CN111868965A - Separator for electricity storage device, and method for manufacturing electricity storage device - Google Patents
Separator for electricity storage device, and method for manufacturing electricity storage device Download PDFInfo
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- CN111868965A CN111868965A CN201980020186.8A CN201980020186A CN111868965A CN 111868965 A CN111868965 A CN 111868965A CN 201980020186 A CN201980020186 A CN 201980020186A CN 111868965 A CN111868965 A CN 111868965A
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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
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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
- H01M50/403—Manufacturing processes of separators, membranes or diaphragms
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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
- H01M50/4295—Natural cotton, cellulose or wood
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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
- H01M50/409—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
- 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
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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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- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The growth and short circuit of dendrite become remarkable after over-discharge, so the charge-discharge characteristics after over-discharge are obviously deteriorated. A separator in which a specific polyether copolymer is supported on a porous film so that the rate of change in Gurley number is within a certain value, and an electric storage device using the separator.
Description
Technical Field
The present invention relates to a separator for an electric storage device, a method for manufacturing the separator for the electric storage device, and particularly relates to a separator for a lithium ion secondary battery, a method for manufacturing the separator, and the lithium ion secondary battery.
Background
As represented by power supplies for memory backup of various electronic devices, microelectronics have recently become remarkable. That is, with the battery being housed in an electronic device, integration of the battery and an electronic component, and the like, a power storage device having a small size, a light weight, and a high energy density is desired. In recent years, with the miniaturization and weight reduction of various small electronic devices such as camcorders, portable communication devices, and notebook computers, there has been an increasing demand for high-energy-density power storage devices as driving power sources for these devices, and the development of these devices has been actively carried out.
High energy density electric storage devices such as lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors are provided with a pair of electrodes and a separator, impregnated with an electrolyte solution, and used in various industrial or consumer electric and electronic devices.
Conventionally, in an electric storage device such as a lithium ion secondary battery, a lithium ion capacitor, and an electric double layer capacitor using an electrochemical reaction, improvement of a separator has been required because of further increase in capacity, improvement in function, reduction in size, and reduction in weight. For example, in order to cope with the increase in capacity of an electric storage device, a separator having heat resistance, mechanical strength, and dimensional stability capable of withstanding self-heating during charge and discharge or abnormal heating during abnormal charge is required. In order to realize higher functionality of the electric storage device, particularly to improve rapid charge/discharge characteristics and high output characteristics, a separator that is made thin and has improved uniformity is urgently required.
In order to satisfy these requirements, for example, patent document 1 proposes a separator in which a through-hole is formed in a microporous membrane (stretched membrane) having high permeability, which is produced by stretching a polyolefin, by a needle or a laser beam, to further improve the permeability. However, when such a microporous resin film is used alone, the positive electrode and the negative electrode may be short-circuited due to the through-holes. In addition, the electrode has a property of easily shrinking in a melting temperature range equal to or higher than the shutdown temperature, and as a result, the electrodes easily come into direct contact with each other when the temperature reaches a high temperature. In addition, as a method for securing heat shrinkage resistance and mechanical strength in a thin film state, it is considered to reduce the porosity of the separator, but in this case, the ionic conductivity is reduced with an increase in internal resistance, and therefore, the demand for higher functionality cannot be satisfied.
Further, when the electrolyte penetrates into the separator, unevenness occurs, ion transfer is concentrated locally, and a metal such as copper, which is often used for a negative electrode current collector, is dissolved, and precipitation, dendrite growth, and short circuit may occur on the electrode, which is a problem, and deterioration of charge and discharge characteristics is suggested.
Therefore, the present applicant has disclosed a separator for an electric storage device excellent in charge-discharge characteristics, load characteristics, and low-temperature characteristics (patent document 2).
Documents of the prior art
Patent document
Patent document 1: international publication No. 01/67536
Patent document 2: japanese patent laid-open publication No. 2013-152857
Disclosure of Invention
Problems to be solved by the invention
However, growth and short-circuiting of dendrites are significantly changed after overdischarge, and charge-discharge characteristics after overdischarge are significantly deteriorated. The purpose of the present invention is to improve the charge-discharge cycle performance of an electric storage device, particularly a lithium secondary battery, after overdischarge.
Means for solving the problems
As a result of extensive studies to achieve the above object, the present inventors have found that when a separator in which a specific polyether copolymer is supported on a porous film so that the change rate of the gurley value is within a certain value is used, a separator for an electric storage device and an electric storage device capable of improving the permeability of an electrolyte into the separator and capturing metal ions of a current collecting foil can be obtained, and have completed the present invention.
That is, the present invention relates to the following.
Item 1 is an energy storage device separator comprising a porous film and a polyether copolymer and/or a crosslinked product thereof supported thereon,
the polyether copolymer comprises 2 to 40 mol% of a repeating unit derived from a monomer represented by the following formula (1), 98 to 60 mol% of a repeating unit derived from a monomer represented by the following formula (2), and 0 to 15 mol% of a repeating unit derived from a monomer represented by the following formula (3),
the change rate of the Gurley value before and after the polyether copolymer and/or the crosslinked product thereof is supported is within a range of. + -. 10%,
[ chemical formula 1 ]
In the formula (1), R is an alkyl group having 1-12 carbon atoms or-CH2O(CR1R2R3)；R1、R2、R3Is a hydrogen atom or-CH2O(CH2CH2O)nR4At R1、R2、R3In which n and R4The same or different; r4Is alkyl or aryl with 1-12 carbon atoms, and n is an integer of 0-12;
[ chemical formula 2 ]
[ chemical formula 3 ]
In the formula (3), R5Is a group having an ethylenically unsaturated group.
Item 2. the separator for an electric storage device according to item 1, wherein,
the weight average molecular weight of the polyether copolymer is 30-250 ten thousand.
Item 3. the separator for an electric storage device according to item 1 or 2, wherein,
the porous film is a nonwoven fabric of polyolefin resin or fibers selected from the group consisting of polyester fibers, cellulose fibers and polyamide fibers.
Item 4 the separator for an electric storage device according to any one of items 1 to 3, wherein,
the porous membrane has a thickness of 3 to 40 μm.
The method of manufacturing the separator for an electric storage device according to any one of items 1 to 4, comprising:
the solution obtained by dissolving the polyether copolymer in an aprotic organic solvent is applied to at least one surface of the porous film and dried.
An electricity storage device according to any one of claims 1 to 4, comprising the separator for an electricity storage device.
