical reaction, for example, various batteries, a part of solar cells, a capacitor (capacitor), and the like are known. The electrolyte used in these electrochemical devices has conventionally used a liquid (electrolyte solution). However, if the electrolyte is a general electrolyte, the possibility of electrolyte leakage from the electrochemical device cannot be negated. In recent years, therefore, for example, as in an electrochemical cell and a method for producing the same disclosed in patent document 1, a structure using a gel electrolyte obtained by gelling an electrolyte has been proposed.
Prior art literature
Patent literature
Patent document 1: japanese patent application laid-open No. 2011-519116
Disclosure of Invention
Technical problem to be solved by the invention
Here, in a structure using a gel electrolyte as an electrolyte of an electrochemical device, a step of injecting an electrolyte (electrolyte injection step) is required. In addition, in order to gel the electrolyte, a prepolymer is generally used. The prepolymer is dissolved in the electrolyte in advance, but the viscosity of such an electrolyte (prepolymer electrolyte) is higher than that of a usual electrolyte.
Therefore, in the electrolyte injection step, since it is necessary to inject the prepolymer electrolyte having a high viscosity into the electrochemical device, the time required for the electrolyte injection step may be long. Therefore, the electrochemical device manufacturing process may not be sufficiently efficient.
In addition, for example, when the electrochemical device is large, the amount of the injected prepolymer electrolyte is large in the electrolyte injection step. Therefore, insufficient injection of the prepolymer electrolyte may easily occur. If insufficient injection of the prepolymer electrolyte occurs, there is a possibility that sufficient device performance may not be achieved in the electrochemical device.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a gel electrolyte that can achieve high efficiency in manufacturing an electrochemical device and can achieve good device performance in the obtained electrochemical device.
Means for solving the problems
In order to solve the above problems, the gel electrolyte according to the present invention has the following structure: the electrolyte is a gel-like body composed of at least a matrix material and an electrolyte, and contains a crosslinkable reactive group, and the electrolyte is used as an electrolyte of an electrochemical device by curing the reactive group by a crosslinking reaction, wherein the electrolyte is composed of at least an ionic substance and an electrolyte solvent, the mass of the reactive group contained in the gel-like body is in the range of 0.03 mass% to 6.5 mass% inclusive relative to the mass of the electrolyte solvent, and the gel-like body has a shear elastic modulus of 1MPa or more in a state in which the reactive group is unreacted.
According to the above constitution, an appropriate amount of reactive groups are contained in the gel electrolyte in an uncured state. Therefore, even in the gel electrolyte (hard gel electrolyte) in which the crosslinking reaction of the reactive groups has been sufficiently performed, the hard gel electrolyte can hold a sufficient amount of the electrolyte. In addition, as the crosslinking reaction proceeds, a part of the electrolyte solution can be leaked from the matrix material. Therefore, if the electrochemical device is produced using the gel electrolyte in a state where the gel electrolyte is not sufficiently cured (uncured state), and then the crosslinking reaction is performed, the leaked electrolyte can be brought into good contact with the contact surface of the electrode provided in the electrochemical device. Based on this, a good electrochemical reaction can be achieved in the electrochemical device.
In addition, the gel electrolyte has a shear elastic modulus of 1MPa or more even in an uncured state, and thus the gel electrolyte has good strength. Therefore, good handleability can be achieved in the gel electrolyte, and therefore, inefficiency in manufacturing the electrochemical device can be suppressed. As described above, since the electrochemical device is produced using the gel electrolyte in an uncured state and then the crosslinking reaction is performed, the liquid injection step is not required in the production process of the electrochemical device. Therefore, the possibility of insufficient injection or the possibility of performance degradation or the like due to insufficient injection can be avoided.
As a result, the electrochemical device can be manufactured with high efficiency, and excellent device performance can be achieved in the obtained electrochemical device.
In the gel electrolyte having the above-described structure, the gel-like body may contain a post-curing agent having the reactive group in addition to the matrix material and the electrolyte.
In the gel electrolyte having the above-described structure, the mass of the electrolyte solvent may be in a range of 20 mass% to 80 mass% with respect to the total mass of the gel-like body.
In the gel electrolyte having the above-described structure, the mass of the matrix material may be in a range of 1.0 mass% to 10 mass% based on the total mass of the gel-like body.
In the gel electrolyte having the above-described structure, the following structure may be used: the gel-like body contains a diluting solvent which is a component different from the electrolyte solvent and is removed before the crosslinking reaction of the reactive groups, and the mass range of the electrolyte solvent or the mass range of the matrix material is specified with respect to the total mass of the gel-like body other than the diluting solvent.
In the gel electrolyte having the above-described structure, the gel-like body may have a sheet shape.
In the gel electrolyte having the above-described structure, the gel-like body may have a thickness of 5 μm or more and 100 μm or less.
The hard gel electrolyte according to the present invention is a gel electrolyte having the above-described structure, in which the reactive groups undergo a crosslinking reaction to increase the hardness.
In the hard gel electrolyte having the above-described structure, the following structure may be used: at least one of an ion conductivity of 0.8mS/cm or more and a shear elastic modulus of 6MPa or more is satisfied.
The electrochemical device according to the present invention may have a hard gel electrolyte having the above-described structure.
Effects of the invention
In the present invention, the above structure is used, and the following effects are obtained: it is possible to provide a gel electrolyte which can achieve high efficiency in manufacturing an electrochemical device and can achieve good device performance in the obtained electrochemical device.
Drawings
Fig. 1 is a schematic cross-sectional view showing an example of the structure of a lithium ion battery as an example of an electrochemical device according to an embodiment of the present invention.
Symbol description
10: lithium ion battery
11: laminated structure
12: positive electrode
13: negative electrode
14: hard gel electrolyte
15: sealing material
21: positive electrode base material
22: positive electrode active material layer
31: negative electrode base material
32: negative electrode active material layer
Detailed Description
The gel electrolyte according to the present invention is a gel-like body composed of at least a matrix material and an electrolyte solution, and contains a crosslinkable reactive group, and is cured by crosslinking reaction of the reactive group, thereby being used as an electrolyte provided in an electrochemical device. The electrolyte solution is composed of at least an ionic substance and an electrolyte solution solvent, but in the gel electrolyte according to the present invention, the mass of the reactive group contained in the gel electrolyte (gel-like body) is in the range of 0.03 mass% to 6.5 mass% with respect to the mass of the electrolyte solution solvent, and the gel electrolyte (gel-like body) in a state where the reactive group is not reacted has a strength of 1MPa or more in shear elastic modulus.
A typical structural example of the gel electrolyte according to the present invention will be specifically described below. Since the gel electrolyte according to the present invention contains unreacted reactive groups as described above, the degree of solidification of the gel electrolyte increases by performing a crosslinking reaction of the reactive groups. In the following description, the gel electrolyte having the degree of solidification increased by performing the crosslinking reaction in this way is referred to as "hard gel electrolyte". In addition, in the case of simply called "gel electrolyte", it means a gel electrolyte before the curing degree increases.
[ composition of gel electrolyte (gel-like body) ]
As described above, the gel electrolyte according to the present invention is a gel-like body containing a matrix material and an electrolyte as main components, but the gel-like body contains unreacted reactive groups. The reactive group may be present in the matrix material, in the electrolyte, in both the matrix material and the electrolyte, or in components other than the matrix material and the electrolyte. As described later, the gel-like body (gel electrolyte) may contain components other than the matrix material and the electrolyte. As typical other components, there may be mentioned: curing agents having reactive groups.
The matrix material constituting the gel-like body is not particularly limited as long as the gel-like body can be formed in a state of containing the electrolyte. The matrix material may be a physical gel that forms a three-dimensional structure by non-covalent bond such as hydrogen bond, or a chemical gel that forms a three-dimensional structure by covalent bond. In the present invention, the gel-like body may have a reactive group capable of crosslinking reaction, and thus the matrix material may have an unreacted reactive group.
That is, in the present invention, the following structures can be exemplified: for example, the matrix material is a compound that forms a physical gel (for convenience of explanation, referred to as a physical gel compound), and by adding an electrolyte to the matrix material, a gel-like body (gel electrolyte) having an unreacted reactive group is formed by a non-covalent bond. Alternatively, in the present invention, the structure may be such that: the matrix material is a chemical gel-forming compound (for convenience of explanation, referred to as a chemical gel compound), and a part of the reactive groups of the matrix material is crosslinked to form a gel-like body (gel electrolyte) in a semi-cured state, and unreacted reactive groups remain in the gel-like body in the semi-cured state.
In this case, as described above, the mass ratio of the reactive groups (or remaining reactive groups) in the gel-like body may be in the range of 0.03 mass% to 6.5 mass% based on the mass of the electrolyte solvent (first condition of the gel electrolyte described later). As described above, the reactive group may be a reactive group of at least one of the matrix material and the electrolyte solution, or may be a reactive group of another component. Therefore, as will be exemplified in examples to be described later, the mass ratio of the reactive groups can be calculated using the ratio of the molecular weight of the reactive groups to the molecular weight of 1 molecule of the component having the reactive groups (molecular weight ratio).
