WO2014185378A1 - 非水電解質二次電池用構造体、非水電解質二次電池および該構造体の製造方法 - Google Patents
非水電解質二次電池用構造体、非水電解質二次電池および該構造体の製造方法 Download PDFInfo
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- WO2014185378A1 WO2014185378A1 PCT/JP2014/062592 JP2014062592W WO2014185378A1 WO 2014185378 A1 WO2014185378 A1 WO 2014185378A1 JP 2014062592 W JP2014062592 W JP 2014062592W WO 2014185378 A1 WO2014185378 A1 WO 2014185378A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/417—Polyolefins
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/42—Acrylic resins
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
- H01M50/426—Fluorocarbon polymers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
- H01M50/411—Organic material
- H01M50/429—Natural polymers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- 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
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2220/00—Batteries for particular applications
- H01M2220/30—Batteries in portable systems, e.g. mobile phone, laptop
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- 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
Definitions
- the present invention relates to a structure for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery, and a method for producing the structure.
- a non-aqueous electrolyte secondary battery using lithium is used as a battery capable of obtaining large energy with a small volume and mass.
- a nonaqueous electrolyte secondary battery as an energy source for a hybrid car, an electric vehicle, etc., and its practical use has begun.
- a non-aqueous electrolyte secondary battery usually has a positive electrode and a negative electrode, and a separator for insulating the positive electrode and the negative electrode is disposed therebetween.
- a separator used in a nonaqueous electrolyte secondary battery a polyolefin polymer porous film has been conventionally used.
- Nonaqueous electrolyte secondary batteries can be charged and discharged by moving ions (lithium ions (Li + ) in the case of lithium ion secondary batteries) between the positive electrode and the negative electrode through the separator. .
- the separator is required not to prevent free movement of ions, and a porous film having a plurality of fine pores is used as the separator.
- the separator is required to have a so-called shutdown function.
- the shutdown function means that when a minute short circuit occurs inside the battery, it blocks the hole of the part, thereby preventing the movement of ions and losing the battery function of the part. This is a function that improves safety.
- the shutdown function is achieved by the fact that when a minute short circuit occurs inside the battery, the temperature of that part rises and the part melts and the hole closes. ing.
- Patent Document 1 when the surface layer contains polymer particles having a melting point lower than that of the separator, when the temperature in the battery becomes high, the polymer particles having a melting point lower than that of the separator are melted before the separator. It is disclosed that the pores of the separator, which is a porous film, can be closed before the separator shrinks by forming a film on the substrate.
- Patent Document 2 discloses that the heat-resistant resin porous layer has excellent wear resistance by containing fluorine-based resin fine particles.
- the resin constituting the layer is dissolved or dispersed in a solvent and applied to the separator, and then the resin constituting the layer is formed.
- a porous process such as drying after passing through a poor solvent was necessary.
- the present invention provides a structure for a nonaqueous electrolyte secondary battery, a method for producing the same, and a nonaqueous electrolyte obtained from the structure, which can be produced without passing through complicated steps such as passing through a poor solvent.
- An object is to provide a secondary battery.
- the present inventors perform complicated processes such as passing an intermediate layer containing a specific amount of vinylidene fluoride polymer particles through a poor solvent.
- the present invention was completed by finding an electrolyte solution injection path.
- the non-aqueous electrolyte secondary battery structure of the present invention is a non-aqueous electrolyte secondary battery structure having a positive electrode, a separator, and a negative electrode, and includes a vinylidene fluoride polymer particle.
- An intermediate layer is provided between at least one of the positive electrode and the separator and between the negative electrode and the separator, and 100 parts by mass of the raw material constituting the intermediate layer contains 60 vinylidene fluoride polymer particles. ⁇ 100 parts by mass.
- the intermediate layer preferably has a structure in which a plurality of vinylidene fluoride polymer particles are bonded to each other directly or via a water-soluble polymer.
- the vinylidene fluoride polymer particles preferably have an average particle size of 10 to 700 nm.
- the nonaqueous electrolyte secondary battery of the present invention is obtained from the structure for a nonaqueous electrolyte secondary battery.
- the method for producing a structure for a non-aqueous electrolyte secondary battery according to the present invention is a method for producing the structure for a non-aqueous electrolyte secondary battery, wherein the intermediate layer is any one of the following (1) to (4): It is formed.
- the intermediate layer is formed by applying an aqueous dispersion containing vinylidene fluoride polymer particles to at least one selected from a positive electrode, a separator, and a negative electrode and drying.
- the intermediate layer is formed by immersing and drying at least one selected from a positive electrode, a separator, and a negative electrode in an aqueous dispersion containing vinylidene fluoride polymer particles.
- the intermediate layer is formed by applying an aqueous dispersion containing vinylidene fluoride polymer particles to a base material and drying it, and then peeling it from the base material.
- the intermediate layer is formed by immersing the base material in an aqueous dispersion containing vinylidene fluoride polymer particles and drying it, and then peeling the base material from the base material.
- the structure for a non-aqueous electrolyte secondary battery of the present invention is a structure having a layer using a resin on at least one side of a separator, and can be manufactured by a simpler method than before. Therefore, the structure for nonaqueous electrolyte secondary batteries and the nonaqueous electrolyte secondary battery of the present invention are excellent in productivity.
- FIG. 2 is a SEM photograph of a cross section of a separator having an intermediate layer formed in Experimental Example 1. It is a SEM photograph of the section of the separator with which the intermediate layer was formed obtained in comparative experimental example 1.
- FIG. 4 is a diagram showing a positive electrode discharge capacity in a cycle test of a laminate cell performed in Example 2.
- the non-aqueous electrolyte secondary battery structure of the present invention is a non-aqueous electrolyte secondary battery structure having a positive electrode, a separator, and a negative electrode, and is an intermediate layer formed by including vinylidene fluoride polymer particles In at least one of the positive electrode and the separator and between the negative electrode and the separator, and in 100 parts by mass of the raw material constituting the intermediate layer, the vinylidene fluoride polymer particles are 60 to 100 Part by mass.
- the structure for the non-aqueous electrolyte secondary battery structure of the present invention includes an intermediate layer formed containing vinylidene fluoride polymer particles, at least between the positive electrode and the separator, and between the negative electrode and the separator. Except for the one, it is the same as the conventional structure for non-aqueous electrolyte secondary batteries, and the positive electrode, separator, and negative electrode can be structured as well as known structures for non-aqueous electrolyte secondary batteries. Can be used without limitation.
- the positive electrode and the negative electrode may be collectively referred to as “electrode”, and the positive electrode current collector and the negative electrode current collector may be collectively referred to as “current collector”.
- the positive electrode included in the nonaqueous electrolyte secondary battery structure of the present invention is not particularly limited as long as it has a positive electrode active material that is responsible for the positive electrode reaction and has a current collecting function. It consists of a positive electrode mixture layer containing a positive electrode active material, and a positive electrode current collector that functions as a current collector and holds the positive electrode mixture layer.
- the intermediate layer is It is preferable to arrange between the positive electrode mixture layer and the separator.
- the positive electrode mixture layer contains a positive electrode active material and a binder, and can further contain a conductive auxiliary agent if necessary.
- the mixing ratio of the positive electrode active material, the binder, and the conductive additive in the positive electrode mixture layer is set to a general mixing ratio used in non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries. However, it can be adjusted as appropriate according to the type of the secondary battery.
- the thickness of the positive electrode mixture layer is usually 20 to 250 ⁇ m.
- the positive electrode active material used in the nonaqueous electrolyte secondary battery of the present invention can be used without particular limitation as long as it functions as a positive electrode active material, including conventionally known electrode active materials for positive electrodes.
- a lithium-based positive electrode active material containing at least lithium is preferable as the positive electrode active material constituting the positive electrode mixture layer.
- the lithium-based positive active material for example, LiCoO 2, LiNi x Co 1 -x O 2 (0 ⁇ x ⁇ 1)
- Formula Limy 2 (M such is, Co, Ni, Fe, Mn , Cr, V-like
- Y is a chalcogen element such as O and S)
- a composite metal oxide having a spinel structure such as LiMn 2 O 4
- an olivine-type lithium compound such as LiFePO 4 It is done.
- the specific surface area of the positive electrode active material is preferably 0.05 to 50 m 2 / g.
- the specific surface area of the positive electrode active material can be determined by a nitrogen adsorption method.
- the positive electrode active material constituting the nonaqueous electrolyte secondary battery of the present invention is not limited to these, and may be appropriately selected according to the type of the secondary battery.
- the positive electrode mixture layer may further contain a conductive aid as necessary.
- This conductive auxiliary agent is added for the purpose of improving the conductivity of the positive electrode mixture layer when using an active material with low electronic conductivity such as LiCoO 2 , and is used for carbon black, graphite fine powder, fiber, etc. Carbonaceous materials, metal fine powders such as nickel and aluminum, or fibers are used.
- the binder serves to bind the positive electrode active material and the conductive additive.
- the binder is not particularly limited, but those widely used in conventionally known lithium ion secondary batteries can be suitably used.