Effects of the invention
According to the present invention, it is possible to improve charge-discharge cycle performance after overdischarge, and to provide a separator and an electric storage device having excellent stability.
Detailed Description
In this specification, the electric storage device includes a secondary battery (such as a lithium ion secondary battery or a nickel hydrogen secondary battery) and an electrochemical capacitor.
In addition, the electric storage device of the present invention is characterized in that the positive electrode and the negative electrode are laminated via a separator which carries and integrates the following polyether copolymer.
<1. separator for electric storage device >
The separator of the present invention is characterized in that the separator comprises a porous film and a polyether copolymer and/or a crosslinked product thereof supported thereon, wherein the polyether copolymer comprises 2 to 40 mol% of a repeating unit derived from a monomer represented by the following formula (1), 98 to 60 mol% of a repeating unit derived from a monomer represented by the following formula (2), and 0 to 15 mol% of a repeating unit derived from a monomer represented by the following formula (3), and the rate of change in the Gurley value before and after the polyether copolymer and/or the crosslinked product thereof are supported is within a range of. + -. 10%.
[ chemical formula 4 ]
[ in the formula (1), R is an alkyl group having 1 to 12 carbon atoms or-CH2O(CR1R2R3)；R1、R2、R3Is a hydrogen atom or-CH2O(CH2CH2O)nR4At R1、R2、R3In which n and R4The same or different; r4Is an alkyl group or an aryl group having 1 to 12 carbon atoms, and n is an integer of 0 to 12.]
[ chemical formula 5 ]
[ chemical formula 6 ]
[ in the formula (3), R5Is a group having an ethylenically unsaturated group.]
The separator of the present invention, having these configurations, can reduce the deposition of metal ions eluted from the negative electrode current collector on the electrode, particularly during overdischarge, and can improve the charge-discharge cycle performance after overdischarge, and has excellent stability. Hereinafter, the separator of the present invention will be described in detail.
The gurley number is a value measured in accordance with JIS P8117(ISO 5636/5). The change rate of the gurley value is calculated by the following equation.
Change rate (%) of gurley { (gurley value of porous membrane after supporting polyether copolymer and/or crosslinked product thereof-gurley value of porous membrane before supporting polyether copolymer and/or crosslinked product thereof)/gurley value of porous membrane before supporting polyether copolymer and/or crosslinked product thereof } × 100
The thickness of the separator of the present invention is not particularly limited as long as it is the rate of change in the gurley value, but the difference between the thickness of the porous membrane after the polyether copolymer and/or the crosslinked product thereof is supported and the thickness of the porous membrane before the polyether copolymer and/or the crosslinked product thereof is supported is preferably 2.5 μm or less.
In order to obtain a good charge-discharge cycle, the change rate of the gurley value is preferably within a range of ± 10%, and in order to further effectively improve the charge-discharge cycle performance after overdischarge, the change rate of the gurley value is preferably within a range of ± 7%. In the separator in which the variation rate of the gurley value before and after coating of the polymer film is more than ± 10%, the porosity is greatly reduced or the porous film is collapsed, and it tends to be impossible to obtain good charge-discharge cycle performance after overdischarge.
Porous membrane
The porous film used in the separator of the present invention is not particularly limited in material, and conventionally known materials can be used, and examples thereof include polyolefin resins such as polyethylene resins, polypropylene resins, and mixed resins of polyethylene and polypropylene, and polyester fibers such as polyethylene terephthalate fibers, polybutylene terephthalate fibers, and polytrimethylene terephthalate fibers; cellulose fibers such as cotton and rayon; nylon-based fibers such as nylon 6, nylon 66, and nylon 610; and nonwoven fabrics made of polyamide fibers such as aramid fibers including para-aramid fibers and meta-aramid fibers. These fibers may be used alone or as a composite of two or more kinds.
The thickness of the porous film used in the separator of the present invention is preferably 3 to 40 μm, more preferably 5 to 30 μm. By setting the range, sufficient mechanical strength as a separator can be obtained, and a power storage device provided with the separator of the present invention can obtain good electrical properties.
The gurley number of the porous film used in the separator of the present invention (that is, the gurley number before the polyether copolymer and/or the crosslinked product thereof is supported on the porous film) is not particularly limited if the variation rate of the gurley number is within a range of ± 10%, but from the viewpoint of improving the charge-discharge cycle performance after overdischarge, the lower limit is preferably 10 seconds/100 ml or more, more preferably 15 seconds/100 ml or more, particularly preferably 20 seconds/100 ml or more, and the upper limit is preferably 400 seconds/100 ml or less, more preferably 350 seconds/100 ml or less, and particularly preferably 300 seconds/100 ml or less.
Polyether copolymer and/or crosslinked product thereof
The polyether copolymer used for the separator of the present invention comprises 2 to 40 mol% of a repeating unit derived from a monomer represented by the following general formula (1), 98 to 60 mol% of a repeating unit derived from a monomer represented by the following general formula (2), and 0 to 15 mol% of a repeating unit derived from a monomer represented by the following general formula (3).
[ chemical formula 7 ]
[ wherein R is an alkyl group having 1 to 12 carbon atoms or-CH2O(CR1R2R3)；R1、R2、R3Is a hydrogen atom or-CH2O(CH2CH2O)nR4At R1、R2、R3In which n and R4The same or different. R4Is an alkyl group or an aryl group having 1 to 12 carbon atoms, and n is an integer of 0 to 12.]
[ chemical formula 8 ]
[ chemical formula 9 ]
[ in the formula, R5Is a group having an ethylenically unsaturated group.]
The compound of formula (1) can be obtained as a commercially available product or can be easily synthesized from an epihalohydrin and an alcohol by a commonly used ether synthesis method or the like. Examples of the compounds available as commercially available products include propylene oxide, butylene oxide, methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, tert-butyl glycidyl ether, benzyl glycidyl ether, 1, 2-epoxydodecane, 1, 2-epoxyoctane, 1, 2-epoxyheptane, 2-ethylhexyl glycidyl ether, 1, 2-epoxydecane, 1, 2-epoxyhexane, glycidyl phenyl ether, 1, 2-epoxypentane, and isopropyl glycidyl ether. Among these commercially available products, propylene oxide, butylene oxide, methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, and isopropyl glycidyl ether are preferable, and propylene oxide, butylene oxide, methyl glycidyl ether, and ethyl glycidyl ether are particularly preferable.
