CN111095655A

CN111095655A - Gel electrolyte, hard gel electrolyte and electrochemical device

Info

Publication number: CN111095655A
Application number: CN201880058761.9A
Authority: CN
Inventors: 齐藤恭辉; 奥原淳史
Original assignee: Dai Ichi Kogyo Seiyaku Co Ltd
Current assignee: DKS Co Ltd
Priority date: 2017-09-21
Filing date: 2018-09-11
Publication date: 2020-05-01
Anticipated expiration: 2038-09-11
Also published as: KR102658513B1; CN111095655B; WO2019059053A1; KR20200054949A; JP2019057425A; JP6971105B2

Abstract

Provided is a gel electrolyte which can realize high efficiency in the production of an electrochemical device and can realize 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 electrolytic solution and contains a crosslinkable reactive group, and the gel electrolyte is cured by causing the reactive group to undergo 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, the mass of the reactive group contained in the gel is in the range of 0.03 mass% to 6.5 mass% relative to the mass of the electrolyte solution, and the shear modulus of elasticity of the gel in a state where the reactive group is unreacted is 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, a gel electrolyte which is cured by crosslinking the reactive group and can be used as an electrolyte of an electrochemical device, a hard gel electrolyte (hard geleletrolyte) 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 been a liquid (electrolyte solution). However, if the electrolyte is a general electrolyte solution, the possibility of electrolyte leakage from the electrochemical device cannot be denied. Therefore, in recent years, as in the electrochemical cell and the method for manufacturing the same disclosed in patent document 1, for example, a structure using a gel electrolyte in which an electrolytic solution is gelled has been proposed.

Documents of the prior art

Patent document

Patent document 1: japanese patent publication 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 electrolytic solution (electrolytic solution injection step) is required. In addition, in order to gel the electrolytic solution, 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 normal electrolyte.

Therefore, in the electrolyte injection step, since the prepolymer electrolyte having a high viscosity needs to be injected into the electrochemical device, the time required for the electrolyte injection step may be long. Therefore, there is a possibility that the electrochemical device manufacturing process cannot be sufficiently efficiently performed.

In addition, for example, in the case where the electrochemical device is large-sized, the amount of the prepolymer electrolyte to be injected in the electrolyte injection step becomes large. 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 cannot be achieved in the electrochemical device.

The present invention has been made to solve the above problems, and an object thereof is to provide a gel electrolyte that can realize high efficiency in manufacturing an electrochemical device and can realize good device performance in the obtained electrochemical device.

Means for solving the problems

In order to solve the above problems, a gel electrolyte according to the present invention has the following configuration: the gel-like material is a gel-like material composed of at least a matrix material and an electrolytic solution, and contains a crosslinkable reactive group, and is cured by causing the reactive group to undergo a crosslinking reaction, thereby being used as an electrolyte of an electrochemical device, wherein the electrolytic solution is composed of at least an ionic substance and an electrolytic solution solvent, the mass of the reactive group contained in the gel-like material is in a range of 0.03 mass% or more and 6.5 mass% or less relative to the mass of the electrolytic solution solvent, and the shear modulus of elasticity of the gel-like material in a state in which the reactive group is unreacted is 1MPa or more.

According to the above configuration, an appropriate amount of reactive groups is contained in the uncured gel electrolyte. Therefore, even in a gel electrolyte (hard gel electrolyte) in which the crosslinking reaction of the reactive group has sufficiently proceeded, the hard gel electrolyte can hold a sufficient amount of the electrolytic solution. In addition, a part of the electrolyte can also leak out of the matrix material as the crosslinking reaction proceeds. Therefore, if the electrochemical device is produced using the gel electrolyte in a state in which 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 included in the electrochemical device. Accordingly, a favorable 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 therefore the gel electrolyte also has good strength. Therefore, good operability can be achieved in the gel electrolyte, and thus, non-high efficiency in the production of 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.

As a result, the electrochemical device can be manufactured with high efficiency, and the obtained electrochemical device can have good device performance.

In the gel electrolyte having the above-described configuration, the gel may further include a post-curing agent having the reactive group in addition to the matrix material and the electrolytic solution.

In the gel electrolyte having the above configuration, the mass of the electrolyte solvent may be in a range of 20 mass% or more and 80 mass% or less with respect to the total mass of the gel.

In the gel electrolyte having the above configuration, the mass of the matrix material may be in a range of 1.0 mass% to 10 mass% with respect to the total mass of the gel.

In the gel electrolyte having the above configuration, the following configuration may be adopted: 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 configuration, the gel may have a sheet-like shape.

In the gel electrolyte having the above-described configuration, the gel 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, wherein the reactive groups are crosslinked to improve the hardness.

In the hard gel electrolyte having the above configuration, the following configuration may be adopted: at least one of an ionic 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 structure including the above-described hard gel electrolyte.

Effects of the invention

In the present invention, the above structure provides the following effects: it is possible to provide a gel electrolyte which can realize high efficiency in the production of an electrochemical device and can realize 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.

Description of the symbols

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 electrolytic solution, and contains a crosslinkable reactive group, and is cured by a crosslinking reaction of the reactive group, thereby being used as an electrolyte provided in an electrochemical device. The electrolytic solution is composed of at least an ionic substance and an electrolytic solution solvent, but in the gel electrolyte according to the present invention, the mass of the reactive group contained in the gel electrolyte (gel) is in the range of 0.03 mass% or more and 6.5 mass% or less with respect to the mass of the electrolytic solution solvent, and the gel electrolyte (gel) in a state where the reactive group is not reacted has a strength with a shear elastic modulus of 1MPa or more.

Hereinafter, a typical example of the structure of the gel electrolyte according to the present invention will be specifically described. Since the gel electrolyte according to the present invention contains unreacted reactive groups as described above, the degree of curing of the gel electrolyte is increased by the crosslinking reaction of the reactive groups. In the following description, the gel electrolyte in which the degree of curing is increased by the crosslinking reaction is referred to as a "hard gel electrolyte". In addition, the term "gel electrolyte" refers to a gel electrolyte before the degree of solidification is increased.

[ composition of gel electrolyte (gel-like body) ]

As described above, the gel electrolyte according to the present invention is a gel-like body mainly composed of a matrix material and an electrolytic solution, but contains unreacted reactive groups in the gel-like body. The reactive group may be possessed by the matrix material, may be possessed by the electrolyte solution, may be possessed by both the matrix material and the electrolyte solution, or may be possessed by a component other than the matrix material and the electrolyte solution. As described later, the gel (gel electrolyte) may contain components other than the matrix material and the electrolytic solution. As representative other components, there may be mentioned: a curing agent having a reactive group.