- polytetrafluoroethylene, polyvinylidene fluoride, fluororubber Fluorine-containing resins such as styrene butadiene rubber and carboxymethyl cellulose, thermoplastic resins such as polypropylene and polyethylene can be used.
- a vinylidene fluoride copolymer can be used as the fluorine-containing resin.
- a vinylidene fluoride copolymer a vinylidene fluoride-maleic acid monomethyl ester copolymer or the like can be used.
- the positive electrode current collector is not particularly limited as long as it has good conductivity so that electricity can be supplied to the outside of the secondary battery and does not hinder the electrode reaction in the secondary battery.
- Examples of the positive electrode current collector include those generally used as a positive electrode current collector of a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery.
- the positive electrode current collector is preferably made of aluminum or an alloy thereof, and among them, an aluminum foil is preferable.
- the positive electrode current collector is not limited to these, and may be appropriately selected according to the type of secondary battery.
- the thickness of the positive electrode current collector is usually 5 to 100 ⁇ m.
- the method for producing a positive electrode comprising the positive electrode current collector and the positive electrode mixture layer that can be used in the present invention is not particularly limited, but a positive electrode mixture containing each component constituting the positive electrode mixture layer is collected. It can be obtained by applying and drying on an electric body.
- the positive electrode active material, the binder, the conductive aid used as necessary, and the non-aqueous solvent may be mixed in a uniform slurry.
- the order is not particularly limited.
- N-methyl-2-pyrrolidone can be used as the non-aqueous solvent used for dispersing the positive electrode active material, the conductive additive, and the binder.
- the positive electrode used in the present invention is produced by applying and drying the positive electrode mixture on a current collector, and the application is performed on at least one surface, preferably both surfaces, of the current collector.
- the method for coating is not particularly limited, and examples thereof include a method using a bar coater, a die coater, or a comma coater.
- drying performed after the coating is usually performed at a temperature of 50 to 150 ° C. for 1 to 300 minutes.
- the pressure at the time of drying is not particularly limited, but it is usually carried out under atmospheric pressure or reduced pressure.
- heat treatment may be further performed after drying.
- press treatment may be further performed.
- it is usually performed at 1 to 200 MPa-G. It is preferable to perform the press treatment because the electrode density can be improved.
- the separator used in the present invention is a separator constituting a non-aqueous electrolyte secondary battery structure.
- the positive electrode and the negative electrode are electrically insulated and electrolysis is performed. It plays the role of holding the liquid.
- the separator used in the present invention is not particularly limited.
- a polyolefin polymer such as polyethylene and polypropylene
- a polyester polymer such as polyethylene terephthalate
- an aromatic polyamide polymer such as polyetherimide.
- Single-layer and multilayer porous membranes, nonwoven fabrics composed of molecules, polyethersulfone, polysulfone, polyetherketone, polystyrene, polyethylene oxide, polycarbonate, polyvinyl chloride, polyacrylonitrile, polymethylmethacrylate, ceramics, etc., and mixtures thereof, Glass, paper, etc. can be mentioned.
- a modified polymer may be used as the aforementioned polymer.
- a porous film of a polyolefin polymer for example, polyethylene or polypropylene.
- a polyolefin-based polymer porous membrane examples include a single-layer polypropylene separator, a single-layer polyethylene separator, and a polypropylene / polyethylene / polypropylene three-layer separator, which are commercially available as Celgard (registered trademark) from Polypore Corporation. Can do.
- Celgard registered trademark
- surface treatment may be given as a separator.
- the separator is preferably larger than the positive electrode and the negative electrode in order to ensure insulation between the positive electrode and the negative electrode.
- the negative electrode included in the nonaqueous electrolyte secondary battery structure of the present invention is not particularly limited as long as it has a negative electrode active material that plays a role in the negative electrode reaction and has a current collecting function. It consists of a negative electrode mixture layer containing a negative electrode active material, and a negative electrode current collector that functions as a current collector and holds the negative electrode mixture layer.
- the intermediate layer is It is preferable to dispose between the negative electrode mixture layer and the separator.
- the negative electrode mixture layer contains a negative electrode active material and a binder, and can further contain a conductive auxiliary agent if necessary.
- the compounding ratio of the negative electrode active material, the binder, and the conductive additive in the negative electrode mixture layer may be a general compounding ratio used in non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries. However, it can be adjusted as appropriate according to the type of the secondary battery.
- the thickness of the negative electrode mixture layer is usually 20 to 250 ⁇ m.
- the negative electrode active material used in the nonaqueous electrolyte secondary battery of the present invention can be used without particular limitation as long as it functions as a negative electrode active material including a conventionally known electrode active material for a negative electrode.
- examples of the negative electrode active material constituting the negative electrode mixture layer include carbon materials, metal / alloy materials, metal oxides, and the like, among which carbon materials are preferable.
- the carbon material artificial graphite, natural graphite, non-graphitizable carbon, graphitizable carbon and the like are used.
- the said carbon material may be used individually by 1 type, or may use 2 or more types.
- the artificial graphite can be obtained, for example, by carbonizing an organic material, heat-treating it at a high temperature, pulverizing and classifying it.
- the non-graphitizable carbon can be obtained, for example, by firing a material derived from petroleum pitch at 1000 to 1500 ° C.
- the specific surface area of the negative electrode active material is preferably 0.3 to 10 m 2 / g. When the specific surface area exceeds 10 m 2 / g, the decomposition amount of the electrolytic solution increases and the initial irreversible capacity may increase.
- the specific surface area of the negative electrode active material can be determined by a nitrogen adsorption method.
- the negative electrode active material constituting the nonaqueous electrolyte secondary battery of the present invention is not limited to these, and may be appropriately selected according to the type of secondary battery.
- the negative electrode mixture layer may further contain a conductive aid as necessary.
- This conductive auxiliary agent is added for the purpose of improving the conductivity of the negative electrode mixture layer.
- Carbon black, graphite fine powder or carbonaceous material such as fiber, metal fine powder such as nickel or aluminum, or fiber is used. Is done.
- the binder serves to bind the negative electrode active material and the conductive additive.
- examples of the binder include the same binders as described in the above [Positive electrode] section.
- the negative electrode current collector is not particularly limited as long as it has good conductivity so that electricity can be supplied to the outside of the secondary battery and does not hinder the electrode reaction in the secondary battery.
- As said negative electrode collector what is generally used as a negative electrode collector of nonaqueous electrolyte secondary batteries, such as a lithium ion secondary battery, is mentioned.
- the negative electrode current collector is preferably made of copper, and copper foil is particularly preferable.
- the negative electrode current collector is not limited to these, and may be appropriately selected according to the type of secondary battery.
- the thickness of the negative electrode current collector is usually 5 to 100 ⁇ m.
- a method for producing a negative electrode comprising the negative electrode current collector and the negative electrode mixture layer that can be used in the present invention is not particularly limited, but a negative electrode mixture containing each component constituting the negative electrode mixture layer is collected. It can be obtained by applying and drying on an electric body.
- the method for preparing the negative electrode mixture and the method for producing the negative electrode can be carried out by the same method as the method for preparing the positive electrode mixture and the method for producing the positive electrode in the above [Positive electrode] section.
- the structure for a non-aqueous electrolyte secondary battery of the present invention has an intermediate layer formed including vinylidene fluoride polymer particles between at least one of a positive electrode and a separator and between a negative electrode and a separator. .
- the non-aqueous electrolyte secondary potential structure according to the present invention includes an intermediate layer formed by containing the vinylidene fluoride polymer particles at least one between the positive electrode and the separator and between the negative electrode and the separator. Preferably between the positive electrode and the separator, but not between the negative electrode and the separator, or between the positive electrode and the separator, and between the negative electrode and the separator. And between the negative electrode and the separator are more preferable. That is, the nonaqueous electrolyte secondary potential structure of the present invention preferably has an intermediate layer formed by including the vinylidene fluoride polymer particles at least between the positive electrode and the separator.
- the nonaqueous electrolyte secondary potential structure of the present invention has an intermediate layer formed by including the vinylidene fluoride polymer particles at least between the positive electrode and the separator, the oxidation-reduction resistance of the separator is improved. It is preferable because it improves.
- the vinylidene fluoride polymer particles are particles formed by including a vinylidene fluoride polymer, and as the vinylidene fluoride polymer, any one of a vinylidene fluoride homopolymer and a vinylidene fluoride copolymer is used. But you can.
- the vinylidene fluoride polymer particles used in the present invention may be formed from a mixture of vinylidene fluoride polymers, or a plurality of types of vinylidene fluoride polymer particles may be used.
- the vinylidene fluoride polymer is a vinylidene fluoride copolymer
- the monomers other than vinylidene fluoride constituting the copolymer are not particularly limited.
- the other monomers may be used alone or in combination of two or more.
- vinylidene fluoride polymer is a vinylidene fluoride copolymer
- vinylidene fluoride is usually used in an amount of 50 mol% or more, preferably 80 mol% or more is used, more preferably 85 mol% or more is used, and most preferably 90 mol% or more is used.