In the monomer represented by the formula (1) obtained by synthesis, R is preferably-CH2O(CR1R2R3) Preferably R1、R2、R3At least one of which is-CH2O(CH2CH2O)nR4。R4The alkyl group preferably has 1 to 6 carbon atoms, and more preferably has 1 to 4 carbon atoms. n is preferably 0 to 6, more preferably 0 to 4.
(2) The compound (4) is a basic chemical, and a commercially available product can be easily obtained.
In the compound of formula (3), R5Is a substituent comprising an ethylenically unsaturated group. As the ethylenically unsaturated group-containing monomer component, allyl glycidyl ether, 4-vinylcyclohexyl glycidyl ether, α -terpinyl glycidyl ether, cyclohexenyl methyl glycidyl ether, p-vinylbenzyl etherGlycidyl ether, allyl phenyl glycidyl ether, vinyl glycidyl ether, 3, 4-epoxy-1-butene, 3, 4-epoxy-1-pentene, 4, 5-epoxy-2-pentene, 1, 2-epoxy-5, 9-cyclododecadiene, 3, 4-epoxy-1-vinylcyclohexene, 1, 2-epoxy-5-cyclooctene, glycidyl acrylate, glycidyl methacrylate, glycidyl sorbate, glycidyl cinnamate, glycidyl crotonate, glycidyl-4-hexenoate. Allyl glycidyl ether, glycidyl acrylate and glycidyl methacrylate are preferred.
The polyether copolymer of the present invention is composed of (a): a repeating unit derived from a monomer of formula (1), (B): a repeating unit derived from a monomer of formula (2), and (C): a repeating unit derived from a monomer of formula (3),
[ chemical formula 10 ]
[ wherein R is an alkyl group having 1 to 12 carbon atoms or-CH2O(CR1R2R3)；R1、R2、R3Is a hydrogen atom or-CH2O(CH2CH2O)nR4At R1、R2、R3In which n and R4The same or different; r4Is an alkyl group having 1 to 12 carbon atoms or an aryl group optionally having a substituent, and n is an integer of 0 to 12.]
[ chemical formula 11 ]
[ chemical formula 12 ]
[ in the formula, R5Is a substituent comprising a group having an ethylenically unsaturated group.]
Wherein the repeating units (A) and (C) may be derived from two or more monomers, respectively.
In the polyether copolymer of the present invention, the molar ratio of the repeating unit (a), the repeating unit (B) and the repeating unit (C) is (a)2 to 40 mol%, (B)98 to 60 mol%, and (C)0 to 15 mol%, preferably (a)5 to 35 mol%, (B)95 to 60 mol%, and (C)0 to 10 mol%, more preferably (a)5 to 30 mol%, (B)95 to 65 mol%, and (C)0 to 7 mol%. If the repeating unit (B) exceeds 98 mol%, the glass transition temperature rises and the ethylene oxide chain crystallizes, causing a serious deterioration in the ionic conductivity. It is known that the ionic conductivity is generally improved by lowering the crystallinity of polyethylene oxide, but the polyether copolymer of the present invention is particularly excellent in this point.
The molecular weight of the polyether copolymer of the present invention is preferably 5 ten thousand or more, more preferably 30 ten thousand or more, and even more preferably 50 ten thousand or more, in order to obtain good processability, mechanical strength, and flexibility, and the lower limit of the weight average molecular weight is preferably 250 ten thousand or less, and preferably 150 ten thousand or less. A copolymer having a weight average molecular weight within this range is preferable in that the copolymer has a weight average molecular weight within this range, since the viscosity of a polymer solution in which the polyether copolymer is dissolved is appropriate and the workability is good, and when the lower limit of the weight average molecular weight is 30 ten thousand or more, the polyether copolymer or a crosslinked product thereof supported on the separator is not dissolved in the electrolyte solution and therefore is not easily peeled off from the porous film, and the copolymer has more good charge and discharge characteristics as an electricity storage device.
The polyether copolymer of the present invention may be any of block copolymers and random copolymers. The random copolymer is preferable because it has a higher effect of reducing the crystallinity of polyethylene oxide.
The polyether copolymer of the present invention can be synthesized as follows. Polyether copolymers are obtained by reacting monomers with stirring in the presence or absence of a solvent at a reaction temperature of 10 to 120 ℃ while stirring the monomers, using a coordinating anion initiator such as an organoaluminum-based catalyst system, an organolead-based catalyst system, or an organotin-phosphate condensate catalyst system, or an anionic initiator such as potassium alcoholate, diphenylmethyl potassium, or potassium hydroxide containing K + in the counter ion as a ring-opening polymerization catalyst. The coordinating anion initiator is preferable from the viewpoint of polymerization degree or properties of the obtained copolymer, and among them, the organotin-phosphate ester condensate catalyst system is particularly preferable because it is easy to handle.
In the separator of the present invention, the polyether copolymer to be carried may be a crosslinked product of the polyether copolymer. The strength of the separator is improved by supporting the crosslinked material, and the crosslinked material is preferable in this point.
In the separator of the present invention, the change rate of the gurley value is not particularly limited if the unit weight of the polyether copolymer and/or the crosslinked product thereof supported on the porous film is within a range of ± 10%, but preferably 1 to 6g/m from the viewpoint of improving the charge-discharge cycle performance after overdischarge2About 2 to 4g/m is more preferable2Left and right.
Method for manufacturing separator for electricity storage device
The method for producing the separator of the present invention is not particularly limited, and the following methods can be exemplified: dipping the separator in a solution obtained by dissolving a polyether copolymer in water or an organic solvent, and then drying it; in order to easily obtain the above-mentioned change rate of the gurley value, a method of coating a solution obtained by dissolving a polyether copolymer in water or an organic solvent on at least one surface of a separator and then drying the solution is preferable.
The organic solvent used in the present invention is not particularly limited, and is a substance capable of dissolving the polyether copolymer, and may be selected from aprotic organic solvents such as acetone, 2-butanone, toluene, xylene, THF, acetonitrile, methanol, isopropanol, N-methyl-2-pyrrolidone, and the like. These solvents may be used alone or in combination of two or more.
The concentration of the polyether copolymer in the solution is not particularly limited, but is preferably 5 to 40% by mass, and more preferably 8 to 30% by mass.
The method for coating the polyether copolymer used in the present invention on the porous film is not particularly limited, and a solution obtained by dissolving the polyether copolymer in water or an organic solvent is coated on the porous film by an appropriate method such as micro gravure coating, slot die, knife coating, or the like, depending on the solution viscosity and the target coating film thickness.
