CN112640181B - Resin-dispersed electrolyte solution, polymer gel electrolyte and method for producing same, and secondary battery and method for producing same - Google Patents

Resin-dispersed electrolyte solution, polymer gel electrolyte and method for producing same, and secondary battery and method for producing same Download PDF

Info

Publication number
CN112640181B
CN112640181B CN201980054939.7A CN201980054939A CN112640181B CN 112640181 B CN112640181 B CN 112640181B CN 201980054939 A CN201980054939 A CN 201980054939A CN 112640181 B CN112640181 B CN 112640181B
Authority
CN
China
Prior art keywords
resin
particles
dispersed
electrolyte
dispersion
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201980054939.7A
Other languages
Chinese (zh)
Other versions
CN112640181A (en
Inventor
冈田佳余子
铃木梦乃
小林正太
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kureha Corp
Original Assignee
Kureha Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kureha Corp filed Critical Kureha Corp
Publication of CN112640181A publication Critical patent/CN112640181A/en
Application granted granted Critical
Publication of CN112640181B publication Critical patent/CN112640181B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F214/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
    • C08F214/18—Monomers containing fluorine
    • C08F214/22—Vinylidene fluoride
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F214/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
    • C08F214/18—Monomers containing fluorine
    • C08F214/28—Hexyfluoropropene
    • 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
    • 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
    • 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
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/002—Inorganic electrolyte
    • 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
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • 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
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention provides a resin-dispersed electrolyte solution having sufficient dispersibility (fluidity and dispersion stability) and capable of homogeneous gelation, a polymer gel electrolyte and a method for producing the same, and a secondary battery and a method for producing the same. The electrolyte solution containing particles of the vinylidene fluoride polymer dispersed in the nonaqueous electrolyte solution is filled in a container, and heated or heated with pressing, and cooled to be gelled, thereby obtaining a polymer gel electrolyte and a secondary battery. The particles have a dispersion particle diameter of 80 [ mu ] m or less, the difference between the melting point at the first temperature rise and the melting point at the second temperature rise of the particles by DSC is-30 ℃ or more and 2 ℃ or less, and the absolute value of the height of the first melting peak is 21mW/g or more.