- other monomers are usually used in an amount of 50 mol% or less, preferably 20 mol% or less, more preferably 15 mol% or less, and most preferably 10 mol% or less.
- a vinylidene fluoride copolymer it is preferable that properties derived from other monomers are expressed, and it is preferable to use 95 mol% or less of vinylidene fluoride and 5 mol% or more of other monomers.
- fluorine-based monomer copolymerizable with vinylidene fluoride examples include vinyl fluoride, trifluoroethylene (TrFE), tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), Examples thereof include perfluoroalkyl vinyl ethers represented by perfluoromethyl vinyl ether.
- unsaturated monobasic acid unsaturated dibasic acid, monoester of unsaturated dibasic acid and the like are preferable.
- unsaturated monobasic acid include acrylic acid, methacrylic acid, 2-carboxyethyl acrylate, 2-carboxyethyl methacrylate and the like.
- unsaturated dibasic acid include maleic acid and citraconic acid.
- the unsaturated dibasic acid monoester preferably has 5 to 8 carbon atoms, and examples thereof include maleic acid monomethyl ester, maleic acid monoethyl ester, citraconic acid monomethyl ester, and citraconic acid monoethyl ester. Can do.
- acrylic acid, methacrylic acid, maleic acid, citraconic acid, maleic acid monomethyl ester, and citraconic acid monomethyl ester are preferable as the carboxyl group-containing monomer.
- carboxyl group-containing monomer acryloyloxyethyl succinic acid, methacryloyloxyethyl succinic acid, acryloyloxyethyl phthalic acid, methacryloyloxyethyl phthalic acid, or the like may be used.
- carboxylic acid anhydride group-containing monomer examples include acid anhydrides of the unsaturated dibasic acid, specifically maleic anhydride and citraconic anhydride.
- a crosslinked polymer may be used as the vinylidene fluoride polymer.
- a polyfunctional monomer may be used as the other monomer.
- a cross-linking reaction may be performed.
- vinylidene fluoride copolymer a copolymer of vinylidene fluoride and a fluorine-based monomer copolymerizable with vinylidene fluoride is preferable.
- vinylidene fluoride (VDF) -TFE copolymer is used.
- VDF-TFE-HFP copolymer, VDF-HFP copolymer, VDF-CTFE copolymer, VDF-TFE-CTFE copolymer, VDF-HFP-CTFE copolymer are preferred, and VDF-TFE-HFP copolymer is preferred.
- a polymer, a VDF-HFP copolymer, a VDF-CTFE copolymer, and a VDF-HFP-CTFE copolymer are more preferable.
- the vinylidene fluoride polymer may be a vinylidene fluoride homopolymer or a vinylidene fluoride copolymer. From the nonaqueous electrolyte secondary battery structure of the present invention, the nonaqueous electrolyte secondary battery may be used. It is preferable to use a vinylidene fluoride copolymer because the adhesive strength between the separator and the intermediate layer and the adhesive strength between the electrode and the intermediate layer are excellent when the battery is manufactured.
- the method for obtaining the vinylidene fluoride polymer is not particularly limited, and can be obtained by a polymerization method such as emulsion polymerization, soap-free emulsion polymerization, miniemulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization and the like. Among these, it is preferable to obtain by the manufacturing method which can obtain a vinylidene fluoride polymer as particle
- a vinylidene fluoride polymer When a vinylidene fluoride polymer is obtained in a shape other than the particles, it needs to be pulverized in order to be used as the vinylidene fluoride polymer particles, so the particulate vinylidene fluoride polymer That is, it is preferable to employ a method capable of obtaining vinylidene fluoride polymer particles.
- Examples of a method for obtaining vinylidene fluoride polymer particles include emulsion polymerization, soap-free emulsion polymerization, miniemulsion polymerization, and suspension polymerization, and obtain vinylidene fluoride polymer particles having an average particle size of 1 ⁇ m or less. Emulsion polymerization, soap-free emulsion polymerization, and miniemulsion polymerization that are easy to handle are preferred.
- Emulsion polymerization is a method of obtaining vinylidene fluoride polymer particles using a monomer, an emulsifier, water, and a polymerization initiator.
- Any emulsifier may be used as long as it can form micelles and can stably disperse the vinylidene fluoride polymer particles to be produced, and an ionic emulsifier, a nonionic emulsifier, or the like can be used.
- the polymerization initiator a water-soluble peroxide or a water-soluble azo compound is used, and a redox initiator system such as ascorbic acid-hydrogen peroxide is used.
- Soap-free emulsion polymerization is emulsion polymerization that is performed without using a normal emulsifier such as that used in the aforementioned emulsion polymerization. Since the vinylidene fluoride polymer particles obtained by soap-free emulsion polymerization do not leave the emulsifier in the polymer particles, the emulsifier is used when the intermediate layer formed including the vinylidene fluoride polymer particles is formed. Is preferable because it does not bleed out to the surface. Soap-free emulsion polymerization can be performed by changing the emulsifier in the emulsion polymerization to a reactive emulsifier. When the monomer is dispersed, soap-free polymerization can be performed without using a reactive emulsifier.
- the reactive emulsifier is a substance having a polymerizable double bond in the molecule and acting as an emulsifier.
- a reactive emulsifier When a reactive emulsifier is used, micelles are formed at the initial stage of polymerization as in the case where the aforementioned emulsifier is present in the system, but as the reaction proceeds, the reactive emulsifier is consumed as a monomer, and finally In the reaction system, the reactive emulsifier is hardly present in a free state.
- Mini-emulsion polymerization is a method in which monomer droplets are refined to submicron size by applying a strong shearing force using an ultrasonic oscillator or the like, and polymerization is performed. Mini-emulsion polymerization is performed by adding a slightly water-soluble substance called hydrophobe to stabilize the finely divided monomer oil droplets. In miniemulsion polymerization, ideally, monomer oil droplets are polymerized, and each oil droplet is converted into fine particles of a vinylidene fluoride polymer.
- Suspension polymerization is a method in which a water-insoluble polymerization initiator is dissolved in a water-insoluble monomer, which is suspended in water by mechanical stirring and heated. In suspension polymerization, polymerization proceeds in monomer droplets, and a dispersion solution of vinylidene fluoride polymer fine particles is obtained.
- the particle size of the polymer fine particles obtained by suspension polymerization generally tends to be larger than the particle size of the polymer fine particles obtained by emulsion polymerization, soap-free emulsion polymerization, or miniemulsion polymerization.
- Emulsifiers hereinafter also referred to as surfactants
- dispersants used in the production of vinylidene fluoride polymers and dispersion of particles obtained by suspension polymerization remain in the battery.
- those having good oxidation-reduction resistance are preferable.
- the surfactant may be a nonionic surfactant, a cationic surfactant, an anionic surfactant, or an amphoteric surfactant, or a plurality of types.
- the surfactant used in the polymerization those conventionally used for polymerization of polyvinylidene fluoride such as perfluorinated, partially fluorinated, and non-fluorinated surfactants are preferable. Of these, it is preferable to use a perfluoroalkylsulfonic acid and a salt thereof, a perfluoroalkylcarboxylic acid and a salt thereof, a fluorosurfactant having a fluorocarbon chain or a fluoropolyether chain. It is more preferable to use a salt.
- examples of the reactive emulsifier include, but are not limited to, polyoxyalkylene alkenyl ether, sodium alkylallylsulfosuccinate, sodium methacryloyloxypolyoxypropylene sulfate, alkoxy polyethylene glycol methacrylate, and the like.
- Polymerization conditions such as a polymerization temperature when polymerization is performed by each of the above-described polymerization methods can be arbitrarily set.
- the average particle size of the vinylidene fluoride polymer particles used in the present invention is preferably 10 to 700 nm, more preferably 20 to 500 nm. In the said range, since the thickness and air permeability of a layer are easy to control, it is preferable.
- the average particle diameter is a cumulant average particle diameter determined by a dynamic light scattering method, and can be measured using, for example, ELSZ-2 (Otsuka Electronics).
- the intermediate layer formed by including the vinylidene fluoride polymer particles included in the nonaqueous electrolyte secondary battery structure of the present invention may be formed only from the aforementioned vinylidene fluoride polymer particles, Usually, it is formed from the polymer particles and other components (hereinafter referred to as other components).
- the water-soluble polymer is preferably a polymer having adhesiveness to the vinylidene fluoride polymer particles, the electrode, and the separator.
- the water-soluble polymer include carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), polyethylene oxide (PEO), and the like, such as carboxymethyl cellulose (CMC), Polyvinyl alcohol (PVA) or the like is preferable from the viewpoint of using the battery for a long time.
- an inorganic filler or the like conventionally used when a resin film (intermediate layer) is provided between the positive electrode or the negative electrode and the separator can be used without any limitation.
- the inorganic filler examples include silicon dioxide (SiO 2 ), alumina (Al 2 O 3 ), titanium dioxide (TiO 2 ), calcium oxide (CaO), strontium oxide (SrO), barium oxide (BaO), and magnesium oxide (MgO).
- the inorganic filler alumina, silicon dioxide, magnesium oxide, and zinc oxide are preferable from the viewpoint of battery safety and coating solution stability.