The polyether copolymer used in the present invention can be removed from water or an organic solvent by supporting the polyether copolymer on a porous film by coating, dipping, or the like, and then drying the supported polyether copolymer. As the drying method, a heater type, hot air drying type, infrared irradiation type, vacuum type, or the like drying device can be used.
In the present invention, a solution in which a polyether copolymer is dissolved and which further contains a photoreaction initiator or a thermal polymerization initiator is used, and after the solution is coated on a separator or after the separator is immersed therein, active energy rays such as ultraviolet rays or heat is applied, whereby a crosslinked product of the polyether copolymer can be supported on the separator. If necessary, an electrolyte salt or a crosslinking assistant may be added to the solution obtained by dissolving the polyether copolymer.
Examples of the photoreaction initiator that can be used in the present invention include alkyl benzophenones, acylphosphine oxides, titanocenes, triazines, diimidazoles, and oxime esters. It is preferable to use an alkylbenzene-based, benzophenone-based or acylphosphine oxide-based photoinitiator. Two or more of the above compounds may be used in combination as the photoreaction initiator.
Examples of the thermal polymerization initiator that can be used in the present invention include radical initiators selected from organic peroxide-based initiators, azo compound-based initiators, and the like. As the organic peroxide system, ketone peroxide, peroxyketal, hydrogen peroxide, dialkyl peroxide, diacyl peroxide, peroxyester, and the like are preferably used, and as the azo compound system, a thermal polymerization initiator such as an azonitrile compound, an azoamide compound, an azoamidine compound, and the like is preferably used. Further, it is preferable to use an organic peroxide-based initiator, and two or more of these compounds may be used in combination.
The amount of the photoreaction initiator or thermal polymerization initiator used in the present invention is preferably in the range of 0.1 to 10 parts by mass, more preferably 0.1 to 4.0 parts by mass, based on 100 parts by mass of the polyether copolymer.
In the present invention, a crosslinking assistant may be used in combination with the photoreaction initiator. The crosslinking coagent is typically a polyfunctional compound (e.g., containing at least two CH's)2＝CH－、CH2＝CH－CH2-, CF2 ═ CF-compounds). Specific examples of the crosslinking coagent are triallyl cyanurate, triallyl isocyanurate, 1,3, 5-triacryloylhexahydro-1, 3, 5-triazine, triallyl trimellitate, N' -m-phenylene bismaleimide, dipropargyl terephthalate, diallyl phthalate, tetraallylterephthalamide, triallyl phosphate, hexafluorotriallyl isocyanurate, N-methyltetrafluorodiallylisocyanate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, etc.
The amount of the crosslinking assistant used in the present invention is preferably in the range of 0.1 to 30 parts by mass, and more preferably 0.5 to 20 parts by mass, based on 100 parts by mass of the polyether copolymer.
As the actinic energy ray for crosslinking the polyether copolymer used in the present invention, ultraviolet rays, visible light, electron beams, and the like can be used. Among them, ultraviolet rays are preferable in particular from the viewpoint of the price of the apparatus and the ease of control.
When heat is used, the crosslinking reaction can be performed by heating at a temperature of about room temperature to 200 ℃ for about 10 minutes to 24 hours. When ultraviolet light is used, a xenon lamp, a mercury lamp, a high-pressure mercury lamp, or a metal halide lamp can be used, and the light intensity can be 1 to 50mW/cm at a wavelength of 365nm2The electrolyte is irradiated for 0.1 to 30 minutes to perform a crosslinking reaction.
The crosslinking reaction may be performed before, during, or after the separator is dried, after the solution containing the photoreaction initiator and the thermal polymerization initiator and the polyether copolymer dissolved therein is applied to the separator or after the separator is immersed therein.
<2. Power storage device >
The electric storage device of the present invention is formed using the above "1. separator for electric storage device", and specifically, has a positive electrode, a negative electrode, the above-mentioned separator for electric storage device interposed between the positive electrode and the negative electrode, and an electrolyte (solution).
Positive electrode
The positive electrode has a positive electrode composition containing a positive electrode active material and a binder on a current collector.
As a material of the current collector used in the electrode for an electric storage device of the present invention, for example, metal, carbon, conductive polymer, or the like can be used, and metal is preferably used. As the metal for the collector, aluminum, platinum, nickel, tantalum, titanium, stainless steel, copper, other alloys, and the like are generally used. Among them, copper, aluminum, or an aluminum alloy is preferably used from the viewpoint of conductivity and voltage resistance, and a metal foil such as an aluminum foil is preferably used as the current collector for the positive electrode.
As the positive electrode active material, a metal oxide, a metal sulfide, or a specific polymer can be used according to the type of the target battery.
For example, in the case of manufacturing a lithium battery using dissolution and precipitation of lithium, TiS can be used2、MoS2、NbS2、V2O5And the like, metal sulfides or oxides containing no lithium, and polymers such as polyacetylene, polypyrrole, and the like.
In the case of manufacturing a lithium ion battery using doping and dedoping of lithium ions, LixMO can be used2(wherein M represents one or more transition metals, and x is usually 0.05 to 1.10) or LixMPO, depending on the charge/discharge state of the battery)4(wherein M represents one or more transition metals, and x is usually 0.05 to 1.10) depending on the charge/discharge state of the battery). As transition metal constituting the lithium composite oxide or lithium phosphorus oxideM is preferably Co, Ni, Mn, Al, Fe or the like. Specific examples of such a lithium composite oxide include: LiCoO2、LiNiO2、LiNiyCozMn1－y－zO2(in the formula, 0<y、z<1)、LiNiyCozAl1－y－zO2(in the formula, 0<y、z<1)、LiMn2O4、LiFePO4And the like.
The lithium composite oxide is a positive electrode active material that can generate a high voltage and has excellent energy density. A plurality of these positive electrode active materials may be used in combination. When the positive electrode active material is formed using the positive electrode active material as described above, a known binder or the like can be added.
As the binder used in the positive electrode composition, for example, one or more compounds selected from the group consisting of a fluorine-based binder, an acrylic rubber, a modified acrylic rubber, a styrene-butadiene rubber, an acrylic polymer, and a vinyl polymer can be used. Further, it is preferable to use an acrylic polymer because oxidation resistance can be obtained, and a small amount of the acrylic polymer has sufficient adhesion and flexibility of the electrode plate can be obtained. In particular, an aqueous binder such as one dissolved in water is preferable because the aqueous binder does not dissolve the organic active material. The binder is added to the positive electrode current collector in a proportion of preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, as the positive electrode composition.