Description

Resin-dispersed electrolyte solution, polymer gel electrolyte and method for producing same, and secondary battery and method for producing same
Technical Field
The present invention relates to a resin-dispersed electrolyte solution, a polymer gel electrolyte and a method for producing the same, and a secondary battery and a method for producing the same.
Background
Nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries can achieve both high capacity and miniaturization, and are therefore used as power sources for small portable devices such as smartphones and electric vehicles and hybrid vehicles. As an electrolyte of a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte solution in which a lithium electrolyte salt is dissolved in a nonaqueous organic solvent is used.
In recent years, polymer gel electrolytes obtained by impregnating a polymer with a nonaqueous electrolytic solution have been developed in order to suppress leakage of the nonaqueous electrolytic solution and the like. As a polymer used for such a polymer gel electrolyte, a vinylidene fluoride polymer is preferably used from the viewpoint of ion conductivity and oxidation reduction resistance.
As a method for producing a polymer gel electrolyte, the following methods are known: a polymer gel electrolyte composition containing a nonaqueous electrolytic solution and a vinylidene fluoride polymer is heated or diluted with a nonaqueous solvent to be converted into a sol, and the sol is applied to a positive electrode and/or a negative electrode (see, for example, patent document 1).
As a method for forming a polymer gel electrolyte in a container, the following method is known. First, a nonaqueous electrolytic solution in which vinylidene fluoride polymer powder is dispersed is injected into a laminate film container in which a positive electrode, a negative electrode, and a separator are accommodated. After the container is sealed, heat and pressure are applied to the sealed container to melt the vinylidene fluoride polymer, and the vinylidene fluoride polymer is cooled to solidify the vinylidene fluoride polymer. In this manner, a polymer gel electrolyte is formed in the container (see, for example, patent document 2).
Documents of the prior art
Patent document
Patent document 1: international publication No. 2000/013252
Patent document 2: japanese laid-open patent publication No. 2005-56701
Disclosure of Invention
Problems to be solved by the invention
However, the polymer gel electrolyte is almost entirely suitable for a battery having a laminate film or the like as a battery container. In order to form the polymer gel electrolyte, the manufacturing process of the polymer gel electrolyte includes: a step of applying the polymer gel electrolyte composition to an electrode and heating/drying the same, a step of heating and pressurizing a battery container into which the polymer gel electrolyte composition is injected, and the like. Therefore, it is not easy to apply a simple method of filling only a nonaqueous electrolytic solution into a battery container in which all components constituting a battery, such as electrodes, are assembled in the final stage to a cylindrical or rectangular battery manufacturing process for manufacturing a battery. Thus, the electrolyte of the nonaqueous electrolytic solution is still used in the cylindrical and square batteries.
In the production method described in patent document 1, since the vinylidene fluoride polymer is in a molten sol state, the viscosity is high, and it is difficult to produce a battery by a method of charging a battery container with a nonaqueous electrolytic solution. Further, in the case of using a diluent for the purpose of sol-gel, it is not easy to apply to batteries using cylindrical or square containers from the viewpoint of the need to volatilize and remove the diluent.
In addition, in the method of patent document 2, if the dispersion stability of the vinylidene fluoride polymer is insufficient, it is difficult to accurately inject a desired amount of the polymer gel electrolyte composition into the battery container. Further, before the polymer gel electrolyte forming step, precipitation of the vinylidene fluoride polymer occurs, and a homogeneous polymer gel electrolyte cannot be obtained. In the method of patent document 2, when the control of the meltability of the vinylidene fluoride polymer in the electrolyte solution is insufficient, the vinylidene fluoride polymer may be partially melted in the electrolyte solution and thickened. Therefore, the injection into the cylindrical and square containers and the formation of a homogeneous polymer gel electrolyte thereafter sometimes become difficult. Further, the method of patent document 2 is not easily applicable to a cylindrical or rectangular battery in which only an electrolyte is injected, from the viewpoint that only heating and pressurization are not necessary.
As described above, in the conventional art, there is room for study in view of application to batteries of various forms by satisfying both good dispersibility (fluidity and dispersion stability) and good gel-forming ability of the polymer gel electrolyte composition. The various forms are not limited to, for example, a laminate film type represented by a cylindrical type and a square type.
The present invention addresses the problem of providing a resin-dispersed electrolyte solution that has sufficient dispersibility (fluidity and dispersion stability) that enables the polymer gel electrolyte to be used in batteries of various forms, and that can form a homogeneous polymer gel electrolyte.
Another object of the present invention is to provide a homogeneous polymer gel electrolyte and a secondary battery which can be applied to batteries of various forms.
Technical scheme
In order to solve the above-mentioned problems, a resin-dispersed electrolyte solution according to one aspect of the present invention includes a nonaqueous electrolyte solution and particles of a vinylidene fluoride polymer dispersed in the nonaqueous electrolyte solution, the particles have a dispersion particle diameter of 80 [ mu ] m or less in the case where a nonaqueous solvent is used as a dispersion medium, wherein a value obtained by subtracting b from a is-30 ℃ to 2 ℃ when a peak temperature of a melting peak of the particle having the largest endothermic amount obtained by a first temperature rise measurement with a differential scanning calorimeter at 5 ℃/min is a ℃ and a peak temperature of a melting peak of the particle having the largest endothermic amount obtained by a second temperature rise measurement with a differential scanning calorimeter at 5 ℃/min is b ℃, the absolute value of the peak height of the melting peak having the largest endothermic amount obtained by the first temperature rise measurement is 21mW/g or more.
In order to solve the above-described problems, a polymer gel electrolyte according to an aspect of the present invention is a polymer gel electrolyte using the above-described resin-dispersed electrolytic solution.
In order to solve the above-described problems, a method for producing a polymer gel electrolyte according to an aspect of the present invention is a method for producing a polymer gel electrolyte using the above-described resin-dispersed electrolytic solution.
In order to solve the above-described problems, a secondary battery according to one aspect of the present invention is a secondary battery including a positive electrode, a negative electrode, and the above-described polymer gel electrolyte interposed between the positive electrode and the negative electrode.
In order to solve the above problems, a method for manufacturing a secondary battery according to an aspect of the present invention includes: and a step of injecting the resin-dispersed electrolyte into a battery container containing a battery element including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, heating the battery container or heating with pressing (hereinafter, heating or heating with heating is also referred to as "heating (pressing)"), and cooling the battery container to gel the resin-dispersed electrolyte.
Advantageous effects
According to an aspect of the present invention, a polymer gel electrolyte resin dispersion electrolyte solution having sufficient dispersibility (fluidity, dispersion stability) and capable of forming a homogeneous state can be provided. The resin-dispersed electrolyte solution of the present invention can be applied to batteries of various forms, and is not limited to batteries using a laminate film or the like as a battery container, because a homogeneous polymer gel electrolyte can be formed by heating (pressing) and cooling the container after charging the container into various battery containers.
Drawings
Fig. 1 is a diagram for explaining a melting peak in a Differential Scanning Calorimeter (DSC).
Detailed Description
< electrolyte solution dispersed in resin >
The resin-dispersed electrolytic solution of the present embodiment includes a nonaqueous electrolytic solution and vinylidene fluoride polymer particles dispersed in the nonaqueous electrolytic solution. The resin-dispersed electrolytic solution may be configured in the same manner as a normal nonaqueous electrolytic solution for a secondary battery, except that the resin-dispersed electrolytic solution contains particles described later.
[ nonaqueous electrolytic solution ]
The nonaqueous electrolytic solution contains a nonaqueous solvent and an electrolyte dissolved in the solvent. As the nonaqueous electrolytic solution, for example, a known nonaqueous electrolytic solution for a secondary battery can be used. The content of the nonaqueous solvent and the electrolyte in the nonaqueous electrolytic solution may be appropriately determined depending on the use of the resin-dispersed electrolytic solution.
(non-aqueous solvent)
The nonaqueous solvent is a solvent in which an electrolyte described later is dissolved. The nonaqueous solvent may be one kind or one or more kinds. Examples of the nonaqueous solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, and difluoroethylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, methylethyl carbonate, and fluoro-substituted products thereof; cyclic esters such as γ -butyrolactone and γ -valerolactone; and mixed solvents thereof, and the like. The nonaqueous solvent is preferably one or more compounds selected from the group consisting of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, from the viewpoint of dispersion stability of the vinylidene fluoride polymer.
(electrolyte)
The electrolyte is dissolved in a nonaqueous solvent and supplies and receives electric charges. As the electrolyte, an electrolyte for a secondary battery can be preferably used. One or more electrolytes may be used. The electrolyte may be LiPF6、LiBF4、LiClO4、LiAsF6、LiSbF6、LiCF3SO3、LiC4F9SO3、LiBPh4、LiCl、LiBr、LiCH3SO3、LiN(CF3SO2)2And LiC (CF)3SO2)3And the like. Among them, preferred is a compound selected from the group consisting of LiPF6、LiAsF6、LiClO4、LiBF4、LiCl、LiBr、LiCH3SO3、LiCF3SO3、LiN(CF3SO2)2And LiC (CF)3SO2)3One or more compounds of the group consisting of.
[ particles ]
The particles contained in the resin-dispersed electrolyte solution are composed of a vinylidene fluoride polymer.
(vinylidene fluoride Polymer)
The vinylidene fluoride polymer of the present embodiment has a structural unit derived from vinylidene fluoride as a main component. Here, "as a main component" means that the vinylidene fluoride polymer has a content of a structural unit derived from vinylidene fluoride of 50 mol% or more.
The vinylidene fluoride polymer may be a vinylidene fluoride homopolymer, or may be a copolymer of a structural unit derived from vinylidene fluoride and a structural unit derived from another monomer copolymerizable with vinylidene fluoride. From the viewpoint of dispersion stability of the resin-dispersed electrolytic solution and appropriate setting of the heating (pressing) temperature in the heating (pressing) step of the resin-dispersed electrolytic solution in the formation process of the polymer gel electrolyte, a copolymer is preferable.
The copolymer may contain one or more other monomers copolymerizable with vinylidene fluoride. Specific examples of the other monomers include: a fluorine-containing monomer other than vinylidene fluoride; hydrocarbon monomers such as ethylene and propylene; acrylic monomers such as alkyl (meth) acrylate compounds and carboxyl group-containing acrylate compounds; unsaturated dibasic acid derivative monomers such as maleic acid, monomethyl maleate, and dimethyl maleate; and a monomer containing a carboxylic anhydride group. For example, acryloxyethyl succinate, methacryloxyethyl succinate, acryloxypropyl succinate, methacryloxypropyl succinate, acryloxyethyl phthalate, methacryloxyethyl phthalate, 2-carboxyethyl acrylate, 2-carboxyethyl methacrylate, and the like can also be used.
Examples of the fluorine-containing monomer include vinyl fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, hexafluoroethylene, fluoroalkyl vinyl ether, perfluoroalkyl vinyl ether typified by perfluoromethyl vinyl ether, and the like. From the viewpoint of dispersion stability of the particles in the electrolytic solution and easy control of the temperature in the heating (pressing) step of the resin dispersion electrolytic solution in the process of forming the polymer gel electrolyte, one or more compounds selected from the group consisting of hexafluoropropylene, chlorotrifluoroethylene, trifluoroethylene, tetrafluoroethylene, hexafluoroethylene, and fluoroalkyl vinyl ether are preferable. Among them, Hexafluoropropylene (HFP) is more preferable from the above viewpoint.
The melting point of the vinylidene fluoride polymer may be appropriately determined depending on the desired melting temperature of the particles, and is preferably 85 to 175 ℃. If the melting point is too low, the particles may melt in the electrolyte solution when the particles are subjected to a heat treatment as described later. If the melting point is too high, the heating (pressing) temperature for melting the particles in the electrolyte dispersion liquid is high in the formation of the polymer gel electrolyte in which the particles are melted by heating (pressing) and solidified by cooling, and the electrolyte may be deteriorated. The melting point can be determined from the melting peak obtained by DSC. In addition, the melting point can be adjusted by the kind or content of the structural unit derived from other monomer in the copolymer.
When the vinylidene fluoride polymer contains a vinylidene fluoride-derived structural unit and a hexafluoropropylene-derived structural unit, the vinylidene fluoride polymer preferably has a predetermined composition and a melting peak. That is, when the content of the hexafluoropropylene-derived structural unit in the vinylidene fluoride polymer is X, X is preferably 0 mass% or more and 35 mass% or less. When the peak temperature of the melting peak of the particles obtained by the second temperature rise measurement using a differential scanning calorimeter is Y, Y is preferably 85 ℃ to 175 ℃.
When such a relationship is satisfied, the resin-dispersed electrolytic solution exhibits sufficient dispersibility (fluidity, dispersion stability), and the heating (pressing) temperature in the heating step in the polymer gel electrolyte formation process is preferably an appropriate temperature condition. The particles satisfying the above relationship can be realized by the production conditions of the vinylidene fluoride polymer particles described later.
The other monomers may further include a polyfunctional monomer for crosslinking within a range that achieves the effects of the present embodiment. The polyfunctional monomer may be one or more. As the vinylidene fluoride polymer used in the present embodiment, a crosslinked copolymer may also be used. In the production of a vinylidene fluoride polymer, a vinylidene fluoride polymer having a crosslinked structure can be obtained by containing a polyfunctional monomer as another monomer.
