WO2010044264A1 - 蓄電デバイス用セパレータ - Google Patents
蓄電デバイス用セパレータ Download PDFInfo
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- WO2010044264A1 WO2010044264A1 PCT/JP2009/005365 JP2009005365W WO2010044264A1 WO 2010044264 A1 WO2010044264 A1 WO 2010044264A1 JP 2009005365 W JP2009005365 W JP 2009005365W WO 2010044264 A1 WO2010044264 A1 WO 2010044264A1
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- fiber
- separator
- storage device
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- electricity storage
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/02—Diaphragms; Separators
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/52—Separators
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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
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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
- H01M50/423—Polyamide 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
- H01M50/429—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
- H01M50/44—Fibrous material
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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
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
- H01M50/491—Porosity
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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
- H01M50/4295—Natural cotton, cellulose or wood
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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
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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
- Y02E60/13—Energy storage using capacitors
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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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
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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
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/249921—Web or sheet containing structurally defined element or component
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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
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/249921—Web or sheet containing structurally defined element or component
- Y10T428/249953—Composite having voids in a component [e.g., porous, cellular, etc.]
- Y10T428/249962—Void-containing component has a continuous matrix of fibers only [e.g., porous paper, etc.]
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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
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
- Y10T428/268—Monolayer with structurally defined element
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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
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
- Y10T428/269—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension including synthetic resin or polymer layer or component
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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
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T442/00—Fabric [woven, knitted, or nonwoven textile or cloth, etc.]
- Y10T442/60—Nonwoven fabric [i.e., nonwoven strand or fiber material]
- Y10T442/69—Autogenously bonded nonwoven fabric
- Y10T442/692—Containing at least two chemically different strand or fiber materials
Definitions
- the present invention relates to a separator for an electricity storage device, and more particularly to a separator for a lithium ion secondary battery, a polymer lithium secondary battery, an electric double layer capacitor, or an aluminum electrolytic capacitor.
- lithium-ion secondary batteries due to the increasing demand for electrical and electronic equipment regardless of industrial equipment and consumer equipment and the development of hybrid vehicles, etc., lithium-ion secondary batteries, polymer lithium secondary batteries, electric double layer capacitors and aluminum electrolytic capacitors, which are electronic components, have been developed. Demand has increased significantly. These electric and electronic devices are steadily increasing in capacity and functionality. Lithium ion secondary batteries, polymer lithium secondary batteries, electric double layer capacitors, and aluminum electrolytic capacitors also have higher capacities and higher functions. The use in severe environments is increasing.
- a lithium ion secondary battery and a polymer lithium secondary battery include a positive electrode in which an active material, a lithium-containing oxide, and a binder such as polyvinylidene fluoride are mixed with 1-methyl-2-pyrrolidone and formed into a sheet on an aluminum current collector.
- An electrode body obtained by winding or laminating a membrane in the order of a positive electrode, an electrolyte membrane, and a negative electrode is impregnated with a driving electrolyte solution and sealed with an aluminum case.
- An electric double layer capacitor is a mixture of activated carbon, conductive agent and binder, which is attached to both sides of the positive and negative current collectors made of aluminum and driven to a wound or laminated electrode body via a separator made of cellulose or the like.
- the positive electrode lead and the negative electrode lead are passed through the sealing body so as not to be short-circuited by being impregnated with an electrolytic solution and packed with an aluminum case and a sealing body.
- An aluminum electrolytic capacitor is an electrode obtained by etching or laminating an aluminum positive foil having a dielectric film formed thereon by etching, and an etched aluminum negative foil through a separator made of cellulose or the like.
- the body is impregnated with a driving electrolyte solution, packed with an aluminum case and a sealing body, and has a structure in which a positive electrode lead and a negative electrode lead are passed through the sealing body and pulled out so as not to be short-circuited.
- porous membranes such as polyethylene and polypropylene have been used as separators for lithium ion secondary batteries and polymer lithium secondary batteries, and paper made of cellulose pulp has been used as separators for electric double layer capacitors and aluminum electrolytic capacitors.
- the nonwoven fabric which consists of a cellulose fiber is used.
- a spunbond method using a dry nonwoven fabric or a woven fabric using an olefin resin such as polyethylene or polypropylene as a material there are a spunbond method using a dry nonwoven fabric or a woven fabric using an olefin resin such as polyethylene or polypropylene as a material, and a wet papermaking method using cellulose or the like as a material.
- a wet manufacturing method has been proposed in which a fluid flow is applied to a fiber web formed of split type composite fibers having a fiber length of 3 to 25 mm (see, for example, Patent Document 1).
- the action of jetting fluid at a high pressure to split the fibers creates through holes such as pinholes, causing internal short circuit between the electrodes. It was generated.
- the above-described lithium ion secondary battery, polymer lithium secondary battery, electric double layer capacitor, and aluminum electrolytic capacitor use an organic solvent or ionic liquid as a driving electrolyte, and a separator such as cellulose has a high temperature. There was a problem that it deteriorated considerably in the long-term durability test.
- a separator for example, a microporous resin film (stretched film) produced by stretching polyolefin and having a relatively high air permeability value provided with a through hole with a needle or a laser is used as the separator. It is proposed to use as (for example, refer patent document 3).
- the separator tends to be deteriorated in strength and durability due to mass reduction of the separator in a high temperature environment in the presence of an organic solvent or an ionic liquid. Further, since the highly durable chemical fiber and the low durable cellulose fiber are made randomly, the separator is deteriorated unevenly with respect to the organic solvent, and current concentration tends to occur. Furthermore, since the separator has a single-layer structure, an internal short circuit is likely to occur when the separator is thinned. Further, as another document, in order to prevent an internal short circuit, it has been proposed to combine two or more layers into one layer using a circular net paper machine (see, for example, Patent Document 5).
- the present invention provides a thin film separator for an electricity storage device having heat resistance, solvent resistance, and dimensional stability.
- the conventional technology has not realized a separator for an electricity storage device using a polymer electrolyte that can be thinned and that can achieve high performance and high reliability such as an increase in capacity of the electricity storage device. Therefore, the present invention can further reduce the thickness, has excellent ion permeability and low resistance, is not easily short-circuited between electrodes and is not self-discharged, and is in a high temperature environment in the presence of an organic solvent or ionic liquid.
- a separator for an electricity storage device that is excellent in durability even after long-term use.
- the electricity storage device separator (hereinafter referred to as “separator”) according to the first aspect of the present invention includes at least thermoplastic synthetic fiber A (hereinafter referred to as “fiber A”) and heat-resistant synthetic fiber B (hereinafter referred to as “fiber separator”). Fiber B ”) and natural fiber C (hereinafter referred to as fiber“ C ”), and the fiber A is made of a polyester fiber having a crystallinity of 50% or more.
- the separator according to the second aspect of the present invention is a separator formed by laminating two or more fiber layers, and at least one of the fiber layers contains a polyester fiber having a crystallinity of 50% or more. It is characterized by doing. That is, the present invention relates to the following (1) to (20).
- thermoplastic synthetic fiber A comprises a polyester fiber having a crystallinity of 50% or more.
- thermoplastic synthetic fiber A is composed of at least one selected from polyethylene terephthalate, polybutylene terephthalate, and wholly aromatic polyarylate having a crystallinity of 50% or more.
- the heat-resistant synthetic fiber B is composed of at least one selected from wholly aromatic polyamide, wholly aromatic polyester, semi-aromatic polyamide, polyphenylene sulfide, and polyparaphenylene benzobisoxazole ( The separator for electrical storage devices as described in 1) or (2).
- thermoplastic synthetic fiber A has a blending ratio of 25 to 50% by mass
- the heat-resistant synthetic fiber B has a blending ratio of 60 to 10% by mass
- the natural fiber C has a blending ratio of 15 to 40% by mass
- the heat resistant synthetic fiber B has a fiber diameter of 1 ⁇ m or less and a fiber length of 3 mm or less, and is fibrillated according to any one of (1) to (5) For electricity storage devices.
- the separator for an electricity storage device wherein the fiber layer containing the polyester fiber having a crystallinity of 50% or more further contains other synthetic fibers.
- the polyester fiber is at least one selected from polyethylene terephthalate having a crystallinity of 50% or more, polybutylene terephthalate, and wholly aromatic polyarylate (13) or (14)
- the electricity storage device separator according to any one of (13) to (15), wherein the polyester fiber and the synthetic fiber have a fiber diameter of 5 ⁇ m or less and a fiber length of 10 mm or less.
- the synthetic fiber is at least one selected from wholly aromatic polyamide, wholly aromatic polyester, semi-aromatic polyamide, polyphenylene sulfide, polyparaphenylene benzobisoxazole, polyethylene, and polypropylene.
- the separator for electrical storage devices according to any one of (16).
- the fiber layer is formed by overlapping and making a paper-making net using an inclined wire paper machine having two or more heads. For electricity storage devices.
- the multi-tank type wet papermaking in which the fiber layer can simultaneously form a plurality of layers having a structure in which the lower part of the second flow box is located in the vicinity of the intersection of the floodline in the first flow box and the papermaking net.
- the separator for an electricity storage device according to any one of (13) to (17), wherein the separator is made by overlapping a paper on a papermaking net using a machine.