In addition to the above, the positive electrode composition for a positive electrode may further contain a conductive auxiliary, a solvent, and a thickener. Examples of the conductive assistant include: carbon compounds such as conductive carbon, e.g., acetylene black, ketjen black, carbon fiber, graphite, conductive polymers, metal powder, etc., and particularly conductive carbon is preferable. As the solvent, any solvent can be used as long as it can dissolve the positive electrode active material and the binder, and water, N-methyl-2-pyrrolidone, and the like are preferably used. The thickener is carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, etc., or their alkali metal salts, polyethylene oxide, etc. As the thickener, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, or the like, or alkali metal salts thereof, polyethylene oxide, or the like can be used.
Negative electrode
The negative electrode has a negative electrode composition containing a negative electrode active material and a binder on a current collector.
As a material of the current collector used in the electrode for an electric storage device of the present invention, for example, metal, carbon, conductive polymer, or the like can be used, and metal is preferably used. As the metal for the collector, aluminum, platinum, nickel, tantalum, titanium, stainless steel, copper, other alloys, and the like are generally used. Among them, from the viewpoint of conductivity and voltage resistance, copper, aluminum or an aluminum alloy is preferably used, and as the current collector for the negative electrode, for example, a metal foil such as a copper foil is preferably used.
As the negative electrode active material, for example, in the case of manufacturing a lithium battery utilizing dissolution and precipitation of lithium, metallic lithium, a lithium alloy capable of absorbing and releasing lithium, or the like can be used.
In the case of manufacturing a lithium ion battery using doping/dedoping of lithium ions, a carbon material of a non-graphitizable carbon system or a graphite system can be used. More specifically, carbon materials such as graphite, mesophase carbon microspheres, carbon fibers such as mesophase carbon fibers, pyrolytic carbon, coke (pitch coke, needle coke, petroleum coke), glassy carbon, an organic polymer compound fired body (a material obtained by firing and carbonizing a phenol resin, a furan resin, or the like at an appropriate temperature), and activated carbon can be used. When the negative electrode is formed of such a material, a known binder or the like can be added.
As the binder used in the electrode composition for a negative electrode, for example, one or more compounds selected from the group consisting of a fluorine-based binder, an acrylic rubber, a modified acrylic rubber, a styrene-butadiene rubber, an acrylic polymer, and a vinyl polymer can be used. Further, it is preferable to use an acrylic polymer because oxidation resistance can be obtained, and a small amount of the acrylic polymer has sufficient adhesion and flexibility of the electrode plate can be obtained. In particular, an aqueous binder such as one dissolved in water is preferable because the aqueous binder does not dissolve the organic active material. The binder is added to the negative electrode current collector in a proportion of preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, as the negative electrode composition.
In addition to the above, a conductive auxiliary, a solvent, a thickener, and the like may be contained in the electrode composition for a negative electrode of a negative electrode. Examples of the conductive assistant include: carbon compounds such as conductive carbon, e.g., acetylene black, ketjen black, carbon fiber, graphite, conductive polymers, metal powder, etc., and particularly conductive carbon is preferable. As the solvent, any solvent can be used as long as it can dissolve the negative electrode active material and the binder, and water, N-methyl-2-pyrrolidone, and the like are preferably used. As the thickener, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, or the like, or alkali metal salts thereof, polyethylene oxide, or the like can be used.
Method for producing electrode (positive electrode, negative electrode)
The electrode (positive electrode/negative electrode) for an electric storage device of the present invention is obtained by forming a composition for an electrode (positive electrode/negative electrode) on a current collector. Specifically, the following methods can be mentioned: laminating the electrode composition for an electrical storage device formed into a sheet shape on a current collector (a kneading sheet forming method); coating a paste-like electrode composition for an electricity storage device on a current collector and drying it (wet forming method); composite particles of an electrode composition for an electricity storage device were prepared, sheet-shaped on a current collector, and roll-pressed (dry forming method). Among them, wet molding and dry molding are preferable, and wet molding is more preferable.
Electrolyte (solution)
The electrolyte solution is obtained by dissolving an electrolyte salt in an aprotic organic solvent, and an ambient temperature molten salt (ionic liquid) can be used.
In the present invention, the electrolyte salt compounds exemplified below are preferably used. That is, there may be mentioned compounds composed of a cation and an anion, wherein the cation is selected from the group consisting of a metal cation, an ammonium ion, an amidine ion, and a guanidine ion; the anion is selected from chloride ion and bromide ionIodide ion, perchlorate ion, thiocyanate ion, tetrafluoroborate ion, nitrate ion, AsF 6 －、PF6 －Stearyl sulfonic acid ion, octyl sulfonic acid ion, dodecylbenzenesulfonic acid ion, naphthalenesulfonic acid ion, dodecylnaphthalenesulfonic acid ion, 7,8, 8-tetracyano-p-quinodimethane ion, X1SO3 －、[(X1SO2)(X2SO2)N]－、[(X1SO2)(X2SO2)(X3SO2)C]－And [ (X)1SO2)(X2SO2)YC]－. Wherein, X1、X2、X3And Y is an electron withdrawing group. Preferably X1、X2And X3Independently represents a C1-6 perfluoroalkyl group or a C6-18 perfluoroaryl group, and Y represents a nitro group, a nitroso group, a carbonyl group, a carboxyl group or a cyano group. X1、X2And X3The same or different.
As the metal cation, a cation of a transition metal can be used. Preferably, cations of metals selected from the group consisting of Mn, Fe, Co, Ni, Cu, Zn and Ag metals are used. In addition, even if cations of metals selected from the group consisting of Li, Na, K, Rb, Cs, Mg, Ca and Ba metals are used, preferable results can be obtained. As the electrolyte salt compound, two or more of the above-mentioned compounds may be used in combination.
In particular, in a lithium ion capacitor, a Li salt compound is preferably used as the electrolyte salt compound.
As the Li salt compound, a Li salt compound having a wide potential window, which is generally used for a lithium ion capacitor or the like, is used. Examples thereof include: LiBF4、LiPF6、LiClO4、LiCF3SO3、LiN(CF3SO2)2、LiN(C2F5SO2)2、LiN[CF3SC(C2F5SO2)3]2And the like, but not limited thereto. These may be used alone or in combination of two or more.
As the electrolyte salt or the solution for the electrolyte, an ambient temperature molten salt can be used.
The normal temperature molten salt is a salt at least partially in a liquid state at normal temperature, and normal temperature is a temperature range in which normal operation of the power supply is estimated. The upper limit of the temperature range in which the normal operation of the power supply is estimated is about 120 ℃, and may be about 60 ℃, and the lower limit thereof is about-40 ℃, and may be about-20 ℃.