Among the polyfunctional monomers, various known compounds can be used. As the polyfunctional monomer, divinylbenzene, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1, 3-butylene glycol dimethacrylate, propylene glycol dimethacrylate, 1, 4-butylene glycol dimethacrylate, 1, 6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, allyl methacrylate, allyl acrylate, 2-hydroxy 1, 3-dimethacryloxypropane, bisphenol dimethacrylate, bisphenol diacrylate, cyclic aliphatic diacrylate, diacrylylated isocyanurate, trimethylolpropane trimethacrylate, triacrylate (triacrylformal), triacrylate isocyanurate (triacrylisocyanurate), triallyl cyanurate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, aliphatic triacrylates, pentaerythritol tetramethacrylate, pentaerythritol tetraacrylate, aliphatic tetraacrylate, and the like.
(method for producing particles)
The particles in the present embodiment can be obtained by a known polymerization method for synthesizing a vinylidene fluoride polymer. Examples of the polymerization method include emulsion polymerization, soap-free emulsion polymerization, miniemulsion polymerization, suspension polymerization, solution polymerization, and bulk polymerization. Among them, from the viewpoint of obtaining sufficiently small particles, emulsion polymerization, soap-free emulsion polymerization, miniemulsion polymerization, or suspension polymerization are preferable, and emulsion polymerization and suspension polymerization are particularly preferable. In addition, the above-mentioned particles can be produced by crushing and classifying the vinylidene fluoride polymer lumps.
[ optional Components of the resin-dispersed electrolyte ]
The resin-dispersed electrolytic solution may further contain other components than the particles, the nonaqueous solvent, and the electrolyte, within a range in which the effects of the present embodiment are obtained. Such other components may be appropriately selected from materials of known electrolytic solutions in secondary batteries and materials for improving gel strength or heat resistance when gelling a resin. Examples of the other component include aluminum oxide (Al)2O3) And silicon dioxide (SiO)2) And the like.
[ Properties of resin-dispersed electrolyte ]
(particle diameter of particle Dispersion)
From the viewpoint of achieving a good dispersion state of the particles in the resin-dispersed electrolyte solution, the dispersion particle diameter of the particles in a dispersion (resin dispersion) using a nonaqueous solvent as a dispersion medium is 80 μm or less. The dispersed particle diameter of the particles is preferably 70 μm or less, more preferably 60 μm or less. The lower limit of the dispersion particle size of the particles is not limited, but is preferably 0.01 μm or more, more preferably 0.05 μm or more, and even more preferably 0.1 μm or more, from the viewpoint of productivity of the particles or from the viewpoint of handling of the particles at the time of production of the resin-dispersed electrolyte solution.
The dispersion particle diameter of the particles in the nonaqueous solvent can be measured by a laser diffraction/scattering method. The dispersion particle size of the particles may be adjusted by pulverizing or classifying the resin material, or by a method of polymerizing the particles of the vinylidene fluoride polymer or a method of granulating the particles.
(melting Properties of particles)
In the particles of the present embodiment, the value obtained by subtracting b from a is-30 ℃ or higher and 2 ℃ or lower. "a" is the peak temperature (c) of the melting peak (also referred to as "first peak") having the largest endothermic amount obtained by the first temperature rise measurement at 5 ℃/min of only the particles by a differential scanning calorimeter. "b" is the peak temperature (. degree. C.) of the melting peak (also referred to as "second peak") having the largest endothermic amount obtained by the second temperature rise measurement at 5 ℃ per minute of the particles by a differential scanning calorimeter. When the difference between a and b is-30 ℃ or higher and 2 ℃ or lower, the viscosity of the resin-dispersed electrolyte solution is not easily increased even after the particles are dispersed in the electrolyte solution, and good fluidity is exhibited. When the value obtained by subtracting b from a is larger than 2 ℃, when the particles are dispersed in the electrolyte solution, the low-crystallinity portions of the particles may melt, and the viscosity of the resin-dispersed electrolyte solution may increase. From the viewpoint of the above-mentioned fluidity, a-b is preferably from-30 ℃ to 1 ℃, a-b is more preferably 0 ℃ or less, and a-b is further preferably-3 ℃ or less.
Both the a ℃ and the b ℃ were determined by measuring only the particles by DSC.
a ℃ shows thermal characteristics of a particle structure including dispersed particles (distribution in the particle interior including a crystal portion and an amorphous portion, stability of the crystal portion), and indicates a temperature at which the particles melt when only the particles are heated in a state of not being dispersed in an electrolyte solution. From the viewpoint of exhibiting good dispersibility (fluidity) of the resin-dispersed electrolyte solution, a ℃ is preferably 90 ℃ or higher, more preferably 100 ℃ or higher, and still more preferably 103 ℃ or higher. In addition, the a ℃ is preferably 165 ℃ or lower, more preferably 150 ℃ or lower, and still more preferably 130 ℃ or lower, from the viewpoint of preventing the heating (pressing) temperature from increasing and the electrolytic solution from decomposing in the melting step of the particles by heating (pressing) for forming the polymer gel electrolyte from the resin-dispersed electrolytic solution, and thus preventing the desired battery capacity from being obtained.
b ℃ represents thermal characteristics when the particles are once melted to make the structure in the particles uniform, and may also be referred to as thermal characteristics of sequences (sequences) of vinylidene fluoride polymers constituting the particles. From the viewpoint of dispersibility (fluidity) of the resin-dispersed electrolyte solution, b ℃ is preferably 100 ℃ or higher, more preferably 110 ℃ or higher, and still more preferably 117 ℃ or higher. In addition, from the viewpoint of preventing failure to obtain a desired battery capacity due to decomposition of the electrolytic solution in the step of melting the particles by heating (pressing) for forming the polymer gel electrolyte from the resin-dispersed electrolytic solution, b ℃ is preferably 165 ℃ or less, more preferably 150 ℃ or less, and still more preferably 130 ℃ or less.
The melting peak temperature is a temperature of a melting peak having the largest endothermic amount among melting peaks in the first or second temperature raising step in the DSC. The temperature raising step may be performed at least during the temperature raising process to a temperature at which all the peaks detected are completely detected, but is preferably performed to a sufficiently high temperature at which the particles are melted.
The temperature of the melting peak is, for example, a temperature at which the endothermic heat is the largest when a straight line connecting a base on the low temperature side of the melting peak derived from the lowest temperature side of the vinylidene fluoride polymer and a base on the high temperature side of the melting peak of the highest temperature is taken as a base line. The base line may be set as described above, but may be automatically corrected by a computer, or may be a line connecting points of the melting curve at which the amount of heat absorption before and after the peak is substantially negligible.
Fig. 1 is a diagram for explaining a melting peak in DSC. C1 shown by the solid line is the melting peak curve in the first temperature-rise-cooling cycle of DSC, and C2 shown by the dashed line is the melting curve in the second temperature-rise-cooling cycle of DSC.
In the figure, BL is a base line of an endothermic peak having a melting point of a ℃. The baseline is, for example, a straight line connecting a point before the endothermic amount of the melting curve is detected and a point after all peaks are detected. CA is the central axis of the melting peak, passing through the peak top of the melting peak. a ℃ is the peak temperature of the melting peak (first peak) having the largest endothermic amount in the first melting peak curve C1. In FIG. 1, a ℃ is 115 ℃. Although not shown, b ℃ is the peak temperature of the melting peak (second peak) having the largest endothermic amount in the second melting peak curve C2.
In the melting peak curve indicated by C1 in fig. 1, the region surrounded by the central axis CA, the melting peak curve C1, and the base line BL has a high temperature region AH at a higher temperature than the central axis CA and a low temperature region AL at a lower temperature than the central axis CA. The more AL, the more easily the dispersed particles swell and melt in the electrolyte at low temperature, and the more easily the electrolyte thickens. The ratio of these regions will be described later.
The above-mentioned a ℃ can be adjusted by heat treatment of the particles. For example, by subjecting the particles to a heating treatment at an arbitrary temperature within a predetermined range (e.g., b-60 ℃ to 0 ℃) with respect to b ℃ for a sufficient time, the melting peak of the particles having b ℃ as the melting peak temperature at which the endothermic heat is the largest can be changed to a ℃. Further, the shape of the melting peak having a ° c as the peak temperature can be made sharper by sufficiently slowing down the cooling after the above-mentioned heat treatment (for example, 1 ℃/min or less).
(melting Peak area of particles)
In the dispersed particles of the present embodiment, AL/AH is preferably less than 1.5 from the viewpoint of improving dispersibility (fluidity). "AL" is an area on the lower temperature side than 115 ℃ in the first temperature rise measurement at 5 ℃/min by a differential scanning calorimeter, and "AH" is an area on the higher temperature side than 115 ℃. From the viewpoint of improving dispersibility (fluidity), the smaller the AL, the more preferable.
When AL/AH is 1.5 or more, the resin-dispersed electrolyte may be thickened due to local melting of particles at a dispersion temperature, and the fluidity may be insufficient.
The areas AL and AH of the melting peaks can be obtained as the areas of predetermined regions in the first temperature rise curve of the DSC measurement of the dispersed particles. The predetermined region is a region divided by a base line of a melting peak having the largest endothermic heat quantity, an axis drawn at a position of 115 ℃ so as to be perpendicular to the base line, and a melting peak curve.
(Peak height of particle)
The absolute value of the peak height of the first peak is 21mW/g or more. Here, the "peak height" refers to a distance (HP in the figure) from the base line to the peak top of the first peak. If the absolute value of the peak height is too low, the crystallinity of the particles becomes low, and when the particles are dispersed in the nonaqueous electrolytic solution, the particles melt and the viscosity of the nonaqueous electrolytic solution increases, so that the fluidity may become insufficient. From the viewpoint of suppressing melting of the dispersed particles in the nonaqueous electrolytic solution, the absolute value of the peak height of the first peak is preferably 21mW/g or more, and more preferably 30mW/g or more.
The absolute value of the peak height of the first peak can be determined by temperature rise measurement at 5 ℃/min in a Differential Scanning Calorimeter (DSC).
(dispersibility of particles (Dispersion stability))
In the resin-dispersed electrolyte solution of the present embodiment, from the viewpoint of dispersibility (dispersion stability), it is preferable that the rate of change of the solid content fraction a and the solid content fraction B is 90% or less when a resin dispersion in which resin particles are dispersed using a nonaqueous solvent as a dispersion medium is contained in a container and stirred at room temperature. The solid content fraction a referred to herein means the solid content fraction of the resin dispersion in a stirred state, and the solid content fraction B means the solid content fraction of the upper layer portion of the resin dispersion when left standing thereafter. From the above-described viewpoint, the smaller the rate of change in the solid content is, the more preferable is, for example, 80% or less, and the more preferable is 50% or less.
Here, the "upper portion" refers to a portion of the resin dispersion contained in the container, which is located on the upper side of the container in the depth direction. The "resin dispersion liquid in a stirred state" refers to a resin dispersion liquid in a state in which a stirring treatment is being performed. This is because a part of the resin dispersion is collected while stirring is continued in consideration of particles which settle immediately after the stirring is stopped, and the solid content fraction is measured. In consideration of influences other than stirring, for example, when stirring is accompanied by a temperature rise, the temperature of the resin dispersion is returned to room temperature while stirring is continued, and collection is performed when the temperature is returned to room temperature. The term "at the time of standing" means a state in which an external force for dispersing particles is not applied to the resin dispersion liquid and is continuously maintained for a certain period of time. For example, the stirring may be stopped immediately after 15 minutes has elapsed.
The solid content ratio is a ratio of the weight of a given amount of sample before drying to the weight of the sample after drying, and is a value represented by formula (1).
[ numerical formula 1]
Figure BDA0002944217980000111
The rate of change in solid content fraction (hereinafter, sometimes referred to as "rate of change in solid content") can be determined from equation (2) by expressing the solid content fraction in the sample collected from the resin dispersion under stirring as W1 and the solid content fraction in the sample collected after leaving the resin dispersion for 15 minutes as W2.
[ numerical formula 2]
Figure BDA0002944217980000112
More specifically, the solid content change rate can be obtained as follows. For example, a dispersion liquid in which 5 mass% of particles are dispersed in Propylene Carbonate (PC) is stirred at room temperature. A certain amount of the sample during stirring (hereinafter, sometimes referred to as "sample immediately after dispersion") and a certain amount of the sample collected by leaving for 15 minutes from immediately after stopping stirring (hereinafter, sometimes referred to as "sample after leaving") were each subjected to weight measurement. Thereafter, each sample was dried, the weight of the solid content in the sample was measured, and the solid content fractions of the sample immediately after dispersion and the sample after standing were calculated from (formula 1). The solid content change rate can be determined by the formula (2).
The solid content change rate can be adjusted by, for example, the particle size of the particles dispersed therein.
(viscosity)
In the viscosity of the resin-dispersed electrolyte solution of the present embodiment, from the viewpoint of improving the dispersibility (fluidity) in the resin-dispersed electrolyte solution, it is preferable that the C/D is 200 or less when the viscosity of the dispersion of the particles in which the nonaqueous solvent is used as the dispersion medium at 25 ℃ is C and the viscosity of the nonaqueous solvent is D. From the above viewpoint, C/D is preferably 100 or less, and more preferably 70 or less. When the C/D exceeds 200, the particles may be locally melted, the resin-dispersed electrolyte may be thickened, and the dispersibility (flowability) may be insufficient.