- the electricity storage device is any one of a lithium ion secondary battery, a polymer lithium secondary battery, an electric double layer capacitor, and an aluminum electrolytic capacitor. For electricity storage devices.
- the separator for an electricity storage device is a thin film, and is extremely excellent in durability during long-term use in a high-temperature environment in the presence of an organic solvent or an ionic liquid. It is suitably used for an electricity storage device such as a capacitor, and is excellent in preventing a short circuit between electrodes and suppressing self-discharge. In addition, it has good heat resistance and solvent resistance and is stable for long-term use at high temperatures.
- the separator according to the second aspect of the present invention can be thinned, has excellent ion permeability and low resistance, is excellent in prevention of short circuit between electrodes, and suppression of self-discharge, and is also an organic solvent.
- the separator of the present invention can be suitably used for power storage devices, particularly for lithium ion secondary batteries, polymer lithium secondary batteries, electric double layer capacitors, and aluminum electrolytic capacitors.
- the fiber A used in the separator according to the first aspect of the present invention is made of a resin selected from polyester fibers such as polyethylene terephthalate, polybutylene terephthalate, wholly aromatic polyarylate having a crystallinity of 50% or more. Are preferably used.
- polyester fibers such as polyethylene terephthalate, polybutylene terephthalate, wholly aromatic polyarylate having a crystallinity of 50% or more.
- the fiber A has a crystallinity of 50% or more, it is highly resistant to organic solvents, ionic liquids, and high-temperature conditions, and provides a separator that does not deteriorate even if it is used in a high-temperature atmosphere for a long period of time. can do.
- the fiber B may be at least one selected from wholly aromatic polyamide, wholly aromatic polyester, semi-aromatic polyamide, polyphenylene sulfide, and polyparaphenylene benzobisoxazole, and may use two or more. These materials can be fibrillated into fine fibers without dissolving in the organic solvent or ionic liquid used for the driving electrolyte.
- the fiber B By including the fiber B in the separator, durability against an organic solvent, an ionic liquid, and further a high temperature condition is increased, and it is difficult to deteriorate even if the separator is used for a long time in a high temperature atmosphere.
- the fiber C constituting the present invention for example, cotton, hemp, kenaf, banana, pineapple, wool, silk, angora, cashmere, rayon, cupra, polynosic, solvent-spun cellulose and the like can be used.
- the material constituting the fiber C may be one type or two or more types. Separators using these materials have improved electrolyte impregnation properties.
- the fibrillated solvent-spun cellulose is excellent in electrolytic solution impregnation and has sufficient fiber entanglement, so that it becomes a separator excellent in mechanical strength.
- the fiber A has a fiber diameter of 5 ⁇ m or less and a fiber length of preferably 10 mm or less, particularly preferably a fiber diameter of 3 ⁇ m or less and a fiber length of 7 mm or less.
- the fiber diameter is less than 5 ⁇ m and the fiber length is more than 10 mm, there is a high possibility that a through hole will be formed when the film is thinned, which is likely to cause an internal short circuit.
- the crystallinity of the fiber A is 50% or more, and particularly preferably 70% or more. When the degree of crystallinity is less than 50%, it becomes easy to dissolve in an organic solvent or an ionic liquid, and when used in a high temperature atmosphere for a long time, it causes deterioration.
- the crystallinity of the polyester fiber can be measured by quantifying the endothermic peak derived from crystallization using a DSC (differential scanning calorimeter). Further, it can be measured by obtaining the correlation between the peak band in which the difference in crystallinity appears and the density using FT-Raman spectroscopy.
- the fiber diameter of the fibrillated fiber B is 1 ⁇ m or less
- the fiber length is preferably 3 mm or less, and particularly preferably the fiber length is 1 mm or less.
- the fiber diameter of the fibrillated fiber C is preferably 1 ⁇ m or less, the fiber length is preferably 3 mm or less, and particularly preferably the fiber length is 1 mm or less.
- the fiber diameter exceeds 1 ⁇ m and the fiber length exceeds 3 mm, there is a high possibility that a through-hole will be formed when the film is thinned, which is likely to cause an internal short circuit, the entanglement between fibers becomes weak, and the mechanical strength becomes weak.
- the fiber A, the fiber B, and the fiber C are the following compounding ratios in all the fibers.
- the fiber A is mixed in a range of 25 to 50% by mass of the total fibers constituting the separator. If it is less than 25% by mass, the effect of preventing the separator from being crushed in the Z-axis direction (spacer effect) cannot be sufficiently exhibited, and a short circuit is likely to occur due to compression. If it exceeds 50% by mass, the porosity is reduced or the hole is blocked, leading to an increase in internal resistance. In addition, because it is thermoplastic, it becomes unstable at high temperatures, leading to a decrease in durability. Furthermore, the amount of fibrillated fine fibers in the separator is less than 50% by mass, the pore diameter of the separator cannot be controlled, and an internal short circuit is likely to occur.
- the fiber B is mixed in a range of 60 to 10% by mass of the total fibers constituting the separator. If the amount is less than 10% by mass, the amount of fine fibers fibrillated is insufficient, the pore diameter of the separator cannot be controlled, and an internal short circuit tends to occur. If it exceeds 60% by mass, the amount of fibrillated fine fibers is too large and the separator becomes too dense, resulting in an increase in internal resistance. Furthermore, it is preferable that the fiber C is mixed in a range of 15 to 40% by mass of the total fibers constituting the separator.
- the pore diameter of the fiber layer is preferably from 0.1 ⁇ m to 15 ⁇ m, more preferably from 0.1 ⁇ m to 5.0 ⁇ m, as the average pore diameter by the bubble point method.
- the average pore diameter is smaller than 0.1 ⁇ m, the ionic conductivity is lowered and the internal resistance tends to be high. Further, since it is difficult for water to escape during the production of the separator, it is difficult to produce the separator. If it exceeds 15 ⁇ m, an internal short circuit is likely to occur when the film is thinned.
- the measurement of the hole diameter by the bubble point method may be performed by using a porometer manufactured by Seika Industrial Co., Ltd.
- the separator according to the first aspect of the present invention has sufficient tensile strength and compressive strength, but it is also possible to mix a binder resin or binder fiber in order to obtain higher strength.
- the binder resin or binder fiber includes various materials such as polyvinyl alcohol, polyacrylonitrile, polyethylene, and derivatives thereof, but is not limited thereto.
- the thickness of the separator according to the first aspect of the present invention is preferably 60 ⁇ m or less. If the thickness of the separator exceeds 60 ⁇ m, it will be disadvantageous for thinning of the electricity storage device, and at the same time, the amount of electrode material that can be put in a certain cell volume will be reduced, the capacity will be reduced, and the resistance will be increased. It is not preferable.
- the density of the separator according to the first aspect of the present invention is preferably 0.20 g / cm 3 to 0.70 g / cm 3 . More preferably from 0.25g / cm 3 ⁇ 0.65g / cm 3, particularly preferably 0.30g / cm 3 ⁇ 0.60g / cm 3.
- the void portion of the separator becomes excessive, and problems such as occurrence of short circuits and deterioration of self-discharge resistance are likely to occur.
- the density is larger than 0.70 g / cm 3 , the material constituting the separator becomes excessively clogged, so that ion migration is hindered and resistance is likely to increase.
- the air permeability of the separator according to the first aspect of the present invention is preferably 100 seconds / 100 ml or less. Ionic conductivity can be suitably maintained.
- the air permeability in the separator of this invention says the value measured using the Gurley air permeability measuring device.
- the separator according to the first aspect of the present invention contains the fiber A, the fiber B, and the fiber C, and the fiber A is made of polyester fiber having a crystallinity of 50% or more. Even underneath, deterioration due to organic solvents and ionic liquids hardly occurs, and it can be suitably used for power storage devices such as lithium ion secondary batteries, lithium ion capacitors, polymer batteries, and electric double layer capacitors.
- power storage devices such as lithium ion secondary batteries, lithium ion capacitors, polymer batteries, and electric double layer capacitors.
- what is conventionally well-known can be used for the materials which comprise electrochemical elements, such as a positive electrode, a negative electrode, and electrolyte solution.
- one or more kinds of fibers A cut or beaten to a fiber diameter of 5 ⁇ m or less and a fiber length of 10 mm or less, a fiber B fibrillated to a fiber diameter of 1 ⁇ m or less and a fiber length of 3 mm or less, a fiber diameter of 1 ⁇ m or less, a fiber length Fiber C fibrillated to 3 mm or less is dispersed in water. The order in which it is put into the water is not fixed.
- the fibers used in the present invention are very fine and difficult to disperse uniformly in the disaggregation step, good dispersion is possible by using a dispersing device such as a pulper or an agitator or an ultrasonic dispersing device.
- the water used in this dispersion step is preferably ion-exchanged water in order to reduce ionic impurities as much as possible.
- the same synthetic fiber or different fiber as described above is dispersed in water by a dispersing device such as a pulper or agitator different from the above.
- the beating can be performed using a general beating machine such as a ball mill, beater, lampel mill, PFI mill, SDR (single disc refiner), DDR (double disc refiner), high-pressure homogenizer, homomixer, or other refiner. it can.