- the average particle size of the inorganic filler is preferably 5 nm to 2 ⁇ m, and more preferably 10 nm to 1 ⁇ m.
- AKP3000 manufactured by Sumitomo Chemical Co., Ltd.
- high-purity alumina particles can be used.
- the intermediate layer of the structure for a non-aqueous electrolyte secondary battery of the present invention has 60 to 100 parts by mass of vinylidene fluoride polymer particles in 100 parts by mass of the raw material constituting the intermediate layer.
- the amount of the vinylidene fluoride polymer particles in 100 parts by mass of the raw material constituting the intermediate layer is preferably from 65 to 100 parts by mass, and preferably from 70 to 100 parts by mass of the vinylidene fluoride polymer particles. It is more preferable.
- the intermediate layer of the non-aqueous electrolyte secondary battery structure of the present invention is a particulate vinylidene fluoride polymer, so that an intermediate layer having air permeability can be used without using an inorganic filler. It is possible to form. When the inorganic filler is not used, it is possible to reduce the wear of the manufacturing apparatus when forming the intermediate layer with the inorganic filler, and to improve the weight energy density of the obtained nonaqueous electrolyte secondary battery.
- the separator or the vinylidene fluoride polymer particles forming the intermediate layer are exposed to a high temperature in the resulting nonaqueous electrolyte secondary battery,
- the presence of the inorganic filler in the intermediate layer can prevent a short circuit from occurring.
- the water-soluble polymer When a water-soluble polymer is used as the raw material constituting the intermediate layer, the water-soluble polymer is usually 0.01 to 20 parts by mass, preferably 0.01 to 15 parts per 100 parts by mass of the raw material. Part by mass, particularly preferably 0.01 to 10 parts by mass.
- the inorganic filler When an inorganic filler is used as a raw material constituting the intermediate layer, the inorganic filler is usually 0.01 to 40 parts by weight, preferably 0.01 to 35 parts by weight in 100 parts by weight of the raw material. Particularly preferred is 0.01 to 30 parts by mass.
- the thickness of the intermediate layer is usually 0.5 to 25 ⁇ m, preferably 1 to 20 ⁇ m.
- the intermediate layer is mainly formed using vinylidene fluoride polymer particles as a raw material. Usually, when the SEM observation is performed on the intermediate layer, it can be confirmed that the vinylidene fluoride polymer particles are present while maintaining the particle shape. That is, in the structure for a non-aqueous electrolyte secondary battery of the present invention, the vinylidene fluoride polymer particles constituting the intermediate layer are usually not melted and integrated.
- the intermediate layer preferably has a structure in which a plurality of vinylidene fluoride polymer particles are bonded to each other directly or via a water-soluble polymer.
- the vinylidene fluoride polymer particles may not be bonded to each other or bonded by a water-soluble polymer, and the non-aqueous electrolyte secondary battery The surface of the particles may be dissolved or swelled by the electrolytic solution injected when the non-aqueous electrolyte secondary battery is manufactured from the structural body.
- the intermediate layer is a polymer particle having adhesiveness as the vinylidene fluoride polymer particles, or when heat treatment is performed under conditions where the particle surface is melted in the process of forming the intermediate layer
- the intermediate layer preferably has a structure in which polymer particles are directly joined to each other. In this structure, each particle can be observed by SEM or the like, but the polymer particles are integrated by being directly joined to each other.
- the polymer particles are in contact with each other. It is preferable to have a structure joined by a water-soluble polymer.
- the structure is formed by producing an intermediate layer using a liquid containing the polymer particles, a water-soluble polymer and the like. In this structure, each particle can be observed by SEM or the like, and a water-soluble polymer exists between the particles.
- the intermediate layer is usually formed using an aqueous dispersion containing vinylidene fluoride polymer particles.
- the aqueous dispersion containing the vinylidene fluoride polymer particles contains the vinylidene fluoride polymer particles, and may contain the above-described other components as necessary.
- the vinylidene fluoride polymer particles are usually dispersed and other components may be dissolved or dispersed.
- the other component is a water-soluble polymer, it is usually dissolved, and when an inorganic filler is used as the other component, it is dispersed.
- a component with high specific gravity, such as an inorganic filler is included, it is preferable to use the said aqueous dispersion for formation of an intermediate
- the aqueous dispersion containing vinylidene fluoride polymer particles is generally 30 to 99 parts by weight, preferably 35 to 98 parts by weight of water as a dispersion medium, assuming that the total dispersion is 100 parts by weight. Used in a range.
- the intermediate layer can be formed by any of the following (1) to (4), for example.
- the intermediate layer is formed by applying an aqueous dispersion containing vinylidene fluoride polymer particles to at least one selected from a positive electrode, a separator, and a negative electrode and drying.
- the intermediate layer is formed by immersing and drying at least one selected from a positive electrode, a separator, and a negative electrode in an aqueous dispersion containing vinylidene fluoride polymer particles.
- the intermediate layer is formed by applying an aqueous dispersion containing vinylidene fluoride polymer particles to a substrate and drying it, and then peeling the substrate.
- the intermediate layer is formed by detaching the substrate after immersing and drying the substrate in an aqueous dispersion containing vinylidene fluoride polymer particles.
- coating the aqueous dispersion containing a vinylidene fluoride type polymer particle to a positive electrode, a separator, a negative electrode, and a base material what is necessary is just to apply
- a base material made of polyethylene terephthalate (PET) or the like can be used as the base material.
- the drying time is usually 40 to 190 ° C., and preferably 50 to 180 ° C., and the drying time is usually 1 minute to 15 hours.
- the temperature in the case of performing the heat treatment it is necessary to consider the separator, electrode, base material, vinylidene fluoride polymer particles, melting point of other components, decomposition temperature, etc. Although it varies depending on the system, it is usually from 60 to 220 ° C, preferably from 65 to 215 ° C.
- the time for the heat treatment is usually 1 minute to 5 hours.
- the non-aqueous electrolyte secondary battery structure of the present invention is a non-aqueous electrolyte secondary battery structure having a positive electrode, a separator, and a negative electrode as described above, and includes a vinylidene fluoride polymer particle.
- the intermediate layer is provided between at least one of the positive electrode and the separator and between the negative electrode and the separator, and in 100 parts by mass of the raw material constituting the intermediate layer, 60 vinylidene fluoride polymer particles are present. It is characterized by being ⁇ 100 parts by mass.
- the intermediate layer of the present invention includes a step of providing at least one of a positive electrode and a separator and a negative electrode and a separator. It can be manufactured by the same method as before.
- the method for producing a structure for a non-aqueous electrolyte secondary battery according to the present invention is characterized in that the intermediate layer is usually formed of any one of (1) to (4) as described above.
- the nonaqueous electrolyte secondary battery structure according to the present invention is a separator in which the intermediate layer is formed or an electrode in which the intermediate layer is formed. It can manufacture by the method similar to the past except using.
- the nonaqueous electrolyte secondary battery structure of the present invention includes the intermediate layer between the positive electrode and the separator, and the negative electrode. It can be produced by the same method as in the prior art, except that a step for placing the separator is required.
- the intermediate layer is formed to include vinylidene fluoride polymer particles, an electrolyte solution injection path is provided in the intermediate layer without performing the porous step. Can be produced, which is preferable.
- the resin constituting the layer is dissolved or dispersed in a solvent and applied to the separator, and then the resin constituting the layer is formed.
- a porous step such as drying after passing through a poor solvent was necessary, but the nonaqueous electrolyte secondary battery structure of the present invention was such that the intermediate layer was passed through the poor solvent as described above. It can be formed without complicated processes.
- nonaqueous electrolyte secondary battery structure of the present invention and the nonaqueous electrolyte secondary battery described later are excellent in productivity.
- Nonaqueous electrolyte secondary battery The nonaqueous electrolyte secondary battery of the present invention is obtained from the structure for a nonaqueous electrolyte secondary battery.
- non-aqueous electrolyte secondary battery well-known battery structures, such as a coin-type battery, a button-type battery, a cylindrical battery, and a square battery, can be taken.
- a member which comprises a non-aqueous electrolyte secondary battery a non-aqueous electrolyte, a cylindrical can, a laminate pouch etc. are mentioned other than the said structure for non-aqueous electrolyte secondary batteries, for example.
- the nonaqueous electrolytic solution is obtained by dissolving an electrolyte in a nonaqueous solvent.
- the non-aqueous solvent include an aprotic organic solvent capable of transporting a cation and an anion constituting an electrolyte and substantially not impairing the function of the secondary battery.
- examples of such non-aqueous solvents include organic solvents commonly used as non-aqueous electrolytes for lithium ion secondary batteries, such as carbonates, halogenated hydrocarbons, ethers, ketones, nitriles, lactones, Esters, oxolane compounds and the like can be used.
- propylene carbonate ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, ⁇ -butyrolactone, methyl propionate, ethyl propionate, and the like are preferable.
- These non-aqueous solvents may be used alone or in combination of two or more.
- the type of electrolyte is not particularly limited as long as it can transport constituent cations and anions by the non-aqueous solvent and does not substantially function as a secondary battery. It is not something.