Here, the gel electrolyte having unreacted reactive groups is said to be in a state of insufficient curing, but for convenience of explanation, this state is referred to as "uncured state". In addition, in the gel electrolyte in the uncured state, if the crosslinking reaction of the reactive groups proceeds and the hardness increases, the gel electrolyte becomes a hard gel electrolyte, this state will be referred to as "cured state" for convenience of description. The term "semi-cured state" refers to a state after a part of all the reactive groups contained in the chemical gel compound are reacted when the matrix material is a chemical gel compound.
Therefore, the chemical gel compound does not form a gel in a state where most of all the reactive groups of the chemical gel compound are unreacted. The state in which a part of the reactive groups of the chemical gel compound undergo a crosslinking reaction is a "semi-cured state", and the chemical gel compound undergoes gelation. The chemical gel compound in the semi-cured state has a residual reactive group in the range of 0.03 to 6.5 mass% relative to the mass of the electrolyte solvent, and thus corresponds to the gel electrolyte (gel-like body) according to the present invention. Thus, the chemical gel compound in a semi-cured state (i.e., gel electrolyte) can be said to be in an "uncured state". Then, if the reactive groups remaining in the chemical gel compound in the semi-cured state undergo a crosslinking reaction to increase the hardness, the chemical gel compound becomes a hard gel electrolyte in the cured state.
The specific structure of the matrix material is not particularly limited. In general, the matrix material may be a polymer material. According to the use of the gel electrolyte according to the present invention, that is, according to the kind of electrochemical device manufactured (manufactured) using the gel electrolyte according to the present invention, an appropriate matrix material may be appropriately selected. For example, in the embodiment described later, although a lithium ion battery is exemplified as an example of an electrochemical device, in this case, a polymer, an inorganic substance, or a low-molecular substance may be reasonably used as a matrix material.
Examples of the polymer include: fluoride polymers such as polyvinylidene fluoride (PDVF) and vinylidene fluoride-hexafluoropropylene copolymer (PDVF-HFP); acrylic resins such as Polyacrylonitrile (PAN) and methacrylic resins; and the like, but are not particularly limited. Examples of the inorganic substance include: silica particles, alumina particles, silica/alumina mixed particles, titania particles, zinc oxide particles, zirconia particles, and the like, but are not particularly limited. Examples of the low molecular weight compound include: fatty acid ester derivatives, cyclohexane derivatives, amino acid derivatives, cyclic peptide derivatives, alkyl hydrazide derivatives, and the like are not particularly limited.
The matrix material may be used in an amount of 1, or may be used in an amount of 2 or more. For example, a plurality of polymer matrix materials may be used in combination, or 1 or more of polymer matrix materials and inorganic matrix materials may be used in combination. Alternatively, 1 or more kinds of polymers, inorganic substances, and low-molecular substances may be selected and used together.
As described above, the gel-like body may contain a post-curing agent having a reactive group. The post-curing agent may be regarded as a component different from the matrix material in a state where the reactive group is unreacted, but if the crosslinking reaction by the reactive group proceeds sufficiently, it constitutes a part of the matrix material. Therefore, the post-curing agent may be treated as part of the matrix material, although it also depends on the composition of the gel-like body, etc.
The specific structure of the post-curing agent is not particularly limited, and a suitable reactive compound may be selected according to the composition of the gel electrolyte according to the present invention, the kind of use (electrochemical device), and the like. For example, in the embodiment described later, a lithium ion battery is exemplified as one example of an electrochemical device, and the aforementioned polymer or inorganic substance is exemplified as a matrix material, but in this case, as a post-curing agent, there may be mentioned: reactive compounds of the acrylic or oxetane type.
Specific examples of the acrylate compound include: the tetrafunctional polyether acrylate, difunctional polyether acrylate, other AO addition acrylate, polyethylene glycol diacrylate, and the like, but are not particularly limited. The oxetane compound may be: methyl methacrylate-oxetanyl methacrylate copolymer, etc., but is not particularly limited. These post-curing agents may be used alone in 1 kind, or may be used in combination of 2 or more kinds.
In the case where the matrix material is a chemical gel compound having an unreacted reactive group as described above, for example, a curing agent of the same kind or a different kind from the post-curing agent may be used to crosslink a part of the reactive groups to form a gel-like body (gel electrolyte) in a semi-cured state. In this case, a curing agent that is used first to achieve a semi-cured state is referred to as a "pre-curing agent" unlike a post-curing agent.
The reactive groups contained in the gel electrolyte crosslink to increase the curing degree of the gel electrolyte. The specific type of the reactive group is not particularly limited, and an appropriate reactive group may be selected according to the composition of the gel electrolyte, the type of the application (electrochemical device), and the like. For example, in the embodiment described later, a lithium ion battery is exemplified as one example of an electrochemical device, and the aforementioned polymer or inorganic substance is exemplified as a matrix material. In this case, the following exemplified reactive groups can be reasonably used.
Specific examples of the reactive group include: a double-bond functional group such as a (meth) acrylic group (acrylic group, methacrylic group), or allyl group; epoxy and oxetane epoxide (oxetane) type functional groups; a thiol group; a combination of functional groups of a condensation reaction system such as amino groups and carboxyl groups (amide bonds), hydroxyl groups and carboxyl groups (ester bonds); a combination of isocyanate-based reactive functional groups such as isocyanate groups and hydroxyl groups (urethane bonds), isocyanate groups, and amino groups (urea bonds); etc. In the gel electrolyte (gel-like body), these functional groups (or a combination of functional groups) may be contained in 1 kind or 2 or more kinds. In addition, in the case where the matrix material is a chemical gel compound having an unreacted reactive group, the compound may have a structure having at least 1 of these functional groups (or a combination thereof).
The electrolyte constituting the gel electrolyte may be any electrolyte capable of exhibiting an electrochemical reaction in the electrochemical device. The more specific structure of the electrolyte is not particularly limited as in the case of the matrix material, and an electrolyte having an appropriate composition can be suitably used depending on the composition of the gel electrolyte, the type of the application (electrochemical device), the type of the electrolyte, the type of the matrix material constituting the gel electrolyte, and the like.
As described above, the electrolyte in the present invention may be any composition comprising at least an ionic substance and an electrolyte solvent. In the present embodiment, the electrolyte solvent refers to a solvent of an electrolyte constituting an electrochemical device. As the ionic substance, various salts can be used. For example, in the examples described later, lithium ion batteries are exemplified as one example of electrochemical devices, and therefore, in the present embodiment, lithium salts are exemplified as the ionic substances.
As the lithium salt, there may be typically mentioned: lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium hexafluorophosphate (LiPF) 6 ) Lithium bis (fluorosulfonyl)Imide (LiSSI), lithium perchlorate (LiClO) 4 ) Lithium tetraborate (LiBF) 4 ) And the like, but are not particularly limited.
In the case where the electrochemical device is a lithium ion battery, examples of the electrolyte solvent include: the carbonate-based solvent, ionic liquid, nitrile-based solvent, ether-based solvent, and the like, but are not particularly limited.
As a representative electrolyte solvent, there may be mentioned: a mixed solvent of a cyclic carbonate and a chain carbonate. As the cyclic carbonate, representatively listed are: as the chain carbonate, ethylene Carbonate (EC) or Propylene Carbonate (PC) is typically exemplified by: dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), and the like, but are not particularly limited.
In addition, as another representative electrolyte solvent, ionic liquids may be mentioned. Specifically, examples thereof include: 1, 2-ethylmethylimidazolium bis (fluorosulfonyl) imide, 1, 2-ethylmethylimidazolium bis (trifluoromethanesulfonyl) imide, 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide (abbreviated as EMImFSI), N-methylpropylpyrrolidinium bis (fluorosulfonyl) imide, N-methylpropylpyrrolidinium bis (trifluoromethanesulfonyl) imide, diethylmethylmethoxyethylammonium bis (trifluoromethanesulfonyl) imide, diethylammonium bis (fluorosulfonyl) imide, diallyldimethylammonium (trifluoromethanesulfonyl) imide, diallyldimethylammonium (fluorosulfonyl) imide, and the like, but are not particularly limited thereto.
The gel electrolyte before the curing degree increases may contain other components (other components) in addition to the matrix material and the electrolyte. The other components include the aforementioned post-curing agent, but in addition to this, various additives may be mentioned, for example. Specific examples of the additive include an initiator used for promoting a crosslinking reaction of an uncrosslinked reactive group contained in the matrix material. For example, in examples described later, 2' -azobis (2, 4-dimethylvaleronitrile) was used as an initiator.
[ Structure of gel electrolyte and hard gel electrolyte ]
In the gel electrolyte according to the present invention, the mass of the reactive group contained in the gel electrolyte (gel-like body) may be in the range of 0.03 to 6.5 mass% relative to the mass of the electrolyte solvent. In the gel electrolyte according to the present invention, the shear elastic modulus is 1MPa or more. That is, the gel electrolyte according to the present invention satisfies both "first conditions" that the mass ratio of unreacted reactive groups is limited to a predetermined range and "second conditions" that the lower limit of the shear elastic modulus in the state where the reactive groups are unreacted is limited to a predetermined value.