- a general beating machine such as a ball mill, beater, lampel mill, PFI mill, SDR (single disc refiner), DDR (double disc refiner), high-pressure homogenizer, homomixer, or other refiner. it can.
- the paper dispersion obtained above is made by applying a wet paper machine such as a long-mesh type, a short-mesh type, a circular net type, or an inclined type. Dehydrate in a continuous wire mesh dewatering part.
- a separator is obtained.
- the separator which is a 1st aspect of this invention can be obtained by passing through drying parts, such as a multi-cylinder type
- At least one layer contains polyester fibers having a crystallinity of 50% or more.
- the polyester fiber having a degree of crystallinity of 50% or more one made of at least one resin selected from polyester fibers such as polyethylene terephthalate, polybutylene terephthalate, and wholly aromatic polyarylate is preferably used. Because the polyester fiber has a crystallinity of 50% or more, it is highly resistant to organic solvents, ionic liquids, and high-temperature conditions, and provides a separator that does not easily deteriorate even if it is used in a high-temperature atmosphere for a long period of time. can do.
- the degree of crystallinity of the polyester fiber is 50% or more, particularly preferably 70% or more.
- the degree of crystallinity is less than 50%, it is easy to dissolve in an organic solvent or an ionic liquid, and when used under a high temperature atmosphere for a long time, it tends to cause deterioration.
- the crystallinity of the polyester fiber can be measured by quantifying the endothermic peak derived from crystallization using a DSC (differential scanning calorimeter). Further, it can be measured by obtaining the correlation between the peak band in which the difference in crystallinity appears and the density using FT-Raman spectroscopy.
- other synthetic fibers may be contained. As other synthetic fibers, at least one selected from wholly aromatic polyamide, wholly aromatic polyester, semi-aromatic polyamide, polyphenylene sulfide, polyparaphenylene benzobisoxazole, polyethylene and polypropylene is preferably used.
- any material can be used as long as it has high heat resistance and does not dissolve in an organic solvent or ionic liquid used in the driving electrolyte.
- any material can be used as long as it has high heat resistance and does not dissolve in an organic solvent or ionic liquid used in the driving electrolyte.
- the fiber diameter of the polyester fiber and other synthetic fibers is preferably 5 ⁇ m or less, and the fiber length is preferably 10 mm or less. Particularly preferably, the fiber diameter is 3 ⁇ m or less and the fiber length is 3 mm or less. When the fiber diameter is larger than 5 ⁇ m and the fiber length is longer than 10 mm, there is a high possibility that a through-hole is formed when the film is thinned, which is likely to cause an internal short circuit.
- the fiber used for the fiber layer laminated with the fiber layer containing the polyester fiber may be selected from the synthetic fibers, or other synthetic fibers or natural pulp other than those described above. Any of cellulose fibers and the like can be used. These synthetic fibers, cellulose fibers, and the like are preferably beaten in order to improve the retention of the electrolytic solution and to form a uniform fiber layer.
- the pore diameter of the fiber layer in the separator according to the second aspect of the present invention is preferably in the range of 0.1 ⁇ m to 15 ⁇ m, more preferably 0.1 ⁇ m to 5.0 ⁇ m, as the average pore diameter measured by the bubble point method. .
- the measurement of the hole diameter by the bubble point method may be performed by using a porometer manufactured by Seika Sangyo Co., Ltd.
- the separator according to the second aspect of the present invention has sufficient tensile strength and compressive strength, but in order to obtain higher strength, it is also possible to mix a binder resin or binder fiber.
- the binder resin or binder fiber includes various materials such as polyvinyl alcohol, polyacrylonitrile, polyethylene, and derivatives thereof, but is not limited thereto.
- the thickness of the separator according to the second aspect of the present invention is preferably 50 ⁇ m or less. If the thickness of the separator exceeds 50 ⁇ m, it will be disadvantageous for thinning of the electricity storage device, and at the same time, the amount of electrode material that can be put in a certain cell volume will be reduced, the capacity will be reduced, and the resistance will be increased. It is not preferable.
- the density of the separator according to the second aspect of the present invention is preferably 0.20 g / cm 3 to 0.75 g / cm 3 . If it is less than 0.20 g / cm 3 , the void portion of the separator becomes excessive, and problems such as occurrence of short circuits and deterioration of self-discharge resistance are likely to occur. On the other hand, if the density is larger than 0.75 g / cm 3 , the material constituting the separator becomes excessively clogged, so that ion migration is hindered and resistance is likely to increase.
- the porosity of the separator according to the second aspect of the present invention is preferably in the range of 30% to 90% in order to achieve both prevention of short circuit and suppression of increase in resistance.
- the porosity here is calculated
- Porosity (%) [1 ⁇ (M / T) / D] ⁇ 100
- the manufacturing method of the separator according to the second aspect of the present invention will be described, but the method is not limited to this, and the separator of the present invention can be manufactured by other methods.
- one or more kinds of polyester fibers having a crystallinity of 50% or more that are cut or beaten to have a fiber diameter of 5 ⁇ m or less and a fiber length of 10 mm or less are dispersed in water. Since the fibers used in the present invention are very fine and difficult to disperse uniformly in the disaggregation step, good dispersion is possible by using a dispersing device such as a pulper or an agitator or an ultrasonic dispersing device.
- the water used in this dispersion step is preferably ion-exchanged water, particularly preferably pure water, in order to reduce ionic impurities as much as possible.
- the same synthetic fiber or heterogeneous fiber as described above is dispersed in water by a dispersing device such as a pulper or agitator different from the above.
- the beating can be performed using a general beating machine such as a ball mill, beater, lampel mill, PFI mill, SDR (single disc refiner), DDR (double disc refiner), high-pressure homogenizer, homomixer, or other refiner. it can.
- the paper dispersion (slurry) obtained above is made by applying a wet paper machine such as a long-mesh type, a short-mesh type, a circular net type, or an inclined type.
- a wet paper machine such as a long-mesh type, a short-mesh type, a circular net type, or an inclined type.
- the separator according to the second aspect of the present invention can be obtained by passing through a drying part such as a multi-cylinder type or Yankee type dryer.
- a drying part such as a multi-cylinder type or Yankee type dryer.
- a separator formed by laminating fiber layers on a net is more preferable because the fibers of the fiber layers are entangled between layers and are difficult to peel off.
- the separator obtained by the multi-tank inclined type wet paper machine is difficult to form a boundary between fiber layers, and a uniform separator without a pinhole is obtained.
- Such a multi-tank inclined type wet paper machine has a configuration as shown in FIG. As shown in FIG.
- the papermaking net 10 travels in the arrow ⁇ direction by a plurality of guide rollers.
- the inclined paper making net 10 between the guide roller 11 and the guide roller 12 is referred to as an inclined traveling unit 13.
- the lower part of the second flow box 15 is located in the vicinity A of the intersection of the floodline WL and the inclined traveling part 13 in the first flow box 14.
- the dispersion 16 containing the fibers in the first flow box 14 and the dispersion 17 containing the fibers in the second flow box 15 are adjacent to each other with a partition wall 18 therebetween.
- the separator according to the second aspect of the present invention is a laminate in which two or more fiber layers are laminated, and at least one of them contains polyester fibers having a crystallinity of 50% or more.
- polyester fibers having a crystallinity of 50% or more by forming a laminate of two or more fiber layers, pinholes are less likely to be generated, and thus have an excellent effect in preventing a short circuit.
- polyester fibers having a crystallinity of 50% or more the durability to organic solvents and ionic liquids, and further to high temperature conditions is enhanced, and it has an excellent effect on deterioration under a high temperature atmosphere for a long time. .
- any material that constitutes the electricity storage device such as a positive electrode, a negative electrode, and an electrolytic solution can be used as long as it is conventionally known.
- a wet sheet was made from the above papermaking material using a standard type handmaking apparatus defined in JIS P8222. Thereafter, the obtained wet sheet was taken out from the hand-making apparatus and then dried at 130 ° C. with a Yankee dryer to obtain the separator of the present invention.
- the thickness of the separator was 31 ⁇ m
- the density was 0.41 g / cm 3
- the air permeability was 8 seconds / 100 ml.
- a wet sheet was made from the above papermaking material using a standard type handmaking apparatus defined in JIS P8222. Thereafter, the obtained wet sheet was taken out from the hand-making apparatus and then dried at 130 ° C. with a Yankee dryer to obtain the separator of the present invention.
- the thickness of the separator was 30 ⁇ m
- the density was 0.41 g / cm 3
- the air permeability was 8 seconds / 100 ml.
- the separator of the present invention was obtained in the same manner as in Example 1.
- the film thickness of the separator was 49 ⁇ m
- the density was 0.32 g / cm 3
- the air permeability was 15 seconds / 100 ml.
- Fiber A made of polyethylene terephthalate fiber having a fiber diameter of 2.5 ⁇ m, fiber length of 6 mm, and crystallinity of 55%
- Fiber B made of polyphenylene sulfide fibrillated to a fiber diameter of 0.8 ⁇ m and fiber length of 1.5 mm
- fiber Fibers C made of solvent-spun cellulose fibrillated to a diameter of 0.5 ⁇ m and a fiber length of 1 mm were charged in ion exchange water at a mass ratio of 30:30:40, respectively, into a pulper at a concentration of 0.05% by mass.