- the non-aqueous electrolyte secondary battery is a lithium ion secondary battery, taking an electrolyte that can be used as an example, a lithium salt of a fluoro complex anion such as LiPF 6 , LiAsF 6 , LiBF 4 , Inorganic lithium salts such as LiClO 4 , LiCl and LiBr, and sulfonic acid lithium salts such as LiCH 3 SO 3 and LiCF 3 SO 3 , Li (CF 3 OSO 2 ) 2 N, Li (CF 3 OSO 2 ) 3 C, Examples thereof include organic lithium salts such as Li (CF 3 SO 2 ) 2 N and Li (CF 3 SO 2 ) 3 C. These electrolytes may be used alone or in combination of two or more.
- the nonaqueous electrolyte secondary battery of the present invention can be obtained from the above-described nonaqueous electrolyte secondary battery structure, but the intermediate layer of the nonaqueous electrolyte secondary battery structure is used when the battery is manufactured. It may swell by the injected electrolyte and act as a gel electrolyte.
- a polymer that easily swells with an electrolyte solution such as a VDF-HFP copolymer or a VDF-CTFE copolymer is used as the vinylidene fluoride polymer
- a non-aqueous electrolyte secondary battery is obtained as the intermediate layer. When used, it tends to act as a gel electrolyte.
- CMC carboxymethyl cellulose
- CMC used in the production example (Serogen PR, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was dried at 130 ° C. for 30 minutes, and the moisture content of CMC determined by measuring the weight before and after drying was 10.8%. there were.
- CMC aqueous solution (1-1) An additional 35 g of water was added to the obtained CMC aqueous solution (1-1) to obtain a CMC aqueous solution (1-2). A portion of the CMC aqueous solution (1-2) was dried at 150 ° C. for 2 hours. From the weight of the CMC after drying and the weight of the dried CMC aqueous solution (1-2), the CMC aqueous solution (1-2) When the CMC concentration was determined, the CMC concentration was 1.5 wt%.
- a part of the PVA aqueous solution (1) was dried at 100 ° C. for 2 hours, and the PVA concentration of the PVA aqueous solution (1) was determined from the weight of the dried PVA and the weight of the dried PVA aqueous solution (1).
- the PVA concentration was 24.3 wt%.
- VDF-HFP copolymer latex (1) (dispersion liquid (1) containing VDF-HFP copolymer particles) was obtained.
- the resin concentration of the obtained VDF-HFP copolymer latex (1) was 18.8% by mass, and the average particle size of the VDF-HFP copolymer particles was 163.5 nm.
- the average particle size of the polymer particles in the dispersion containing the polymer particles prepared in the production example was measured using ELSZ-2 manufactured by Otsuka Electronics.
- the obtained coating solution is applied to a separator (NH616, Asahi Kasei) using a wire bar # 4 (wet coating amount 36 ⁇ m), dried at 100 ° C. for 10 minutes, and formed to contain VDF-HFP copolymer particles. A layer (intermediate layer) was formed on the separator.
- the separator (NH616) is a polyolefin-made separator having a thickness of 16 ⁇ m.
- the separator on which the intermediate layer was formed was subjected to a freeze fracture method using methanol, and SEM observation was performed.
- FIG. 1 The obtained SEM photograph is shown in FIG. In FIG. 1, the intermediate layer (left side) was formed on the separator (right side), and it was clearly confirmed that the particles constituting the intermediate layer were in contact with each other.
- the obtained coating solution is applied to a separator (NH616, Asahi Kasei) using a wire bar # 4 (wet coating amount 36 ⁇ m), dried at 100 ° C. for 10 minutes, and formed to contain VDF-HFP copolymer particles. A layer (intermediate layer) was formed on the separator.
- Example 3 To dispersion (1) containing 6.70 g of VDF-HFP copolymer particles prepared in Production Example 4, 0.54 g of alumina (AKP3000, average particle size 500 nm, Sumitomo Chemical) and 5.00 g of Production Example 1 The CMC 1.5 wt% aqueous solution prepared in step 1 was added and stirred. Further, 0.3 g of water was added to 1 g of the obtained solution and stirred.
- the obtained coating solution is applied to a separator (NH616, Asahi Kasei) using a wire bar # 3 (wet coating amount 24 ⁇ m), dried at 100 ° C. for 10 minutes, and contains VDF-HFP copolymer particles and alumina particles.
- a layer (intermediate layer) formed in (1) was formed on the separator.
- the obtained coating solution is applied to a separator (NH616, Asahi Kasei) using a wire bar # 8 (wet coating amount 100 ⁇ m), dried at 100 ° C. for 10 minutes, and formed to contain VDF-HFP copolymer particles. A layer (intermediate layer) was formed on the separator.
- the separator on which the intermediate layer was formed was subjected to a freeze fracture method using methanol, and SEM observation was performed.
- the obtained SEM photograph is shown in FIG. In FIG. 2, it is confirmed that the intermediate layer (left side) is formed on the separator (right side), and that the particles constituting the intermediate layer are in contact with each other because a large amount of CMC resin exists. I could not.
- VDF-HFP copolymer latex (2) (dispersion liquid (2) containing VDF-HFP copolymer particles) was obtained.
- the resin concentration of the obtained VDF-HFP copolymer latex (2) was 20.8% by mass, and the average particle size of the VDF-HFP copolymer particles was 171.3 nm.
- CMC 3.5 wt% aqueous solution prepared in 1.00 g of Production Example 2 was added and stirred.
- the obtained coating solution is applied to a separator (NH616, Asahi Kasei) using wire bar # 3 (wet coating amount 24 ⁇ m), dried at 100 ° C. for 10 minutes, and formed to contain VDF-HFP copolymer particles. A layer (intermediate layer) was formed on the separator.
- VDF-HFP copolymer latex (3) (dispersion liquid (3) containing VDF-HFP copolymer particles) was obtained.
- the resin concentration of the obtained VDF-HFP copolymer latex (3) was 18.3% by mass, and the average particle size of the VDF-HFP copolymer particles was 294.3 nm.
- Example 5 To a dispersion liquid (3) containing 1.97 g of VDF-HFP copolymer particles prepared in Production Example 6, 1.00 g of CMC 1.5 wt% aqueous solution prepared in Production Example 1 was added and stirred.
- the obtained coating solution is applied to a separator (NH616, Asahi Kasei) using a wire bar # 4 (wet coating amount 36 ⁇ m), dried at 100 ° C. for 10 minutes, and formed to contain VDF-HFP copolymer particles. A layer (intermediate layer) was formed on the separator.
- VDF homopolymer latex ( 1) (Dispersion (1) containing VDF homopolymer particles) was obtained.
- the resin concentration of the obtained VDF homopolymer latex (1) was 7.5% by mass, and the average particle size of the VDF homopolymer particles was 67.9 nm.
- Example 6 To the dispersion liquid (1) containing VDF homopolymer particles prepared in 10.44 g of Production Example 7, 3.33 g of CMC 1.5 wt% aqueous solution prepared in Production Example 1 was added and stirred.
- the obtained coating solution is applied to a separator (NH616, Asahi Kasei) using a wire bar # 4 (wet coating amount 36 ⁇ m), dried at 100 ° C. for 10 minutes, and a layer formed containing VDF homopolymer particles (Intermediate layer) was formed on the separator.
- the air permeability of the laminate in which the intermediate layer obtained in each experimental example and comparative experimental example was formed on the separator was measured using a Gurley type densometer (Toyo Seiki Seisakusho). The results are shown in Table 1.
- the dispersion liquid (1) containing the VDF homopolymer particles prepared in Production Example 7 is used as a separator using a wire bar # 4 (wet coating amount: 36 ⁇ m) (eco-drawing paper, 170-8, Hokuetsu Kishu Paper) ) And dried at 100 ° C. for 10 minutes to form a layer (intermediate layer) formed containing VDF homopolymer particles on a cardboard.
- Example 7 Since paper is used for the base material, the air permeability is very low compared to other experiments.
- the intermediate layer was not peeled off from the cardboard (separator) when measuring the air permeability described later or manufacturing the structure. It was. That is, in the present invention, it is not essential to use a water-soluble polymer such as CMC, and the separator is not limited to polyolefin.
- the air permeability of the separator (NH616) used in the above experimental example is 194.0 [sec / 100 ml]
- the air permeability of cardboard (eco-image paper, 170-8) is It was 8.1 [sec / 100 ml].
- Example 1 By sandwiching the laminate in which the intermediate layer obtained in each of Experimental Examples 1 to 7 is formed on the separator between the positive electrode and the negative electrode so that the intermediate layer is located between the separator and the positive electrode, A structure having an intermediate layer between the separator and the electrode was obtained.
- VDF-HFP copolymer latex (4) (dispersion liquid (4) containing VDF-HFP copolymer particles) was obtained.
- the resin concentration of the obtained VDF-HFP copolymer latex (4) was 21.5% by mass, and the average particle size of the VDF-HFP copolymer particles was 172.7 nm.