The mass ratio of the reactive group to the electrolyte solvent, which is the first condition of the gel electrolyte, is calculated as described above using the ratio of the molecular weight of the reactive group to the molecular weight of 1 molecule of the component having the reactive group (molecular weight ratio). For example, in examples described later, the post-curing agent of the gel electrolyte has a reactive group, but the ratio of the molecular weight of the reactive group to the molecular weight of the post-curing agent is calculated, and the mass of the reactive group is calculated from the amount of the post-curing agent blended based on the molecular weight ratio. The mass of the reactive group may be in the range of 0.03 to 6.5 mass% relative to the mass of the electrolyte solvent contained in the gel electrolyte.
The gel electrolyte in the uncured state contains an appropriate amount of unreacted reactive groups by allowing the gel electrolyte to satisfy the first condition. Therefore, even if the crosslinking reaction of the reactive groups proceeds to become a hard gel electrolyte, the hard gel electrolyte can hold a sufficient amount of the electrolyte. In addition, as the crosslinking reaction proceeds, a part of the electrolyte may leak out of the matrix material. Therefore, if an electrochemical device is produced using the gel electrolyte in an uncured state and then a crosslinking reaction is performed, the leaked electrolyte can be brought into good contact with the contact surface of the electrode provided in the electrochemical device. Based on this, a good electrochemical reaction can be achieved in the electrochemical device.
The second condition of the gel electrolyte, namely the shear elastic modulus of the gel electrolyte in an uncured state, is determined according to a known measuring methodThe shear modulus of elasticity of the gel electrolyte may be measured or evaluated by a method of measurement or evaluation. In examples described later, a bench type precision universal tester (product name: AUTOGRAPH AGS-X) manufactured by Shimadzu corporation was used for the gel electrolyte in an uncured state obtained in each example or comparative example, and was mounted After a 0.05N preliminary load was applied, a press-in test was performed at a speed of 0.05 mm/min, and the shear modulus of elasticity (unit: MPa) was measured according to the result of the press-in test by the following formula (1).
Shear modulus of elasticity (G) =0.36 Fg [ (D-h)/h] 3/2 /R 2 (1)
Here, F in the above formula (1) is a load (test force) in the press-in test, g is a gravitational acceleration, D is a thickness (film thickness) of the gel electrolyte (gel-like body), h is a change in thickness (film thickness) due to the load, and R is a spherical radius of the spherical indenter in the press-in test. In addition, in the calculation of the shear elastic modulus using the above formula (1), reference is made to reference 1: d J Taylor and A M Kragh, "Determination of the rigidity modulus of thin soft coatings by indentation measurements" Journal of Physics D Applied Physics, united Kingdom, IOP Publishing, january 1970,Volume 3,Number 1,29.
The gel electrolyte satisfies the second condition and is in an uncured state, so that the gel electrolyte has a shear elastic modulus of 1MPa or more, and thus has good strength. Therefore, in the gel electrolyte, good operability can be achieved, and thus, inefficiency in manufacturing the electrochemical device can be suppressed. Further, as described above, since the electrochemical device is produced using the gel electrolyte in an uncured state and then the crosslinking reaction is performed, the liquid injection step is not required in the production process of the electrochemical device. Therefore, the possibility of insufficient injection or the possibility of performance degradation due to insufficient injection can be avoided.
Here, the lower limit of the mass ratio of the reactive groups, which is the first condition of the gel electrolyte, may be 0.03 mass% or more, preferably 0.04 mass% or more, and more preferably 0.05 mass% or more, with respect to the mass of the electrolyte solvent. If the mass of the reactive group is less than 0.03 mass% of the mass of the electrolyte solvent, the amount of the reactive group contained in the gel electrolyte becomes smaller than an appropriate amount, and good strength cannot be achieved in the hard gel electrolyte in a cured state, and short-circuiting and the like may easily occur. In addition, as the crosslinking reaction proceeds, the amount of leakage of the electrolyte decreases, and there is a possibility that the contact surface between the electrolyte and the electrode of the electrochemical device may not be brought into good contact, and sufficient performance may not be achieved in the electrochemical device.
The upper limit of the mass ratio of the reactive group to the mass of the electrolyte solvent is not more than 6.5 mass%, preferably not more than 6.3 mass%, and more preferably not more than 6.0 mass%. If the mass of the reactive group exceeds 6.5 mass% of the mass of the electrolyte solvent, the amount of the reactive group contained in the gel electrolyte is excessive, and the ionic conductivity of the hard gel electrolyte may be lowered, so that sufficient performance may not be achieved in the electrochemical device. In addition, as the crosslinking reaction proceeds, the amount of leakage of the electrolyte increases, and there is a possibility that a sufficient amount of the electrolyte cannot be maintained in a cured state (hard gel electrolyte).
The shear elastic modulus in the uncured state, which is the second condition of the gel electrolyte, is only required to have a lower limit of 1MPa or more, preferably 2MPa or more, and more preferably 5MPa or more. If the shear elastic modulus is less than 1MPa, the strength of the gel electrolyte in an uncured state is lowered, and therefore the handleability thereof is also lowered, and there is a possibility that the production (manufacturing) of the electrochemical device is not efficient. The upper limit of the shear elastic modulus is not particularly limited as long as a sufficient electrolyte solution can be maintained in the hard gel electrolyte in a cured state.
In the gel electrolyte according to the present invention, in addition to the first condition and the second condition described above, it is preferable that either one of the third condition and the fourth condition is satisfied, and it is more preferable that both the third condition and the fourth condition are satisfied, wherein the third condition is a range of 20 mass% to 80 mass% with respect to the total mass of the gel electrolyte (gel-like body) and the fourth condition is a range of 1.0 mass% to 10 mass% with respect to the total mass of the gel electrolyte (gel-like body).
By making the gel electrolyte satisfy the third condition, a more appropriate amount of electrolyte is held in either one of the gel electrolyte and the hard gel electrolyte. Therefore, excellent ion conductivity can be achieved in the electrochemical device, and the performance of the electrochemical device can be further improved. However, even when the gel electrolyte does not satisfy the third condition, an electrochemical device having sufficient practicality can be manufactured by satisfying both the first condition and the second condition.
In addition, by making the gel electrolyte satisfy the fourth condition, a more appropriate amount of the matrix material is contained in either one of the gel electrolyte and the hard gel electrolyte. Therefore, in the hard gel electrolyte, good strength can be achieved, and the performance of the electrochemical device can be further improved. However, even when the gel electrolyte does not satisfy the fourth condition, an electrochemical device having sufficient practicality can be manufactured by satisfying both the first condition and the second condition.
The specific shape of the gel electrolyte is not particularly limited, and may be formed into an appropriate shape according to various conditions such as the kind and use of the electrochemical device. In particular, in the present invention, the gel electrolyte is gel-like, and thus can be easily formed into a desired shape. For example, in the embodiment described later, a lithium ion battery is exemplified as an example of an electrochemical device, and thus a sheet shape is exemplified as the shape of the gel electrolyte.
When the gel electrolyte is in the form of a sheet, the thickness (film thickness of the gel electrolyte) is not particularly limited, and generally, a range of 5 μm to 100 μm is included. If the thickness of the sheet-like gel electrolyte is outside this range, the battery performance (or the performance of other electrochemical devices) may not be sufficiently exhibited, although the thickness may depend on various conditions such as the type, size, and specific shape of the lithium ion battery (or other electrochemical devices).
The hard gel electrolyte is an electrolyte in which the hardness is improved by allowing the crosslinking reaction of the reactive groups of the gel electrolyte to proceed, but the specific structure of the hard gel electrolyte is not particularly limited. However, in the hard gel electrolyte, either one of the first condition that the ionic conductivity is 0.8mS/cm or more or the second condition that the shear elastic modulus is 6MPa or more is preferably satisfied, and both the first condition and the second condition are more preferably satisfied.
If the ionic conductivity in the hard gel electrolyte is 0.8mS/cm or more, preferably 1.0mS or more, a good electrochemical reaction can be achieved, and therefore, sufficient performance can be exhibited in an electrochemical device. On the other hand, if the ionic conductivity is less than 0.8mS/cm, although depending on the kind of electrochemical device, there is a possibility that a good electrochemical reaction cannot be achieved, and therefore, there is a possibility that sufficient performance cannot be exhibited.
In addition, if the shear elastic modulus in the hard gel electrolyte is 6MPa or more, the electrolyte layer in the electrochemical device can be well held, and therefore, sufficient performance can be exhibited. In contrast, if the shear elastic modulus of the hard gel electrolyte is less than 6MPa, the electrolyte layer may not be held well depending on the type of electrochemical device, and therefore, sufficient performance may not be exhibited.