- a papermaking material made of a fiber dispersion was prepared by dispersing for a minute. Thereafter, the separator of the present invention was obtained in the same manner as in Example 1. As the physical properties of the obtained separator, the thickness of the separator was 22 ⁇ m, the density was 0.45 g / cm 3 , and the air permeability was 5 seconds / 100 ml.
- a papermaking material made of a fiber dispersion was prepared by dispersing for 30 minutes.
- the separator of the present invention was obtained in the same manner as in Example 1.
- the thickness of the separator was 57 ⁇ m
- the density was 0.36 g / cm 3
- the air permeability was 19 seconds / 100 ml.
- a papermaking material made of a fiber dispersion was prepared by dispersing for 30 minutes. Thereafter, the separator of the present invention was obtained in the same manner as in Example 1. As the physical properties of the obtained separator, the thickness of the separator was 32 ⁇ m, the density was 0.45 g / cm 3 , and the air permeability was 11 seconds / 100 ml.
- the fibers C made of solvent-spun cellulose fibrillated to a fiber diameter of 0.5 ⁇ m and a fiber length of 1 mm were charged into the pulper at a mass ratio of 25:50:25 in ion exchange water at a concentration of 0.05% by mass. Then, a paper-making material comprising a fiber dispersion was produced by dispersing for 30 minutes.
- the separator of the present invention was obtained in the same manner as in Example 1.
- the thickness of the separator was 38 ⁇ m
- the density was 0.62 g / cm 3
- the air permeability was 42 seconds / 100 ml.
- a wet sheet was made from the above papermaking material using a standard type handmaking apparatus defined in JIS P8222. Thereafter, the obtained wet sheet was taken out from the hand-making apparatus and then dried at 130 ° C. with a Yankee dryer to obtain the separator of the present invention.
- the thickness of the separator was 30 ⁇ m
- the density was 0.41 g / cm 3
- the air permeability was 8 seconds / 100 ml.
- Comparative Example 2 A fiber C made of solvent-spun cellulose fibrillated to a fiber diameter of 0.5 ⁇ m and a fiber length of 1 mm is charged into ion exchange water at a concentration of 0.05% by mass in a pulper and dispersed for 30 minutes. A papermaking material consisting of a dispersion of only fibers C not containing was prepared. Thereafter, a comparative separator was obtained in the same manner as in Example 1. As physical properties of the obtained separator, the thickness of the separator was 35 ⁇ m, the density was 0.41 g / cm 3 , and the air permeability was 5 seconds / 100 ml.
- a fiber A made of polyethylene terephthalate fiber having a fiber diameter of 2.5 ⁇ m, a fiber length of 6 mm, and a crystallinity of 55%, and a fiber C made of solvent-spun cellulose fibrillated to a fiber diameter of 0.5 ⁇ m and a fiber length of 1 mm were each 80 :
- a papermaking material composed of a dispersion of fibers A and C not containing fiber B was prepared by adding it into a pulper at a mass ratio of 20 in ion exchange water at a concentration of 0.05% by mass and dispersing for 30 minutes. Thereafter, a comparative separator was obtained in the same manner as in Example 1.
- the thickness of the separator was 70 ⁇ m
- the density was 0.32 g / cm 3
- the air permeability was 39 seconds / 100 ml.
- the electric double layer capacitor using the separator of the present invention maintains a sufficient discharge capacity of 8.9 F or more even after 40000 hours of application of a voltage of 2.5 V at 80 ° C. and durability. It was confirmed that it was excellent.
- the electric double layer capacitors using the separators of Comparative Examples 1 to 4 had a very large reduction in discharge capacity, and some of them caused an internal short circuit, and the characteristics were extremely inferior.
- the separator of the present invention maintains a difference from the initial film thickness within 3 ⁇ m even after application of a voltage of 80 ° C., 2.5 V, and 4000 hours. It was confirmed that the property was good and stable in the high-temperature long-term test.
- the separators of Comparative Examples 1 to 4 have a difference between the film thickness after 4000 hours of voltage application and the initial film thickness of 6 ⁇ m or more, which is very thin, and are inferior in stability to a high-temperature long-term test.
- a polyethylene terephthalate fiber having a fiber diameter of 2.5 ⁇ m, a fiber length of 6 mm, and a crystallinity of 55% was charged into ion exchange water at a concentration of 0.05 mass% and dispersed for 30 minutes to prepare a fiber dispersion A.
- a wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 ⁇ m and a fiber length of 0.6 mm and a solvent-spun cellulose fibrillated to a fiber diameter of 0.5 ⁇ m and a fiber length of 1 mm are in a mass ratio of 1: 1.
- the fibers were mixed at a ratio, charged in ion-exchanged water at a concentration of 0.05% by mass in a pulper different from the above, and dispersed for 30 minutes to prepare a fiber dispersion B.
- the dispersion A was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, Dispersion B was made on the sheet. Thereafter, the obtained wet sheet was taken out from the hand-making apparatus and then dried at 130 ° C. with a Yankee dryer to obtain the separator of the present invention. Regarding the physical properties of the obtained separator, the density was 0.40 g / cm 3 , the porosity was 73%, and the thickness of the separator was 30 ⁇ m.
- Polyethylene terephthalate fiber having a fiber diameter of 2.5 ⁇ m, a fiber length of 6 mm, and a crystallinity of 73% was charged into ion exchange water at a concentration of 0.05 mass% and dispersed for 30 minutes to prepare a fiber dispersion C.
- a wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 ⁇ m and a fiber length of 0.6 mm and a solvent-spun cellulose fibrillated to a fiber diameter of 0.5 ⁇ m and a fiber length of 1 mm are in a mass ratio of 1: 1.
- the mixture was mixed at a ratio, and charged into ion-exchanged water at a concentration of 0.05% by mass in a pulper different from the above, and dispersed for 30 minutes to prepare a fiber dispersion D.
- the dispersion C was made using a standard hand-making apparatus specified in JIS P8222 to obtain a wet paper sheet. Further, Dispersion D was made on the sheet. Thereafter, the obtained wet sheet was taken out from the hand-making apparatus and then dried at 130 ° C. with a Yankee dryer to obtain the separator of the present invention. Regarding the physical properties of the obtained separator, the density was 0.41 g / cm 3 , the porosity was 73%, and the thickness of the separator was 30 ⁇ m.
- Polyethylene terephthalate fiber having a fiber diameter of 2.5 ⁇ m, fiber length of 6 mm, and crystallinity of 55% and wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 ⁇ m and fiber length of 0.6 mm in a mass ratio of 1: 1.
- the mixture was mixed, poured into ion exchange water at a concentration of 0.05% by mass into the pulper, and dispersed for 30 minutes to prepare a fiber dispersion E.
- solvent-spun cellulose fibrillated to a fiber diameter of 0.5 ⁇ m and a fiber length of 1 mm was charged into ion-exchanged water at a concentration of 0.05% by mass in a different pulper and dispersed for 30 minutes.
- Dispersion F was produced.
- the dispersion E was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, Dispersion F was made on the sheet. Thereafter, the obtained wet sheet was taken out from the hand-making apparatus and then dried at 130 ° C. with a Yankee dryer to obtain the separator of the present invention. Regarding the physical properties of the obtained separator, the density was 0.39 g / cm 3 , the porosity was 74%, and the thickness of the separator was 30 ⁇ m.
- a polyethylene terephthalate fiber having a fiber diameter of 2.5 ⁇ m, a fiber length of 6 mm, and a crystallinity of 55% was mixed with polyphenylene sulfide fibrillated to a fiber diameter of 0.8 ⁇ m and a fiber length of 1.5 mm in a mass ratio of 1: 1. Then, the dispersion was added to ion exchange water at a concentration of 0.05% by mass in a pulper and dispersed for 30 minutes to prepare a fiber dispersion G.
- Dispersion H was produced.
- the dispersion G was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, a dispersion H was made on the sheet. Thereafter, the obtained wet sheet was taken out from the hand-making apparatus and then dried at 130 ° C. with a Yankee dryer to obtain the separator of the present invention. Regarding the physical properties of the obtained separator, the density was 0.40 g / cm 3 , the porosity was 74%, and the thickness of the separator was 30 ⁇ m.
- Totally aromatic polyester fiber having a fiber diameter of 0.2 ⁇ m and a fiber length of 0.6 mm and having a crystallinity of 85% is charged into ion exchange water at a concentration of 0.05% by mass in a pulper and dispersed for 30 minutes.
- a fiber dispersion I was prepared.
- solvent-spun cellulose fibrillated to a fiber diameter of 0.5 ⁇ m and a fiber length of 1 mm was charged into ion-exchanged water at a concentration of 0.05% by mass in a different pulper and dispersed for 30 minutes.
- Dispersion J was prepared.
- the dispersion I was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, the dispersion J was made on the sheet. Thereafter, the obtained wet sheet was taken out from the hand-making apparatus and then dried at 130 ° C. with a Yankee dryer to obtain the separator of the present invention. Regarding the physical properties of the obtained separator, the density was 0.40 g / cm 3 , the porosity was 73%, and the thickness of the separator was 30 ⁇ m.