- Example 8 To the dispersion (4) containing 9.0 g of VDF-HFP copolymer particles prepared in Production Example 8, 9.0 g of CMC 1.2 wt% aqueous solution prepared in the same manner as in Production Example 1 and 12.0 g of water were added. And stirred.
- the obtained coating solution is applied to a separator (ND420, Asahi Kasei) using wire bar # 3 (wet coating amount 24 ⁇ m), dried at 100 ° C. for 10 minutes, and formed to contain VDF-HFP copolymer particles.
- the separator (ND420) is a polyolefin separator having a thickness of 20 ⁇ m.
- the total thickness of the intermediate layer was 1.8 ⁇ m.
- the air permeability of the laminate in which the intermediate layer was formed on the separator was measured using a Gurley type densometer (Toyo Seiki Seisakusho), the air permeability was 686 sec / 100 ml.
- Example 2 (Preparation of positive electrode) Lithium cobalt oxide (cell seed C5, manufactured by Nippon Chemical Industry Co., Ltd.), conductive additive (manufactured by SuperP TIMCAL), and PVDF (polyvinylidene fluoride) (manufactured by Kureha KF # 1100 Kureha) have a solid concentration of 69 wt. % N-methyl-2-pyrrolidone solvent slurry was coated on an Al foil using a 115 ⁇ m spacer, dried at 120 ° C. for 3 hours, and then pressed to a bulk density of 3.6 [g / cm 3 ], basis weight A positive electrode with an amount of 150 [g / m 2 ] was obtained.
- Lithium cobalt oxide cell seed C5, manufactured by Nippon Chemical Industry Co., Ltd.
- conductive additive manufactured by SuperP TIMCAL
- PVDF polyvinylidene fluoride
- BTR918 made by modified natural graphite BTR
- conductive additive made by SuperP TIMCAL
- SBR styrene butadiene rubber latex BM-400 made by Nippon Zeon
- CMC Carboxymethylcellulose Cellogen 4H Daiichi Kogyo Seiyaku Co., Ltd.
- An aqueous solvent slurry having a solid content concentration of 53 wt% was prepared so as to be 2: 3: 1, coated on Cu foil using a 90 ⁇ m spacer, dried at 120 ° C. for 3 hours, and then pressed to a bulk density of 1.5 [g / Cm 3 ] and a weight per unit area of 56 [g / m 2 ] were obtained.
- the peel strength of the separator / positive electrode on which the intermediate layer was formed was measured using a Tensilon universal testing machine (manufactured by A & D Co., Ltd.) by fixing the positive electrode and pulling the separator at 180 °.
- the peel strength between the separator on which the intermediate layer produced in Experimental Example 8 was formed and the positive electrode was 1.6 gf / mm. It was shown that the separator having no intermediate layer can be bonded to the positive electrode by providing the intermediate layer.
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Abstract
Description
例えば、セパレータの少なくとも片側にセパレータよりも融点の低い高分子粒子および結着剤を含む表面層を設けることが提案されている(例えば、特許文献1参照)。
特許文献2では、耐熱性樹脂多孔質層がフッ素系樹脂微粒子を含有することにより、優れた耐摩耗性を有することが開示されている。
前記フッ化ビニリデン系重合体粒子の平均粒径が10~700nmであることが好ましい。
本発明の非水電解質二次電池は、前記非水電解質二次電池用構造体から得られる。
本発明の非水電解質二次電池用構造体の製造方法は、前記非水電解質二次電池用構造体の製造方法であって、前記中間層が下記(1)~(4)のいずれかにより形成されることを特徴とする。
(4)前記中間層が、フッ化ビニリデン系重合体粒子を含む水分散液に、基材を浸漬し乾燥した後、前記基材から剥離することにより形成される。
よって、本発明の非水電解質二次電池用構造体および非水電解質二次電池は生産性に優れる。
本発明の非水電解質二次電池用構造体は、正極、セパレータ、および負極を有する非水電解質二次電池用構造体であって、フッ化ビニリデン系重合体粒子を含んで形成される中間層を、前記正極と前記セパレータとの間、および前記負極と前記セパレータとの間の少なくとも一方に有し、前記中間層を構成する原料100質量部中、フッ化ビニリデン系重合体粒子が60~100質量部である。
〔正極〕
本発明の非水電解質二次電池用構造体が有する正極としては、正極反応の担い手となる正極活物質を有し、かつ集電機能を有するものであれば特に限定されないものの、多くの場合、正極活物質を含む正極合剤層と、集電体として機能するとともに正極合剤層を保持する役割を果たす正極集電体とからなる。
ここで、正極合剤層における、正極活物質、結着剤、導電助剤の配合比は、リチウムイオン二次電池等の非水電解質二次電池で用いられる一般的な配合比とすることができるが、二次電池の種類に応じて適宜調整しうる。
本発明の非水電解質二次電池において用いられる正極活物質は、従来公知の正極用の電極活物質を始め、正極活物質として作用するものであれば特に制限なく用いることができる。
リチウム系正極活物質としては例えば、LiCoO2、LiNixCo1-xO2(0≦x≦1)等の一般式LiMY2(Mは、Co、Ni、Fe、Mn、Cr、V等の遷移金属の少なくとも一種:YはO、S等のカルコゲン元素)で表わされる複合金属カルコゲン化合物、LiMn2O4などのスピネル構造をとる複合金属酸化物、LiFePO4などのオリビン型リチウム化合物等が挙げられる。なお、前記正極活物質としては市販品を用いてもよい。
なお、正極活物質の比表面積は、窒素吸着法により求めることができる。
ただ、本発明の非水電解質二次電池を構成する正極活物質は、これらのものに限られるものではなく、二次電池の種類に応じて適宜選択しうる。
ここで、結着剤としては、特に限定されないものの、従来公知のリチウムイオン二次電池において広く用いられているものを好適に用いることができ、例えば、ポリテトラフルオロエチレン、ポリフッ化ビニリデン、フッ素ゴム等の含フッ素樹脂、スチレンブタジエンゴムとカルボキシメチルセルロースの共重合体、ポリプロピレン、ポリエチレン等の熱可塑性樹脂を用いることができる。また、前記含フッ素樹脂としては、フッ化ビニリデン系共重合体を用いることもできる。フッ化ビニリデン系共重合体としては、フッ化ビニリデン‐マレイン酸モノメチルエステル共重合体等を用いることができる。
前記正極集電体としては、リチウムイオン二次電池等の非水電解質二次電池の正極集電体として一般的に用いられているものが挙げられる。