As the ambient temperature molten salt, also called an ionic liquid, a quaternary ammonium organic cation of a pyridine type, an aliphatic amine type, or an alicyclic amine type is known. Examples of quaternary ammonium organic cations include: imidazolium ions such as dialkylimidazolium and trialkylimidazolium, tetraalkylammonium ions, alkylpyridinium ions, pyrazolium ions, pyrrolidinium ions, piperidinium ions, and the like. Imidazolium cations are particularly preferred.
Examples of imidazolium cations include: 1, 3-dimethylimidazolium ion, 1-ethyl-3-methylimidazolium ion, 1-methyl-3-ethylimidazolium ion, 1-methyl-3-butylimidazolium ion, 1-butyl-3-methylimidazolium ion, 1,2, 3-trimethylimidazolium ion, 1, 2-dimethyl-3-ethylimidazolium ion, 1, 2-dimethyl-3-propylimidazolium ion, 1-butyl-2, 3-dimethylimidazolium ion, and the like, but is not limited thereto.
The ambient temperature molten salt having these cations may be used alone or in combination of two or more.
In the present invention, the content of the electrolyte salt is preferably 0.1 to 3.0mol/L, and particularly preferably 1.0 to 2.0 mol/L. If the content of the electrolyte salt is less than 0.1mol/L, the resistance of the electrolyte solution increases, and the large current and low-temperature discharge characteristics decrease, while if it exceeds 3.0mol/L, the solubility deteriorates, and crystals are likely to precipitate.
The aprotic organic solvent used in the electrolyte solution of the present invention is also not particularly limited. Specific examples of the aprotic organic solvent include propylene carbonate, ethylene carbonate, diethyl carbonate, methylethyl carbonate, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, γ -butyrolactone, tetrahydrofuran, 1, 3-dioxolane, dipropyl carbonate, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, anisole, acetate, and propionate, and two or more of these solvents may be used alone or in combination.
< method for producing electric storage device >
The electric storage device of the present invention can be produced by stacking a positive electrode and a negative electrode, which are electrodes obtained by forming the electrode composition on a current collector, with the separator interposed therebetween, and injecting an electrolyte solution.
Examples
Specific modes for carrying out the present invention will be described below by way of examples. However, the present invention is not limited to the following examples as long as the invention does not depart from the gist thereof.
Synthesis example (production of catalyst for polyether copolymerization)
10g of tributyltin chloride and 35g of tributyl phosphate were charged into a three-necked flask equipped with a stirrer, a thermometer, and a distillation apparatus, and heated at 250 ℃ for 20 minutes while stirring under a nitrogen flow, thereby distilling off the distillate and obtaining a solid condensed substance as a residue. The following polymerization examples are used as polymerization catalysts.
By passing1The H NMR spectrum was used to determine the monomer-converted composition of the polyether copolymer.
The molecular weight of the polyether copolymer was measured by Gel Permeation Chromatography (GPC), and the weight average molecular weight was calculated based on standard polystyrene. GPC measurement was carried out at 60 ℃ using RID-6A manufactured by Shimadzu corporation, Shodex KD-807, KD-806M and KD-803 columns manufactured by Showa Denko K.K., and DMF as a solvent.
[ polymerization example 1]
A four-necked flask made of glass having an internal volume of 3L was internally substituted with nitrogen, 1g of the condensation product shown in the synthesis example of the catalyst as a polymerization catalyst, 158g of the glycidyl ether compound (a) having a water content of 10ppm or less, 22g of allyl glycidyl ether, and 1000g of n-hexane as a solvent were charged therein, and 125g of ethylene oxide was sequentially added while following the polymerization rate of the compound (a) by gas chromatography. The polymerization temperature at this time was 20 ℃ and the reaction was carried out for 10 hours. During the polymerization, 1mL of methanol was added to stop the reaction. After the polymer was decanted, the mixture was dried at 40 ℃ for 24 hours under normal pressure and then at 45 ℃ for 10 hours under reduced pressure to obtain 280g of a polymer. The results of analysis of the weight average molecular weight and the monomer-equivalent composition of the obtained polyether copolymer are shown in table 1.
[ chemical formula 13 ]
[ polymerization example 2]
The same operation was carried out with the exception that 170g of the glycidyl ether compound (a) and 130g of ethylene oxide were charged in the charge of polymerization example 1 without adding allyl glycidyl ether, and polymerization was carried out, thereby obtaining 285g of a polymer. The results of analysis of the weight average molecular weight and the monomer-equivalent composition of the obtained polyether copolymer are shown in table 1.
[ polymerization example 3]
The same operation was carried out with the exception that 170g of the glycidyl ether compound (a), 20g of allyl glycidyl ether, 110g of ethylene oxide and 0.02g of n-butanol were charged in the charge of polymerization example 1 and polymerization was carried out, to obtain 250g of a polymer. The results of analysis of the weight average molecular weight and the monomer-equivalent composition of the obtained polyether copolymer are shown in table 1.
[ polymerization example 4]
The same operation was carried out with the exception that 230g of the glycidyl ether compound (a), 70g of ethylene oxide and 0.02g of n-butanol were charged in the charge of polymerization example 1 without adding allyl glycidyl ether to polymerize, thereby obtaining 240g of a polymer. The results of analysis of the weight average molecular weight and the monomer-equivalent composition of the obtained polyether copolymer are shown in table 1.
[ Table 1]
| Composition of copolymer (mol%) | Polymerization example 1 | Polymerization example 2 | Polymerization example 3 | Polymerization example 4 |
| Ethylene oxide | 72 | 75 | 68 | 55 |
| Compound (a) | 23 | 25 | 27 | 45 |
| Allyl glycidyl ether | 5 | 0 | 5 | 0 |
| Weight average molecular weight of copolymer | 100 ten thousand | 110 ten thousand | 20 ten thousand | 16 ten thousand |
Example 1 production of lithium ion Battery 1 comprising negative electrode 1/separator 1/Positive electrode 1
< preparation of negative electrode 1 >
Graphite powder (porous structure material) 90 parts by mass, polyvinylidene fluoride 10 parts by mass, and N-methyl-2-pyrrolidone 100 parts by mass as a solvent were stirred with a stainless ball mill for 1 hour, then applied to a copper current collector with a bar coater having a gap of 50 μm, dried in a vacuum state at 80 ℃ for 12 hours or more, and then rolled to obtain a negative electrode sheet.