As described above, if the hardness is increased by the crosslinking reaction of the reactive groups in the gel electrolyte in the uncured state, the gel electrolyte in the cured state is obtained, but the shear elastic modulus of the gel electrolyte is 6MPa as a target of the cured state. Of course, the hardness of the gel electrolyte may be measured by a known measurement method and the cured state may be determined based on the value of the hardness, the rate of increase in the hardness, or the like, but in the present invention, since the strength of the uncured gel electrolyte and the hard gel electrolyte is evaluated based on the shear elastic modulus, if the shear elastic modulus of the gel electrolyte after the increase in the hardness is 6MPa or more, it can be determined that the gel electrolyte is a hard gel electrolyte.
[ method for producing gel electrolyte ]
The method for producing the gel electrolyte according to the present invention is not particularly limited, but typical production methods include: a first method using 2 kinds of diluting solvents, a second method using 1 kind of diluting solvents, and a third method not using diluting solvents. The diluting solvent is a component different from the electrolyte solvent, and is a component removed before the crosslinking reaction of the reactive groups contained in the gel-like body (gel electrolyte). Therefore, the gel electrolyte according to the present invention may contain a diluting solvent as a component other than the matrix material and the electrolyte solution.
The third condition and the fourth condition in the gel electrolyte in the uncured state, that is, the mass range of the electrolyte solvent in the gel electrolyte and the mass range of the matrix material in the gel electrolyte are defined with respect to the total mass of the gel electrolyte other than the diluent solvent. This is because, as described above, the diluting solvent is removed before the crosslinking reaction of the reactive groups, in other words, because the diluting solvent is substantially not contained in the hard gel electrolyte in the cured state.
The specific type of the diluting solvent is not particularly limited, and may be appropriately selected depending on the respective conditions such as the type of the electrochemical device, the type of the matrix material, and the composition of the electrolyte. For example, in the embodiment described later, a lithium ion battery is exemplified as one example of an electrochemical device, and therefore, as a diluting solvent, the following exemplified solvents can be reasonably used.
Specifically, examples of the diluting solvent that can be contained in the gel electrolyte include: ketone solvents such as acetone, methyl Ethyl Ketone (MEK), and cyclohexanone; ether solvents such as 1, 2-Dimethoxyethane (DME); nitrile solvents such as Acetonitrile (ACN); pyrrolidone solvents such as N-methylpyrrolidone (NMP); a lactone-based solvent such as gamma-butyrolactone (GBL); carbonate solvents such as Ethylene Carbonate (EC), propylene Carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and Ethyl Methyl Carbonate (EMC); etc. Of these solvents, 1 kind of the diluting solvent of the present invention may be used, or 2 or more kinds may be appropriately selected and used. In the case where 2 or more of these solvents are used, the solvents may be used for different dilution purposes, or may be used as a mixed solvent in which 2 or more solvents are mixed.
A first method using 2 kinds of diluting solvents in a representative manufacturing method of a gel electrolyte according to the present invention will be described.
In the first method, first, a gel-like body (non-electrolyte gel-like body) containing no electrolyte is formed by mixing a matrix material and a first diluting solvent (non-electrolyte gel-like body forming step). The method of mixing the matrix material and the first diluting solvent is not particularly limited, but typically, a method of dissolving the matrix material in the first diluting solvent by heating the matrix material and the first diluting solvent is exemplified. After dissolution, the gel is cooled to room temperature, for example, to obtain a non-electrolyte gel. The first diluent solvent may be referred to as a diluent solvent for gel used for forming a non-electrolyte gel-like body.
Next, in the first method, a diluted solution of an electrolyte solution or the like is prepared by dissolving an electrolyte component (a lithium salt plasma substance), an electrolyte solution solvent, and other components (a post-curing agent, an initiator, or the like) in a second diluted solvent. For convenience of explanation, this diluted solution will be referred to as a substitution solution (substitution solution preparation step). The method for preparing the substitution solution is not particularly limited, and a known stirrer or the like may be used. Then, the substitution solution is added to the non-electrolyte gel-like body (substitution solution adding step). The method of adding the substitution solution is not particularly limited, and examples thereof include application or accumulation of the substitution solution on the non-electrolyte gel-like body. The added substitution solution is absorbed by the non-electrolyte gel-like body, and thus a gel-like body containing a diluting solvent is obtained.
In the first method, the diluting solvent is then removed from the gel-like body containing the diluting solvent (diluting solvent removal step). The method for removing the diluting solvent is not particularly limited, and for example, the diluting solvent may be evaporated under reduced pressure or at high temperature. In this step, although the gel-forming diluent and the replacement diluent are both removed, if attention is paid to the initially formed non-electrolyte gel-like body, the gel-forming diluent contained in the non-electrolyte gel-like body is replaced with an electrolyte. The gel electrolyte according to the present invention may be a gel containing a diluting solvent, or may be a gel after the diluting solvent is removed. That is, the removal of the diluting solvent may be performed immediately before the electrochemical device is produced (manufactured), or the diluting solvent may be removed in advance.
Next, a second method using 1 kind of diluting solvent in a representative manufacturing method of the gel electrolyte according to the present invention will be described.
In the second method, as in the first method, a diluted solution of the matrix material is prepared by mixing the matrix material and the diluting solvent. For convenience of explanation, the diluted solution of the matrix material is referred to as "solution a" (solution a preparation step). Next, a diluted solution of an electrolyte solution or the like is prepared by dissolving an electrolyte component (a lithium salt plasma substance), an electrolyte solution solvent, and other components (a post-curing agent, an initiator, and the like) in a diluted solvent of the same kind as the solution a. For convenience of explanation, the diluted solution of the electrolytic solution or the like is referred to as "solution B" (solution B preparation step).
Next, in the second method, the prepared liquid a and liquid B are mixed, and the resulting mixed liquid is formed into a predetermined shape (mixing forming step). The method for molding the mixed solution is not particularly limited, and a molding die, a support, or the like corresponding to the shape of the gel electrolyte to be obtained may be used. For example, in the embodiment described later, a lithium ion battery is exemplified as an example of an electrochemical device, and therefore, a positive electrode of the lithium ion battery is used as a support, and a mixed solution is applied to a surface of the positive electrode. Based on this, a gel-like body containing a diluting solvent is formed. Then, as in the first method, the diluting solvent is removed from the gel-like body containing the diluting solvent (diluting solvent removal step).
Next, a third method without using a diluting solvent in a representative manufacturing method of the gel electrolyte according to the present invention will be described. In the third method, a diluting solvent that dissolves the matrix material, the electrolyte, or the like is not used, but an electrolyte solvent is used instead.
In the third method, an electrolyte solvent solution of the matrix material is prepared by mixing the matrix material and the electrolyte solvent. For convenience of explanation, this solution of the matrix material will be referred to as "solution a" similarly to the second method (solution a preparation step). Next, an electrolyte component (a lithium salt plasma substance) and other components (a post-curing agent, an initiator, etc.) are dissolved in an electrolyte solvent of the same kind as or different from the a liquid, to prepare an electrolyte solvent solution such as an electrolyte solution. For convenience of explanation, the solution of the electrolytic solution or the like is referred to as "solution B" similarly to the second method (solution B preparation step). Then, the prepared liquid a and liquid B are mixed, and the obtained mixed liquid is molded into a predetermined shape (mixing molding step). Based on this, a gel-like body containing an electrolyte solution or the like, that is, a gel electrolyte is obtained.
These first, second and third methods have unique advantages in terms of manufacture, respectively, and thus it cannot be concluded which method is particularly preferred. For example, in the first method, as described above, a substitution solution is prepared using a diluting solvent, and the liquid component of the non-electrolyte gel-like body is substituted with an electrolyte using the substitution solution. Therefore, by appropriately changing the composition of the substitution solution, various changes can be easily made to the obtained gel electrolyte.
In the second method, when a lithium ion battery is manufactured, a positive electrode or a negative electrode can be used as a support, and the positive electrode or the negative electrode can be coated with the mixed solution. Therefore, compared with the first method, the number of steps for manufacturing the lithium ion battery can be reduced, and therefore, the manufacturing method of the lithium ion battery can be simplified. Further, in the third method, the electrolyte solvent is used without using the diluting solvent. In this case, the gel electrolyte can be obtained by merely molding the mixed solution into a predetermined shape, and therefore, the method is not limited to the step of removing the diluting solvent as compared with the first method or the second method. Therefore, the manufacturing method of the electrochemical device can be simplified.
[ electrochemical device ]
Next, a representative example of the electrochemical device according to the present invention manufactured using the gel electrolyte having the above-described structure will be specifically described. The electrochemical device according to the present invention is not particularly limited as long as it is a device that utilizes an electrochemical reaction (a device capable of converting chemical energy and electric energy), but a typical structure includes a pair of electrodes and an electrolyte disposed therebetween.