本発明に用いられる正極は集電体に、前記正極合剤を塗布・乾燥することにより製造されるが、該塗布は正極合剤を集電体の少なくとも一面、好ましくは両面に行われる。塗布する際の方法としては特に限定は無く、バーコーター、ダイコーター、コンマコーターで塗布する等の方法が挙げられる。
本発明の非水電解質二次電池用構造体が有するセパレータとしては、特に限定はない。
本発明に用いられるセパレータは、非水電解質二次電池構造体を構成するセパレータであり、該構造体から得られた非水電解質二次電池において、正極と負極とを電気的に絶縁し、電解液を保持する役割を果たすものである。本発明で用いられるセパレータとしては、特に限定されないものの、例えば、ポリエチレン、ポリプロピレンなどのポリオレフィン系高分子、ポリエチレンテレフタレートなどのポリエステル系高分子、芳香族ポリアミド系高分子、ポリエーテルイミドなどのポリイミド系高分子、ポリエーテルスルホン、ポリスルホン、ポリエーテルケトン、ポリスチレン、ポリエチレンオキサイド、ポリカーボネート、ポリ塩化ビニル、ポリアクリロニトリル、ポリメチルメタクリレート、セラミックス等、およびこれらの混合物からなる単層、および多層の多孔膜、不織布、ガラス、紙などを挙げる事ができる。なお、前述のポリマーとしては、変性されたものを用いてもよい。
〔負極〕
本発明の非水電解質二次電池用構造体が有する負極としては、負極反応の担い手となる負極活物質を有し、かつ集電機能を有するものであれば特に限定されないものの、多くの場合、負極活物質を含む負極合剤層と、集電体として機能するとともに負極合剤層を保持する役割を果たす負極集電体とからなる。
ここで、負極合剤層における、負極活物質、結着剤、導電助剤の配合比は、リチウムイオン二次電池等の非水電解質二次電池で用いられる一般的な配合比とすることができるが、二次電池の種類に応じて適宜調整しうる。
本発明の非水電解質二次電池において用いられる負極活物質は、従来公知の負極用の電極活物質始め、負極活物質として作用するものであれば特に制限なく用いることができる。
前記炭素材料としては、人造黒鉛、天然黒鉛、難黒鉛化炭素、易黒鉛化炭素などが用いられる。また、前記炭素材料は、1種単独で用いても、2種以上を用いてもよい。
前記人造黒鉛としては、例えば、有機材料を炭素化しさらに高温で熱処理を行い、粉砕・分級することにより得られる。前記難黒鉛化炭素としては、例えば、石油ピッチ由来の材料を1000~1500℃で焼成することにより得られる。
前記負極活物質の比表面積は、0.3~10m2/gであることが好ましい。比表面積が10m2/gを超えると、電解液の分解量が増加し、初期の不可逆容量が増えることがある。
ただ、本発明の非水電解質二次電池を構成する負極活物質は、これらのものに限られるものではなく、二次電池の種類に応じて適宜選択しうる。
ここで、結着剤としては、上述の〔正極〕の項で記載したものと同様の結着剤が挙げられる。
前記負極集電体としては、リチウムイオン二次電池等の非水電解質二次電池の負極集電体として一般的に用いられているものが挙げられる。
本発明の非水電解質二次電池用構造体は、正極とセパレータとの間、および負極とセパレータとの間の少なくとも一方に、フッ化ビニリデン系重合体粒子を含んで形成される中間層を有する。
前記不飽和一塩基酸としては、アクリル酸、メタクリル酸、2-カルボキシエチルアクリレート、2-カルボキシエチルメタクリレート等が挙げられる。前記不飽和二塩基酸としては、マレイン酸、シトラコン酸等が挙げられる。また、前記不飽和二塩基酸のモノエステルとしては、炭素数5~8のものが好ましく、例えばマレイン酸モノメチルエステル、マレイン酸モノエチルエステル、シトラコン酸モノメチルエステル、シトラコン酸モノエチルエステル等を挙げることができる。中でも、カルボキシル基含有モノマーとしては、アクリル酸、メタクリル酸、マレイン酸、シトラコン酸、マレイン酸モノメチルエステル、シトラコン酸モノメチルエステルが好ましい。また、カルボキシル基含有モノマーとしてはアクリロイロキシエチルコハク酸、メタクリロイロキシエチルコハク酸、アクリロイロキシエチルフタル酸、メタクリロイロキシエチルフタル酸等を用いてもよい。
また、本発明に用いられるフッ化ビニリデン系重合体としては、架橋された重合体を用いてもよい。フッ化ビニリデン系重合体として、架橋されたものを用いる場合には、前記他のモノマーとして、多官能性モノマーを用いてもよく、未架橋の重合体を得た後に、多官能性モノマーを用いて架橋反応を行ってもよい。
重合において使用される界面活性剤は、過フッ素化、部分フッ素化、および非フッ素化界面活性剤など、ポリフッ化ビニリデンの重合に従来から使用されるものが好適である。それらのうち、パーフルオロアルキルスルホン酸およびその塩、パーフルオロアルキルカルボン酸およびその塩、フルオロカーボン鎖またはフルオロポリエーテル鎖を有するフッ素系界面活性剤を使用することが好ましく、パーフルオロアルキルカルボン酸およびその塩を用いることがより好ましい。
本発明に用いられるフッ化ビニリデン系重合体粒子の平均粒径は、10~700nmが好ましく、20~500nmがより好ましい。前記範囲では、層の厚みや透気度がコントロールしやすいため好ましい。前記平均粒径は、動的光散乱法により求められるキュムラント平均粒子径であり、例えば、ELSZ‐2(大塚電子)を用いて測定することが出来る。
前記水溶性高分子としては、例えばカルボキシメチルセルロース(CMC)、ポリアクリル酸(PAA)、ポリビニルピロリドン(PVP)、ポリビニルアルコール(PVA)、ポリエチレンオキシド(PEO)などが挙げられ、カルボキシメチルセルロース(CMC)、ポリビニルアルコール(PVA)等が長期にわたる電池使用時の観点から好ましい。
無機フィラーの平均粒子径としては5nm~2μmが好ましく、10nm~1μmがより好ましい。
前記中間層を構成する原料100質量部中のフッ化ビニリデン系重合体粒子の量としては、フッ化ビニリデン系重合体粒子が65~100質量部であることが好ましく、70~100質量部であることがより好ましい。
前記中間層は、主にフッ化ビニリデン系重合体粒子を原料として形成される。前記中間層は通常、SEM観察を行った際に、フッ化ビニリデン系重合体粒子が、粒子形状を保った状態で存在することが確認できる。すなわち、本発明の非水電解質二次電池用構造体は、中間層を構成するフッ化ビニリデン系重合体粒子が溶融し、一体化していることは通常はない。前記中間層は、複数のフッ化ビニリデン系重合体粒子が直接または水溶性高分子を介して互いに接合されている構造を有することが好ましい。また、本発明の非水電解質二次電池用構造体の時点では、フッ化ビニリデン系重合体粒子は、相互に接合または水溶性高分子により接合されていなくてもよく、該非水電解質二次電池用構造体から非水電解質二次電池を製造する際に注入される電解液によって、粒子表面が溶解または膨潤することにより、接合されてもよい。
(1)前記中間層を、フッ化ビニリデン系重合体粒子を含む水分散液を、正極、セパレータ、および負極から選択される少なくとも一種に塗布し乾燥することにより形成する。
(3)前記中間層を、フッ化ビニリデン系重合体粒子を含む水分散液を、基材に塗布し乾燥した後、前記基材を剥離することにより形成する。
なお、フッ化ビニリデン系重合体粒子を含む水分散液を、正極、セパレータ、負極、基材に塗布する場合には、少なくとも一面に塗布すればよく、片面でも、両面でもよい。
なお、前記基材としては、ポリエチレンテレフタレート(PET)製の基材等を用いることができる。
〔非水系電解質二次電池用構造体〕
本発明の非水電解質二次電池用構造体は、前述のように正極、セパレータ、および負極を有する非水電解質二次電池用構造体であって、フッ化ビニリデン系重合体粒子を含んで形成される中間層を、前記正極とセパレータとの間、および前記負極とセパレータとの間の少なくとも一方に有し、前記中間層を構成する原料100質量部中、フッ化ビニリデン系重合体粒子が60~100質量部であることを特徴とする。
〔非水系電解質二次電池〕
本発明の非水電解質二次電池は、前記非水電解質二次電池用構造体から得られる。
また、非水電解質二次電池を構成する部材としては、前記非水電解質二次電池用構造体以外には、例えば非水電解液、円筒缶、ラミネートパウチ等が挙げられる。
前記非水系溶媒として、電解質を構成するカチオンおよびアニオンを輸送可能な非プロトン性の有機溶媒であって、且つ、実質的に二次電池の機能を損なわないものが挙げられる。そのような非水系溶媒として、リチウムイオン二次電池の非水電解液として通常用いられる有機溶媒が挙げられ、例えば、カーボネート類、ハロゲン化炭化水素、エーテル類、ケトン類、ニトリル類、ラクトン類、エステル類、オキソラン化合物等を用いることができる。中でも、プロピレンカーボネート、エチレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート、1,2-ジメトキシエタン、1,2-ジエトキシエタン、テトラヒドロフラン、γ-ブチロラクトン、プロピオン酸メチル、プロピオン酸エチル等などが好ましい。これらの非水系溶媒は、1種単独でも2種以上を用いてもよい。
製造例で用いたカルボキシメチルセルロース(CMC)(セロゲン4H、第一工業製薬製)を、130℃で30分乾燥し、乾燥の前後の重量を測定することにより求めた、CMCの含水率は、7.9%であった。
(CMC1.5wt%水溶液の製造)
三角フラスコに、196.0gの水に1.0gの5%アンモニア水と、3.8gのカルボキシメチルセルロース(CMC)(セロゲン4H、第一工業製薬製)とを加えて加熱溶解し、CMC水溶液(1-1)を得た。
CMC水溶液(1-2)の一部を、150℃で2時間乾燥し、乾燥後のCMCの重量と、乾燥させたCMC水溶液(1-2)の重量から、CMC水溶液(1-2)のCMC濃度を求めたところ、CMC濃度が1.5wt%であった。
(CMC3.5wt%水溶液の製造)