< preparation of Positive electrode 1 >
LiNi of 10 μm was used as a positive electrode active material0.80Co0.15Al0.05O2. To 90 parts by mass of the positive electrode active material, 3 parts by mass of spherical carbon fine particles produced by thermal decomposition of acetylene as a conductive aid, 7 parts by mass of polyvinylidene fluoride as a binder, and 50 parts by mass of N-methyl-2-pyrrolidone as a solvent were stirred with a stainless ball mill for 1 hour, then applied to an aluminum current collector using a bar coater with a gap of 100 μm, dried in a vacuum state at 80 ℃ for 12 hours or more, and then rolled to form a positive electrode sheet.
< preparation of electrolyte solution >
15 parts by mass of mixed Ethylene Carbonate (EC), 15 parts by mass of Propylene Carbonate (PC), 50 parts by mass of diethyl carbonate, and an electrolyte salt LiBF420 parts by mass to prepare a nonaqueous electrolyte solution.
< production of separator 1 >
20 parts by mass of the polyether copolymer 1 obtained in polymerization example 1, 0.1 part by mass of benzophenone as a photoreaction initiator, and 1 part by mass of N, N' -m-phenylene bismaleimide as a crosslinking assistant were dissolved in 180 parts by mass of acetonitrile to obtain a solution, and the solution was applied to both surfaces of a polyethylene porous membrane having a thickness of 15 μm so that the thickness of one surface after drying was 0.5 μm (about 1.2g/m in unit weight)2) And dried at 60 ℃ for 10 hours by an atmospheric dryer. Next, the surface was covered with a laminate film, and the film was irradiated for 30 seconds with a high-pressure mercury lamp (30 mW/cm) manufactured by GS YUASA2) Crosslinking to produce a crosslinked polypropylene porous membraneThe separator 1 was formed from the polyether copolymer after the polymerization and had a film thickness of 16 μm.
Finally, the negative electrode 1 sheet and the positive electrode 1 sheet are pressed through the separator 1 to form a laminate. Next, the laminate was housed in an aluminum laminate, and a nonaqueous electrolyte solution was injected to produce the lithium ion battery 1.
Example 2 production of lithium ion Battery 2 comprising negative electrode 2/separator 2/Positive electrode 2
< preparation of negative electrode 2 >
Graphite powder (porous structure material) 90 parts by mass, polyvinylidene fluoride 10 parts by mass, and N-methyl-2-pyrrolidone 100 parts by mass as a solvent were stirred with a stainless ball mill for 1 hour, then coated on a copper current collector using a bar coater with a gap of 50 μm, dried in a vacuum state at 80 ℃ for 12 hours or more, and then rolled to prepare a negative electrode sheet.
< preparation of Positive electrode 2 >
LiNi having an average particle diameter of 10 μm was used as the positive electrode active material0.80Co0.15Al0.05O2. To 90 parts by mass of the positive electrode active material, 3 parts by mass of spherical carbon fine particles produced by thermal decomposition of acetylene as a conductive aid, 7 parts by mass of polyvinylidene fluoride as a binder, and 50 parts by mass of N-methyl-2-pyrrolidone as a solvent were stirred with a stainless ball mill for 1 hour, then applied to an aluminum current collector using a bar coater with a gap of 100 μm, dried in a vacuum state at 80 ℃ for 12 hours or more, and then rolled to form a positive electrode sheet.
< preparation of electrolyte solution >
15 parts by mass of mixed Ethylene Carbonate (EC), 15 parts by mass of Propylene Carbonate (PC), 50 parts by mass of diethyl carbonate, and an electrolyte salt LiBF420 parts by mass to prepare a nonaqueous electrolyte solution.
< production of separator 2 >
20 parts by mass of the polyether copolymer 2 obtained in polymerization example 2 was dissolved in 180 parts by mass of acetonitrile to obtain a solution, and the solution was applied to both surfaces of an aramid fiber nonwoven fabric having a film thickness of 28 μm so that one surface of the dried film has a film thickness of 1 μm (about 2.4g per unit weight)/m2) And dried at 60 ℃ for 10 hours by an atmospheric pressure dryer to produce a separator 2 having a film thickness of 30 μm in which a polyether copolymer is supported on a cellulose-based nonwoven fabric.
Finally, the positive electrode 2 sheet and the negative electrode 2 sheet are pressed through the separator 2 to form a laminate. Next, the laminate was housed in an aluminum laminate, and a nonaqueous electrolyte solution was injected to produce the lithium ion battery 2.
EXAMPLE 3 production of lithium ion Battery 3 comprising negative electrode 1/separator 3/Positive electrode 1
< production of separator 3 >
In the production of the separator 1, the polyether copolymer 3 obtained in polymerization example 3 was used instead of the polyether copolymer 1 obtained in polymerization example 1 to produce the separator 3.
A lithium ion battery 3 was produced in the same manner as in example 1, except that the separator 3 was used.
Comparative example 1 production of lithium ion Battery 4 comprising negative electrode 2/separator 4/Positive electrode 2
< production of separator 4 >
In the production of the separator 1, the polyether copolymer 4 obtained in polymerization example 4 was used instead of the polyether copolymer 1 obtained in polymerization example 1 to produce the separator 4.
A lithium ion battery 4 was produced by the same method as in example 2, except that the separator 4 was used.
Comparative example 2 production of lithium ion Battery 5 comprising negative electrode 2/separator 5/Positive electrode 2
< production of separator 5 >
20 parts by mass of the polyether copolymer 1 obtained in polymerization example 1, 0.1 part by mass of benzophenone as a photoreaction initiator, and 1 part by mass of N, N' -m-phenylene bismaleimide as a crosslinking assistant were dissolved in 180 parts by mass of acetonitrile to obtain a solution, and the solution was applied to both surfaces of a porous polyethylene membrane having a thickness of 8 μm and dried to give a thickness of 3.5 μm on one surface (about 8.4g/m in unit weight) after drying2). Next, the surface was covered with a laminate film, and the film was irradiated with a high-pressure mercury lamp (30 mW/cm) manufactured by GSYUASA corporation for 30 seconds2) The resulting porous polypropylene membrane was crosslinked to prepare a separator 5 having a thickness of 15 μm, the separator being formed by supporting the crosslinked polyether copolymer on the porous polypropylene membrane.
A lithium ion battery 5 was produced by the same method as in example 2, except that the separator 5 was used.