- Totally aromatic polyester fiber having a fiber diameter of 0.2 ⁇ m and a fiber length of 0.6 mm and having a crystallinity of 85% is charged into ion exchange water at a concentration of 0.05% by mass in a pulper and dispersed for 30 minutes.
- a fiber dispersion K was prepared.
- a wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 ⁇ m and a fiber length of 0.6 mm and a solvent-spun cellulose fibrillated to a fiber diameter of 0.5 ⁇ m and a fiber length of 1 mm are in a mass ratio of 1: 1.
- the mixture was mixed at a ratio, charged in deionized water at a concentration of 0.05% by mass in a pulper different from the above, and dispersed for 30 minutes to prepare a fiber dispersion L.
- the dispersion K was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, the dispersion L was made on the sheet. Thereafter, the obtained wet sheet was taken out from the hand-making apparatus and then dried at 130 ° C. with a Yankee dryer to obtain the separator of the present invention. Regarding the physical properties of the obtained separator, the density was 0.40 g / cm 3 , the porosity was 73%, and the thickness of the separator was 30 ⁇ m.
- Polyethylene terephthalate fiber having a fiber diameter of 0.5 ⁇ m, a fiber length of 5 mm, and a crystallinity of 55% was charged into ion exchange water at a concentration of 0.05% by mass in a pulper and dispersed for 30 minutes to prepare a fiber dispersion M.
- a wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 ⁇ m and a fiber length of 0.6 mm and a solvent-spun cellulose fibrillated to a fiber diameter of 0.5 ⁇ m and a fiber length of 1 mm are in a mass ratio of 1: 1.
- the mixture was mixed at a ratio, and charged into ion-exchanged water at a concentration of 0.05% by mass in a pulper different from the above, and dispersed for 30 minutes to prepare a fiber dispersion N.
- the dispersion M was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Further, the dispersion N was made on the sheet. Thereafter, the obtained wet sheet was taken out from the hand-making apparatus and then dried at 130 ° C. with a Yankee dryer to obtain the separator of the present invention. Regarding the physical properties of the obtained separator, the density was 0.40 g / cm 3 , the porosity was 73%, and the thickness of the separator was 30 ⁇ m.
- a polyethylene terephthalate fiber having a fiber diameter of 2.5 ⁇ m, a fiber length of 6 mm, and a crystallinity of 55% was charged into ion exchange water at a concentration of 0.05 mass% and dispersed in a pulper for 30 minutes to prepare a fiber dispersion P. .
- a wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 ⁇ m and a fiber length of 0.6 mm and a solvent-spun cellulose fibrillated to a fiber diameter of 0.5 ⁇ m and a fiber length of 1 mm are in a mass ratio of 1: 1.
- the fibers were mixed at a ratio, charged in deionized water at a concentration of 0.05% by mass in a pulper different from the above, and dispersed for 30 minutes to prepare a fiber dispersion Q.
- the dispersion P was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Furthermore, the dispersion Q was made on the sheet. Thereafter, the obtained wet sheet was taken out from the hand-making apparatus and then dried at 130 ° C. with a Yankee dryer to obtain the separator of the present invention. Regarding the physical properties of the obtained separator, the density was 0.40 g / cm 3 , the porosity was 73%, and the thickness of the separator was 19 ⁇ m.
- a polyethylene terephthalate fiber having a fiber diameter of 2.5 ⁇ m, a fiber length of 6 mm, and a crystallinity of 55% was charged into ion exchange water at a concentration of 0.05 mass% and dispersed for 30 minutes to prepare a fiber dispersion R. .
- a wholly aromatic polyamide fibrillated to a fiber diameter of 0.6 ⁇ m and a fiber length of 1.5 mm is charged into ion exchange water at a concentration of 0.05% by mass in a pulper and dispersed for 30 minutes to obtain a fiber dispersion. S was produced.
- the solvent-spun cellulose fibrillated to a fiber diameter of 0.5 ⁇ m and a fiber length of 1 mm is charged into ion-exchanged water at a concentration of 0.05% by mass in a pulper different from the above and dispersed for 30 minutes to disperse the fiber.
- a body T was prepared.
- the dispersion R was made using a standard hand-making device specified in JIS P8222 to obtain a wet paper sheet. Furthermore, the dispersion S was made on the sheet. Thereafter, the dispersion T was made on the sheet. The obtained wet sheet was taken out from the handmaking apparatus and then dried at 130 ° C. with a Yankee dryer to obtain the separator of the present invention. Regarding the physical properties of the obtained separator, the density was 0.40 g / cm 3 , the porosity was 73%, and the thickness of the separator was 35 ⁇ m.
- the dispersion U is supplied to both the first flow box 14 and the second flow box 15 in the multi-tank inclined wet paper machine shown in FIG. Shed from.
- a wet sheet in which fiber layers having the same fiber composition are sequentially laminated is made, dried at 130 ° C. with a Yankee dryer, a thickness of 20 ⁇ m, a density of 0.45 g / cm 3 , and a porosity of 70%.
- a separator without a pinhole was obtained.
- a fiber made of polyethylene terephthalate fiber having a fiber diameter of 2.5 ⁇ m, a fiber length of 6 mm, and a crystallinity of 55% is put into a pulper at a concentration of 0.05% by mass in ion-exchanged water and dispersed for 30 minutes to prepare dispersion V. did.
- a fiber made of wholly aromatic polyamide fibrillated to a fiber diameter of 0.2 ⁇ m and a fiber length of 0.6 mm and a fiber made of solvent-spun cellulose fibrillated to a fiber diameter of 0.5 ⁇ m and a fiber length of 1 mm were each 80: Dispersion W was prepared by charging the ion exchange water at a mass ratio of 20 into the pulper at a concentration of 0.05 mass% and dispersing for 30 minutes.
- the dispersion V was supplied to the first flow box 14 of the multi-tank inclined wet paper machine in FIG. 1, and the dispersion W was supplied to the second flow box 15.
- the papermaking net 10 was run, and the dispersion was poured out from each flow box to the inclined running unit 13.
- a wet sheet in which fiber layers of different fiber types are sequentially laminated is made and dried at 130 ° C. with a Yankee dryer, the thickness is 20 ⁇ m, the density is 0.45 g / cm 3 , and the porosity is 69%.
- the separators with different fiber types were obtained.
- the dispersion a was made using a standard hand-making apparatus defined in JIS P8222 to obtain a wet paper sheet having a basis weight of 6 g / cm 2 . Furthermore, the dispersion b was made on the sheet with a basis weight of 6 g / cm 2 . Thereafter, the obtained wet sheet was taken out from the hand-making apparatus and then dried at 130 ° C. with a Yankee dryer to obtain a comparative separator. As for the physical properties of the comparative separator obtained, the density was 0.40 g / cm 3 , the porosity was 73%, and the thickness of the comparative separator was 30 ⁇ m.
- the dispersion c was made using a standard handmaking apparatus defined in JIS P8222 to obtain a wet paper sheet having a basis weight of 6 g / cm 2 . Thereafter, the obtained wet sheet was taken out from the hand-making apparatus and then dried at 130 ° C. with a Yankee dryer to obtain a comparative separator. Regarding the physical properties of the comparative separator obtained, the density was 0.41 g / cm 3 , the porosity was 74%, and the thickness of the comparative separator was 32 ⁇ m.
- Table 4 shows the physical properties of film thickness, density, and porosity for each separator.
- the electric double layer capacitor using the separator of the present invention maintains a sufficient discharge capacity of 6.6 F or more after 4000 hours test at 80 ° C. and 2.5 V, and 2 A voltage of .26 V or higher was maintained, and it was confirmed to have excellent performance.
- the electric double layer capacitor using the separator of the comparative example has a large decrease in discharge capacity, very poor voltage holding performance, and is extremely inferior. From the above results, it was found that the separator of the present invention is a thin film and very excellent in durability under a high temperature environment in the presence of an organic solvent or an ionic liquid. Therefore, the separator of the present invention is suitably used for an electricity storage device such as an electric double layer capacitor, and is excellent in preventing a short circuit between electrodes and suppressing self-discharge.
- the separator for an electricity storage device of the present invention is a thin film, and is excellent in durability during long-term use in a high temperature environment in the presence of an organic solvent or an ionic liquid, and an electricity storage device such as an electric double layer capacitor And is extremely useful in the industry since it is excellent in preventing short-circuiting between electrodes and suppressing self-discharge.
- the separator of the present invention can be thinned, has excellent ion permeability and low resistance, is excellent in preventing short circuit between electrodes and suppressing self-discharge, and in the presence of an organic solvent or ionic liquid. Excellent durability after long-term use at high temperatures. Therefore, the separator of the present invention can be suitably used for an electricity storage device, particularly for a lithium ion secondary battery, a polymer lithium secondary battery, an electric double layer capacitor, and an aluminum electrolytic capacitor, and thus is extremely useful industrially. .