The viscosity can be determined using a known viscometer such as a rotational rheometer. The C/D can be appropriately adjusted by a parameter relating to the dispersibility (fluidity), such as the difference between a ℃ and b ℃.
(Primary particle diameter)
In the resin-dispersed electrolyte solution of the present embodiment, the primary particle diameter of the particles is preferably 10nm to 1 μm from the viewpoint of improving the dispersion stability of the resin-dispersed electrolyte solution and from the viewpoint of uniform and rapid gelation. The primary particle size may be an average value of the primary particle sizes. From the above viewpoint, the smaller the primary particle size is, the more preferable, but the particle size can be appropriately determined from the range in which the effects of the present embodiment are obtained in consideration of the handling properties of the particles. For example, the primary particle diameter is preferably 10nm or more, more preferably 30nm or more, and further preferably 50nm or more. From the above viewpoint, the upper limit of the primary particle size is preferably 700nm or less, more preferably 600nm or less, and still more preferably 500nm or less. From the above viewpoint, it is preferable that 50% or more of the primary particle diameter of the particles fall within the above range, and more preferably 70% or more is contained. If the primary particle diameter is too large, the particles in the resin-dispersed electrolyte are likely to settle, and the dispersion stability of the resin-dispersed electrolyte may become insufficient.
The primary particle diameter can be determined by a known method such as a method of imaging the powdered particles with a Scanning Electron Microscope (SEM) and calculating the primary particle diameter by image analysis or a laser diffraction/scattering method.
(turbidity)
In the resin dispersion electrolyte of the present embodiment, when the dispersoid is only particles, the turbidity when the resin dispersion is heated to 60 ℃ is preferably 2 or more. When the turbidity is high, when the resin-dispersed electrolyte is heated (pressed), the diffusion of the resin is appropriately suppressed, and the polymer gel electrolyte is appropriately retained between the members after cooling, whereby the polymer gel electrolyte can be appropriately fixed between the members. From this viewpoint, the turbidity is more preferably 8 or more, and still more preferably 15 or more.
The turbidity of the resin-dispersed electrolyte can be determined by a known method for measuring turbidity. For measuring the turbidity, a solution obtained by dispersing or melting the particles in a nonaqueous solvent at 60 ℃ so that the content of the particles becomes 1 mass% can be used. The turbidity can be adjusted by, for example, a polymerization method. The turbidity is more effectively 2 or more from the viewpoint of dispersing a sufficient amount of particles in a good state and forming a gel having desired physical properties when the particles in the dispersion are melted in the polymer gel electrolyte forming step.
[ method for producing resin-dispersed electrolyte ]
The resin-dispersed electrolytic solution of the present embodiment can be produced by a known production method of a resin-dispersed liquid, except that particles having the above absolute values of the dispersed particle diameter and melting peak height and having a value obtained by subtracting b from a is dispersed in a nonaqueous electrolytic solution at-30 ℃ or higher and 2 ℃ or lower. The particles having the above thermal characteristics can be obtained by heat treatment of the particles.
The heat treatment comprises: a heating step of heating the particles to a predetermined temperature; and a cooling step of slowly cooling the heated particles. The particles subjected to the heat treatment may be in the form of particles themselves, or may be particles containing a solvent such as water or particles dispersed in a solvent. The polymer may be particles after polymerization in a liquid and before a dehydration step or latex before pulverization.
The predetermined temperature in the heating step may be a temperature at which only a portion of the particles that is relatively easily melted is melted. For example, the temperature may be any temperature selected from the range of b-60 to 0 ℃.
The cooling step resolidifies the portion of the particles melted in the heating step. At this time, by sufficiently slow cooling, a denser crystal structure is reformed. The final temperature of cooling in the cooling step may be a temperature sufficiently low to recrystallize the particles, and may be, for example, room temperature (25 ℃). The cooling rate in the cooling step may be a rate that is sufficiently long enough for the portion melted in the heating step to solidify so that the portion has a denser crystal structure than that before heating, and may be, for example, 0.1 to 1.5 ℃/min.
The resin-dispersed electrolyte containing particles dispersed in the nonaqueous electrolyte solution may be prepared at a temperature sufficiently low to suppress the melting of the particles.
[ Effect of the action of the resin-dispersed electrolyte ]
The resin-dispersed electrolytic solution of the present embodiment is partially melted by the temperature rise, and the viscosity of the resin-dispersed electrolytic solution starts to increase. Then, the melting is rapidly performed with the temperature at which the viscosity becomes a peak as a boundary. Then, after the particles are melted, the particles are cooled to be gelled, thereby forming a polymer gel electrolyte. As described above, the resin-dispersed electrolyte solution of the present embodiment has sufficiently small particles, and therefore has excellent dispersion stability in the resin-dispersed electrolyte solution, and has high fluidity because the vinylidene fluoride polymer constituting the particles is not melted and the thickening is suppressed at a temperature lower than the viscosity peak temperature. Further, at a temperature higher than the viscosity peak temperature, the particles are rapidly melted, and the resin-dispersed electrolyte is gelled by cooling. The viscosity peak temperature is a temperature at which the resin particles are melted in the nonaqueous solvent, and is also referred to as a melting point of the particles in the nonaqueous solvent.
The peak temperature a of the first peak (melting peak) corresponds to the melting point of only the particles (vinylidene fluoride polymer) in the case where the particles are not dispersed. For example, if the value obtained by subtracting b from a in the particles is-30 ℃ or higher and 2 ℃ or lower, the crystal structure of the resin becomes dense, the viscosity of the resin-dispersed electrolyte solution can be suppressed to be low, and the viscosity increase starting temperature due to temperature rise can be increased. Therefore, the resin-dispersed electrolytic solution is excellent in particle fluidity in a wider temperature range.
< Polymer gel electrolyte and method for producing the same >
The resin-dispersed electrolytic solution of the present embodiment described above is preferably used for production of a polymer gel electrolyte. Such a polymer gel electrolyte is produced by heating (pressing) and cooling the resin dispersion electrolyte solution to gel the electrolyte solution. In the production of the polymer gel electrolyte, the temperature of the resin-dispersed electrolyte to be heated (pressed) may be appropriately determined depending on the melting point of the nonaqueous electrolyte of the vinylidene fluoride polymer, and may be, for example, 50 to 150 ℃. When the particles are dispersed in the resin-dispersed electrolytic solution, the dispersed particles swell moderately in the nonaqueous solvent in the electrolytic solution, and therefore the melting point of the particles in the nonaqueous electrolytic solution is lower than the melting point of only the particles. The heating (pressing) time may be appropriately determined in accordance with the environment surrounding the resin-dispersed electrolyte at the time of heating (pressing), for example, in the range from 1 second to 8 hours.
In the production of a polymer gel electrolyte, when the above-mentioned ratio C/D is 200 or less, the resin-dispersed electrolytic solution has sufficiently high fluidity and is easily injected into various battery containers, which is preferable.
< separator and electrode >
The resin-dispersed electrolytic solution can be gelled in the presence of a predetermined member to provide a member having a polymer gel electrolyte. Such a predetermined member is preferably used in a state of having a polymer gel electrolyte, and examples thereof include a separator and an electrode for a secondary battery. Such a separator provided with a polymer gel electrolyte or an electrode provided with a polymer gel electrolyte can be used as one component for a secondary battery as its final product.
< Secondary Battery and method for producing the same >
The resin-dispersed electrolytic solution described above is used for an electrolyte of a secondary battery. A secondary battery having a polymer gel electrolyte formed of a resin-dispersed electrolytic solution has, for example: the positive electrode includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and a polymer gel electrolyte integrally interposed between the positive electrode, the negative electrode, and the separator. The term "the polymer gel is integrally sandwiched" means that, for example, the members to be bonded such as the electrode and the separator are bonded by the polymer gel after gelation once. The polymer gel can prevent the members from being displaced from each other and also prevent a gap from being generated between the members by being integrally sandwiched.
The secondary battery may be manufactured by a method including: injecting the resin-dispersed electrolytic solution into a battery container that contains a battery element including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; and a step (heating (pressing) step and cooling step) of heating (pressing) and cooling the battery container to melt and gel the particles in the resin-dispersed electrolytic solution.
In the above-described injection step, the resin-dispersed electrolytic solution is injected into the battery container in which the battery element is accommodated at a temperature lower than the viscosity increase start temperature. Thereby, the resin-dispersed electrolytic solution having high fluidity reaches each corner in the battery container. The viscosity increase starting temperature can be determined from the viscosity of the dispersion of the particles in which the nonaqueous solvent is used as the dispersion medium, when measured at a varying measurement temperature. The viscosity of the dispersion tends to increase sharply with a certain temperature as a boundary. The temperature immediately before the rapid increase can be determined as the viscosity increase start temperature.
The content of the particles in the resin-dispersed electrolytic solution in the injection step may be appropriately determined depending on the application. For example, in the case of the secondary battery, the strength required for the polymer gel electrolyte and the adhesion strength required for the polymer gel electrolyte for adhering the battery elements to each other may be appropriately determined, for example, from the range of 1 to 10 mass%.
In the heating (pressing) step, the particles of the resin-dispersed electrolytic solution in the battery container are melted, and in the cooling step, the resin-dispersed electrolytic solution in which the particles are melted is gelled.
The heating step is preferably a step (heating-pressing step) involving pressing (pressing) from the viewpoint of enhancing adhesion between the battery elements in the battery container. The pressurizing force in the heating and pressurizing step may be appropriately determined within a range in which the battery elements are not deformed or damaged and the battery elements can be relatively fixed to each other at the time of gelation of the resin-dispersed electrolytic solution.
The method for manufacturing a secondary battery according to the present embodiment may further include other steps than the above-described injection, heating step, and cooling step, within a range in which the effects of the present embodiment are obtained. Examples of such other steps include a step of sealing an opening of a battery container in which the battery element is accommodated and the resin-dispersed electrolytic solution is injected.
[ Effect of Polymer gel electrolyte ]
The polymer gel electrolyte is formed by injection of the resin dispersion electrolytic solution described above, heating (pressing), and cooling. The particles in the resin-dispersed electrolyte have good fluidity because the difference between the temperatures a ℃ and b ℃ is-30 ℃ or higher and 2 ℃ or lower. This allows the electrolyte to rapidly flow into the secondary battery even in a fine structure of the battery element. Further, the particles of the resin-dispersed electrolytic solution have a sufficiently small dispersed particle diameter as described above. This allows the microstructure to be filled with the resin in a sufficiently uniform state. The particles in the resin-dispersed electrolyte melt rapidly at a temperature substantially higher than the viscosity peak temperature. This can sufficiently lower the heating (pressing) temperature for gelation and sufficiently shorten the heating (pressing) time, as compared with the polymerization (gelation) in the conventional polymer gel electrolyte. As a result, thermal deterioration due to heating (pressing) for melting and gelling the resin can be suppressed in the polymer gel electrolyte and members (the battery elements and the like described above) in contact therewith, as compared with polymerization (gelling) in a conventional polymer gel electrolyte. Further, the resin dispersion liquid of the present embodiment can also adjust the heating (pressing) temperature and time by adjusting the particle size of the resin and the composition of the vinylidene fluoride polymer, and therefore it is expected to form a polymer gel electrolyte which is homogeneous and in which decomposition of the electrolytic solution is suppressed.
< summary >
As is apparent from the above description, the resin-dispersed electrolytic solution of the present embodiment includes a nonaqueous electrolytic solution and particles of a vinylidene fluoride polymer dispersed in the nonaqueous electrolytic solution. The particle size of the particles dispersed in a nonaqueous solvent as a dispersion medium (in the resin dispersion) is 80 μm or less. And, when the peak temperature of a first peak of the particles having the largest amount of heat absorption obtained by the first temperature rise measurement at 5 ℃/min by a differential scanning calorimeter is a ℃, and the peak temperature of a second peak of the particles having the largest amount of heat absorption obtained by the second temperature rise measurement at 5 ℃/min by a differential scanning calorimeter is b ℃, the value obtained by subtracting b from a is-30 ℃ to 2 ℃, and the absolute value of the peak height of the first peak is 21mW/g or more.