The matrix material constituting the gel is not particularly limited as long as the gel can be formed in a state of containing the electrolytic solution. The matrix material may be a physical gel having a three-dimensional structure formed by non-covalent bonds such as hydrogen bonds, or may be a chemical gel having a three-dimensional structure formed by covalent bonds. In the present invention, the matrix material may have an unreacted reactive group, as long as the gel has a reactive group capable of crosslinking reaction.

That is, in the present invention, the following structure can be cited: for example, the matrix material is a physical gel-forming compound (referred to as a physical gel compound for convenience of description), and a gel (gel electrolyte) having unreacted reactive groups is formed by non-covalent bonding by adding an electrolytic solution to the matrix material. Alternatively, in the present invention, the structure may be such that: the matrix material is a chemical gel-forming compound (referred to as a chemical gel compound for convenience of description), and a semi-cured gel (gel electrolyte) is formed by crosslinking a part of the reactive groups of the matrix material, and unreacted reactive groups remain in the semi-cured gel.

In this case, as described above, the mass ratio of the reactive groups contained (or remaining) in the gel-like material to the mass of the electrolyte solvent may be in the range of 0.03 mass% to 6.5 mass% (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 exemplified in examples described later, the mass ratio of the reactive groups can be calculated using the ratio (molecular weight ratio) of the molecular weight of the reactive groups to the molecular weight of 1 molecule of the component having the reactive groups.

Here, the gel electrolyte having an unreacted reactive group is in a state where it is not sufficiently cured, but for convenience of explanation, this state is referred to as an "uncured state". In the uncured gel electrolyte, if the crosslinking reaction of the reactive groups proceeds to increase the hardness and the gel electrolyte becomes hard, this state is referred to as a "cured state" for convenience of description. The "semi-cured state" refers to a state in which, when the matrix material is a chemical gel compound, some of all the reactive groups of the compound are reacted.

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. In addition, the state in which a part of the reactive groups of the chemical gel compound are subjected to a crosslinking reaction is a "half-cured state", and the chemical gel compound undergoes gelation. The semi-cured chemical gel compound has a reactive group remaining in a range of 0.03 to 6.5 mass% relative to the mass of the electrolyte solvent, and thus corresponds to the gel electrolyte (gel) according to the present invention. Therefore, the chemical gel compound in a semi-cured state (i.e., the gel electrolyte) can be said to be in an "uncured state". Then, if the reactive groups remaining in the semi-cured chemical gel compound undergo a crosslinking reaction to increase the hardness, the chemical gel compound becomes a cured hard gel electrolyte.

The specific structure of the matrix material is not particularly limited. In general, the matrix material may be a polymer material. Depending on the application of the gel electrolyte according to the present invention, that is, depending on the type of an 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 examples described below, a lithium ion battery is illustrated as an example of an electrochemical device, but in this case, a polymer type, an inorganic type, or a low molecular weight type can be used as appropriate 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 or methacrylic resins such as Polyacrylonitrile (PAN); and the like, but are not particularly limited. Examples of the inorganic substances 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 compounds include: the fatty acid ester derivative, cyclohexane derivative, amino acid derivative, cyclic peptide derivative, alkyl hydrazide derivative, and the like are not particularly limited.

These matrix materials may be used alone in 1 kind, or 2 or more kinds may be appropriately selected and used in combination. For example, a plurality of polymer-based matrix materials may be used in combination, or 1 or more of each of the polymer-based and inorganic-based 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 in combination.

As described above, the gel may contain a post-curing agent having a reactive group. The post-curing agent may be considered 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 is sufficiently advanced, it constitutes a part of the matrix material. Therefore, the post-curing agent may be treated as a part of the matrix material, although it depends on the composition of the gel-like material and the like.

The specific structure of the post-curing agent is not particularly limited, and an appropriate reactive compound may be selected according to the composition of the gel electrolyte, the kind of application (electrochemical device), and the like of the present invention. For example, in the examples described later, a lithium ion battery is exemplified as an example of an electrochemical device, and the aforementioned polymer-based or inorganic-based material is exemplified as a matrix material, but in this case, as a post-curing agent, there can be mentioned: acrylate or oxetane reactive compounds.

Specific examples of the acrylate-based compound include: tetrafunctional polyether acrylates, difunctional polyether acrylates, other AO addition acrylates, polyethylene glycol diacrylates and the like, but are not particularly limited. Examples of the oxetane compound include: methyl methacrylate-oxetanyl methacrylate copolymer, etc., but is not particularly limited. These post-curing agents may be used alone in 1 kind, or 2 or more kinds may be appropriately selected and used in combination.

In the case where the matrix material is, for example, a chemical gel compound having unreacted reactive groups as described above, the same or different type of curing agent as the post-curing agent may be used in order to crosslink a part of the reactive groups first to form a semi-cured gel (gel electrolyte). In this case, the curing agent used first to achieve a semi-cured state is referred to as a "pre-curing agent" separately from the post-curing agent.

The reactive groups contained in the gel electrolyte increase the degree of curing of the gel electrolyte through crosslinking. Specific types of the reactive groups are not particularly limited, and suitable reactive groups can be selected depending on the composition of the gel electrolyte, the type of the application (electrochemical device), and the like. For example, in the embodiments described later, a lithium ion battery is exemplified as an example of an electrochemical device, and the polymer-based or inorganic-based materials described above are exemplified as the matrix material. In this case, the reactive groups exemplified below can be used as appropriate.

As specific reactive groups, there may be mentioned: double-bond functional groups such as (meth) acrylic groups (acrylic groups and methacrylic groups) and allyl groups; epoxy, oxetanyl epoxide (oxirane) type functional groups; a thiol group; a combination of functional groups of a condensation reaction system such as an amino group, a carboxyl group (amide bond), a hydroxyl group, and a carboxyl group (ester bond); a combination of isocyanate-reactive functional groups such as an isocyanate group, a hydroxyl group (urethane bond), an isocyanate group, and an amino group (urea bond); and the like. In the gel electrolyte (gel), these functional groups (or combinations of functional groups) may be contained in only 1 kind, or may be contained in 2 or more kinds. In addition, in the case where the matrix material is a chemical gel compound having unreacted reactive groups, the compound may also have a structure having at least 1 of these functional groups (or a combination thereof).

The electrolyte solution constituting the gel electrolyte may be any electrolyte solution that can exhibit an electrochemical reaction in an electrochemical device. The more specific structure of the electrolytic solution is not particularly limited, as with the matrix material, and an electrolytic solution of an appropriate composition can be used appropriately depending on the composition and application (electrochemical device) of the gel electrolyte, the type of the electrolytic solution and the matrix material constituting the gel electrolyte, and the like.

As described above, the electrolyte solution in the present invention may be a composition composed of at least an ionic substance and an electrolyte solution solvent. In the present embodiment, the electrolyte solvent refers to a solvent of an electrolyte constituting an electrochemical device. In addition, as the ionic substance, various salts can be used. For example, in the examples described below, a lithium ion battery is illustrated as an example of an electrochemical device, and therefore, in the present embodiment, a lithium salt is used as an ionic material.

As the lithium salt, there are typically mentioned: lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium hexafluorophosphate (LiPF)₆) Lithium bis (fluorosulfonyl) imide (LiFSI), lithium perchlorate (LiClO)₄) Lithium tetraborate (LiBF)₄) And the like, but are not particularly limited.

When the electrochemical device is a lithium ion battery, examples of the electrolyte solvent include: carbonate solvents, ionic liquids, nitrile solvents, ether solvents, and the like, but are not particularly limited.

As representative electrolyte solvents, there may be mentioned: a mixed solvent of a cyclic carbonate and a chain carbonate. As the cyclic carbonate, there are typically mentioned: ethylene Carbonate (EC) or Propylene Carbonate (PC), and as chain carbonates, there are typically mentioned: dimethyl carbonate (DMC), diethyl carbonate (DEC), Ethyl Methyl Carbonate (EMC), and the like, but are not particularly limited.

In addition, as other typical electrolyte solvents, ionic liquids can be cited. Specifically, for example, there may be mentioned: 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, diethylmethyloxyethylammonium bis (trifluoromethanesulfonyl) imide, diethylammonium bis (fluorosulfonyl) imide, diallyldimethylammonium (trifluoromethanesulfonyl) imide, diallyldimethylammonium (fluorosulfonyl) imide and the like, but are not particularly limited.

The gel electrolyte before the increase in the degree of solidification may contain other components (other components) in addition to the matrix material and the electrolytic solution. The post-curing agent is exemplified as the other component, but other than these, various additives are exemplified. Specific examples of the additives include initiators used for promoting a crosslinking reaction of uncrosslinked reactive groups contained in the matrix material. For example, in examples described later, 2' -azobis (2, 4-dimethylvaleronitrile) was used as an initiator.

[ structures 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) may be in the range of 0.03 to 6.5 mass% with respect to the mass of the electrolyte solvent. In the gel electrolyte according to the present invention, the shear elastic modulus may be 1MPa or more. That is, the gel electrolyte according to the present invention satisfies both of the "first condition" in which the mass ratio of the unreacted reactive group is limited within a predetermined range and the "second condition" in which the lower limit of the shear elastic modulus in a state in which the reactive group is 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, may be calculated 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), as described above. 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 is preferably in the range of 0.03 to 6.5 mass% relative to the mass of the electrolyte solvent contained in the gel electrolyte.

By allowing the gel electrolyte to satisfy the first condition, an appropriate amount of unreacted reactive groups is contained in the gel electrolyte in an uncured state. Therefore, even if the crosslinking reaction of the reactive group proceeds to become a hard gel electrolyte, the hard gel electrolyte can hold a sufficient amount of the electrolytic solution. In addition, as the crosslinking reaction proceeds, a part of the electrolyte may leak from the matrix material. Therefore, if an electrochemical device is produced using an uncured gel electrolyte and then a crosslinking reaction is performed, the leaked electrolyte can be brought into good contact with the contact surface of the electrode of the electrochemical device. Accordingly, a favorable electrochemical reaction can be achieved in the electrochemical device.

The second condition of the gel electrolyte, that is, the shear elastic modulus of the gel electrolyte in an uncured state, may be measured or evaluated according to a known measurement method or evaluation method. In the examples described later, the gel electrolyte obtained in each example or comparative example in an uncured state was subjected to a bench precision universal tester (product name: AUTOGRAPH AGS-X) manufactured by Shimadzu corporation

The press-fitting jig of (1) was subjected to a press-fitting test at a speed of 0.05 mm/min after applying a preliminary load of 0.05N, and the shear modulus (unit: MPa) was measured from the results of the press-fitting test by using the following formula (1).

Modulus of elasticity in shear (G) ═ 0.36Fg [ (D-h)/h]^3/2/R²(1)

Where F in the above formula (1) is the load (test force) of the press-in test, g is the gravitational acceleration, D is the thickness (film thickness) of the gel electrolyte (gel), h is the change in thickness (film thickness) due to the load, and R is the spherical radius of the spherical indenter of the press-in test. In addition, in the calculation of the shear elastic modulus using the above formula (1), reference 1 is referred to: d JTaylor and A M Kragh, "Determination of the fundamental module of the software coatings by indexing mechanisms" Journal of Physics D: Applied Physics, United Kingdom, IOP Publishing, January 1970, Volume 3, Number 1, 29.

By allowing the gel electrolyte to satisfy the second condition and be in an uncured state, the shear modulus of elasticity of the gel electrolyte is 1MPa or more, and therefore the gel electrolyte has good strength. Therefore, the gel electrolyte can achieve good operability, and thus can suppress the increase in the efficiency of manufacturing an electrochemical device. Further, as described above, since the electrochemical device is manufactured using the gel electrolyte in an uncured state and then the crosslinking reaction is performed, the liquid injection step is not required in the manufacturing 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 a good strength cannot be achieved in the cured hard gel electrolyte, and there is a possibility that short-circuiting and the like are likely to occur. In addition, as the crosslinking reaction proceeds, the amount of electrolyte leakage decreases, and there is a possibility that the electrolyte cannot be brought into good contact with the contact surface of the electrode of the electrochemical device, and sufficient performance cannot be achieved in the electrochemical device.

The upper limit of the mass ratio of the reactive group to the mass of the electrolyte solvent may be 6.5 mass% or less, preferably 6.3 mass% or less, and more preferably 6.0 mass% or less. 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 becomes excessive, and the ion conductivity of the hard gel electrolyte decreases, and there is a possibility that sufficient performance cannot be achieved in an electrochemical device. Further, as the crosslinking reaction proceeds, the amount of leakage of the electrolytic solution increases, and there is a possibility that a sufficient amount of the electrolytic solution cannot be held in a cured state (hard gel electrolyte).

The shear modulus of the gel electrolyte in the uncured state, which is the second condition, may be 1MPa or more, preferably 2MPa or more, and more preferably 5MPa or more, as long as the lower limit thereof is 1MPa 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 handling property is also lowered, and there is a possibility that the efficiency of manufacturing (manufacturing) an electrochemical device is not increased. The upper limit of the shear elastic modulus is not particularly limited as long as a sufficient amount of the electrolytic solution can be retained in the cured hard gel electrolyte.

In the gel electrolyte according to the present invention, in addition to the first condition and the second condition described above, either one of a third condition and a fourth condition, more preferably both of the third condition and the fourth condition, is preferably satisfied, where the third condition is a range in which the mass of the electrolyte solvent is 20 mass% or more and 80 mass% or less with respect to the total mass of the gel electrolyte (gel), and the fourth condition is a range in which the mass of the matrix material is 1.0 mass% or more and 10 mass% or less with respect to the total mass of the gel electrolyte (gel).

By allowing the gel electrolyte to satisfy the third condition, a more appropriate amount of the electrolytic solution is retained in either one of the gel electrolyte and the hard gel electrolyte. Therefore, good ionic 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 the gel electrolyte or 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 appropriately formed according to various conditions such as the type and the application of the electrochemical device. In particular, in the present invention, the gel electrolyte is in a gel state, and therefore can be easily formed into a desired shape. For example, in the embodiment described below, a lithium ion battery is illustrated as an example of an electrochemical device, and therefore, a sheet shape is given as an example of a shape of a gel electrolyte.

When the gel electrolyte is in the form of a sheet, the thickness (the thickness of the gel electrolyte) is not particularly limited, but generally, it may be in the range of 5 μm to 100 μm. If the thickness of the sheet-like gel electrolyte is outside this range, the battery performance (or the performance of another electrochemical device) may not be sufficiently exhibited, although the thickness depends on various conditions such as the type, size, and specific shape of the lithium ion battery (or another electrochemical device).

The hard gel electrolyte is an electrolyte in which the hardness is increased by allowing a crosslinking reaction of 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, it is preferable that either 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 satisfied, and it is more preferable that both the first condition and the second condition are 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, a good electrochemical reaction may not be achieved depending on the type of electrochemical device, and thus sufficient performance may not 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. On the other hand, if the shear elastic modulus of the hard gel electrolyte is less than 6MPa, the electrolyte layer may not be well retained depending on the type of electrochemical device, and thus sufficient performance may not be exhibited.

As described above, if the crosslinking reaction of the reactive groups is advanced in the uncured gel electrolyte to increase the hardness, the cured gel electrolyte is obtained, but the shear elastic modulus of the cured gel electrolyte is 6 MPa. It is needless to say that the hardness of the gel electrolyte may be measured by a known measurement method and the cured state may be judged based on the numerical value of the hardness, the rate of increase in hardness, or the like, but in the present invention, the strength of the uncured gel electrolyte and the hard gel electrolyte is evaluated based on the shear elastic modulus, and therefore, if the shear elastic modulus of the gel electrolyte after the hardness is increased is 6MPa or more, it can be judged 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 dilution solvents, a second method using 1 dilution solvent, and a third method without using a dilution solvent. The diluting solvent is a component different from the electrolyte solvent and is a component removed before the reactive group contained in the gel (gel electrolyte) undergoes a crosslinking reaction. Therefore, the gel electrolyte according to the present invention may contain a diluting solvent as a component other than the matrix material and the electrolytic solution.

The third condition and the fourth condition in the uncured gel electrolyte, 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 excluding the diluting solvent. This is because, as described above, the diluting solvent is removed before the crosslinking reaction of the reactive group, in other words, because the diluting solvent is not substantially contained in the hard gel electrolyte in a cured state.

The specific type of the diluting solvent is not particularly limited, and may be appropriately selected depending on various conditions such as the type of the electrochemical device, the type of the matrix material, and the composition of the electrolyte solution. For example, in the embodiment described later, since a lithium ion battery is exemplified as an example of the electrochemical device, the following solvents can be used as appropriate as the diluting solvent.

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-based solvents such as N-methylpyrrolidone (NMP); lactone solvents such as γ -butyrolactone (GBL); carbonate-based solvents such as Ethylene Carbonate (EC), Propylene Carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and Ethyl Methyl Carbonate (EMC); and the like. Of these solvents, 1 kind may be used as the diluting solvent of the present invention, and 2 or more kinds may be appropriately selected and used. When 2 or more of these solvents are used, each solvent may be used for different dilution purposes, or may be used as a mixed solvent in which 2 or more solvents are mixed.

The first method using 2 types of diluting solvents in the typical production method of the gel electrolyte according to the present invention will be described.

In the first method, first, a matrix material and a first diluent solvent are mixed to form a gel (non-electrolyte gel) containing no electrolyte solution (non-electrolyte gel forming step). The method of mixing the matrix material and the first diluting solvent is not particularly limited, but a method of dissolving the matrix material in the first diluting solvent by heating the matrix material and the first diluting solvent is typically exemplified. After the dissolution, the non-electrolyte gel is obtained by, for example, cooling to room temperature. The first diluting solvent may be referred to as a gel-diluting solvent used for forming a non-electrolyte gel.

Next, in the first method, an electrolyte component (lithium salt or the like), an electrolyte solvent, and other components (a post-curing agent, an initiator, and the like) are dissolved in a second diluent solvent to prepare a diluted solution of the electrolyte solution and the like. For convenience of explanation, this diluted solution is 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 (substitution solution addition step). The method of adding the substitution solution is not particularly limited, and examples thereof include coating or accumulating the substitution solution on the non-electrolyte gel. The added replacement solution is absorbed by the non-electrolyte gel, and thus a gel containing a diluting solvent is obtained.

In the first method, the diluting solvent is then removed from the gel containing the diluting solvent (diluting solvent removing step). The method for removing the diluting solvent is not particularly limited, and for example, the diluting solvent may be evaporated and distilled off under reduced pressure or at high temperature. In this step, although both the diluting solvent for gel and the diluting solvent for replacement are removed, if attention is paid to the initially formed non-electrolyte gel, the diluting solvent for gel contained in the non-electrolyte gel is replaced with the electrolyte solution. The gel electrolyte according to the present invention may be a gel containing a diluting solvent, or may be a gel obtained by removing the diluting solvent. That is, the diluting solvent may be removed immediately before the electrochemical device is manufactured (manufactured), or the diluting solvent may be removed in advance.

Next, a second method using 1 type of diluting solvent in a typical production method of a 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 a diluting solvent. For convenience of explanation, this 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 (lithium salt or the like), an electrolyte solution solvent, and other components (a post-curing agent, an initiator, and the like) in a diluting solvent of the same type as the solution a. For convenience of explanation, this diluted solution such as the electrolytic solution 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 obtained mixed liquid is molded into a predetermined shape (mixing molding step). The method of 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, since a lithium ion battery is exemplified as an example of an electrochemical device, 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. Thereby, a gel containing a diluting solvent is formed. Then, the diluting solvent is removed from the gel containing the diluting solvent in the same manner as in the first method (diluting solvent removing step).

Next, a third method without using a diluting solvent in a typical production method of a 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 electrolytic solution 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 is referred to as "solution a" as in the second method (solution a preparation step). Next, an electrolyte component (lithium salt or the like) and other components (a post-curing agent, an initiator, and the like) are dissolved in an electrolyte solvent of the same type as or different from the solution a to prepare an electrolyte solvent solution such as an electrolyte solution. For convenience of explanation, the solution such as the electrolyte solution is referred to as "solution B" as in the second method (solution B preparation step). Then, the prepared solution a and solution B are mixed, and the resulting mixed solution is molded into a predetermined shape (mixing molding step). Based on this, a gel-like body containing an electrolytic solution or the like, i.e., a gel electrolyte, is obtained.

These first, second and third methods each have unique advantages in manufacturing, and therefore it is impossible to tell 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 is substituted with the electrolytic solution 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, the positive electrode or the negative electrode can be used as a support, and the mixed solution can be applied to the positive electrode or the negative electrode when the lithium ion battery is manufactured. Therefore, the number of manufacturing steps of the lithium ion battery can be reduced as compared with the first method, and thus the method for manufacturing the lithium ion battery can be simplified. Further, in the third method, the electrolyte solvent is used without using a dilution solvent. Because the gel electrolyte can be obtained by merely forming the mixed solution into a predetermined shape, 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 method for manufacturing the electrochemical device can be simplified.

[ electrochemical device ]

Next, a typical 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 utilizing an electrochemical reaction (a device capable of converting chemical energy and electrical energy), and a typical structure includes a pair of electrodes and an electrolyte interposed 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 respectively configured as 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 as appropriate depending on 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 powder (or particles) of an electrode material (active material) on the surface of an electrode substrate in a layer form is mentioned. As a method for forming such a powdery material into a layer, there is a method of mixing a powder of an electrode material (active material) in an organic vehicle (solvent, binder resin, or the like) to be gelatinized, applying the gelatinized powder to the surface of an electrode base material, and drying, curing, or firing the pasted powder.

The electrolyte of the electrochemical device is present between the pair of electrodes, but in the present invention, as described above, the electrolyte may be a hard gel electrolyte in a cured state in which the degree of curing of the gel electrolyte in an uncured state is increased.

In addition, a 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 thereto, and the electrochemical device may have a pair of electrodes and a gel electrolyte or a structural element or member other than a hard gel electrolyte. The specific structure of such other constituent elements or other members is not particularly limited, and various constituent elements or elements corresponding to specific types of electrochemical devices can be used.

More specific examples of the structure of the electrochemical device according to the present invention include: 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 the electrochemical device according to the present invention, will be specifically described with reference to fig. 1.

As shown in fig. 1, a lithium ion battery 10, which is one of electrochemical devices, has the following structure: the positive electrode 12 and the negative electrode 13 are provided as a pair of electrodes, and the hard gel electrolyte 14 is held between the positive electrode 12 and the negative electrode 13. For convenience of description, a structure in which the positive electrode 12, the hard gel electrolyte 14, and the negative electrode 13 are stacked (a structure in which the hard gel electrolyte 14 is held on the positive electrode 12 and the negative electrode 13) is referred to as a stacked 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 21 (the surface facing the negative electrode 13 and 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 31 (the surface facing the positive electrode 12 and in contact with the hard gel electrolyte 14).

The cathode substrate 21 and the anode substrate 31 function as current collectors that collect electrons generated by the electrochemical reaction of the cathode active material layer 22 and the anode active material layer 32. Specific configurations of the positive electrode base 21 and the negative electrode base 31 are not particularly limited, and a known metal plate or metal foil may be used. In the examples described later, aluminum foil was used as the positive electrode substrate 21. In addition, as the negative electrode substrate 31, a copper foil is typically used.

The positive electrode active material used in the positive electrode active material layer 22 is typically a lithium salt of a transition metal oxide, but is not particularly limited. In the 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, typically, a lithium metal foil or a carbon material is used. In the examples described later, lithium metal foil was used as the negative electrode active material. The positive electrode active material layer 22 may be composed of only the positive electrode active material, and the negative electrode active material layer 32 may be composed of only the negative electrode active material.

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 assistant 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. From the viewpoint of increasing the frequency of contact with the positive electrode active material layer 22 or the negative electrode active material layer 32, the coating solution may contain a gel electrolyte before the degree of curing is increased or a gel electrolyte (hard gel electrolyte component) after the degree of curing is increased to the same extent as that of the hard gel electrolyte 14.

The positive electrode active material layer 22 constitutes an opposed surface of the positive electrode 12 opposed to the negative electrode 13 and also constitutes a contact surface with the hard gel electrolyte 14. Similarly, the negative electrode active material layer 32 constitutes an opposed surface of the negative electrode 13 opposed to the positive electrode 12, and constitutes a contact surface with the hard gel electrolyte 14. Therefore, as described above, at least either one of the cathode active material layer 22 and the anode active material layer 32 is preferably formed in a porous state.

The method for forming these active material layers 22 and 32 in a porous state is not particularly limited, and various known methods can be used. Typically, as described above, a method of applying and drying a paste containing an active material is exemplified. In addition, any one of the active material layers 22 and 32 may not be porous. In the later-described embodiment, the cathode active material layer 22 is formed in a porous state, but the anode active material layer 32 is formed only of lithium foil.

Since the lithium foil doubles as a current collector (negative electrode base material 31) together with the negative electrode active material, in the example described later, the negative electrode 13 is formed of only the lithium foil. Therefore, at least one of the cathode 12 and the anode 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 the reactive groups contained in the gel electrolyte in an uncured state to cause a crosslinking reaction, thereby increasing the degree of curing of the gel electrolyte.

The sealing material 15 is not particularly limited as long as it can seal the stacked 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 can be representatively exemplified. The laminate film is typically a laminate 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: and a known sealing agent such as a thermoplastic ionomer resin.

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 have a separator, or may have components other than the positive electrode 12, the negative electrode 13, and the hard gel electrolyte 14.

Thus, according to the present invention, a proper amount of reactive groups are contained in the gel electrolyte in an uncured state. Therefore, even in a gel electrolyte (hard gel electrolyte) in which the reactive groups have sufficiently undergone the crosslinking reaction, the hard gel electrolyte can retain a sufficient amount of the electrolytic solution. In addition, as the crosslinking reaction proceeds, a part of the electrolyte can also leak out of the matrix material. Therefore, if the electrochemical device is produced using a gel electrolyte in a state in which the gel electrolyte is not sufficiently cured (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 included in the electrochemical device. Accordingly, a favorable 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 therefore the gel electrolyte has good strength. Therefore, good operability can be achieved in the gel electrolyte, and thus, non-high efficiency in the production of the electrochemical device can be suppressed. In addition, 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.

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. Those skilled in the art can make various changes, modifications and alterations without departing from the scope of the present invention. In the following examples, various synthetic reactions, measurement and evaluation of physical properties, and the like were performed as follows.

(measurement of shear elastic modulus of gel electrolyte)

The gel electrolyte obtained in each example or each comparative example had a shear modulus of elasticity measured by a bench precision universal tester (product name: AUTOGRAPH AGS-X) manufactured by Shimadzu corporation

The press-fitting jig of (1) was subjected to a press-fitting test at a speed of 0.05 mm/min after applying a preliminary load of 0.05N, and based on the result of the press-fitting test, the shear modulus (unit: MPa) was measured by using the following formula (1) with reference to the above reference 1.

Modulus of elasticity in shear (G) ═ 0.36Fg [ (D-h)/h]^3/2/R²(1)

(F: load (test force) of indentation test, g: gravitational acceleration, D: thickness (film thickness) of gel electrolyte (gel), h: change in thickness (film thickness) due to load, R: spherical radius of spherical indenter of indentation 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. The gel electrolyte was sandwiched between stainless steel foils and then allowed to stand in a thermostatic bath at 80 ℃ for 12 hours to undergo a crosslinking reaction, and the temperature was returned to room temperature, thereby turning the gel electrolyte into a hard gel electrolyte. The volume resistance of the gel electrolyte was measured by Electrochemical Impedance Spectroscopy (EIS) using an impedance analyzer (product name: SP-150) manufactured by BIOLOGIC corporation (Bio-Logic SAS) at a frequency of 1MHz to 0.1 Hz. 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 Battery Performance of electrochemical device)

The evaluation coin cells (electrochemical devices according to the present invention) obtained in each example or each comparative example were subjected to charge at a time rate of 0.1C at 25 ℃ and discharge at a time rate of 0.1C to 1C using a charge/discharge test device (product name: TOSCAT3100, manufactured by tokyo systems corporation), and evaluated for a capacity retention rate (Q1C/Q0.1C) of 1C discharge capacity to 0.1C discharge capacity.

The evaluation was "○" (good) if the capacity retention rate was 90% or more, "△" (normal) if the capacity retention rate was 70% or more, and "x" (unsuitable) if the capacity retention rate was less than 70%.

(evaluation of element stability of electrochemical device)

In each example or each comparative example, 10 coin cells for evaluation (electrochemical device according to the present invention) were prepared in total, and an element stability test was performed by using a charge/discharge test device (product name: TOSCAT3100) manufactured by toyoyo systems corporation, charging was performed at a time rate of 1C under a condition of 25 ℃, and discharging was performed 100 times under a condition of a time rate of 1C, and the prepared 10 coin cells for evaluation were evaluated as "○" (good) if short circuit occurred in 1 or less, as "△" (normal) if short circuit occurred in less than 5, and as "x" (inappropriate) if short circuit occurred in 5 or more.

(example 1)

The following operations were carried out 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 KUREHA K.K.: KF POLYMER #7200) as a matrix material was dissolved by heating at 80 ℃ in 33 parts by mass of acetone (manufactured by Wako pure chemical industries, Ltd.) as a diluting solvent for gel, and the resulting solution was allowed to stand at room temperature to prepare a 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, 49 parts by mass of 1-ethyl-3-methylimidazolium bis (fluorosulfonyl) imide (EMImFSI, first Industrial pharmaceutical Co., Ltd., product name: Elexcel IL-110) as an electrolyte solvent of an ionic liquid system, 1.3 parts by mass of tetrafunctional polyether acrylate (product name: Elexcel TA-210, first Industrial pharmaceutical Co., Ltd., product name: Elexcel TA-210) as a post-curing agent, 0.49 parts by mass of 2, 2' -azobis (2, 4-dimethylvaleronitrile) (Wako pure chemical Co., Ltd., product name; V-65) as an initiator of an azo system, and 3.8 parts by mass of Acetonitrile (ACN) as a diluting solvent for substitution were mixed and mixed, a displacement solution is prepared.

The substitution solution was added to PVDF/acetone gel, and acetone (a dilution solvent for gel) and acetonitrile (a dilution solvent for substitution) were distilled off at room temperature under vacuum to prepare (produce) a 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, and the molecular weight of 4 acrylate groups contained in 1 molecule was 220, so that the mass of acrylate groups contained in 1g of the tetrafunctional polyether acrylate was 0.02 g.

As described above, in example 1, the amount of tetrafunctional polyether acrylate 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 EMImFSI added as an 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 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 was within a range of 20 to 80 mass%, and the mass ratio of the matrix material to the total mass was 2.9 mass% and was within a range of 1.0 to 10 mass%.

LiNi as a positive electrode active material was weighed_1/3Mn_1/3Co_1/3O₂100g of acetylene Black (product name: Denka Black HS-100, manufactured by DENKA K.K.) 7.8g as a conductive auxiliary, 3.3g of polyvinylidene fluoride (PVDF, manufactured by KUREHA, having a weight average molecular weight Mw of 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 to prepare a coating liquid of a positive electrode active material layer having a solid content of 51%. The coating liquid was applied on an aluminum foil (positive electrode substrate) having a thickness of 15 μm with a coating apparatus, dried at 130 ℃ and then subjected to a roll-pressing treatment to obtain a coating film having a thickness of 2.3mg/cm²The positive electrode active material layer of (3).

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 with a diameter of 14mm, and sealed in a button cell holder to prepare a sealed body. The sealed body was left to stand in a thermostatic bath at 80 ℃ for 12 hours to sufficiently progress the crosslinking reaction of the reactive groups contained in the gel electrolyte (to cure the gel electrolyte to become a hard gel electrolyte), and then was returned to room temperature. In this manner, a button cell (lithium ion battery) for evaluation, which is the electrochemical device according to example 1, was produced (manufactured).

The gel electrolyte of example 1 was measured or evaluated for shear elastic modulus, film thickness, and ion 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 1.

(examples 2 and 3)

A gel electrolyte according to example 2 or a gel electrolyte according to example 3 was produced, and a coin cell for evaluation as an electrochemical device according to example 2 or an electrochemical device according to example 3 was produced, in the same manner as in example 1, except that the amount of the electrolyte solution solvent and the amount of the post-curing agent were changed as shown in table 1.

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%.

The obtained gel electrolyte according to example 2 or 3 was measured or evaluated for shear elastic modulus, film thickness, and ion conductivity as described above, and the obtained coin cell for evaluation was evaluated for battery performance and element stability (short circuit). 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, as in examples 1 to 3. As shown in Table 2, 2.9 parts by mass of a vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP, manufactured by KUREHA K.K., product name: KFPOLYMER #8500, abbreviated as "PVDF-HFP [1 ]" in Table 2) as a matrix material was dissolved by heating at 80 ℃ in 29.5 parts by mass of dimethyl ether (DME, manufactured by Wako pure chemical industries, Ltd.) as a diluting solvent. Based on this, solution 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 to prepare a solution B as a DME diluent for an electrolyte solution 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 (dilution solvent) was distilled off under vacuum at room temperature to prepare (produce) a laminate of the gel electrolyte and the positive electrode according to example 4.

As shown in table 2, in the gel electrolyte according to example 4, as a post-curing agent, a tetrafunctional polyether acrylate was blended 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 punched into a circular shape having a diameter of 14mm, and a lithium foil having a diameter of 14mm as a negative electrode was bonded to the gel electrolyte side of the obtained punched body, thereby providing a bipolar battery (トムセル). In this manner, a button cell (lithium ion battery) for evaluation, which is an electrochemical device according to example 4, was produced (manufactured).

The obtained gel electrolyte (gel electrolyte/positive electrode laminate) according to example 4 was measured or evaluated for shear elastic modulus, film thickness, and ion conductivity as described above, and the obtained coin cell for evaluation was evaluated for battery performance and element stability (short circuit). The results are shown in Table 2.

(examples 5 to 13)

The amount of the electrolyte solvent and the amount of the post-curing agent were changed as shown in Table 2 (examples 5 and 6), or difunctional polyether acrylate (product name: MP-150, first Industrial pharmaceutical Co., Ltd.) was used as the post-curing agent and the amount of the electrolyte solvent was changed as shown in Table 2 or 3 (examples 7 to 9), or polyethylene glycol diacrylate (product name: Elexcel EG2500, first Industrial pharmaceutical Co., Ltd.) 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 (product name: Elexcel ACG-127, first Industrial pharmaceutical Co., Ltd.) was used as the post-curing agent and the amount of the electrolyte solvent was changed as shown in Table 3 (examples 11 to 13), except for the above, gel electrolytes according to examples 5 to 13 were produced in the same manner as in example 4. Further, coin cells for evaluation as electrochemical devices according to examples 5 to 13 were produced using these gel electrolytes.

In the gel electrolytes according to examples 7 to 9, the crosslinkable reactive group is 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 11000, and the molecular weight of 2 acrylate groups contained in 1 molecule was 110, so that the mass of acrylate groups contained in 1g of the difunctional polyether acrylate was 0.010 g.

For example, in example 7, as shown in table 2, the blending 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 EMImFSI added as an 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 in the range of 0.03 to 6.5 mass%.

Similarly, as shown in table 2 or table 3, in the gel electrolyte according to example 8 or example 9, as the post-curing agent, a bifunctional polyether acrylate was also blended 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 both were in the range of 0.03 to 6.5 mass%.

In addition, in the gel electrolyte according to example 10, the crosslinkable reactive group was an acrylate group contained in polyethylene glycol diacrylate (product name: Elexcel EG2500) 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 0.033 g.

In example 10, as shown in table 3, the blending amount of polyethylene glycol diacrylate as the 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 EMImFSI added 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 group contained in a methyl methacrylate-oxetanyl methacrylate copolymer (product name: Elexcel ACG-127) as a post-curing agent. Since 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, the mass of the oxetane moiety contained in 1g of the methyl methacrylate-oxetanyl methacrylate copolymer was 0.13 g.

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 part by mass. Therefore, the mass of the reactive group (oxetane portion) contained in the gel electrolyte according to example 11 was 0.015 part by mass. In example 11, as shown in table 3, the amount of EMImFSI added as an electrolyte solvent was 29 parts by mass. 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 in the range of 0.03 to 6.5 mass%.

Similarly, as shown in table 3, in the gel electrolyte according to example 12 or example 13, a methyl methacrylate-oxetanyl methacrylate copolymer was also blended as a post-curing agent 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, as a post-curing agent, a tetrafunctional polyether acrylate was blended 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 within a range of 20 to 80 mass%, and the mass ratio of the matrix material to the total mass was within a range of 1.0 to 10 mass%.

The obtained gel electrolytes according to examples 5 to 13 were measured or evaluated for the shear elastic modulus, the film thickness, and the ion conductivity as described above, and the obtained evaluation coin cells were evaluated for the cell performance and the element stability (short circuit). 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 (product name: KFPOLYMER #9300, manufactured by KURIHA corporation; abbreviated as "PVDF-HFP 2" in Table 4) which is different from those of examples 4 to 13 was used as a matrix material (example 14), silica particles (product name: AEROSIL200, manufactured by JAPONIC corporation; abbreviated as "silica" in Table 4) which were inorganic particles were used as a matrix material (example 15), or silica/alumina mixed particles (product name: AEROSIL COK84, manufactured by JAPONIC corporation; abbreviated as "silica/alumina" in Table 4) which were inorganic particles were used as a matrix material (example 16), gel electrolytes according to examples 14 to 16 were produced in the same manner as in example 4, except that the amounts of the electrolyte solvent and the post-curing agent were changed. Further, coin cells for evaluation as electrochemical devices according to examples 14 to 16 were produced using these gel electrolytes.

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 obtained gel electrolytes according to examples 14 to 16 were measured or evaluated for the shear elastic modulus, the film thickness, and the ion conductivity as described above, and the obtained evaluation coin cells were evaluated for the cell performance and the element stability (short circuit). 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, as in examples 1 to 16. As shown in Table 5, 1.0 part by mass of PVDF-HFP [2] (product name: KFPOLYMER #9300, manufactured by KURIKA, K.K.) similar to that of example 14 was dissolved by heating at 80 ℃ in 39.5 parts by mass of a mixture (mixed electrolyte solvent) of 55 parts by mass of dimethyl carbonate (DMC, LBG, manufactured by KISHIDA chemical Co., Ltd.) and 5.3 parts by mass of ethylene carbonate (EC, LBG, manufactured by KISHIDA chemical Co., Ltd.) as a carbonate-based electrolyte solvent. Based on this, solution a was prepared as a DMC diluted solution of PVDF-HFP.

Further, as shown in table 5, lithium hexafluorophosphate (LiPF) as a lithium salt was used₆Solution B was prepared by mixing 14 parts by mass of LBG manufactured by KISHIDA chemical co., ltd., 39.5 parts by mass of a mixed electrolyte solvent of DMC and EC, 0.90 parts by mass of tetrafunctional polyether acrylate (see example 1) as a post-curing agent, and 0.30 parts by mass of azo initiator (see example 1) as an initiator. As shown in table 5, in this example, no dilution 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 punched into a circular shape having a diameter of 14mm, and a lithium foil having a diameter of 14mm as a negative electrode was bonded to the gel electrolyte side of the obtained punched body to provide a bipolar battery (トムセル). In this manner, a button cell (lithium ion battery) for evaluation, which is an electrochemical device according to example 17, was produced (manufactured).

The shear elastic modulus, film thickness, and ion conductivity were measured or evaluated as described above for the obtained gel electrolyte (gel electrolyte/positive electrode laminate) according to example 17, and the battery performance and element stability (short circuit) were evaluated for the obtained coin cell for evaluation. The results are shown in Table 5.

(examples 18 to 20)

As shown in table 5, gel electrolytes according to examples 18 to 20 were prepared in the same manner as in example 17 except that the carbonate electrolyte solvent used for the preparation of solution a was changed to ethyl methyl carbonate (EMC, manufactured by KISHIDA chemical co., ltd., LBG, example 18), diethyl carbonate (DEC, manufactured by KISHIDA chemical co., ltd., LBG, example 19) or propylene carbonate (PC, manufactured by KISHIDA chemical co., ltd., LBG, example 20), and the amount of PC and EC (example 20) were changed when PC was used. Further, coin cells for evaluation as electrochemical devices according to examples 18 to 20 were produced using these gel electrolytes.

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, the film thickness, and the ion conductivity of the obtained gel electrolytes according to examples 18 to 20 were measured or evaluated as described above, and the battery performance and the element stability (short circuit) of the obtained evaluation coin cells were evaluated. The results are shown in Table 5.

[ Table 5]

(examples 21 to 26)

As shown in Table 6, the mass ratio of the reactive group to the electrolyte solvent in the gel electrolyte was in the range of 0.03 to 6.5 mass%, however, in addition to the above, 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 ionic conductivity was made to be less than 0.8mS/cm (example 23), the mass ratio of the matrix material to the total mass in 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 respective components were changed, gel electrolytes according to examples 21 to 26 were produced in the same manner as in example 4 (examples 21 and 23 to 26) or in the same manner as in example 17 (example 22, but only 1 type of EC was used as the electrolyte solvent). Further, coin cells for evaluation as electrochemical devices according to examples 21 to 26 were produced using these gel electrolytes.

The shear modulus, the film thickness, and the ion conductivity of the obtained gel electrolytes according to examples 21 to 26 were measured or evaluated as described above, and the battery performance and the element stability (short circuit) of the obtained evaluation coin cells were evaluated. The results are shown in Table 6.

[ Table 6]

Comparative examples 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 prepared and a coin cell for evaluation was prepared as the electrochemical device according to comparative example 1 or the electrochemical device according to comparative example 2, except that the mass ratio of the reactive group to the electrolyte solution solvent in the gel electrolyte was made less than 0.03 mass% (comparative example 1) or more than 6.5 mass% (comparative example 2) and the amounts of the respective components were changed, in the same manner as in example 4 described above.

The gel electrolyte according to the obtained comparative example 1 or 2 was measured or evaluated for shear elastic modulus, film thickness, and ion conductivity as described above, and the obtained coin cell for evaluation was evaluated for battery performance and element stability (short circuit). 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, the gel electrolyte according to the present invention satisfies the first condition and the second condition, and thus an electrochemical device (lithium ion battery) having good performance can be manufactured. In contrast, it is found that the performance of the electrochemical device cannot be sufficiently obtained particularly when the first condition is not satisfied.

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, it is possible to manufacture an electrochemical device (lithium ion battery) having more excellent performance by satisfying at least one of the third condition and the fourth condition in addition to the first condition and the second condition.

Further, as is clear from comparison among 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 produced by any one of the first, second, and third methods can produce an electrochemical device (lithium ion battery) having good performance.

The present invention is not limited to the above embodiments, and various modifications can be made 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, or gel actuators.

Claims

1. A gel electrolyte characterized in that,

the gel electrolyte is a gel-like body composed of at least a matrix material and an electrolytic solution and contains a crosslinkable reactive group,

the gel electrolyte is cured by a crosslinking reaction of the reactive group, 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 reactive group contained in the gel is in a range of 0.03 to 6.5 mass% with respect to the mass of the electrolyte solvent, and

the gel has a shear elastic modulus of 1MPa or more in a state where the reactive group is unreacted.

2. A gel electrolyte according to claim 1,

the gel contains a post-curing agent having the reactive group in addition to the matrix material and the electrolyte solution.

3. A gel electrolyte according to claim 1 or 2,

the mass of the electrolyte solvent is in a range of 20 mass% to 80 mass% with respect to the total mass of the gel.

4. A gel electrolyte according to any one of claims 1 to 3,

the mass of the matrix material is in a range of 1.0 mass% to 10 mass% with respect to the total mass of the gel.

5. A gel electrolyte according to claim 3 or 4,

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 specified with respect to the total mass of the gel except for the diluting solvent.

6. A gel electrolyte according to any one of claims 1 to 5,

the gel is in the shape of a sheet.

7. A gel electrolyte according to claim 6,

the gel has a thickness of 5 to 100 [ mu ] m.

8. A hard gel electrolyte characterized in that,

the hard gel electrolyte is obtained by subjecting the reactive group in the gel electrolyte according to any one of claims 1 to 7 to a crosslinking reaction to increase the hardness of the gel electrolyte.

9. The hard gel electrolyte as claimed in claim 8,

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.

10. An electrochemical device, characterized in that,

the electrochemical device having the hard gel electrolyte of claim 8 or 9.