Abstract
Description
本願は、2008年10月15日に日本に出願された特願2008-266786号、及び2008年11月26日に日本に出願された特願2008-301428号に基づき優先権を主張し、その内容をここに援用する。
また上述のリチウムイオン二次電池、電気二重層キャパシタには駆動用電解液に有機溶剤やイオン性液体が使用されており、セルロース等のセパレータでは高温での長期耐久試験で放電容量の低下や膜厚の減少を伴う劣化を生ずる問題があった。
このようなセパレータの要求に対して、例えば、ポリオレフィンを延伸して作製される比較的透気度の値が高い微多孔樹脂フィルム(延伸膜)に針やレーザーで貫通孔を設けたものをセパレータとして使用することが提案されている(例えば、特許文献3参照)。しかしながら、このような微多孔樹脂フィルムは、それを単体で使用すると貫通孔があるが故に正極と負極とが短絡を起こしてしまう恐れがあった。また、シャットダウン温度以上のメルトダウン温度域において収縮しやすい性質を有しており、その結果、高温になった場合、電極間の短絡を起こしやすいという問題を有していた。また、駆動用電解液中での熱劣化が少ない化学繊維を含有するセパレータを用いることにより、耐熱性を高め、高温使用時の寿命を長くすることが提案されている(例えば、特許文献4参照)。この文献には、セパレータ中の化学繊維の配合割合が10%程度で、残りはセルロース繊維等の繊維を使用することが可能であるとの記述がある。しかしながら、該セパレータは、有機溶剤やイオン性液体存在下の高温環境下では、セパレータの質量減少が起こることにより、強度、耐久性の劣化が起こりやすい。また、耐久性の高い化学繊維と、耐久性の低いセルロース繊維ランダムに抄造されているために、有機溶剤に対してセパレータの劣化が不均一に起こり、電流集中が起こりやすくなる。さらに、該セパレータの構造は単層構造であるがために、薄膜化した場合、内部短絡が発生しやすい。また、別の文献として、内部短絡を防止するために、円網抄紙機を使用して2層以上の層を1層に抄き合わせることが提案されている(例えば、特許文献5参照)。しかしながら、従来のものは、すべての層が天然繊維で構成されているために、有機溶剤やイオン性液体存在下の高温環境下では、セパレータの質量減少により、強度、耐久性の劣化が起こり、製品特性を維持することができなくなるという問題があった。又、円網抄紙機で1層ずつ個別に抄造したものを張り合わせているために、層間に境界が生じ、イオンの移動を阻害する原因ともなりやすい。
なお従来の技術は、薄膜化が可能で、且つ、蓄電デバイスの高容量化など、高性能化、高信頼性が図れるような高分子電解質を用いた蓄電デバイス用セパレータは実現していない。
そこで本発明はさらに、薄膜化が可能で、イオン透過性に優れて低抵抗であり、且つ、電極間の短絡および自己放電がしにくく、しかも有機溶剤やイオン性液体存在下の高温環境下での長期使用後においても耐久性に優れる蓄電デバイス用セパレータを提供する。
本発明の第2の態様であるセパレータは、2層以上の繊維層を積層してなるセパレータであって、該繊維層の少なくとも1層以上が、結晶化度が50%以上のポリエステル繊維を含有することを特徴とする。
すなわち、本発明は以下の(1)~(20)に関する。
(1)熱可塑性合成繊維A、耐熱性合成繊維Bおよび天然繊維Cを含有し、該熱可塑性合成繊維Aが、結晶化度が50%以上のポリエステル繊維からなることを特徴とする蓄電デバイス用セパレータ。
(2)前記熱可塑性合成繊維Aが、結晶化度が50%以上のポリエチレンテレフタレート、ポリブチレンテレフタレート、全芳香族ポリアリレートから選ばれた少なくとも1種からなることを特徴とする(1)に記載の蓄電デバイス用セパレータ。
(3)前記耐熱性合成繊維Bが、全芳香族ポリアミド、全芳香族ポリエステル、半芳香族ポリアミド、ポリフェニレンサルファイド、ポリパラフェニレンベンゾビスオキサゾールから選ばれた少なくとも1種からなることを特徴とする(1)または(2)に記載の蓄電デバイス用セパレータ。
(4)前記熱可塑性合成繊維Aが25~50質量%、前記耐熱性合成繊維Bが60~10質量%および前記天然繊維Cが15~40質量%の配合比率からなることを特徴とする(1)乃至(3)のいずれかに記載の蓄電デバイス用セパレータ。
(5)前記熱可塑性合成繊維Aの繊維径が5μm以下で、繊維長が10mm以下であることを特徴とする(1)乃至(4)のいずれかに記載の蓄電デバイス用セパレータ。
(6)前記耐熱性合成繊維Bが、繊維径が1μm以下であって、且つ、繊維長が3mm以下にフィブリル化されていることを特徴とする(1)乃至(5)のいずれかに記載の蓄電デバイス用セパレータ。
(7)前記天然繊維Cが、繊維径が1μm以下、繊維長が3mm以下にフィブリル化されている溶剤紡糸セルロースであることを特徴とする(1)乃至(6)のいずれかに記載の蓄電デバイス用セパレータ。
(8)前記セパレータが、熱可塑性合成繊維Aの熱融着と、フィブリル化された耐熱性合成繊維B及び/又はフィブリル化された天然繊維Cの繊維の絡み合いにより構成されていることを特徴とする(1)乃至(7)のいずれかに記載の蓄電デバイス用セパレータ。
(9)前記セパレータの膜厚が60μm以下であることを特徴とする(1)乃至(8)のいずれかに記載の蓄電デバイス用セパレータ。
(10)前記セパレータの密度が0.2~0.7g/cm3であることを特徴とする(1)乃至(9)のいずれかに記載の蓄電デバイス用セパレータ。
(11)前記セパレータの透気度が100秒/100ml以下であることを特徴とする(1)乃至(10)のいずれかに記載の蓄電デバイス用セパレータ。
(12)前記蓄電デバイスが、リチウムイオン二次電池、リチウムイオンキャパシタ、ポリマー電池もしくは電気二重層キャパシタであることを特徴とする(1)乃至(11)のいずれかに記載の蓄電デバイス用セパレータ。
(13)2層以上の繊維層を積層してなる蓄電デバイス用セパレータであって、該繊維層の少なくとも1層以上が、結晶化度が50%以上のポリエステル繊維を含有することを特徴とする蓄電デバイス用セパレータ。
(14)前記結晶化度が50%以上のポリエステル繊維を含む繊維層に、さらにその他合成繊維を含有することを特徴とする(13)に記載の蓄電デバイス用セパレータ。
(15)前記ポリエステル繊維が、結晶化度が50%以上のポリエチレンテレフタレート、ポリブチレンテレフタレート、全芳香族ポリアリレートから選ばれた少なくとも1種以上であることを特徴とする(13)または(14)に記載の蓄電デバイス用セパレータ。
(16)前記ポリエステル繊維および合成繊維の繊維径が5μm以下、繊維長が10mm以下であることを特徴とする(13)乃至(15)のいずれかに記載の蓄電デバイス用セパレータ。
(17)前記合成繊維が、全芳香族ポリアミド、全芳香族ポリエステル、半芳香族ポリアミド、ポリフェニレンサルファイド、ポリパラフェニレンベンゾビスオキサゾール、ポリエチレン、ポリプロピレンから選ばれた少なくとも1種であることを特徴とする(14)乃至(16)のいずれかに記載の蓄電デバイス用セパレータ。
(18)前記繊維層が、2つ以上のヘッドを有する傾斜ワイヤー抄紙機を用い、抄紙ネット上で重ねて抄き合わせてなることを特徴とする(13)乃至(17)のいずれかに記載の蓄電デバイス用セパレータ。
(19)前記繊維層が、第1のフローボックス内の吃水線と抄紙ネットとの交差部近傍に第2のフローボックス下部が位置する構造を持つ複数層を同時に形成できる多槽傾斜型湿式抄紙機を使用し、抄紙ネット上で重ねて抄き合わせてなることを特徴とする(13)乃至(17)のいずれかに記載の蓄電デバイス用セパレータ。
(20)前記蓄電デバイスが、リチウムイオン二次電池、ポリマーリチウム二次電池、電気二重層キャパシタ、アルミニウム電解コンデンサのいずれかであることを特徴とする(13)乃至(19)のいずれかに記載の蓄電デバイス用セパレータ。
また本発明の第2の態様であるセパレータは、薄膜化が可能で、イオン透過性に優れて低抵抗であり、且つ、電極間の短絡防止も自己放電の抑制も優れており、しかも有機溶剤やイオン性液体存在下での高温長期使用後の耐久性に優れている。
従って、本発明のセパレータは、蓄電デバイス用、特に、リチウムイオン二次電池、ポリマーリチウム二次電池、電気二重層キャパシタ及びアルミニウム電解コンデンサ用として好適に用いることができる。
セパレータに繊維Bを含有させることによって、有機溶剤やイオン性液体、更には高温条件に対する耐久性が高くなり、長期間高温雰囲気下で使用し続けても劣化しにくくなる。又、フィブリル化した繊維Bを使用することによって、ピンホールが発生しにくくなるため、短絡防止に優れたセパレータとなる。
本発明において、フィブリル化された繊維Bの繊維径は1μm以下、繊維長は3mm以下が好ましく、特に好ましくは繊維長が1mm以下である。繊維径が1μm超、繊維長が3mm超になると、薄膜化した際に貫通孔ができる可能性が高くなり、内部短絡の原因となりやすく、繊維同士の絡み合いが弱くなり、機械的強度が弱くなる傾向にある。
本発明において、繊維A、繊維Bおよび繊維Cは、全繊維中、下記の配合比であることが好ましい。すなわち、繊維Aはセパレータを構成する全繊維の25~50質量%の範囲で混合されていることが好ましい。25質量%未満であると、セパレータのZ軸方向につぶれにくい効果(スペーサー効果)を十分に発揮できず、圧縮により短絡が発生しやすくなる。50質量%超になると、空隙率を低下させたり孔を塞いでしまい、内部抵抗の増大に繋がる。又、熱可塑性ということで、高温時に不安定になり、耐久性の低下にも繋がる。更に、セパレータ中のフィブリル化された微細繊維の量が50質量%未満になってしまい、セパレータの孔径を制御することができず、内部短絡を起こしやすい。
また、繊維Bは、セパレータを構成する全繊維の60~10質量%の範囲で混合されていることが好ましい。10質量%未満であるとフィブリル化された微細繊維の量が足りず、セパレータの孔径を制御することができず、内部短絡を起こしやすい。60質量%超になると、フィブリル化された微細繊維の量が多すぎてセパレータが緻密に成りすぎ、その結果内部抵抗の増大に繋がる。
さらにまた、繊維Cはセパレータを構成する全繊維の15~40質量%の範囲で混合されていることが好ましい。15質量%未満であると、繊維同士の絡み合いが弱くなり、機械的強度が弱くなる傾向にあり、且つ電解液の含浸性も十分に得られにくい。40質量%超になると、高温雰囲気条件下での有機溶剤やイオン性液体により耐久性の低下を招きやすい。
また、本発明の第1の態様であるセパレータの密度は、0.20g/cm3~0.70g/cm3であることが好ましい。0.25g/cm3~0.65g/cm3であることがさらに好ましく、0.30g/cm3~0.60g/cm3であることが特に好ましい。0.20g/cm3未満であると、セパレータの空隙部分が過多となり、短絡の発生や、耐自己放電性が悪化しやすいなどの不具合を生じやすい。一方、密度が0.70g/cm3より大きいと、セパレータを構成する材料の詰まり方が過多となるために、イオン移動が阻害され抵抗が高くなりやすい。
前記ポリエステル繊維以外にその他合成繊維を含有しても良い。その他合成繊維としては、全芳香族ポリアミド、全芳香族ポリエステル、半芳香族ポリアミド、ポリフェニレンサルファイド、ポリパラフェニレンベンゾビスオキサゾール、ポリエチレン、ポリプロピレンから選ばれた少なくとも1種以上であることが好ましく使用されるが、必ずしもこれらに限定されるものではなく、耐熱性が高く、駆動用電解液に用いる有機溶剤やイオン性液体に対して溶解しないものであれば用いることができる。該合成繊維を含有する繊維層を積層することによって、有機溶剤やイオン性液体に対する耐久性が高くなり、長期間高温雰囲気下で使用され続けても劣化しにくくなる。
本発明の第2の態様であるセパレータにおける繊維層の細孔径は、バブルポイント法による平均孔径が0.1μm~15μmであることが好ましく、より好ましくは0.1μm~5.0μmの範囲である。平均孔径が0.1μmより小さいと、イオン伝導性が低下し、内部抵抗が高くなりやすい。また、セパレータの製造の際に水が抜けにくいため、製造しにくくなる。15μmを超えると、薄膜化した場合に内部短絡を生じやすくなる。尚、バブルポイント法による孔径の測定は、西華産業社製のポロメーターを使用すればよい。
本発明の第2の態様であるセパレータの厚さは、50μm以下であることが好ましい。セパレータの厚さが50μmを超えると、蓄電デバイスの薄型化に不利になると同時に、一定のセル体積に入れられる電極材の量が少なくなり、容量が小さくなってしまうばかりでなく、抵抗が高くなり好ましくない。
ここでいう空隙率は、坪量M(g/m2)、厚さT(μm)、真密度D(g/cm3)を用いて次式により求められる。
空隙率(%)=[1-(M/T)/D]×100
このような多槽傾斜型湿式抄紙機としては、図1のような構成を有する。図1に示したように、抄紙ネット10は、複数のガイドローラーによって矢印α方向に走行される。ガイドローラー11からガイドローラー12の間の傾斜した抄紙ネット10を傾斜走行部13という。本発明においては、第1のフローボックス14内の吃水線WLと傾斜走行部13との交差部近傍Aに第2のフローボックス15の下部が位置する。該交差部近傍Aでは、第1のフローボックス14内の繊維を含む分散体16と第2のフローボックス15内の繊維を含む分散体17が、隔壁18を隔てて隣接している。交差部近傍Aにおける隔壁18と傾斜走行部13との間は、間隙を有し、抄紙ネット10の走行にともない第1のフローボックス14から流れ出された分散体16は、この間隙を通って第2のフローボックス15内の分散体17と混合されるものである。
上記抄紙材料を、JIS P8222に規定する標準型手抄き装置を用いて湿体シートを抄造した。その後、得られた湿体シートを手抄き装置から取り出した後に、ヤンキードライヤーにて130℃で乾燥して本発明のセパレータを得た。得られたセパレータの物性として、セパレータの膜厚は31μm、密度は0.41g/cm3、透気度は8秒/100mlであった。
上記抄紙材料を、JIS P8222に規定する標準型手抄き装置を用いて湿体シートを抄造した。その後、得られた湿体シートを手抄き装置から取り出した後に、ヤンキードライヤーにて130℃で乾燥して本発明のセパレータを得た。得られたセパレータの物性として、セパレータの膜厚は30μm、密度は0.41g/cm3、透気度は8秒/100mlであった。
繊維径2.5μm、繊維長6mm、結晶化度20%のポリエチレンテレフタレート繊維からなる繊維Aと、繊維径0.2μm、繊維長0.6mmにフィブリル化された全芳香族ポリアミドからなる繊維Bと、繊維径0.5μm、繊維長1mmにフィブリル化された溶剤紡糸セルロースからなる繊維Cを、各々25:60:15の質量比率でイオン交換水に0.05質量%の濃度でパルパー内に投入し30分間分散し、繊維の分散体からなる抄紙材料を作製した。
上記抄紙材料を、JIS P8222に規定する標準型手抄き装置を用いて湿体シートを抄造した。その後、得られた湿体シートを手抄き装置から取り出した後に、ヤンキードライヤーにて130℃で乾燥して本発明のセパレータを得た。得られたセパレータの物性として、セパレータの膜厚は30μm、密度は0.41g/cm3、透気度は8秒/100mlであった。
繊維径0.5μm、繊維長1mmにフィブリル化された溶剤紡糸セルロースからなる繊維Cをイオン交換水に0.05質量%の濃度でパルパー内に投入し30分間分散し、繊維A及び繊維Bを含まない繊維Cのみの分散体からなる抄紙材料を作製した。その後、実施例1と同様にして比較用のセパレータを得た。得られたセパレータの物性として、セパレータの膜厚は35μm、密度は0.41g/cm3、透気度は5秒/100mlであった。
繊維径2.5μm、繊維長6mm、結晶化度55%のポリエチレンテレフタレート繊維からなる繊維Aと、繊維径0.5μm、繊維長1mmにフィブリル化された溶剤紡糸セルロースからなる繊維Cを、各々80:20の質量比率でイオン交換水に0.05質量%の濃度でパルパー内に投入し30分間分散し、繊維Bを含まない繊維A及び繊維Cの分散体からなる抄紙材料を作製した。その後、実施例1と同様にして比較用のセパレータを得た。得られたセパレータの物性として、セパレータの膜厚は70μm、密度は0.32g/cm3、透気度は39秒/100mlであった。
繊維径3μm、繊維長6mm、結晶化度55%のポリエチレン繊維と、繊維径0.4μm、繊維長1mmにフィブリル化された溶剤紡糸セルロースからなる繊維Cを、各々30:70の質量比率でイオン交換水に0.05質量%の濃度でパルパー内に投入し30分間分散し、繊維Bを含まないポリエチレン繊維と繊維Cの分散体からなる抄紙材料を作製した。その後、実施例1と同様にして比較用のセパレータを得た。得られたセパレータの物性として、セパレータの膜厚は51μm、密度は0.72g/cm3、透気度は104秒/100mlであった。
実施例1~7及び比較例1~4のセパレータについて、正極、負極の電極を用いて電気二重層キャパシタを組み立てて、各々100個ずつ捲回型セルを作製した。なお、捲回型セルの作製においては、電極として電気二重層キャパシタ用の活性炭電極(宝泉株式会社製)を用いた。また、電解液としてプロピレンカーボネートに、1mol/Lとなるようにテトラエチルアンモニウムテトラフルオロボレート(キシダ化学株式会社製)を溶解したものを用いた。
作製された捲回型セルの放電容量について、初期、2000時間試験後、4000時間試験後にそれぞれLCRメーターで測定し、高温長期試験後の放電容量の変化(低下)を評価した。なお、試験条件は、80℃、2.5V印加で行った。
得られた結果を表2に示す。
前記の高温長期試験4000時間終了した電気二重層キャパシタを分解し、素子内からセパレータを取り出し、メタノールで洗浄し乾燥した後にセパレータの膜厚を測定した。得られた結果を表3に示す。
得られたセパレータの物性は、密度は0.40g/cm3、空隙率は73%、セパレータの厚さは30μmであった。
得られたセパレータの物性は、密度は0.41g/cm3、空隙率は73%、セパレータの厚さは30μmであった。
得られたセパレータの物性は、密度は0.39g/cm3、空隙率は74%、セパレータの厚さは30μmであった。
得られたセパレータの物性は、密度は0.40g/cm3、空隙率は74%、セパレータの厚さは30μmであった。
得られたセパレータの物性は、密度は0.40g/cm3、空隙率は73%、セパレータの厚さは30μmであった。
得られたセパレータの物性は、密度は0.40g/cm3、空隙率は73%、セパレータの厚さは30μmであった。
得られたセパレータの物性は、密度は0.40g/cm3、空隙率は73%、セパレータの厚さは30μmであった。
得られたセパレータの物性は、密度は0.40g/cm3、空隙率は73%、セパレータの厚さは19μmであった。
さらに、繊維径0.5μm、繊維長1mmにフィブリル化された溶剤紡糸セルロースをイオン交換水に0.05質量%の濃度で上記とは別のパルパー内に投入し30分間分散し、繊維の分散体Tを作製した。
得られたセパレータの物性は、密度は0.40g/cm3、空隙率は73%、セパレータの厚さは35μmであった。
繊維径2.5μm、繊維長6mm、結晶化度20%のポリエチレンテレフタレート繊維をイオン交換水に0.05質量%の濃度でパルパー内に投入し30分間分散し、繊維の分散体aを作製した。次に、繊維径0.2μm、繊維長0.6mmにフィブリル化された全芳香族ポリアミドと、繊維径0.5μm、繊維長1mmにフィブリル化された溶剤紡糸セルロースを質量比で1対1の割合で混合し、イオン交換水に0.05質量%の濃度で上記とは別のパルパー内に投入し30分間分散し、繊維の分散体bを作製した。
得られた比較用セパレータの物性は、密度は0.40g/cm3、空隙率は73%、比較用セパレータの厚さは30μmであった。
繊維径0.5μm、繊維長1mmにフィブリル化された溶剤紡糸セルロースをイオン交換水に0.05質量%の濃度でパルパー内に投入し30分間分散し、繊維の分散体cを作製した。
得られた比較用セパレータの物性は、密度は0.41g/cm3、空隙率は74%、比較用セパレータの厚さは32μmであった。
実施例8~18及び比較例5~6のセパレータについて、正極、負極の電極を用いて電気二重層キャパシタを組み立てて、各々100個ずつ捲回型セルを作製した。なお、捲回型セルの作製においては、電極として電気二重層キャパシタ用の活性炭電極(宝泉株式会社製)を用いた。また、電解液としてプロピレンカーボネートに、1mol/Lとなるようにテトラエチルアンモニウムテトラフルオロボレート(キシダ化学株式会社製)を溶解したものを用いた。
得られた結果を表5に示す。
以上の結果から、本発明のセパレータは、薄膜で、有機溶剤やイオン性液体存在下での高温環境下での耐久性に、非常に優れていることが判った。従って、本発明のセパレータは、電気二重層キャパシタのような蓄電デバイスに好適に用いられ、電極間の短絡防止や自己放電の抑制に優れるものであった。
また本発明のセパレータは、薄膜化が可能で、イオン透過性に優れて低抵抗であり、且つ、電極間の短絡防止も自己放電の抑制も優れており、しかも有機溶剤やイオン性液体存在下での高温長期使用後の耐久性に優れている。従って、本発明のセパレータは、蓄電デバイス用、特に、リチウムイオン二次電池、ポリマーリチウム二次電池、電気二重層キャパシタ及びアルミニウム電解コンデンサ用として好適に用いることができるため、産業上極めて有用である。
11 ガイドローラー
12 ガイドローラー
13 傾斜走行部
14 第1のフローボックス
15 第2のフローボックス
16 分散体
17 分散体
18 隔壁
Claims (20)
- 熱可塑性合成繊維A、耐熱性合成繊維Bおよび天然繊維Cを含有し、該熱可塑性合成繊維Aが、結晶化度が50%以上のポリエステル繊維からなることを特徴とする蓄電デバイス用セパレータ。
- 前記熱可塑性合成繊維Aが、結晶化度が50%以上のポリエチレンテレフタレート、ポリブチレンテレフタレート、全芳香族ポリアリレートから選ばれた少なくとも1種からなることを特徴とする請求項1に記載の蓄電デバイス用セパレータ。
- 前記耐熱性合成繊維Bが、全芳香族ポリアミド、全芳香族ポリエステル、半芳香族ポリアミド、ポリフェニレンサルファイド、ポリパラフェニレンベンゾビスオキサゾールから選ばれた少なくとも1種からなることを特徴とする請求項1に記載の蓄電デバイス用セパレータ。
- 前記熱可塑性合成繊維Aが25~50質量%、前記耐熱性合成繊維Bが60~10質量%および前記天然繊維Cが15~40質量%の配合比率からなることを特徴とする請求項1に記載の蓄電デバイス用セパレータ。
- 前記熱可塑性合成繊維Aの繊維径が5μm以下で、繊維長が10mm以下であることを特徴とする請求項1に記載の蓄電デバイス用セパレータ。
- 前記耐熱性合成繊維Bが、繊維径が1μm以下であって、且つ、繊維長が3mm以下にフィブリル化されていることを特徴とする請求項1に記載の蓄電デバイス用セパレータ。
- 前記天然繊維Cが、繊維径が1μm以下、繊維長が3mm以下にフィブリル化されている溶剤紡糸セルロースであることを特徴とする請求項1に記載の蓄電デバイス用セパレータ。
- 前記セパレータが、熱可塑性合成繊維Aの熱融着と、フィブリル化された耐熱性合成繊維B及び/又はフィブリル化された天然繊維Cの繊維の絡み合いにより構成されていることを特徴とする請求項1乃至7のいずれかに記載の蓄電デバイス用セパレータ。
- 前記セパレータの膜厚が60μm以下であることを特徴とする請求項1乃至8のいずれかに記載の蓄電デバイス用セパレータ。
- 前記セパレータの密度が0.2~0.7g/cm3であることを特徴とする請求項1乃至9のいずれかに記載の蓄電デバイス用セパレータ。
- 前記セパレータの透気度が100秒/100ml以下であることを特徴とする請求項1乃至10のいずれかに記載の蓄電デバイス用セパレータ。
- 前記蓄電デバイスが、リチウムイオン二次電池、リチウムイオンキャパシタ、ポリマー電池もしくは電気二重層キャパシタであることを特徴とする請求項1乃至11のいずれかに記載の蓄電デバイス用セパレータ。
- 2層以上の繊維層を積層してなる蓄電デバイス用セパレータであって、該繊維層の少なくとも1層以上が、結晶化度が50%以上のポリエステル繊維を含有することを特徴とする蓄電デバイス用セパレータ。
- 前記結晶化度が50%以上のポリエステル繊維を含む繊維層に、さらにその他合成繊維を含有することを特徴とする請求項13に記載の蓄電デバイス用セパレータ。
- 前記ポリエステル繊維が、結晶化度が50%以上のポリエチレンテレフタレート、ポリブチレンテレフタレート、全芳香族ポリアリレートから選ばれた少なくとも1種以上であることを特徴とする請求項13または14に記載の蓄電デバイス用セパレータ。
- 前記ポリエステル繊維および合成繊維の繊維径が5μm以下、繊維長が10mm以下であることを特徴とする請求項13乃至15のいずれかに記載の蓄電デバイス用セパレータ。
- 前記合成繊維が、全芳香族ポリアミド、全芳香族ポリエステル、半芳香族ポリアミド、ポリフェニレンサルファイド、ポリパラフェニレンベンゾビスオキサゾール、ポリエチレン、ポリプロピレンから選ばれた少なくとも1種であることを特徴とする請求項14乃至16のいずれかに記載の蓄電デバイス用セパレータ。
- 前記繊維層が、2つ以上のヘッドを有する傾斜ワイヤー抄紙機を用い、抄紙ネット上で重ねて抄き合わせてなることを特徴とする請求項13乃至17のいずれかに記載の蓄電デバイス用セパレータ。
- 前記繊維層が、第1のフローボックス内の吃水線と抄紙ネットとの交差部近傍に第2のフローボックス下部が位置する構造を持つ複数層を同時に形成できる多槽傾斜型湿式抄紙機を使用し、抄紙ネット上で重ねて抄き合わせてなることを特徴とする請求項13乃至17のいずれかに記載の蓄電デバイス用セパレータ。
- 前記蓄電デバイスが、リチウムイオン二次電池、ポリマーリチウム二次電池、電気二重層キャパシタ、アルミニウム電解コンデンサのいずれかであることを特徴とする請求項13乃至19のいずれかに記載の蓄電デバイス用セパレータ。
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