In the resin-dispersed electrolytic solution, the melting point of the dispersed particles in the electrolytic solution is lower than the melting point of only the particles. The viscosity of the resin-dispersed electrolytic solution starts to increase due to the start of melting of the particles by temperature rise, and the particles are melted rapidly at a temperature substantially higher than the temperature at which the viscosity reaches a maximum (also referred to as "viscosity peak temperature"). In the dispersed particles in which the value obtained by subtracting b from a is-30 ℃ to 2 ℃ and the absolute value of the peak height of the first peak is 21mW/g or more, the melting of the particles is suppressed at least at the viscosity increase starting temperature or less, and the resin-dispersed electrolyte solution exhibits good fluidity. Further, the particles are sufficiently small and therefore stably and uniformly dispersed in the resin-dispersed electrolyte solution, and are rapidly gelled by heating (pressing) or cooling at a temperature equal to or higher than the viscosity peak temperature. Thus, the above configuration can provide a resin-dispersed electrolyte solution having excellent dispersibility (fluidity, dispersion stability) and gelling properties.
In the resin-dispersed electrolyte solution of the present embodiment, when AL represents an area of the first peak on the lower temperature side than 115 ℃ and AH represents an area of the first peak on the higher temperature side than 115 ℃, if AL/AH is less than 1.5, the amount of the component that melts at a higher temperature is relatively sufficiently large. Thus, the above-described configuration is further effective from the viewpoint of maintaining dispersibility (fluidity) at a temperature lower than the predetermined temperature.
In the resin-dispersed electrolytic solution of the present embodiment, from the viewpoint of stably dispersing a sufficient amount of particles, it is further effective that when a liquid dispersed in a nonaqueous solvent so that the content of particles becomes 5 mass% is contained in a container and stirred as a resin dispersion liquid, the rate of change between the solid content fraction of the resin dispersion liquid in a stirred state and the solid content fraction of the upper layer portion of the resin dispersion liquid at the time of standing after stopping stirring is 90% or less. Therefore, a desired amount of the polymer gel electrolyte composition can be injected. In this way, in the case where the particles are melted by heating in the process of forming the polymer gel electrolyte and the resin-dispersed electrolytic solution in which the particles are melted is cooled, it is more effective from the viewpoint of forming a gel having desired physical properties.
In the resin-dispersed electrolytic solution of the present embodiment, when the viscosity of the dispersion (resin dispersion) of the particles in which the nonaqueous solvent is used as the dispersion medium at 25 ℃ is C and the viscosity of the nonaqueous solvent is D, the particles are sufficiently suppressed from melting in the resin-dispersed electrolytic solution when the C/D ratio is 200 or less. Thus, the above-described configuration is further effective from the viewpoint of achieving good dispersibility (fluidity) of the resin-dispersed electrolytic solution.
In the resin dispersion electrolyte of the present embodiment, the vinylidene fluoride polymer may include only a structural unit derived from vinylidene fluoride or a structural unit derived from vinylidene fluoride and a structural unit derived from a monomer copolymerizable with the vinylidene fluoride, and the melting point of the vinylidene fluoride polymer may be 85 to 175 ℃. According to this configuration, in order to obtain a polymer gel electrolyte having desired characteristics, the heating (pressing) temperature in the heating (pressing) step in the process of forming the polymer gel electrolyte is set to an appropriate temperature. Thus, the above-described configuration is more effective from the viewpoint of improving the performance and productivity of the polymer gel electrolyte formed of the resin-dispersed electrolytic solution.
In the resin dispersion electrolyte solution of the present embodiment, it is more effective that the monomer copolymerizable with vinylidene fluoride is one or more compounds selected from the group consisting of hexafluoropropylene, chlorotrifluoroethylene, trifluoroethylene, tetrafluoroethylene, hexafluoroethylene and fluoroalkyl vinyl ethers, from the viewpoint of improving the dispersion stability of the resin dispersion electrolyte solution and the performance and productivity of a gel formed from the resin dispersion electrolyte solution.
In the resin-dispersed electrolyte solution of the present embodiment, the vinylidene fluoride polymer may include a vinylidene fluoride-derived structural unit and a hexafluoropropylene (HFP-derived structural unit, and when the HFP-derived structural unit content in the vinylidene fluoride polymer is X and b ℃ of the particles is Y, X may be 0 mass% or more and 35 mass% or less, and Y may be 85 ℃ or more and 175 ℃ or less. This structure is further effective from the viewpoint that good dispersibility (fluidity, dispersion stability) is achieved in a desired temperature range in the resin-dispersed electrolyte containing particles of the HFP-derived vinylidene fluoride polymer, and the heating (pressing) temperature during the formation of the polymer gel electrolyte is an appropriate temperature condition.
In the resin-dispersed electrolyte solution of the present embodiment, the primary particle diameter of the particles may be 10nm to 1 μm. According to this configuration, since the particles are more finely dispersed in the resin-dispersed electrolytic solution, the above configuration is more effective from the viewpoint of dispersion stability of the resin-dispersed electrolytic solution and rapid melting in the heating (pressing) step in the gel formation process.
In the resin-dispersed electrolytic solution of the present embodiment, it is further effective that the nonaqueous electrolytic solution contains a nonaqueous solvent and an electrolyte, and the nonaqueous solvent is at least one compound selected from the group consisting of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, from the viewpoint of dispersion stability of the vinylidene fluoride polymer.
In the resin-dispersed electrolytic solution of the present embodiment, the electrolyte is selected from LiPF from the viewpoint of application of the resin-dispersed electrolytic solution to the production of a polymer gel electrolyte for a secondary battery6、LiAsF6、LiClO4、LiBF4、LiCl、LiBr、LiCH3SO3、LiCF3SO3、LiN(CF3SO2)2And LiC (CF)3SO2)3More effective compounds are one or more compounds of the group.
The polymer gel electrolyte of the present embodiment is formed of the resin-dispersed electrolytic solution. The polymer gel electrolyte is formed by flowing a resin-dispersed electrolytic solution into a portion where the polymer gel electrolyte is to be formed, heating (pressing) at a desired temperature, and then cooling. Thus, according to the above configuration, it is possible to provide a polymer gel electrolyte that can be sufficiently filled even in a portion that cannot be sufficiently uniformly filled with a fluid having a high viscosity.
The separator of the present embodiment includes the polymer gel electrolyte described above. According to the above configuration, it is possible to provide a separator applied to a secondary battery, in which the inside of the separator is filled with a polymer gel electrolyte sufficiently uniformly and the surface of the separator is covered with a polymer gel electrolyte at a sufficient thickness as needed.
The electrode of the present embodiment is provided with the polymer gel electrolyte described above. According to the above configuration, an electrode for a secondary battery, which is sufficiently covered with a polymer gel electrolyte, can be provided.
The method for producing a polymer gel electrolyte according to the present embodiment is a method for producing a polymer gel electrolyte in which the resin-dispersed electrolytic solution is gelled by heating (pressing) and cooling the solution at a desired temperature. According to the above configuration, the dispersed particles can be melted at a desired heating (pressing) temperature and cooled to form the polymer gel electrolyte. Thus, according to the above configuration, it is possible to suppress failure to obtain a desired battery capacity due to decomposition of the electrolyte in the resin-dispersed electrolyte.
In the method for producing a polymer gel electrolyte according to the present embodiment, when the C/D is 200 or less, a good dispersion state in the resin-dispersed electrolytic solution is achieved, and the resin-dispersed electrolytic solution has sufficient fluidity, and therefore, it is more effective from the viewpoint of forming a polymer gel electrolyte uniformly filled in fine parts.
Further, the secondary battery of the present embodiment includes: a positive electrode, a negative electrode, a separator disposed between the two electrodes, and the polymer gel electrolyte interposed between the positive electrode, the negative electrode, and the separator. According to the above configuration, the resin-dispersed electrolyte injected into the battery container accommodating the battery element is heated (pressed) at a desired heating (pressing) temperature for a short time and then cooled, whereby the polymer gel electrolyte can be formed to be sufficiently filled in the fine portion of the battery element. Therefore, according to the above configuration, it is possible to provide a secondary battery having high performance, long life, and higher reliability, which can be applied to batteries of various forms including, but not limited to, a laminate film type, a cylindrical type, and a square type. Further, according to the above configuration, it is possible to provide a polymer gel electrolyte and a secondary battery in which thermal degradation is suppressed.
Further, the method for manufacturing a secondary battery of the present embodiment includes: injecting the resin-dispersed electrolytic solution into a battery container that contains a battery element including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; and a step of heating (pressing) and cooling the battery container to gel the resin-dispersed electrolyte. According to the above configuration, the resin-dispersed electrolytic solution injected into the battery container containing the battery element is heated (pressed) and cooled for a short time at a desired temperature, whereby the polymer gel electrolyte can be formed to be sufficiently filled in the fine portion of the battery element. Therefore, according to the above configuration, it is possible to manufacture a secondary battery having high performance, long life, and higher reliability, which is applicable to batteries of various forms including, but not limited to, a laminate film type, a cylindrical type, and a square type.
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 are also included in the technical scope of the present invention.
Examples
< preparation of resin particles >
The following resin particles 1 to 30 were prepared as resin particles of vinylidene fluoride polymer.
[ production example 1 of resin particles ]
330 parts by mass of water was added to the autoclave. After degassing, 0.7 parts by mass of perfluorooctanoic acid ammonium salt (PFOA) and 0.1 parts by mass of ethyl acetate were added, followed by 14.7 parts by mass of vinylidene fluoride (VDF) and 22 parts by mass of Hexafluoropropylene (HFP).
After the liquid in the autoclave was heated to 80 ℃ with stirring, 0.06 part by mass of Ammonium Persulfate (APS) was added to the autoclave, and 63.3 parts by mass of VDF was further continuously added while maintaining the pressure at 2.5 MPa. The polymerization reaction was terminated at the point when the pressure in the autoclave had dropped to 1.5MPa, whereby a latex of VDF-HFP copolymer was obtained. The resulting VDF-HFP copolymer latex was made into powder to obtain resin particles 1. The polymerization method in which the continuous addition of VDF was started after the temperature was increased and before the pressure was reduced was referred to as polymerization method a.
[ production example 2 of resin particles ]
The powder of the resin particles 1 was heated at 100 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ for 60 minutes, to obtain resin particles 2. The cooling rate was 0.6 deg.C/min.
[ production example 3 of resin particles ]
The powder of resin particles 1 was heated at 100 ℃ for 120 minutes in an oven, and then cooled to 65 ℃ over 60 minutes, to obtain resin particles 3. The cooling rate was 0.6 deg.C/min.
[ production example 4 of resin particles ]
The powder of the resin particles 1 was heated at 100 ℃ for 180 minutes in an oven, and then cooled to 65 ℃ over 60 minutes to obtain resin particles 4. The cooling rate was 0.6 deg.C/min.
[ production example 5 of resin particles ]
The powder of resin particles 1 was heated at 110 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ for 60 minutes, to obtain resin particles 5. The cooling rate was 0.8 deg.C/min.
[ production example 6 of resin particles ]
The powder of the resin particles 1 was heated at 110 ℃ for 120 minutes in an oven, and then cooled to 65 ℃ over 60 minutes, to obtain resin particles 6. The cooling rate was 0.8 deg.C/min.
[ production example 7 of resin particles ]
The powder of resin particles 1 was heated at 110 ℃ for 180 minutes in an oven, and then cooled to 65 ℃ over 60 minutes to obtain resin particles 7. The cooling rate was 0.8 deg.C/min.
[ production example 8 of resin particles ]
The powder of the resin particles 1 was heated at 110 ℃ for 60 minutes in an oven, and immediately thereafter taken out of the oven for quenching to obtain resin particles 8. The cooling rate is 15 ℃/min or more.
[ production example 9 of resin particles ]
The powder of the resin particles 1 was heated at 115 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ over 60 minutes to obtain resin particles 9. The cooling rate was 0.8 deg.C/min.
[ production example 10 of resin particles ]
The powder of the resin particles 1 was heated at 120 ℃ for 10 minutes in an oven, and then cooled to 65 ℃ over 60 minutes to obtain resin particles 10. The cooling rate was 0.9 ℃/min.
[ production example 11 of resin particles ]
The powder of the resin particles 1 was heated at 120 ℃ for 15 minutes in an oven, and then cooled to 65 ℃ over 60 minutes to obtain resin particles 11. The cooling rate was 0.9 ℃/min.
[ production example 12 of resin particles ]
The powder of the resin particles 1 was heated at 120 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ over 60 minutes to obtain resin particles 12. The cooling rate was 0.9 ℃/min.
[ production example 13 of resin particles ]
The latex of resin particle 1 was heated in an oven at 110 ℃ for 60 minutes, then maintained at 110 ℃ for 60 minutes, and then cooled to room temperature (RT, 20 ℃) with evening oil. The obtained latex of the resin particles 1 was dried at room temperature for 8 hours by a freeze dryer to obtain resin particles 13.
[ production example 14 of resin particles ]
275 parts by mass of water was charged into the autoclave, and after degassing, 1 part by mass of PFOA was charged, and further 0.25 part by mass of ethyl acetate and 30.6 parts by mass of VDF were charged into the autoclave.
After the liquid in the autoclave was heated to 80 ℃ with stirring, 0.06 part by mass of Ammonium Persulfate (APS) was added to the autoclave to initiate polymerization. 69.4 parts by mass of the remaining VDF were continuously added so that the internal pressure of the autoclave was maintained at 2.5MPa when the internal pressure of the autoclave became 2.5MPa, and after the addition was completed, the polymerization reaction was terminated when the internal pressure of the autoclave was decreased to 1.5MPa, whereby a PVDF latex was obtained. The obtained PVDF latex was powdered to obtain resin particles. The polymerization method of the homopolymer is referred to as polymerization method B.