Comparative example 3 production of lithium ion Battery 6 comprising negative electrode 2/separator 6/Positive electrode 2
< production of separator 6 >
The aramid fiber nonwoven fabric having a film thickness of 28 μm was used as it was without forming a polymer film thereon.
A lithium ion battery 6 was produced by the same method as in example 2, except that the separator 6 was used.
The gurley value of the porous film before the polyether copolymer and/or the crosslinked product thereof was supported and the gurley value of the porous film after the polyether copolymer and/or the crosslinked product thereof was supported were measured with respect to the separators produced in examples 1 to 3 and comparative examples 1 to 3 by the following methods. The measurement results and the change rate of the gurley value are shown in table 2. In table 2, "the gurley value before supporting" is the gurley value of the porous film before supporting the polyether copolymer and/or the crosslinked product thereof, "the gurley value after supporting" is the gurley value of the porous film after supporting the polyether copolymer and/or the crosslinked product thereof, and the rate of change (%) in the gurley value of the separator can be calculated by { ("the gurley value after supporting" - "the gurley value before supporting")/"the gurley value before supporting" } × 100.
< Grignard value >
The Gurley value (sec/100 mL) was measured in accordance with JIS P8117(ISO 5636/5).
The lithium ion batteries manufactured in examples 1 to 3 and comparative examples 1 to 3 were measured for their battery volumes by the archimedes method, and the amounts of gas generated at the time of initial charge and discharge were compared by the method shown below. The measurement results are shown in table 2.
< Rate of Change in Battery volume after initial Charge/discharge >
In order to compare the gas generation amounts at the initial charge and discharge of the laminated batteries manufactured in examples 1 to 3 and comparative examples 1 to 3, the battery volume was measured by the archimedes method. The measurement results and the rate of change in the battery volume after initial charge and discharge are shown in table 2. In table 2, the rate of change (%) in the battery volume after initial charge and discharge can be calculated by { ("battery volume after initial charge and discharge" - "battery volume before initial charge and discharge")/"battery volume before initial charge and discharge" } × 100.
The lithium ion batteries produced in examples 1 to 3 and comparative examples 1 to 3 were measured for charge/discharge cycle performance after overdischarge by the following method. The measurement results are shown in table 2.
< Charge-discharge cycle Performance after overdischarge >
In a 10-hour discharge (1/10C) of theoretical capacity, after a charge-discharge cycle test of 2.0-4.2V was performed once, it was charged to 4.2V, then discharged to 0V at 1/10C, and left at open circuit voltage for 24 hours. Subsequently, the resultant was charged to 4.2V, and the discharge capacity (mAh/g) was measured after 20 charge-discharge cycle tests of 2.0 to 4.2V were carried out.
[ Table 2]
As is clear from table 2, the separator defined in the present invention maintains a low rate of change in the cell volume after initial charge and discharge (maintains good stability of the electric storage device), and at the same time, has a high discharge capacity at the 20 th cycle after overdischarge, and has good charge and discharge cycle performance.
Industrial applicability
The separator of the present invention has good charge-discharge cycle performance after overdischarge, and therefore, an electric storage device having excellent stability can be provided.
Claims (6)
1. A separator for an electricity storage device, which comprises a porous film and a polyether copolymer and/or a crosslinked product thereof supported thereon,
the polyether copolymer comprises 2 to 40 mol% of a repeating unit derived from a monomer represented by the following formula (1), 98 to 60 mol% of a repeating unit derived from a monomer represented by the following formula (2), and 0 to 15 mol% of a repeating unit derived from a monomer represented by the following formula (3),
the change rate of the Gurley value before and after the polyether copolymer and/or the crosslinked product thereof is supported is within a range of. + -. 10%,
in the formula (1), R is an alkyl group having 1-12 carbon atoms or-CH2O(CR1R2R3)；R1、R2、R3Is a hydrogen atom or-CH2O(CH2CH2O)nR4At R1、R2、R3N and R in (1)4The same or different; r4Is alkyl or aryl with 1-12 carbon atoms, and n is an integer of 0-12;
In the formula (3), R5Is a group having an ethylenically unsaturated group.
2. The separator for an electric storage device according to claim 1,
the weight average molecular weight of the polyether copolymer is 30-250 ten thousand.
3. The separator for power storage devices according to claim 1 or 2, wherein,
the porous film is a nonwoven fabric of polyolefin resin or fibers selected from the group consisting of polyester fibers, cellulose fibers and polyamide fibers.
4. The separator for power storage devices according to any one of claims 1 to 3, wherein,
the porous membrane has a thickness of 3 to 40 μm.
5. A method for producing the separator for an electric storage device according to any one of claims 1 to 4, characterized by comprising:
the solution obtained by dissolving the polyether copolymer in an aprotic organic solvent is applied to at least one surface of the porous film and dried.
6. An electricity storage device comprising the separator for an electricity storage device according to any one of claims 1 to 4.
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| AU2019357990A1 (en) | 2018-10-09 | 2021-04-22 | Chart Energy & Chemicals, Inc. | Dehydrogenation separation unit with mixed refrigerant cooling |
| CN114424398A (en) | 2019-11-08 | 2022-04-29 | 株式会社Lg新能源 | Crosslinked separator for lithium secondary battery comprising crosslinked polyolefin and method for producing same |
| CN114243093B (en) * | 2022-02-25 | 2022-05-13 | 湖南中锂新材料科技有限公司 | High-breakdown-strength aramid fiber diaphragm and preparation method and application thereof |
| WO2024071428A1 (en) * | 2022-09-29 | 2024-04-04 | 株式会社大阪ソーダ | Separator for power storage devices, power storage device, method for producing separator for power storage devices, and method for producing power storage device |
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| JP3919346B2 (en) * | 1998-07-17 | 2007-05-23 | 東燃化学株式会社 | Polymer solid electrolyte thin film and method for producing the same |
| JP2012174413A (en) * | 2011-02-18 | 2012-09-10 | Toshiba Corp | Nonaqueous electrolyte battery |
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| JP2013152857A (en) * | 2012-01-25 | 2013-08-08 | Daiso Co Ltd | Separator for power storage device, power storage device and manufacturing method thereof |
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| CN104662067A (en) * | 2012-09-28 | 2015-05-27 | 日本瑞翁株式会社 | Polyether copolymer, crosslinkable polyether copolymer composition, and electrolyte |
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| JPWO2019194094A1 (en) | 2021-04-22 |
| WO2019194094A1 (en) | 2019-10-10 |
| JP7359137B2 (en) | 2023-10-11 |
| KR20200139685A (en) | 2020-12-14 |
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