The specific structure of the pair of electrodes included in the electrochemical device is not particularly limited, and typically, the pair of electrodes are each composed of a positive electrode and a negative electrode. The specific structure of the positive electrode and the negative electrode is not particularly limited, but in order to increase the contact area with the electrolyte solution contained in the electrolyte, for example, the contact surface (the surface facing the electrolyte) is preferably porous. Such a porous contact surface may have only the positive electrode, only the negative electrode, or both the positive electrode and the negative electrode. The more specific structure of the pair of electrodes (positive electrode and negative electrode) is not particularly limited, and electrodes of various materials, shapes, sizes, and the like can be used appropriately according to the type, application, and the like of the electrochemical device.
The method for forming the porous contact surface is not particularly limited, and typically, a method of forming a powder (or particles) of an electrode material (active material) on the surface of an electrode base material in a layer manner is used. As a method for forming such a powdery material into a layer, there is a method in which a powder of an electrode material (active material) is mixed with an organic vehicle (a solvent, a binder resin, or the like) to be gelatinized, and the resultant is applied to the surface of an electrode base material, and then dried, cured, fired, or the like.
In the present invention, the electrolyte is a hard gel electrolyte in a cured state in which the degree of curing of the gel electrolyte in an uncured state is increased, as described above.
The typical structure of the electrochemical device according to the present invention is a structure having a pair of electrodes and a hard gel electrolyte as described above, but the structure of the electrochemical device according to the present invention is not limited to this, and may have a pair of electrodes and a gel electrolyte or structural elements or members other than a hard gel electrolyte. The specific structure of such other structural elements or other members is not particularly limited, and various structural elements or elements corresponding to the specific kind of electrochemical device may be used.
More specific structures of the electrochemical device according to the present invention include, for example: lithium ion batteries, dye sensitized solar cells, electric double layer capacitors, gel actuators, and the like. A specific structure of a lithium ion battery, which is a representative example of an electrochemical device in the present invention, will be specifically described with reference to fig. 1.
As shown in fig. 1, a lithium ion battery 10 as one of electrochemical devices has the following structure: a positive electrode 12 and a negative electrode 13 are provided as a pair of electrodes, and a hard gel electrolyte 14 is held between the positive electrode 12 and the negative electrode 13. For convenience of explanation, a structure in which positive electrode 12, hard gel electrolyte 14, and negative electrode 13 are laminated (a structure in which hard gel electrolyte 14 is held on positive electrode 12 and negative electrode 13) is referred to as laminated structure 11. The lithium ion battery 10 is configured by sealing the laminated structure 11 with a sealing material 15.
As shown in fig. 1, the positive electrode 12 has a structure in which a positive electrode active material layer 22 is formed on the surface of a positive electrode base material 21 (the surface facing the negative electrode 13, the surface in contact with the hard gel electrolyte 14). Similarly, the negative electrode 13 has a structure in which a negative electrode active material layer 32 is formed on the surface of the negative electrode base material 31 (the surface facing the positive electrode 12, the surface in contact with the hard gel electrolyte 14).
The positive electrode base material 21 and the negative electrode base material 31 function as a current collector that collects electrons generated by the electrochemical reaction of the positive electrode active material layer 22 and the negative electrode active material layer 32. The specific structure of the positive electrode base 21 and the negative electrode base 31 is not particularly limited, and a known metal plate or foil may be used. In the embodiment described later, an aluminum foil is used as the positive electrode base material 21. As the negative electrode base material 31, copper foil is typically used.
As the positive electrode active material used in the positive electrode active material layer 22, a lithium salt of a transition metal oxide is typically used, but is not particularly limited. In examples described later, a ternary lithium salt, i.e., li-Ni-Co-Mn oxide (NCM), was used as the positive electrode active material. As the negative electrode active material used in the negative electrode active material layer 32, a lithium metal foil or a carbon material is typically used. In examples described later, a lithium metal foil was used as the negative electrode active material. The positive electrode active material layer 22 may be composed of only a positive electrode active material, and the negative electrode active material layer 32 may be composed of only a negative electrode active material, but may be composed of a layer containing other components.
For example, when the positive electrode active material layer 22 and the negative electrode active material layer 32 are formed by coating with a coating liquid containing an active material, a known binder resin such as polyvinylidene fluoride (PVDF) and a known conductive auxiliary such as carbon black may be contained. The coating liquid may contain a solvent (dispersion medium) in addition to the active material, the binder resin, and the conductive auxiliary agent. In addition, from the viewpoint of increasing the contact frequency with the positive electrode active material layer 22 or the negative electrode active material layer 32, the coating liquid may contain a gel electrolyte before the curing degree is increased or a gel electrolyte (hard gel electrolyte component) after the curing degree is increased to the same extent as the hard gel electrolyte 14.
The positive electrode active material layer 22 forms an opposing surface of the positive electrode 12 that faces the negative electrode 13, and forms a contact surface with the hard gel electrolyte 14. Similarly, the negative electrode active material layer 32 forms an opposing surface of the negative electrode 13 that faces the positive electrode 12, and forms a contact surface with the hard gel electrolyte 14. Therefore, as described above, at least one of the positive electrode active material layer 22 and the negative electrode active material layer 32 is preferably formed in a porous shape.
The method for forming these active material layers 22 and 32 into a porous shape is not particularly limited, and various known methods can be used. Typically, as described above, a method of applying a paste containing an active material and drying the paste is used. In addition, either of the active material layers 22 and 32 may not be porous. In the embodiment described later, the positive electrode active material layer 22 is formed in a porous shape, but the negative electrode active material layer 32 is formed only of lithium foil.
Since the lithium foil serves as a current collector (negative electrode base material 31) together with the negative electrode active material, the negative electrode 13 is composed of only the lithium foil in the embodiment described later. Therefore, at least one of the positive electrode 12 and the negative electrode 13 does not need to be constituted by the active material layers 22 and 32 and the substrates 21 and 31 supporting them as exemplified in fig. 1.
As described above, the hard gel electrolyte 14 is formed by reacting reactive groups contained in the gel electrolyte in an uncured state, and performing a crosslinking reaction to increase the curing degree of the gel electrolyte.
The sealing material 15 is not particularly limited as long as it can seal the laminated structure 11 composed of the positive electrode 12, the negative electrode 13, and the hard gel electrolyte 14. As the sealing material 15, if the electrochemical device is a lithium ion battery 10, a known laminated film, a known metal can, or the like is typically used. The laminated film is typically a laminated film obtained by laminating a resin film such as polypropylene (PP) on a metal foil such as an aluminum foil or a stainless steel foil, but is not particularly limited. In addition, if the electrochemical device is a dye-sensitized solar cell, examples of the sealing material 15 include: thermoplastic ionomer resins, and the like.
The lithium ion battery 10 shown in fig. 1 does not have a separator. This is because the hard gel electrolyte 14 held by the positive electrode 12 and the negative electrode 13 can function similarly to the separator. The lithium ion battery 10 may further include a separator, or may include components other than the positive electrode 12, the negative electrode 13, and the hard gel electrolyte 14.
Thus, according to the present invention, an appropriate amount of reactive groups are contained in the gel electrolyte in an uncured state. Therefore, even in the gel electrolyte (hard gel electrolyte) in which the reactive groups sufficiently undergo the crosslinking reaction, the hard gel electrolyte can retain a sufficient amount of the electrolyte. In addition, as the crosslinking reaction proceeds, a part of the electrolyte solution can be leaked from the matrix material. Therefore, if the crosslinking reaction is performed after the electrochemical device is fabricated using the gel electrolyte in a state where the curing is not sufficiently performed (uncured state), the leaked electrolyte can be brought into good contact with the contact surface of the electrode provided in the electrochemical device. Based on this, a good electrochemical reaction can be achieved in the electrochemical device.
In addition, the gel electrolyte has a shear elastic modulus of 1MPa or more even in an uncured state, and thus has good strength. Therefore, good handleability can be achieved in the gel electrolyte, and therefore, inefficiency in manufacturing the electrochemical device can be suppressed. As described above, since the crosslinking reaction is performed after the electrochemical device is fabricated using the gel electrolyte in an uncured state, the liquid injection step is not required in the fabrication process of the electrochemical device. Therefore, the possibility of insufficient injection or the possibility of performance degradation due to insufficient injection can be avoided.
As a result, according to the present invention, it is possible to achieve high efficiency in manufacturing an electrochemical device and to achieve good device performance in the obtained electrochemical device.
Examples
The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited thereto. Various changes, modifications and alterations can be made by those skilled in the art without departing from the scope of the invention. The measurement and evaluation of various synthetic reactions, physical properties, and the like in the following examples were performed as follows.
(determination of shear elastic modulus of gel electrolyte)
The gel electrolyte obtained in each example or each comparative example was provided with a shear modulus by using a bench type precision universal tester (product name: AUTOGRAPH AGS-X) manufactured by Shimadzu corporationAfter a 0.05N pre-load was applied, a press-in test was performed at a speed of 0.05 mm/min,based on the results of the indentation test, the shear modulus (unit: MPa) was measured using the following formula (1) with reference to the aforementioned reference 1.
Shear modulus of elasticity (G) =0.36 Fg [ (D-h)/h] 3/2 /R 2 (1)
( F: load (test force) of press-in test, g: gravitational acceleration, D: thickness (film thickness) of gel electrolyte (gel-like body), h: thickness (film thickness) change due to load, R: ball radius of ball indenter for press-in test )
(measurement of ion conductivity of gel electrolyte)
The thickness (film thickness) of the gel electrolyte obtained in each example or each comparative example was measured. Further, the gel electrolyte was sandwiched between stainless steel foils and allowed to stand in a constant temperature bath at 80℃for 12 hours, followed by a crosslinking reaction, and the temperature was returned to room temperature to obtain a hard gel electrolyte. This was used as a sample for measuring ion conductivity, and an impedance analyzer (product name: SP-150) manufactured by BIOLOGIC (Bio-Logic SAS) was used for the sample, and Electrochemical Impedance Spectroscopy (EIS) was performed at a frequency of 1MHz to 0.1Hz to obtain the volume resistance value of the gel electrolyte. The ionic conductivity (unit: mS/cm) at 30℃was calculated by dividing the film thickness of the gel electrolyte by the volume resistance value.
(evaluation of cell Performance of electrochemical device)
The button cell for evaluation (electrochemical device according to the present invention) obtained in each example or each comparative example was charged at a time rate of 0.1C at 25 ℃ and discharged at a time rate of 0.1C to 1C using a charge/discharge test device (TOSCAT 3100, product name, manufactured by eastern systems co.) and evaluated for a capacity retention rate (Q1C/Q0.1C) of 1C discharge capacity relative to 0.1C discharge capacity.
The capacity retention rate was evaluated as "good" if it was 90% or more, as "delta" if it was 70% or more (normal), and as "×" if it was less than 70% (unsuitable).
(evaluation of element stability of electrochemical device)
In each example or each comparative example, 10 button cells for evaluation (electrochemical device according to the present invention) were produced in total, and for these button cells for evaluation, a charge/discharge test device (product name: TOSCAT 3100) manufactured by eastern systems corporation was used, and the element stability test was performed by performing charging at 25 ℃ at 1C time rate and performing discharging 100 times at 1C time rate. Among the 10 fabricated button cells for evaluation, those with short circuit of 1 or less were evaluated as "good", those with short circuit of less than 5 were evaluated as "Δ" (normal), and those with short circuit of 5 or more were evaluated as "×" (unsuitable).
Example 1
The following operations were performed in a dry air atmosphere having a dew point of-50 ℃ or lower. As shown in table 1, 1.8 parts by mass of polyvinylidene fluoride (PVDF, manufactured by kuehha, product name: KF POLYMER # 7200) as a matrix material was dissolved in 33 parts by mass of acetone (manufactured by photoplethysmography) as a diluting solvent for gel by heating at 80 ℃, and left standing at room temperature, thereby producing PVDF/acetone gel (non-electrolyte gel).
Further, as shown in Table 1, 10 parts by mass of lithium bis (fluorosulfonyl) imide (LiFSI, KISHIDA chemical Co., ltd., lithium Battery Grade (LBG)) as a lithium salt, 0.49 parts by mass of 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide (EMImFSI) as an electrolyte solvent of an ion liquid system, 49 parts by mass of first Industrial pharmaceutical Co., ltd., product name: elexcel IL-110), 1.3 parts by mass of tetrafunctional polyether acrylate (first Industrial pharmaceutical Co., ltd., product name: elexcel TA-210) as a post-curing agent, and 3.8 parts by mass of 2,2' -azobis (2, 4-dimethylvaleronitrile) (and photo-pure chemical Co., ltd., product name; V-65) as an azo initiator were mixed to prepare a substitution solution.
The substitution solution was added to PVDF/acetone gel, and acetone (a gel-forming diluent) and acetonitrile (a substitution diluent) were distilled off at normal temperature under vacuum conditions, thereby producing (manufacturing) the gel electrolyte according to example 1.
Here, in the gel electrolyte according to example 1, the crosslinkable reactive group is an acrylate group contained in a tetrafunctional polyether acrylate (product name: elexcel TA-210) as a post-curing agent. The weight average molecular weight of the tetrafunctional polyether acrylate used was 11000,1 and the molecular weight of the 4 acrylate groups contained in the molecule was 220, so that the mass of the acrylate groups contained in 1g of the tetrafunctional polyether acrylate was 0.02g.
As described above, in example 1, the amount of the tetrafunctional polyether acrylate to be used as the post-curing agent was 1.3 parts by mass. Therefore, the mass of the reactive group (acrylate group) contained in the gel electrolyte according to example 1 was 0.025 parts by mass. As described above, in example 1, the amount of the EMImFSI to be used as the electrolyte solvent was 49 parts by mass. Therefore, as shown in table 1, in the gel electrolyte according to example 1, the mass ratio of the reactive group to the mass of the electrolyte solvent was 0.050 mass%, and was in the range of 0.03 to 6.5 mass%.
As shown in table 1, in the gel electrolyte according to example 1, the mass ratio of the electrolyte solvent to the total mass was 78 mass%, and the mass ratio of the matrix material to the total mass was 2.9 mass% and the mass ratio was 1.0 to 10 mass% respectively.
LiNi as positive electrode active material was weighed 1/3 Mn 1/3 Co 1/3 O 2 100g of acetylene Black (manufactured by Denka Black HS-100, product name: denka Black Co., ltd.) as a conductive additive, 7.8g of polyvinylidene fluoride (PVDF, manufactured by KUREHA, weight average molecular weight Mw: about 30 ten thousand) as a binder resin, and 38.4g of N-methyl-2-pyrrolidone (NMP) as a dispersion medium were mixed with a planetary mixer, respectively, to prepare a coating liquid of a positive electrode active material layer having a solid content of 51%. The coating solution was applied on an aluminum foil (positive electrode substrate) having a thickness of 15 μm by a coating apparatus, dried at 130℃and then subjected to a roll-pressing treatment to obtain a coating having a thickness of 2.3mg/cm 2 A positive electrode of the positive electrode active material layer of (a).
The positive electrode, the gel electrolyte according to example 1, and a lithium foil as a negative electrode were stacked to form a laminate. The laminate was punched into a circular shape having a diameter of 14mm, and sealed in a button cell holder to prepare a sealed body. The sealing body was allowed to stand in a constant temperature bath at 80℃for 12 hours, so that the crosslinking reaction of the reactive groups contained in the gel electrolyte was sufficiently progressed (the gel electrolyte was cured to become a hard gel electrolyte), and then the temperature was returned to room temperature. In this way, a button cell (lithium ion battery) for evaluation, which is an electrochemical device according to example 1, was produced (manufactured).
As described above, the gel electrolyte according to example 1 was measured or evaluated for shear modulus, film thickness, and ion conductivity, and the obtained coin cell for evaluation was evaluated for cell performance and element stability (short circuit). The results are shown in Table 1.
Example 2, 3
In the same manner as in example 1, except that the amount of the electrolyte solvent and the amount of the post-curing agent to be blended were changed as shown in table 1, the gel electrolyte according to example 2 or the gel electrolyte according to example 3 was produced, and the button cell for evaluation as the electrochemical device according to example 2 or the electrochemical device according to example 3 was produced.
As shown in table 1, in the gel electrolyte according to example 2 or the gel electrolyte according to example 3, the mass ratio of the reactive group to the mass of the electrolyte solvent was in the range of 0.03 to 6.5 mass%, the mass ratio of the electrolyte solvent to the total mass was in the range of 20 to 80 mass%, and the mass ratio of the matrix material to the total mass was in the range of 1.0 to 10 mass%.
As described above, the shear elastic modulus, the film thickness, and the ionic conductivity were measured or evaluated for the obtained gel electrolyte according to example 2 or 3, and the battery performance and the element stability (short circuit) were evaluated for the obtained button cell for evaluation. The results are shown in Table 1.
TABLE 1
Example 4
The following operations were carried out in a dry air atmosphere having a dew point of-50 ℃ or lower in the same manner as in examples 1 to 3. As shown in Table 2, 2.9 parts by mass of vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP, KUREHA, product name: KFPOLYMER #8500, abbreviated as "PVDF-HFP 1" in Table 2) as a matrix material was dissolved in 29.5 parts by mass of dimethyl ether (DME, wako pure chemical industries, ltd.) as a diluent by heating at 80 ℃. Based on this, liquid A was prepared as a DME diluted solution of PVDF-HFP.
As shown in table 2, 9.3 parts by mass of LiFSI (see example 1) as a lithium salt, 28 parts by mass of EMImFSI (see example 1) as an electrolyte solvent of an ionic liquid system, 0.90 parts by mass of tetrafunctional polyether acrylate (see example 1) as a post-curing agent, 0.12 parts by mass of azo initiator (see example 1) as an initiator, and 29.5 parts by mass of DME as a diluent solvent were mixed and mixed to prepare a liquid B as a DME diluent for an electrolyte or the like.
The obtained solution a and solution B were mixed, and the mixed solution was applied to the surface of the positive electrode, and DME (diluent solvent) was distilled off at normal temperature under vacuum conditions, thereby producing (manufacturing) a laminate of the gel electrolyte and the positive electrode according to example 4.
As shown in table 2, a tetrafunctional polyether acrylate was blended as a post-curing agent in the gel electrolyte according to example 4 in the same manner as in examples 1 to 3, and the mass ratio of the reactive groups was derived in the same manner as in example 1. As shown in table 2, the mass ratio of the reactive group to the mass of the electrolyte solvent was in the range of 0.03 to 6.5 mass% (0.063 mass%). As shown in table 2, in the gel electrolyte according to example 4, the mass ratio of the electrolyte solvent to the total mass was in the range of 20 to 80 mass% (68 mass%), and the mass ratio of the matrix material to the total mass was in the range of 1.0 to 10 mass% (7.0 mass%).
The gel electrolyte/positive electrode laminate was pressed into a circular shape having a diameter of 14mm, and a lithium foil having a diameter of 14mm was bonded to the gel electrolyte side of the pressed body as a negative electrode, thereby providing a bipolar battery. In this way, a button cell (lithium ion battery) for evaluation, which is an electrochemical device according to example 4, was produced (manufactured).
The gel electrolyte (gel electrolyte/positive electrode laminate) according to example 4 was measured or evaluated for shear modulus, film thickness, and ionic conductivity as described above, and the obtained coin cell for evaluation was evaluated for cell performance and element stability (short circuit). The results are shown in Table 2.
Examples 5 to 13
Gel electrolytes according to examples 5 to 13 were produced in the same manner as in example 4 except that the amount of the electrolyte solvent and the amount of the post-curing agent to be blended were changed as shown in table 2 (examples 5 and 6), or difunctional polyether acrylate (manufactured by first Industrial pharmaceutical Co., ltd., product name: MP-150) was used as the post-curing agent and the amount of the electrolyte solvent to be blended was changed as shown in table 2 or 3 (examples 7 to 9), or polyethylene glycol diacrylate (manufactured by first Industrial Co., ltd., product name: elexcel EG 2500) was used as the post-curing agent and the amount of the electrolyte solvent was changed as shown in table 3 (example 10), or methyl methacrylate-oxetanyl methacrylate copolymer (manufactured by first Industrial Co., ltd., product name: elexcel ACG-127) was used as the post-curing agent and the amount of the electrolyte solvent to be blended was changed as shown in table 3 (examples 11 to 13). Further, using these gel electrolytes, button cells for evaluation as electrochemical devices according to examples 5 to 13 were produced.
In the gel electrolytes according to examples 7 to 9, the crosslinkable reactive group was an acrylate group contained in a difunctional polyether acrylate (product name: MP-150) as a post-curing agent. The weight average molecular weight of the difunctional polyether acrylate used was 110 for 2 acrylate groups contained in 11000,1 molecules, and thus the mass of acrylate groups contained in 1g of the difunctional polyether acrylate was 0.010g.
For example, in example 7, as shown in table 2, the amount of the difunctional polyether acrylate as the post-curing agent was 1.4 parts by mass. Therefore, the mass of the reactive group (acrylate group) contained in the gel electrolyte according to example 7 was 0.0138 parts by mass. In example 7, as shown in table 2, the amount of the EMImFSI to be used as the electrolyte solvent was 28 parts by mass. Therefore, as shown in table 2, in the gel electrolyte according to example 7, the mass ratio of the reactive group to the mass of the electrolyte solvent was 0.050 mass%, and was in the range of 0.03 to 6.5 mass%.
Similarly, as shown in table 2 or table 3, a difunctional polyether acrylate was blended as a post-curing agent in the gel electrolyte according to example 8 or example 9 in the same manner as in example 7, and the mass ratio of the reactive groups was derived in the same manner as in example 7. As shown in table 2, in examples 8 and 9, the mass ratio of the reactive group to the mass of the electrolyte solvent was 0.44 mass% (example 8) or 2.5 mass% (example 9), and was in the range of 0.03 to 6.5 mass%.
In the gel electrolyte according to example 10, the crosslinkable reactive group is an acrylate group contained in polyethylene glycol diacrylate (product name: elexcel EG 2500) as a post-curing agent. The weight average molecular weight of the polyethylene glycol diacrylate used was 2500, and the molecular weight of the acrylate group contained in 1 molecule was 83, so that the mass of the acrylate group contained in 1g of the polyethylene glycol diacrylate was 0.033g.
In example 10, as shown in table 3, the amount of polyethylene glycol diacrylate as a post-curing agent was 6.7 parts by mass. Therefore, the mass of the reactive group (acrylate group) contained in the gel electrolyte according to example 10 was 0.221 parts by mass. In example 10, as shown in table 3, the amount of the EMImFSI to be used as the electrolyte solvent was 28 parts by mass. Therefore, in the gel electrolyte according to example 10, the mass ratio of the reactive group to the mass of the electrolyte solvent was 1.0 mass% and was in the range of 0.03 to 6.5 mass%.
In the gel electrolytes according to examples 11 to 13, the crosslinkable reactive group was an oxetane moiety contained in a methyl methacrylate-oxetane methacrylate copolymer (product name: elexcel ACG-127) as a post-curing agent. The weight average molecular weight of the methyl methacrylate-oxetanyl methacrylate copolymer used was 30 ten thousand, and the molecular weight of 1 oxetane moiety was 56, so that the mass of the oxetane moiety contained in 1g of the methyl methacrylate-oxetanyl methacrylate copolymer was 0.13g.
For example, in example 11, as shown in table 3, the blending amount of the methyl methacrylate-oxetanyl methacrylate copolymer as the post-curing agent was 0.12 parts by mass. Therefore, the mass of the reactive group (oxetane portion) contained in the gel electrolyte according to example 11 was 0.015 parts by mass. In example 11, the amount of the EMImFSI as the electrolyte solvent was 29 parts by mass as shown in table 3. Therefore, as shown in table 2, in the gel electrolyte according to example 11, the mass ratio of the reactive group to the mass of the electrolyte solvent was 0.050 mass%, and was in the range of 0.03 to 6.5 mass%.
Similarly, as shown in table 3, a methyl methacrylate-oxetanyl methacrylate copolymer was blended as a post-curing agent in the gel electrolyte according to example 12 or example 13 in the same manner as in example 11, and the mass ratio of the reactive groups was derived in the same manner as in example 11. As shown in table 3, in examples 11 and 12, the mass ratio of the reactive group to the mass of the electrolyte solvent was 1.2 mass% (example 12) or 5.6 mass% (example 13), and was in the range of 0.03 to 6.5 mass%.
As shown in table 2, in the gel electrolytes according to examples 5 and 6, a tetrafunctional polyether acrylate was blended as a post-curing agent in the same manner as in examples 1 to 4, and the mass ratio of the reactive groups was derived in the same manner as in example 1. As shown in table 2, in examples 5 and 6, the mass ratio of the reactive group to the mass of the electrolyte solvent was also in the range of 0.03 to 6.5 mass% (see example 1).
Further, as shown in table 2 or table 3, in the gel electrolytes according to examples 5 to 13, the mass ratio of the electrolyte solvent to the total mass was in the range of 20 to 80 mass%, and the mass ratio of the matrix material to the total mass was in the range of 1.0 to 10 mass%.
The shear modulus, film thickness, and ionic conductivity were measured or evaluated for the gel electrolytes of examples 5 to 13, respectively, as described above, and the cell performance and element stability (short circuit) were evaluated for the obtained coin cells for evaluation, respectively. The results are shown in Table 2 or Table 3.
TABLE 2
TABLE 3
Examples 14 to 16
As shown in table 4, PVDF-HFP (manufactured by kuehha corporation, product name: kf polymer #9300, abbreviated as "PVDF-HFP 2" in table 4) of a different type from examples 4 to 13 was used as a matrix material (example 14), silica particles (manufactured by AEROSIL corporation, product name: AEROSIL 200, and "silica" in table 4) as inorganic particles were used as a matrix material (example 15), silica/alumina mixed particles (manufactured by AEROSIL corporation, product name: AEROSIL COK84, and "silica/alumina" in table 4) were used as a matrix material, and the amounts of the electrolyte solvent and the post-curing agent were changed, and gel electrolytes according to examples 14 to 16 were produced in the same manner as in example 4 except for the above. Further, using these gel electrolytes, button cells for evaluation as electrochemical devices according to examples 14 to 16 were produced.
As shown in table 4, in the gel electrolytes according to examples 14 to 16, the mass ratio of the reactive group to the mass of the electrolyte solvent was in the range of 0.03 to 6.5 mass%, the mass ratio of the electrolyte solvent to the total mass was in the range of 20 to 80 mass%, and the mass ratio of the matrix material to the total mass was in the range of 1.0 to 10 mass%.
The shear modulus, film thickness, and ionic conductivity were measured or evaluated as described above for the gel electrolytes of examples 14 to 16, and the cell performance and element stability (short circuit) were evaluated for the obtained coin cells for evaluation. The results are shown in Table 4.
TABLE 4
Example 17
The following operations were carried out in a dry air atmosphere having a dew point of-50 ℃ or lower in the same manner as in examples 1 to 16. As shown in Table 5, as a matrix material, 1.0 part by mass of PVDF-HFP [2] (KUREHA, product name: KFPOLYMER#9300) similar to example 14 was dissolved by heating at 80℃with respect to 55.3 parts by mass of a mixture (mixed electrolyte solvent) of dimethyl carbonate (DMC, manufactured by Kishida chemical Co., ltd., LBG) and ethylene carbonate (EC, manufactured by Kishida chemical Co., ltd., LBG) as a carbonate-based electrolyte solvent. Based on this, solution A was prepared as a DMC dilution solution of PVDF-HFP.
As shown in table 5, lithium hexafluorophosphate (LiPF 6 Liquid B was prepared by mixing 14 parts by mass of KISHIDA chemical company, LBG, 39.5 parts by mass of the mixed electrolyte solvent of DMC and EC, 0.90 part by mass of the tetrafunctional polyether acrylate as a post-curing agent (see example 1), and 0.30 part by mass of an azo initiator as an initiator (see example 1). Needs to be as followsIn this example, as shown in table 5, no diluent solvent was used.
The obtained solution a and solution B were mixed, and the mixed solution was applied to the surface of the positive electrode, thereby producing (manufacturing) a laminate of the gel electrolyte and the positive electrode according to example 17.
As shown in table 5, in the gel electrolyte according to example 17, the mass ratio of the reactive group to the mass of the electrolyte solvent was in the range of 0.03 to 6.5 mass% (0.013 mass%), the mass ratio of the electrolyte solvent to the total mass was in the range of 20 to 80 mass% (79 mass%), and the mass ratio of the matrix material to the total mass was in the range of 1.0 to 10 mass% (1.0 mass%).
The gel electrolyte/positive electrode laminate was pressed into a circular shape having a diameter of 14mm, and a lithium foil having a diameter of 14mm was bonded to the gel electrolyte side of the obtained pressed body as a negative electrode, thereby providing a bipolar battery. In this way, a button cell (lithium ion battery) for evaluation, which is an electrochemical device according to example 17, was produced (manufactured).
The gel electrolyte (gel electrolyte/positive electrode laminate) according to example 17 was measured or evaluated for shear modulus, film thickness, and ionic conductivity as described above, and the obtained coin cell for evaluation was evaluated for cell performance and element stability (short circuit). The results are shown in Table 5.
Examples 18 to 20
As shown in table 5, the carbonate-based electrolyte solvents used in the preparation of the a solution were changed to ethyl methyl carbonate (EMC, manufactured by KISHIDA chemicals, LBG, example 18), diethyl carbonate (DEC, manufactured by KISHIDA chemicals, LBG, example 19), or propylene carbonate (PC, manufactured by KISHIDA chemicals, LBG, example 20), and the amounts of PC and EC blended were changed when PC was used (example 20), and gel electrolytes according to examples 18 to 20 were produced in the same manner as in example 17, except that the above was used. Further, using these gel electrolytes, button cells for evaluation as electrochemical devices according to examples 18 to 20 were produced.
As shown in table 5, in the gel electrolytes according to examples 18 to 20, the mass ratio of the reactive group to the mass of the electrolyte solvent was in the range of 0.03 to 6.5 mass%, the mass ratio of the electrolyte solvent to the total mass was in the range of 20 to 80 mass%, and the mass ratio of the matrix material to the total mass was in the range of 1.0 to 10 mass%.
The shear modulus, film thickness, and ionic conductivity were measured or evaluated as described above for the gel electrolytes of examples 18 to 20, and the cell performance and element stability (short circuit) were evaluated for the button cell for evaluation. The results are shown in Table 5.
TABLE 5
Examples 21 to 26
As shown in table 6, the mass ratio of the reactive groups to the electrolyte solvent in the gel electrolyte was in the range of 0.03 to 6.5 mass%, but the mass ratio of the electrolyte solvent to the total mass of the gel electrolyte was made to be less than 20 mass% (example 21), more than 80 mass% (example 22), the ion conductivity was made to be less than 0.8mS/cm (example 23), the mass ratio of the matrix material to the total mass of the gel electrolyte was made to be less than 1.0 mass% (example 24), more than 10 mass% (example 25), the film thickness of the gel electrolyte was made to be 100 μm or more, and the blending amounts of the components were changed, except that the above were made to be the same as in example 4 (examples 21, 23 to 26) or the same as in example 17 (example 22), but the electrolyte solvent was used only for EC of 1). Further, using these gel electrolytes, button cells for evaluation as electrochemical devices according to examples 21 to 26 were produced.
The shear modulus, film thickness, and ionic conductivity were measured or evaluated as described above for the gel electrolytes of examples 21 to 26, and the cell performance and element stability (short circuit) were evaluated for the obtained coin cells for evaluation. The results are shown in Table 6.
TABLE 6
Comparative example 1 and 2
As shown in table 7, the gel electrolyte according to comparative example 1 or the gel electrolyte according to comparative example 2 was produced and an evaluation button cell as the electrochemical device according to comparative example 1 or the electrochemical device according to comparative example 2 was produced in the same manner as in example 4 described above, except that the mass ratio of the reactive group to the electrolyte solvent in the gel electrolyte was changed to less than 0.03 mass% (comparative example 1) or more than 6.5 mass% (comparative example 2) and the amount of each component to be blended was changed.
The shear elastic modulus, film thickness, and ionic conductivity were measured or evaluated as described above for the obtained gel electrolyte according to comparative example 1 or 2, and the battery performance and element stability (short circuit) were evaluated for the obtained button cell for evaluation. The results are shown in Table 7.
TABLE 7
(comparison of examples and comparative examples)
As is clear from comparison of examples 1 to 26 with comparative examples 1 and 2, in the gel electrolyte according to the present invention, an electrochemical device (lithium ion battery) having good performance can be manufactured by satisfying the first condition and the second condition. In contrast, it is found that, particularly when the first condition is not satisfied, the performance of the electrochemical device cannot be sufficiently obtained.
Further, as is clear from comparison of examples 4 to 13 and examples 17 to 20 with examples 21 to 26, in the gel electrolyte according to the present invention, at least one of the third condition and the fourth condition is satisfied in addition to the first condition and the second condition, whereby an electrochemical device (lithium ion battery) having more excellent performance can be manufactured.
Further, as is clear from comparison of examples 1 to 3, examples 4 to 16, and examples 17 to 20, in the gel electrolyte according to the present invention, the gel electrolyte manufactured in any one of the first method, the second method, or the third method can manufacture an electrochemical device (lithium ion battery) having good performance.
The present invention is not limited to the description of the above embodiments, and various modifications are possible within the scope of the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments and a plurality of modifications are also included in the technical scope of the present invention.
Industrial applicability
The present invention can be widely applied to the field of electrochemical devices using a gel electrolyte, such as lithium ion batteries, dye-sensitized solar cells, electric double layer capacitors, and gel actuators.

Claims (8)

1. A gel electrolyte is characterized in that,
the gel electrolyte is a gel-like body composed of at least a matrix material and an electrolyte and contains crosslinkable reactive groups,
the gel electrolyte is cured by crosslinking reaction of the reactive groups, and is used as an electrolyte of an electrochemical device,
the electrolyte is composed of at least an ionic substance and an electrolyte solvent,
the mass of the electrolyte solvent is in the range of 20 mass% to 80 mass% relative to the total mass of the gel-like body,
the mass of the matrix material is in the range of 1.0 mass% or more and 10 mass% or less relative to the total mass of the gel-like body,
the mass of the reactive group contained in the gel-like body is in a range of 0.03 mass% or more and 6.5 mass% or less with respect to the mass of the electrolyte solvent, and
the gel-like body has a shear elastic modulus of 1MPa or more in a state where the reactive group is unreacted.
2. The gel electrolyte according to claim 1, wherein,
the gel-like body contains a post-curing agent having the reactive group in addition to the matrix material and the electrolyte.
3. The gel electrolyte according to claim 1, wherein,
the gel-like body contains a diluting solvent which is a component different from the electrolyte solvent and is removed before the crosslinking reaction of the reactive group,
the mass range of the electrolyte solvent or the mass range of the matrix material is defined with respect to the total mass of the gel-like body other than the diluting solvent.
4. The gel electrolyte according to any one of claim 1 to 3, wherein,
the gel-like body is in the form of a sheet.
5. The gel electrolyte according to claim 4, wherein,
the thickness of the gel is 5 μm or more and 100 μm or less.
6. A hard gel electrolyte is characterized in that,
the hard gel electrolyte is obtained by subjecting the reactive groups in the gel electrolyte according to any one of claims 1 to 5 to a crosslinking reaction to increase the hardness of the gel electrolyte.
7. The hard gel electrolyte according to claim 6, wherein,
the hard gel electrolyte satisfies at least any one of an ionic conductivity of 0.8mS/cm or more and a shear elastic modulus of 6MPa or more.
8. An electrochemical device, characterized in that,
the electrochemical device having the hard gel electrolyte of claim 6 or 7.
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