The obtained powder of resin particles was heated at 110 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ for 60 minutes, to obtain resin particles 14.
[ production example 15 of resin particles ]
330 parts by mass of water was charged into an autoclave, and after degassing, 0.5 part by mass of PFOA was charged, and 0.15 part by mass of ethyl acetate, 33.7 parts by mass of VDF, and 3 parts by mass of HFP were charged into the autoclave.
After the liquid in the autoclave was heated to 80 ℃ with stirring, 0.05 part by mass of APS was added to the autoclave to initiate polymerization. When the pressure in the autoclave had decreased to 2.5MPa, 63.3 parts by mass of VDF was continuously added (post-addition) to the autoclave to maintain the pressure in the autoclave at 2.5 MPa. After the completion of the post-addition, the polymerization reaction was terminated at the point when the pressure in the autoclave had dropped to 1.5MPa, whereby a VDF-HFP copolymer latex was obtained. The resulting VDF-HFP copolymer latex was made into powder to obtain resin particles. A polymerization method in which VDF was continuously added after the temperature was increased and the pressure was reduced was referred to as a polymerization method C.
The obtained powder of resin particles was heated at 110 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ for 60 minutes, to obtain resin particles 15.
[ production example 16 of resin particles ]
Resin particles were obtained in the same manner as in production example 15 of resin particles except that the amount of PFOA was 1.2 parts by mass, the amount of ethyl acetate was 0.05 parts by mass, the amount of VDF was 31.7 parts by mass, and the amount of HFP was 5 parts by mass.
The obtained powder of resin particles was heated at 110 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ for 60 minutes, to obtain resin particles 16.
[ production example 17 of resin particles ]
Resin particles were obtained in the same manner as in production example 15 of resin particles, except that the amount of VDF was 24.7 parts by mass and the amount of HFP was 12 parts by mass.
The obtained powder of resin particles was heated at 110 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ for 60 minutes, to obtain resin particles 17.
[ production example 18 of resin particles ]
Into an autoclave having a capacity of 2L, 256 parts by mass of ion-exchanged water, 0.15 part by mass of methylcellulose, 90 parts by mass of VDF, 10 parts by mass of HFP, and 0.4 part by mass of di-n-propyl peroxydicarbonate were charged and polymerized at 29 ℃. The resulting VDF-HFP copolymer was subjected to heat treatment at 95 ℃ for 60 minutes, then dehydrated and washed, and further dried at 80 ℃ for 20 hours, to obtain VDF-HFP copolymer particles. The particles are used as the resin particles 18. The suspension polymerization was performed in accordance with polymerization method D.
[ production example 19 of resin particles ]
330 parts by mass of water was charged into the autoclave, and after degassing, 1 part by mass of PFOA was charged, and further 0.05 part by mass of ethyl acetate, 9 parts by mass of VDF, and 30 parts by mass of HFP were charged into the autoclave.
After the liquid in the autoclave was heated to 80 ℃ with stirring, 0.1 part by mass of APS was added to the autoclave to initiate polymerization. When the pressure in the autoclave had dropped to 2.5MPa, 1 part by mass of perfluorodivinyl ether (PFDVE) as a crosslinking agent was added, and 60 parts by mass of VDF was further continuously added to maintain the pressure in the autoclave at 2.5 MPa. After the completion of the post-addition of VDF, the polymerization reaction was terminated at the point when the pressure in the autoclave had dropped to 1.5MPa, and a VDF-HFP copolymer latex was obtained as a dispersion of core particles.
700 parts by mass of ion-exchanged water was charged into an autoclave, and after degassing, 100 parts by mass of a dispersion of core particles and 0.5 part by mass of PFOA were charged, and 0.05 part by mass of ethyl acetate and 100 parts by mass of VDF were added to the autoclave. After warming to 80 ℃ with stirring, APS was added to initiate polymerization. The pressure in the autoclave at this time was 4.09 MPa. After the reaction was started, polymerization of the shell portion was completed when the pressure was reduced to 1.5MPa, and the VDF-HFP copolymer particles were used as core particles to obtain a latex of core-shell particles having a shell of PVDF. The obtained core-shell type particle latex was made into powder to obtain resin particles 19. The polymerization method of such core-shell particles is referred to as polymerization method E.
[ production example 20 of resin particles ]
The powder of the resin particles 19 was heated at 110 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ for 60 minutes, to obtain resin particles 20. The cooling rate was 0.8 deg.C/min.
[ production example 21 of resin particles ]
Resin particles 21 were obtained in the same manner as in production example 15 of resin particles, except that the amount of VDF was 9.7 parts by mass and the amount of HFP was 27.0 parts by mass.
[ production example 22 of resin particles ]
The powder of resin particles 21 was heated at 100 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ over 60 minutes to obtain resin particles 22. The cooling rate was 0.6 deg.C/min.
[ production example 23 of resin particles ]
The powder of the resin particles 21 was heated at 110 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ over 60 minutes, to obtain resin particles 23. The cooling rate was 0.8 deg.C/min.
[ production example 24 of resin particles ]
The powder of resin particles 21 was heated at 115 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ over 60 minutes to obtain resin particles 24. The cooling rate was 0.8 deg.C/min.
[ production example 25 of resin particles ]
The powder of the resin particles 21 was heated at 120 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ for 60 minutes, to obtain resin particles 25. The cooling rate was 0.9 ℃/min.
[ production example 26 of resin particles ]
The powder of the resin particles 21 was heated at 134 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ over 60 minutes to obtain resin particles 26. The cooling rate was 1.2 deg.C/min.
[ production example 27 of resin particles ]
The powder of resin particles 21 was heated at 139 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ over 60 minutes, to obtain resin particles 27. The cooling rate was 1.3 deg.C/min.
[ production example 28 of resin particles ]
The powder of resin particles 21 was heated at 144 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ for 60 minutes, to obtain resin particles 28. The cooling rate was 1.3 deg.C/min.
[ production example 29 of resin particles ]
Resin particles 29 were obtained in the same manner as in production example 1 of resin particles, except that the amount of VDF was 9.0 parts by mass, the amount of HFP was 37.0 parts by mass, the amount of VDF continuously added was 54.0 parts by mass, and the pressure after temperature rise was 3.2 MPa.
[ production example 30 of resin particles ]
The powder of the resin particles 29 was heated at 110 ℃ for 60 minutes in an oven, and then cooled to 65 ℃ for 60 minutes, to obtain resin particles 30. The cooling rate was 0.8 deg.C/min.
In the above-described production examples, the resin particles obtained by emulsion polymerization were pulverized by a pulverization treatment by salting out or freeze drying. The drying temperature after the powdering treatment is 50 ℃ or lower.
The composition of the raw materials, polymerization method, and heat treatment conditions for each of the resin particles 1 to 30 are shown in tables 1 and 2. In tables 1 and 2, the values in parentheses indicate the amount of HFP introduced into the polymer (the content of HFP-derived structural units in the resulting polymer). In addition, in the resin particles 19, 20 in table 1, the upper row indicates the amount of the monomer of the core particle, and the lower row indicates the amount of the monomer of the shell. The weight ratio of the core particles to the shells (core particles/shells) in the resin particles 19 and 20 was 50/50.
Figure BDA0002944217980000261
Figure BDA0002944217980000271
[ Properties of resin particles 1 to 30]
(1) Primary particle diameter
The average particle diameter of the resin particles (resin particles 1 to 17, 19 to 30) obtained by emulsion polymerization was calculated by regularization analysis by a dynamic light diffraction method. Specifically, the particle size of the resin particles in the latex was measured according to JIS Z8828 using "delsa maxcore" manufactured by BECKMAN COULTER corporation, and the value of the maximum peak obtained by regularization analysis was defined as the primary particle size. On the other hand, the primary particle diameter of the resin particles (resin particles 18) obtained by suspension polymerization is determined as follows. That is, images of 3000 powdered VDF-HFP copolymer particles were taken, and from the images, an average value of particle diameters of resin particles in the case where each of the taken particles was assumed to be circular was calculated as a primary particle diameter using arbitrary image analysis software capable of measuring length.
(2) Rate of change of solid content
The resin particles 1 to 30 were dispersed in propylene carbonate at room temperature in a container in such a manner that the amount of the dispersion became 5 mass%, thereby preparing a 5% dispersion. About 2g of the dispersion was taken out while stirring, and the dispersion was used as a sample immediately after dispersion. 5mL of the remaining 5% dispersion was added to a 10mL test tube, allowed to stand for 15 minutes, and 2mL of the supernatant was collected as a sample after 15 minutes. The sample immediately after dispersion and the sample after 15 minutes were dried at 150 ℃ for 3 hours, and the weight W1 of the solid content of the sample immediately after dispersion and the weight W2 of the solid content of the sample after 15 minutes were measured, and the rate of change in the solid content before and after standing was calculated from the following equation.
[ numerical formula 3]
Figure BDA0002944217980000281
(3) Melting Point (melting Peak temperature, melting Peak temperature Difference, melting Peak area ratio)
10mg of each of the resin particles 1 to 30 was placed in a measuring cell of a differential scanning calorimeter "DSC-1" manufactured by METTLER, and two temperature rise-fall cycles were performed in a nitrogen atmosphere to obtain a DSC curve in each cycle. The temperature raising-lowering cycle is a cycle in which the temperature is temporarily raised from 25 ℃ to 230 ℃ at a temperature raising rate of 5 ℃/min, and the temperature is lowered from 230 ℃ to 25 ℃ at a temperature lowering rate of 5 ℃/min. The peak temperature a of the melting peak (first peak) having the largest endothermic amount is obtained from the DSC curve in the first cycle. The peak temperature b of the melting peak (second peak) having the largest endothermic amount is obtained from the DSC curve in the second cycle. Then, a value (a-b) obtained by subtracting b from a is obtained.
Further, a distance HP from a base line of a DSC curve including the first peak to the top of the first peak is obtained.
Further, in the DSC curve in the first cycle, the area AH of the portion having a temperature higher than 115 ℃, the area AL of the portion having a temperature lower than 115 ℃ and the ratio AL/AH of AL to AH were determined.
(4) Dispersed particle size
Each of the resin particles 1 to 30 was dispersed in propylene carbonate at room temperature so as to be 5 mass%, to prepare a dispersion a. The particle diameter of the particles dispersed in the dispersion A was measured by using a particle size analyzer Microtrac MT3300EXII (product of MicrotracBELL). Ethanol was added to the sample circulation line and the mixing tank, and an appropriate amount of the dispersion was dropped into the mixing tank (volume: about 200mL), and then ultrasonic waves were irradiated for 180 seconds to measure the particle diameter, and the particle diameter at 50% of the cumulative value in the volume-based particle size distribution (Dv50) was defined as the dispersed particle diameter.
(5) Turbidity of water
Each of the resin particles 1 to 30 was dispersed (or melted) in propylene carbonate at 60 ℃ so as to be 1 mass%, thereby preparing a 1% dispersion. The turbidity of the 1% dispersion was measured by measuring method 3 (method according to JIS K7136) using a turbidity meter "NDH 2000" (manufactured by Nippon Denshoku industries Co., Ltd.) at 20. + -. 2 ℃.
(6) Viscosity (viscosity, viscosity ratio and viscosity peak temperature)
The resin particles 1 to 30 were dispersed in propylene carbonate at room temperature to give 5 mass% of each resin particle, and a dispersion was prepared. The viscosity of the dispersion was measured at a temperature ranging from 25 ℃ to 80 ℃ using a viscoelasticity measuring apparatus "ARES-G2" (manufactured by TA Instrument Co.). Likewise, the viscosity of the propylene carbonate was measured. Then, the viscosity of the dispersion at 25 ℃ was C, the viscosity of the propylene carbonate was D, and the ratio C/D of the viscosity C to the viscosity D was determined as the viscosity ratio.
In the measurement temperature range, the temperature at which the viscosity of the dispersion liquid becomes maximum is determined as the viscosity peak temperature.
The physical properties of the dispersed particles are shown in tables 3 and 4 for the resin particles 1 to 30. Further, the physical properties of the dispersion liquid for the resin particles 1 to 30 are shown in table 5.
Figure BDA0002944217980000301
Figure BDA0002944217980000311
[ Table 5]
Figure BDA0002944217980000321
[ examination ]
As is apparent from tables 3 to 5, the resin particles 2 to 9, 14 to 17, 19, 20 and 22 to 25 have a-b of 2 ℃ or less, HP of 21mW/g or more and dispersed particle size of 80 μm or less. Also, these resin particles have a low rate of change in solid content. Further, it can be seen that: the temperature range from room temperature to the viscosity peak temperature is wide, and therefore, the dispersion (fluidity) in a nonaqueous solvent is good in a sufficiently wide temperature range. Further, the viscosity peak temperature in the nonaqueous solvent is sufficiently lower than the melting point of the resin particles, and therefore, the polymer gel electrolyte can be formed by melting by heating (pressing) at a low temperature for a short time and then cooling. From this, it can be seen that: a nonaqueous dispersion having sufficient fluidity and homogeneous gelation properties is obtained.
Alternatively, it can also be said that: the resin particles described above have an a-b temperature of 2 ℃ or lower and a C/D of 70 or lower. Thus, according to the above-described embodiments, it can be considered that: the resin particles having the above two features also constitute a nonaqueous dispersion having sufficient fluidity and homogeneous gelation properties.
On the other hand, the resin particles 10 to 12, 18, 21, and 26 to 30 do not have the combination of the above-described features. Therefore, it can be considered that: the dispersion particle size is large, and at least one of the dispersibility (fluidity and dispersion stability) is insufficient due to an increase in viscosity during dispersion. From this, it can be considered that: these resin particles have low expectation values for constituting a nonaqueous dispersion having sufficient dispersibility (fluidity, dispersion stability) and homogeneous gelation properties.
Industrial applicability of the invention
The present invention can be preferably used for an electrolyte of a secondary battery, and according to the present invention, realization of a secondary battery having high reliability and performance can be expected.