三角フラスコに、190.0gの水に1.0gの5%アンモニア水と、9.1gのCMC(セロゲンPR、第一工業製薬製)を加えて加熱溶解し、CMC水溶液(2-1)を得た。
CMC水溶液(2-2)の一部を、150℃で2時間乾燥し、乾燥後のCMCの重量と、乾燥させたCMC水溶液(2-2)の重量から、CMC水溶液(2-2)のCMC濃度を求めたところ、CMC濃度が3.5wt%であった。
(PVA24.3wt%水溶液の製造)
三角フラスコに、15.0gの水に5.0gのポリビニルアルコール(PVA)(ポバールPVA205、クラレ製)を加えて加熱溶解し、PVA水溶液(1)を得た。
(VDF‐HFP共重合体ラテックス(1)の製造)
オートクレーブに0.2質量部のリン酸水素ナトリウム(Na2HPO4)と、330質量部の水を入れ、脱気後、1質量部のパーフルオロオクタン酸(PFOA)アンモニウム塩と、0.25質量部の酢酸エチルを入れ、22.7質量部のフッ化ビニリデン(VDF)と14.0質量部のヘキサフルオロプロピレン(HFP)を入れた。
なお、製造例にて調製した重合体粒子を含む分散液における重合体粒子の平均粒径は、大塚電子製ELSZ-2を用いて測定した。
6.38gの製造例4で調製したVDF‐HFP共重合体粒子を含む分散液(1)に、3.33gの製造例1で調製したCMC1.5wt%水溶液を加えて撹拌した。
中間層が形成されたセパレータを、メタノールを用いた凍結破断法を行い、SEM観察を行った。
2.03gの製造例4で調製したVDF‐HFP共重合体粒子を含む分散液(1)に、0.10gの製造例3で調製したPVA24.3wt%水溶液を加えて撹拌した。
6.70gの製造例4で調製したVDF‐HFP共重合体粒子を含む分散液(1)に、0.54gのアルミナ(AKP3000、平均粒径500nm、住友化学)と5.00gの製造例1で調製したCMC1.5wt%水溶液水を加えて撹拌した。さらに得られた溶液1gに水0.3gを加えて撹拌した。
0.40gの製造例4で調製したVDF‐HFP共重合体粒子を含む分散液(1)に、5.00gの製造例1で調製したCMC1.5wt%水溶液を加えて撹拌した。
得られたSEM写真を図2に示す。図2では、中間層(左側)がセパレータ(右側)上に形成されており、中間層を構成する各粒子が相互に接触していることは、CMC樹脂が多量に存在するため、確認することができなかった。
(VDF‐HFP共重合体ラテックス(2)の製造)
オートクレーブに、0.2質量部のリン酸水素ナトリウム(Na2HPO4)と、330質量部の水を入れ、脱気後、1質量部のパーフルオロオクタン酸(PFOA)アンモニウム塩と、0.25質量部の酢酸エチルを入れ、28.7質量部のフッ化ビニリデン(VDF)と8.0質量部のヘキサフルオロプロピレン(HFP)を入れた。
〔実験例4〕
1.23gの製造例5で調製したVDF‐HFP共重合体粒子を含む分散液(2)に、1.00gの製造例2で調製したCMC3.5wt%水溶液を加えて撹拌した。
(VDF‐HFP共重合体ラテックス(3)の製造)
オートクレーブに、0.2質量部のリン酸水素ナトリウム(Na2HPO4)と、330質量部の水を入れ、脱気後、0.25質量部の酢酸エチルを入れ、22.7質量部のフッ化ビニリデン(VDF)と14.0質量部のヘキサフルオロプロピレン(HFP)を入れた。
〔実験例5〕
1.97gの製造例6で調製したVDF‐HFP共重合体粒子を含む分散液(3)に、1.00gの製造例1で調製したCMC1.5wt%水溶液を加えて撹拌した。
(VDF単独重合体ラテックス(1)の製造)
オートクレーブに、1質量部の炭酸水素ナトリウム(NaHCO3)と、900質量部の水を入れ、脱気後、5質量部のパーフルオロオクタン酸(PFOA)アンモニウム塩と、0.5質量部の酢酸エチルを入れ、100質量部のフッ化ビニリデン(VDF)を入れた。
〔実験例6〕
10.44gの製造例7で調製したVDF単独重合体粒子を含む分散液(1)に、3.33gの製造例1で調製したCMC1.5wt%水溶液を加えて撹拌した。
〔実験例7〕
製造例7で調製したVDF単独重合体粒子を含む分散液(1)を、ワイヤーバー#4(ウェット塗布量36μm)を使用して、セパレータである厚紙(エコ画用紙、170-8、北越紀州製紙)に塗布し、100℃で10min乾燥させ、VDF単独重合体粒子を含んで形成される層(中間層)を、厚紙上に形成した。
各実験例1~7で得られた中間層がセパレータ上に形成された積層体を、前記中間層がセパレータと、正極との間に位置するように、正極と負極の間に挟み込むことにより、セパレータと電極の間に中間層を有する構造体を得た。
(VDF‐HFP共重合体ラテックス(4)の製造)
オートクレーブに、0.2質量部のリン酸水素ナトリウム(Na2HPO4)と、330質量部の水を入れ、脱気後、0.25質量部の酢酸エチルを入れ、26.7質量部のフッ化ビニリデン(VDF)と10.0質量部のヘキサフルオロプロピレン(HFP)を入れた。
〔実験例8〕
9.0gの製造例8で調製したVDF‐HFP共重合体粒子を含む分散液(4)に、9.0gの製造例1と同様に調製したCMC1.2wt%水溶液と水12.0gを加えて撹拌した。
中間層の厚さは合計1.8μmになった。中間層がセパレータ上に形成された積層体の透気度を、ガーレー式デンソメーター(東洋精機製作所)を用いて測定したところ、透気度は686sec/100mlであった。
(正極の作製)
コバルト酸リチウム(セルシード C5 日本化学工業製)、導電助剤(SuperP TIMCAL製)、PVDF(ポリフッ化ビニリデン)(KF#1100 クレハ製)をそれぞれ重量比93:3:4となるよう固形分濃度69wt%のN-メチル-2-ピロリドン溶媒スラリーを作製し、115μmのスペーサーを用いてAl箔にコート後120℃3時間乾燥し、その後プレスして嵩密度3.6[g/cm3]、目付け量150[g/m2]の正極を得た。
BTR918(改質天然黒鉛 BTR製)、導電助剤(SuperP TIMCAL製)、SBR(スチレンブタジエンゴムラテックス BM-400 日本ゼオン製)、CMC(カルボキシメチルセルロース セロゲン4H 第一工業製薬)をそれぞれ重量比90:2:3:1となるよう固形分濃度53wt%の水溶媒スラリーを作製し、90μmのスペーサーを用いてCu箔にコート後120℃3時間乾燥し、その後プレスして嵩密度1.5[g/cm3]、目付け量56[g/m2]の負極を得た。
(剥離強度測定用サンプルの作製および剥離強度の測定)
前記正極、負極を2.5×5.0cm、実験例8で製造した中間層が形成されたセパレータを3.0×6.0cmに切ってそれぞれ接合させ、電解液(エチレンカーボネート(EC):ジメチルカーボネート(DMC):エチルメチルカーボネート(EMC)=1:2:2vol、Li1.3mol/L)を浸み込ませて、アルミニウムパウチ中に真空シーラーを用いて真空脱気封入した。次いで、これに熱プレス機を用いて熱プレス(電極1cm2当たり20kgの加重、温度90℃、余熱3分後1分間)を行うことにより、Alラミネートセル(剥離強度測定用サンプル)を得た。
実験例8で製造した中間層が形成されたセパレータと正極との剥離強度は、1.6gf/mmだった。中間層を持たないセパレータに対し、中間層を持たせることで正極と接着できることが示された。
(電池の作製とサイクル試験)
前記の正極を5×5cm、負極を5.5×11cm、実験例8で製造した中間層が形成されたセパレータを6×12cmに切って、それぞれ接合させ、電解液(EC:DMC:EMC=1:2:2vol、Li1.3mol/L)を浸み込ませて、アルミパウチ中に真空シーラーを用いて真空脱気封入した。次いで、これに熱プレス機を用いて熱プレス(電極1cm2当たり20kgの加重、温度90℃、余熱3分後1分間)を行うことにより、Alラミネートセルを得た。
実験例8で製造した中間層が形成されたセパレータを用いたラミネートセルが、二次電池として作動することを確認した。
Claims (6)
- 正極、セパレータ、および負極を有する非水電解質二次電池用構造体であって、
フッ化ビニリデン系重合体粒子を含んで形成される中間層を、前記正極と前記セパレータとの間、および前記負極と前記セパレータとの間の少なくとも一方に有し、
前記中間層を構成する原料100質量部中、フッ化ビニリデン系重合体粒子が60~100質量部である非水電解質二次電池用構造体。 - 前記中間層は、複数のフッ化ビニリデン系重合体粒子が直接または水溶性高分子を介して互いに接合されている構造を有する、請求項1に記載の非水電解質二次電池用構造体。
- 前記フッ化ビニリデン系重合体粒子の平均粒径が10~700nmである請求項1または2に記載の非水電解質二次電池用構造体。
- 前記中間層を、前記正極と前記セパレータとの間に有する請求項1~3のいずれか一項に記載の非水電解質二次電池用構造体。
- 請求項1~4のいずれか一項に記載の非水電解質二次電池用構造体から得られる非水電解質二次電池。
- 請求項1~4のいずれか一項に記載の非水電解質二次電池用構造体の製造方法であって、
前記中間層が下記(1)~(4)のいずれかにより形成されることを特徴とする非水電解質二次電池用構造体の製造方法。
(1)前記中間層が、フッ化ビニリデン系重合体粒子を含む水分散液を、正極、セパレータ、および負極から選択される少なくとも一種に塗布し乾燥することにより形成される。
(2)前記中間層が、フッ化ビニリデン系重合体粒子を含む水分散液に、正極、セパレータ、および負極から選択される少なくとも一種を浸漬し乾燥することにより形成される。
(3)前記中間層が、フッ化ビニリデン系重合体粒子を含む水分散液を、基材に塗布し乾燥した後、前記基材を剥離することにより形成される。
(4)前記中間層が、フッ化ビニリデン系重合体粒子を含む水分散液に、基材を浸漬し乾燥した後、前記基材を剥離することにより形成される。
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