Claims (17)

1. A resin-dispersed electrolyte comprising a nonaqueous electrolyte and particles of a vinylidene fluoride polymer dispersed in the nonaqueous electrolyte,
the particles have a dispersion particle diameter of 80 [ mu ] m or less in a nonaqueous solvent,
the peak temperature of the melting peak of the particle having the largest endothermic amount obtained by first temperature rise measurement at 5 ℃/min by a differential scanning calorimeter is set as a ℃,
b ℃ represents a peak temperature of a melting peak having the largest endothermic heat quantity obtained by second temperature rise measurement at 5 ℃/min of the particles by a differential scanning calorimeter,
a value obtained by subtracting b from a is-30 ℃ or higher and 2 ℃ or lower,
the absolute value of the peak height of the melting peak having the largest endothermic amount obtained by the first temperature rise measurement is 21mW/g or more.
2. The resin-dispersed electrolyte according to claim 1,
when an area on a lower temperature side than 115 ℃ in a melting peak of the particles having the largest heat absorption amount obtained by a first temperature rise measurement with a differential scanning calorimeter is Al, and an area on a higher temperature side than 115 ℃ is AH, Al/AH is less than 1.5.
3. The resin-dispersed electrolyte according to claim 1 or 2,
when a dispersion of the particles, in which a nonaqueous solvent is used as a dispersion medium, is contained in a vessel and stirred, the rate of change obtained from the solid content fraction of the upper layer portion of the dispersion immediately after the stirring is stopped and the solid content fraction of the upper layer portion of the dispersion at the time of standing thereafter is 90% or less.
4. The resin-dispersed electrolyte according to claim 1 or 2,
when the viscosity of a dispersion of the particles in a nonaqueous solvent as a dispersion medium at 25 ℃ is C and the viscosity of the nonaqueous solvent is D, the ratio of C/D is 200 or less.
5. The resin-dispersed electrolyte according to claim 1 or 2,
the vinylidene fluoride polymer comprises structural units derived from vinylidene fluoride and structural units derived from a monomer copolymerizable with the vinylidene fluoride,
the vinylidene fluoride polymer has a melting point of 85 ℃ to 175 ℃.
6. The resin-dispersed electrolyte according to claim 5,
the monomer copolymerizable with the vinylidene fluoride is at least one compound selected from the group consisting of hexafluoropropylene, chlorotrifluoroethylene, trifluoroethylene, tetrafluoroethylene, hexafluoroethylene and fluoroalkyl vinyl ether.
7. The resin-dispersed electrolyte according to claim 6,
the vinylidene fluoride polymer comprises a structural unit derived from vinylidene fluoride and a structural unit derived from hexafluoropropylene,
when the content of a structural unit derived from hexafluoropropylene in the vinylidene fluoride polymer is represented by X and the b ℃ of the particles is represented by Y, X is 0 mass% or more and 35 mass% or less, and Y is 85 ℃ or more and 175 ℃ or less.
8. The resin-dispersed electrolyte according to claim 1 or 2,
the primary particle diameter of the particles is 10 nm-1 mu m.
9. The resin-dispersed electrolyte according to claim 1 or 2,
the nonaqueous electrolytic solution contains a nonaqueous solvent and an electrolyte,
the nonaqueous solvent is at least one compound selected from the group consisting of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.
10. The resin-dispersed electrolyte according to claim 9,
the electrolyte is selected from LiPF6、LiAsF6、LiClO4、LiBF4、LiCl、LiBr、LiCH3SO3、LiCF3SO3、LiN(CF3SO2)2And LiC (CF)3SO2)3One or more compounds of the group consisting of.
11. A polymer gel electrolyte formed from the resin-dispersed electrolyte of any one of claims 1 to 10.
12. A separator provided with the polymer gel electrolyte of claim 11.
13. An electrode provided with the polymer gel electrolyte according to claim 11.
14. A method for producing a polymer gel electrolyte, which comprises heating a resin-dispersed electrolyte solution or heating with pressing and cooling to gel the electrolyte solution,
the resin-dispersed electrolyte according to any one of claims 1 to 10 is used in the resin-dispersed electrolyte.
15. The method of manufacturing a polymer gel electrolyte according to claim 14,
when the viscosity of a dispersion of the particles in a nonaqueous solvent as a dispersion medium at 25 ℃ is C and the viscosity of the nonaqueous solvent is D, the ratio of C/D is 200 or less.
16. A secondary battery, comprising: a positive electrode, a negative electrode, a separator disposed between the two electrodes, and the polymer gel electrolyte according to claim 11 interposed between the positive electrode, the negative electrode, and the separator.
17. A manufacturing method of a secondary battery, the manufacturing method comprising:
injecting a resin-dispersed electrolyte into a battery container that contains a battery element including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; and a step of heating the battery container or heating with pressing and cooling the battery container to gel the resin-dispersed electrolyte,
the resin-dispersed electrolyte according to any one of claims 1 to 10 is used in the resin-dispersed electrolyte.
CN201980054939.7A 2018-09-14 2019-09-04 Resin-dispersed electrolyte solution, polymer gel electrolyte and method for producing same, and secondary battery and method for producing same Active CN112640181B (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2018172971 2018-09-14
JP2018-172971 2018-09-14
PCT/JP2019/034798 WO2020054548A1 (en) 2018-09-14 2019-09-04 Resin dispersion electrolyte solution, polymer gel electrolyte, production method for polymer gel electrolyte, secondary battery, and production method for secondary battery

Publications (2)

Publication Number Publication Date
CN112640181A CN112640181A (en) 2021-04-09
CN112640181B true CN112640181B (en) 2021-09-24

Family

ID=69776806

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201980054939.7A Active CN112640181B (en) 2018-09-14 2019-09-04 Resin-dispersed electrolyte solution, polymer gel electrolyte and method for producing same, and secondary battery and method for producing same

Country Status (4)

Country Link
JP (1) JP6804709B2 (en)
KR (1) KR102367508B1 (en)
CN (1) CN112640181B (en)
WO (1) WO2020054548A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4293007A1 (en) * 2021-02-10 2023-12-20 Daikin Industries, Ltd. Compound, composition, electrochemical device, lithium ion secondary battery and module
KR20240048563A (en) * 2021-10-05 2024-04-15 가부시끼가이샤 구레하 Vinylidene fluoride polymer solution

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1194278A (en) * 1997-01-20 1998-09-30 松下电器产业株式会社 Polymer electrolyte and lithium-polymer cell using said electrolyte
JPH11204136A (en) * 1998-01-08 1999-07-30 Toyota Motor Corp Bipolar-type lithium-ion secondary battery and manufacture thereof
JP2006104391A (en) * 2004-10-07 2006-04-20 Daikin Ind Ltd Method for producing fluoropolymer aqueous dispersion
CN101005146A (en) * 2005-11-14 2007-07-25 索尼株式会社 Gel electrolyte and gel electrolyte battery
CN108370067A (en) * 2016-03-10 2018-08-03 株式会社吴羽 Gel-like electrolyte with and preparation method thereof

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6059604A (en) * 1983-09-12 1985-04-06 ダイキン工業株式会社 Ferrodielectric polymer material and method of producing same
JPH10261437A (en) * 1997-01-20 1998-09-29 Matsushita Electric Ind Co Ltd Polymer electrolyte and lithium polymer battery using it
JP3841127B2 (en) * 1997-09-16 2006-11-01 株式会社ジーエス・ユアサコーポレーション Gel electrolyte
JP2000013252A (en) 1998-06-26 2000-01-14 Kenwood Corp Transmission circuit
JP2005056701A (en) 2003-08-05 2005-03-03 Sony Corp Manufacturing method and manufacturing device of battery

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1194278A (en) * 1997-01-20 1998-09-30 松下电器产业株式会社 Polymer electrolyte and lithium-polymer cell using said electrolyte
JPH11204136A (en) * 1998-01-08 1999-07-30 Toyota Motor Corp Bipolar-type lithium-ion secondary battery and manufacture thereof
JP2006104391A (en) * 2004-10-07 2006-04-20 Daikin Ind Ltd Method for producing fluoropolymer aqueous dispersion
CN101005146A (en) * 2005-11-14 2007-07-25 索尼株式会社 Gel electrolyte and gel electrolyte battery
CN108370067A (en) * 2016-03-10 2018-08-03 株式会社吴羽 Gel-like electrolyte with and preparation method thereof

Also Published As

Publication number Publication date
WO2020054548A1 (en) 2020-03-19
KR20210054564A (en) 2021-05-13
JP6804709B2 (en) 2020-12-23
KR102367508B1 (en) 2022-02-24
JPWO2020054548A1 (en) 2021-02-15
CN112640181A (en) 2021-04-09

Similar Documents

Publication Publication Date Title
KR20210132000A (en) Functional layer for electrochemical element, functional layer-forming separator for electrochemical element, and electrochemical element
WO2020246394A1 (en) Separator including functional layer for electrochemical element, and electrochemical element
CN112640181B (en) Resin-dispersed electrolyte solution, polymer gel electrolyte and method for producing same, and secondary battery and method for producing same
KR102260002B1 (en) Adhesive composition, separator structure, electrode structure, nonaqueous electrolyte secondary battery, and manufacturing method thereof
EP4366021A2 (en) Vinylidene fluoride copolymer composition and method for producing same, polymer dispersion solution, electrode for nonaqueous electrolyte secondary battery, electrolyte layer for nonaqueous electrolyte secondary battery, and nonaqueous electrolyte secondary battery
KR101409692B1 (en) Vinylidene fluoride polymer powder and vinylidene fluoride polymer solution
CN112930577A (en) Composition for electrochemical element functional layer, functional layer for electrochemical element, and electrochemical element
CN112585795B (en) Resin-dispersed electrolyte solution, polymer gel electrolyte and method for producing same, and secondary battery and method for producing same
CN112585211B (en) Vinylidene fluoride polymer powder, binder composition, electrode mixture, and method for producing electrode
WO2011052669A1 (en) Method for producing heat-treated vinylidene fluoride polymer powder and method for producing vinylidene fluoride polymer solution
JPWO2020022343A1 (en) Non-aqueous secondary battery slurry and its manufacturing method, non-aqueous secondary battery battery member and its manufacturing method, and non-aqueous secondary battery
CN114556680B (en) Functional layer for lithium ion secondary battery separator, separator with functional layer for lithium ion secondary battery separator, lithium ion secondary battery, and method for producing same
JP4781547B2 (en) Polymer gel electrolyte and battery
WO2021200049A1 (en) Composition for electrochemical element functional layer, functional layer for electrochemical element, laminate for electrochemical element, and electrochemical element
TWI442617B (en) Non-aqueous electrolyte secondary battery negative electrode and nonaqueous electrolyte secondary battery
WO2019170694A1 (en) A process for the preparation of a solid polymer electrolyte useful in batteries
US20240010826A1 (en) Vinylidene fluoride polymer composition and method of producing same, resin composition, electrode mixture, and electrode containing these, and method of producing same
CN112789756A (en) Gel electrolyte and nonaqueous electrolyte secondary battery
WO2021200083A1 (en) Composition for electrochemical element functional layer, laminate for electrochemical element, and electrochemical element
JP2024063151A (en) VINYLIDENE FLUORIDE COPOLYMER COMPOSITION AND METHOD FOR PRODUCING SAME, POLYMER DISPERSION, ELECTRODE FOR NONAQUEOUS ELECTROLYTE SECONDARY BATTERY, ELECTROLYTE LAYER FOR NONAQUEOUS ELECTROLYTE SECONDARY BATTERY, AND NONAQUEOUS ELECTROLYTE SECONDARY BATTERY

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant