Separator for power storage devices, power storage device, method for producing separator for power storage devices, and method for producing power storage device

Abstract

Provided is a separator for power storage devices that can provide power storage devices with excellent charge / discharge cycle characteristics and rate characteristics.　This separator for power storage devices comprises: a multilayer body of a porous base material and a ceramic layer; and a resin layer that is supported on at least one surface of the multilayer body. The resin layer is configured from a polyether copolymer and / or a crosslinked product of the polyether copolymer. With respect to this separator for power storage devices, the polyether copolymer is composed of 2-40% by mole of a repeating unit that is derived from a monomer represented by formula (1), 98-60% by mole of a repeating unit that is derived from a monomer represented by formula (2), and 0-15% by mole of a repeating unit that is derived from a monomer represented by formula (3); the weight per square meter of the resin layer is at least 0.10 g / m2 and less than 0.40 g / m2; and the increment in the Gurley value between before and after supporting of the resin layer is at least 10% and not more than 330%.

Description

Separator for power storage device, power storage device, and manufacturing method thereof

[0001] The present invention relates to a separator for an electricity storage device, a method for manufacturing a separator for an electricity storage device, and an electricity storage device, and more particularly to a separator for a lithium ion secondary battery, a method for manufacturing a separator, and a lithium ion secondary battery.

[0002] The recent trend toward microelectronics has become evident, as exemplified by the memory backup power supplies of various electronic devices. Specifically, as batteries are housed within electronic devices and integrated with electronic elements, there is a demand for smaller, lighter batteries and power storage devices with higher energy density. Furthermore, as various small electronic devices, such as camcorders, portable communication devices, and laptop computers, have become smaller and lighter in recent years, there has been an increasing demand for high-energy-density power storage devices as power sources for these devices, and research and development into these devices is actively underway.

[0003] High-energy density electricity storage devices such as lithium-ion secondary batteries, lithium-ion capacitors, and electric double-layer capacitors are configured to include a pair of electrodes and a separator impregnated with an electrolyte solution, and are used in a variety of industrial and consumer electric and electronic devices.

[0004] Conventionally, power storage devices utilizing electrochemical reactions, such as lithium ion secondary batteries, lithium ion capacitors, and electric double layer capacitors, require ever higher capacity, higher functionality, smaller size, and lighter weight, and this has led to a demand for improved separators. For example, to accommodate the increased capacity of power storage devices, separators with heat resistance, mechanical strength, and dimensional stability capable of withstanding self-heating during charge / discharge or abnormal heat generation during abnormal charging are required. Furthermore, to improve the functionality of power storage devices, particularly their rapid charge / discharge characteristics and high-power characteristics, there is a strong demand for separators that are thinner and more uniform.

[0005] To meet these requirements, for example, Patent Document 1 proposes the use of a separator made of a highly breathable microporous film (stretched film) made by stretching polyolefin, with through-holes formed with a needle or laser to further enhance breathability. However, when such a microporous resin film is used alone, the through-holes can cause a short circuit between the positive and negative electrodes. Furthermore, the film tends to shrink in the meltdown temperature range above the shutdown temperature, resulting in the problem of electrodes easily coming into direct contact with each other at high temperatures. Furthermore, reducing the porosity of the separator is considered as a method for ensuring heat shrinkage resistance and mechanical strength in a thin film state, but this increases internal resistance and reduces ionic conductivity, making it impossible to meet the demand for high functionality.

[0006] Furthermore, if the electrolyte solution does not penetrate the separator uniformly, ion migration becomes localized, causing dissolution of metals such as copper, which is commonly used in negative electrode current collectors, which may deposit on the electrode, causing dendrite growth and short circuits, and deteriorating charge-discharge characteristics.

[0007] Therefore, the present applicant has disclosed a separator for an electricity storage device that has excellent charge / discharge characteristics, load characteristics, and low-temperature characteristics (Patent Document 2).

[0008] International Publication No. 2001 / 67536 Japanese Patent Application Laid-Open No. 2013-152857

[0009] A primary object of the present invention is to provide a separator for an electricity storage device that can impart excellent charge / discharge cycle characteristics and rate characteristics to the electricity storage device.

[0010] The inventors conducted extensive research to solve the above-mentioned problems and found that by supporting a resin layer composed of a specific polyether copolymer and / or a crosslinked product thereof on at least one surface of a laminate of a porous substrate and a ceramic layer, and by setting the increase in Gurley value before and after the support of the resin layer to be in the range of 10% to 330%, the electrical storage device has excellent electrical properties, particularly excellent charge / discharge cycle characteristics and rate characteristics after overdischarge. Furthermore, it was also found that a separator provided with this resin layer has low tackiness even after thermoforming, thereby providing high peelability and reducing the risk of peeling of the ceramic layer laminated on the porous substrate. The present invention was completed based on these findings and extensive research.

[0011] That is, the present invention provides the following configuration.

[0012] Item 1. A separator for an electricity storage device, comprising a laminate of a porous substrate and a ceramic layer, and a resin layer supported on at least one surface of the laminate, wherein the resin layer is composed of a polyether copolymer and / or a crosslinked product thereof, and the polyether copolymer is composed of 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 basis weight of the resin layer is 0.10 g / m 2 0.40g / m or more 2 and the rate of increase in Gurley value before and after the support of the resin layer is 10% or more and 330% or less. [In formula (1), R represents an alkyl group having 1 to 12 carbon atoms, or —CH2O(CR 1 R 2 R 3 ) R 1 , R 2 , R 3 is a hydrogen atom or -CH2O(CH2CH2O)nR 4 and n and R 4 is R 1 , R 2 , R 3R 4 is an alkyl group having 1 to 12 carbon atoms or an aryl group, and n is an integer from 0 to 12. [In formula (3), R 5 is a group having an ethylenically unsaturated group.] Item 2. The electricity storage device separator according to Item 1, wherein the porous substrate is a porous film made of at least one resin selected from the group consisting of a polyolefin resin, a polyester-based resin, a cellulose-based resin, and a polyamide-based resin. Item 3. A method for producing the electricity storage device separator according to Item 1 or 2, comprising the steps of applying a solution containing the polyether copolymer and a polar solvent to at least one surface of a laminate of the porous substrate and the ceramic layer, and drying the solution to form the resin layer. Item 4. An electricity storage device comprising the electricity storage device separator according to Item 1 or 2.

[0013] According to the present invention, it is possible to improve the charge-discharge cycle characteristics after overdischarge, and it is possible to provide a separator and an electricity storage device that are excellent in stability.

[0014] In this specification, the term "electricity storage device" includes secondary batteries (lithium ion secondary batteries, nickel-metal hydride secondary batteries, etc.) and electrochemical capacitors.

[0015] The electricity storage device according to the present invention is characterized in that a positive electrode and a negative electrode are stacked via an integrated separator carrying the following polyether copolymer.

[0016] <1. Separator for Electricity Storage Device> The separator of the present invention is a separator for an electricity storage device comprising a laminate of a porous substrate and a ceramic layer, and a resin layer supported on at least one surface of the laminate. The resin layer is composed of a polyether copolymer and / or a crosslinked product thereof. The polyether copolymer is composed of 2 to 40 mol % of repeating units derived from a monomer represented by the following formula (1), 98 to 60 mol % of repeating units derived from a monomer represented by the following formula (2), and 0 to 15 mol % of repeating units derived from a monomer represented by the following formula (3), and the basis weight of the resin layer is 0.10 g / m2 0.40g / m or more 2 The present invention is characterized in that the increase rate of the Gurley value before and after the support of the resin layer is 10% or more and 330% or less.

[0017]

[0018] [In formula (1), R represents an alkyl group having 1 to 12 carbon atoms, or —CH2O(CR 1 R 2 R 3 ) R 1 , R 2 , R 3 is a hydrogen atom or -CH2O(CH2CH2O)nR 4 and n and R 4 is R 1 , R 2 , R 3 R 4 is an alkyl group having 1 to 12 carbon atoms or an aryl group, and n is an integer from 0 to 12.

[0019]

[0020]

[0021] [In formula (3), R 5 is a group having an ethylenically unsaturated group.

[0022] By virtue of these configurations, the separator of the present invention can impart excellent charge-discharge cycle characteristics and rate characteristics to an electricity storage device. Regarding charge-discharge cycle characteristics, in particular, the deposition of metal ions eluted from the negative electrode current collector during overdischarge on the electrode is reduced, thereby improving the charge-discharge cycle characteristics after overdischarge. The separator of the present invention will be described in detail below.

[0023] The separator of the present invention is characterized by comprising a laminate of a porous substrate and a ceramic layer, and a resin layer supported on at least one side of the laminate. Specific examples of the laminate configuration of the separator of the present invention include a laminate configuration in which a porous substrate, a ceramic layer, and a resin layer are laminated in this order; a laminate configuration in which a resin layer, a porous substrate, and a ceramic layer are laminated in this order; and a laminate configuration in which a resin layer, a porous substrate, a ceramic layer, and a resin layer are laminated in this order. It is preferable that the porous substrate and the ceramic layer are adjacent to each other (surface-contacting). Furthermore, when a resin layer is provided on the side of the porous substrate opposite the ceramic layer, it is preferable that the resin layer and the porous substrate are adjacent to each other (surface-contacting). Furthermore, when a resin layer is provided on the side of the ceramic layer opposite the porous substrate, it is preferable that the resin layer and the ceramic layer are adjacent to each other (surface-contacting). When two or more resin layers are provided, the resins constituting the resins may be the same or different.

[0024] The Gurley value is a value obtained by measurement in accordance with JIS P8117 (ISO 5636 / 5). In the present invention, the increase rate of the Gurley value of a separator before and after the formation of a resin layer is calculated by the following formula: Increase rate of Gurley value (%) = {(Gurley value of separator after the formation of a resin layer) - (Gurley value of separator before the formation of a resin layer)} / Gurley value of separator before the formation of a resin layer × 100

[0025] In the present invention, the rate of increase in the Gurley value is 10% or more and 330% or less, and from the viewpoint of more suitably exhibiting the effects of the present invention, it is preferably 25% or more, more preferably 50% or more, and is preferably 300% or less, more preferably 275% or less, and even more preferably 250% or less. Preferred ranges include 10 to 300%, 10 to 275%, 10 to 250%, 25 to 330%, 25 to 300%, 25 to 275%, 25 to 250%, 50 to 330%, 50 to 300%, 50 to 275%, and 50 to 250%.

[0026] The porous substrate is laminated with the ceramic layer to form a laminate. As described above, the porous substrate is preferably adjacent to (in contact with) the ceramic layer.

[0027] The porous substrate is preferably made of a porous film. The material of the porous substrate is not particularly limited, and any conventionally known material can be used.

[0028] The material of the porous substrate is preferably a resin. Examples of resins constituting the porous substrate include at least one selected from the group consisting of polyolefin resins, polyester resins, cellulose resins, and polyamide resins. From the viewpoint of more effectively achieving the effects of the present invention, the porous substrate in the separator of the present invention is preferably composed of a porous resin film containing at least one of these resins. Nonwoven fabrics can also be used as the porous substrate, provided that the effects of the present invention are not impaired. Examples of nonwoven fabrics include those containing at least one of these resins.

[0029] The film thickness of the porous substrate is preferably 3 μm or more, more preferably 5 μm or more, and is also preferably 40 μm or less, more preferably 30 μm or less, with preferred ranges including 3 to 40 μm, 3 to 30 μm, 5 to 40 μm, 5 to 30 μm, etc. By setting the film thickness of the porous substrate within these ranges, sufficient mechanical strength as a separator can be obtained, and an electricity storage device including the separator of the present invention can exhibit good electrical properties.

[0030] From the viewpoint of more suitably exerting the effects of the present invention, the porosity of the porous substrate of the present invention is preferably 30% or more, more preferably 35% or more, even more preferably 40% or more, and also preferably 80% or less, more preferably 75% or less, even more preferably 70% or less, and preferred ranges include 30 to 80%, 30 to 75%, 30 to 70%, 35 to 80%, 35 to 75%, 35 to 70%, 40 to 80%, 40 to 75%, and 40 to 70%. By satisfying these values, the strength of the porous substrate itself is sufficiently maintained.

[0031] The Gurley value of the porous substrate used in the separator of the present invention (i.e., the Gurley value before the resin layer is supported on the porous substrate) is not particularly limited as long as the increase rate of the Gurley value is 10% to 330%, but from the viewpoint of improving the charge-discharge cycle characteristics after overdischarge, the lower limit is preferably 200 seconds / 100 ml or more, more preferably 250 seconds / 100 ml or more, and particularly preferably 300 seconds / 100 ml or more, and is also preferably 2000 seconds / 100 ml or less, more preferably 1500 seconds / 100 ml or less, and even more preferably 1000 seconds / 100 ml or less.

[0032] Ceramic Layer One of the features of the separator of the present invention is that it includes a ceramic layer. The ceramic layer is laminated with the porous substrate to form a laminate. As described above, the ceramic layer is preferably adjacent to (in contact with) the porous substrate.

[0033] The material constituting the ceramic layer is not particularly limited as long as it exerts the effects of the present invention, but preferred examples include alumina, boehmite, titania, etc. The material constituting the ceramic layer may be one type or two or more types.

[0034] From the viewpoint of more suitably exerting the effects of the present invention, the thickness of the ceramic layer is preferably 0.5 μm or more, more preferably 1.0 μm or more, even more preferably 2.0 μm or more, and is preferably 5.0 μm or less, more preferably 4.0 μm or less, even more preferably 3.0 μm or less.

[0035] As the laminate of the porous substrate and the ceramic layer, commercially available products can be used, such as those available under the trade name Celgard (registered trademark) manufactured by CELGARD, those available under the trade name Seapore (registered trademark) manufactured by UBE Inc., and those available under the trade name Setira (registered trademark) manufactured by Toray Industries, Inc.

[0036] Resin Layer The resin layer is composed of a polyether copolymer and / or a crosslinked product thereof. The polyether copolymer is represented by the following general formula (1):

[0037]

[0038] [wherein R is an alkyl group having 1 to 12 carbon atoms, or —CH2O(CR 1 R 2 R 3 ) R 1 , R 2 , R 3 is a hydrogen atom or -CH2O(CH2CH2O)nR 4 and n and R 4 is R 1 , R 2 , R 3 R 4 is an alkyl group or an aryl group having 1 to 12 carbon atoms, and n is an integer of 0 to 12.], and 2 to 40 mol % of a repeating unit derived from a monomer represented by the following general formula (2):

[0039]

[0040] 98 to 60 mol % of a repeating unit derived from a monomer represented by the following general formula (3):

[0041]

[0042] [In the formula, R 5 is a group having an ethylenically unsaturated group.].

[0043] The compound of formula (1) can be obtained from commercial products or easily synthesized by a general ether synthesis method from epihalohydrin and alcohol. Examples of commercially available compounds that can be used include propylene oxide, butylene oxide, methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, tertiary 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 commercial products, propylene oxide, butylene oxide, methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, and isopropyl glycidyl ether are preferred, with propylene oxide, butylene oxide, methyl glycidyl ether, and ethyl glycidyl ether being particularly preferred. In the monomer represented by formula (1) obtained by synthesis, R is —CH2O(CR 1 R 2 R 3 ) is preferred, and R 1 , R 2 , R 3 At least one of the following is -CH2O(CH2CH2O) n R 4 It is preferable that R 4 is preferably an alkyl group having 1 to 6 carbon atoms, and more preferably an alkyl group having 1 to 4 carbon atoms. n is preferably an integer of 0 to 6, and more preferably an integer of 0 to 4.

[0044] The compound of formula (2) is a basic chemical product and is readily available commercially.

[0045] In the compound of formula (3), R 5is a substituent containing an ethylenically unsaturated group. Examples of the ethylenically unsaturated group-containing monomer component include allyl glycidyl ether, 4-vinylcyclohexyl glycidyl ether, α-terpinyl glycidyl ether, cyclohexenylmethyl glycidyl ether, p-vinylbenzyl glycidyl ether, allylphenyl 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-cyclododecanediene, 3,4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5-cyclooctene, glycidyl acrylate, glycidyl methacrylate, glycidyl sorbate, glycidyl cinnamate, glycidyl crotonate, and glycidyl-4-hexenoate. Preferred are allyl glycidyl ether, glycidyl acrylate, and glycidyl methacrylate.

[0046] The polyether copolymer comprises a repeating unit derived from a monomer of formula (1):

[0047] [wherein R is an alkyl group having 1 to 12 carbon atoms, or —CH2O(CR 1 R 2 R 3 ) R 1 , R 2 , R 3 is a hydrogen atom or -CH2O(CH2CH2O)nR 4 and n and R 4 is R 1 , R 2 , R 3 R 4 represents an alkyl group having 1 to 12 carbon atoms or an aryl group which may have a substituent, and n represents an integer of 0 to 12.] and (B): a repeating unit derived from a monomer of formula (2), and and (C): a repeating unit derived from a monomer of formula (3), [In the formula, R 5 is a substituent containing a group having an ethylenically unsaturated group.

[0048] Here, the repeating units (A) and (C) may each be derived from two or more types of monomers.

[0049] In the polyether copolymer, the molar ratios of repeating units (A), (B), and (C) are 2 to 40 mol% (A), 98 to 60 mol% (B), and 0 to 15 mol% (C), preferably 5 to 35 mol% (A), 95 to 60 mol% (B), and 0 to 10 mol% (C), and more preferably 5 to 30 mol% (A), 95 to 65 mol% (B), and 0 to 7 mol% (C). If the repeating unit (B) exceeds 98 mol%, the glass transition temperature increases and the oxyethylene chains crystallize, resulting in a significant deterioration in ionic conductivity. It is generally known that ionic conductivity is improved by reducing the crystallinity of polyethylene oxide, and the polyether copolymer of the present invention is significantly superior in this respect.

[0050] In order to obtain good processability, mechanical strength, and flexibility, the molecular weight of the polyether copolymer of the present invention is preferably such that the lower limit of the weight-average molecular weight is 50,000 or more, more preferably 300,000 or more, and even more preferably 500,000 or more, and the upper limit of the weight-average molecular weight is preferably 2,500,000 or less, and preferably 1,500,000 or less. A copolymer having a weight-average molecular weight in this range has an appropriate viscosity of a polymer solution in which the polyether copolymer is dissolved, resulting in good workability. By setting the lower limit of the weight-average molecular weight to 300,000 or more, the polyether copolymer or its crosslinked product supported on the separator does not dissolve in the electrolyte solution. Therefore, the resin layer is less likely to peel off from the laminate, which is preferable in that better charge / discharge characteristics can be obtained as an electricity storage device.

[0051] The polyether copolymer may be either a block copolymer or a random copolymer, with the random copolymer being preferred since it has a greater effect of reducing the crystallinity of polyethylene oxide.

[0052] Polyether copolymers can be synthesized as follows. Using a ring-opening polymerization catalyst, a coordination anionic initiator such as an organoaluminum-based catalyst system, an organozinc-based catalyst system, or an organotin-phosphate ester condensate catalyst system, or an anionic initiator containing K+ as a counter ion, such as potassium alkoxide, diphenylmethyl potassium, or potassium hydroxide, the monomers are reacted with stirring in the presence or absence of a solvent at a reaction temperature of 10 to 120°C to obtain a polyether copolymer. From the standpoint of the degree of polymerization or the properties of the resulting copolymer, coordination anionic initiators are preferred, and among these, organotin-phosphate ester condensate catalyst systems are particularly preferred due to their ease of handling.

[0053] In the separator of the present invention, the polyether copolymer constituting the resin layer may be at least partially a crosslinked product of the polyether copolymer. By supporting the crosslinked product, the strength of the separator is improved, which is preferable.

[0054] In the separator of the present invention, the weight of the resin layer is 0.10 g / m 2 0.40g / m or more 2 From the viewpoint of more suitably exhibiting the effects of the present invention, the basis weight of the resin layer in the separator of the present invention is preferably less than 0.15 g / m 2 More preferably, 0.20 g / m 2 or more, and preferably 0.37 g / m 2 More preferably, 0.35 g / m or less 2 Below 0.30 g / m, particularly preferably 2 The preferred range is 0.10 to 0.37 g / m 2 ,0.10~0.35g / m 2 ,0.10~0.30g / m 2 , 0.15-0.37g / m 2 , 0.15-0.35g / m 2 ,0.15~0.30g / m 2 ,0.20~0.37g / m 2 ,0.20~0.35g / m 2 ,0.20~0.30g / m 2 Examples include:

[0055] In the separator of the present invention, it is preferable to keep the amount of water contained in the polyether copolymer constituting the resin layer below a certain level. If a large amount of water is present in the resin layer, it acts as a resistor, adversely affecting the ionic conductivity of the lithium-ion secondary battery. Therefore, the amount of water contained in 100% by mass of the polyether copolymer is preferably 2% by mass or less, more preferably 1.8% by mass or less, and preferably 1.5% by mass or less. There is no particular lower limit, but it may be, for example, 0.000% by mass, 0.005% by mass or more, or 0.05% by mass or more. The amount of water in the polyether copolymer can be measured by the method described in JIS K0068:2001.

[0056] The water contained in the polyether copolymer may be removed by a conventional method, for example, by drying at room temperature or under heat (generally 80°C or less) under normal pressure or reduced pressure. Regarding the polyether polymer, a method of drying the polyether copolymer as is (dry method) or a method of preparing a polyether solution by dissolving the polyether copolymer in an organic solvent that forms an azeotrope with water and drying the solution (wet method) can be used. If necessary, a desiccant such as silica gel may be used in combination with the dry method. Furthermore, an anhydrous inorganic salt such as magnesium sulfate or molecular sieves may be used in combination with the wet method.

[0057]

[0033] The method for producing the separator of the present invention is not particularly limited, and examples thereof include a method in which a laminate of a porous substrate and a ceramic layer is immersed in a solution obtained by dissolving a polyether copolymer in water or an organic solvent, and then dried to form a resin layer, and a method in which a solution obtained by dissolving a polyether copolymer in water or an organic solvent is applied to at least one surface of a laminate of the porous substrate and the ceramic layer, and then dried to form a resin layer. In terms of making it easier to obtain the rate of increase in the Gurley value, the method in which a solution obtained by dissolving a polyether copolymer in a polar solvent is applied to a separator, and then dried to form a resin layer is preferred.

[0058] The polar solvent used in the present invention is not particularly limited, but is one that can dissolve the polyether copolymer. Examples of polar solvents include water, organic polar amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and N-methylcaprolactam, water-soluble ether compounds such as tetrahydrofuran and dioxane, water-soluble alcohol compounds such as methanol, ethanol, and ethylene glycol, water-soluble ketone compounds such as acetone and methyl ethyl ketone, and water-soluble nitrile compounds such as acetonitrile and propionitrile. These solvents can be used alone or as a mixture of two or more. These solvents can be selected from the following. These solvents can be used alone or as a mixture of two or more.

[0059] The concentration of the polyether copolymer in the solution is not particularly limited, but is preferably 0.5% by mass to 40% by mass, more preferably 1% by mass to 40% by mass, and even more preferably 3% by mass to 30% by mass.

[0060] There are no particular limitations on the method for applying the polyether copolymer used in the present invention to the laminate, and a solution obtained by dissolving the polyether copolymer in a polar solvent can be applied to the surface of the laminate by a suitable method such as microgravure, slot die, or knife coating depending on the solution viscosity and the desired coating film thickness.

[0061] The polyether copolymer used in the present invention can be supported on at least one surface of a laminate of a porous substrate and a ceramic layer by coating, immersion, etc., and then dried to remove water or organic solvent, thereby forming a resin layer. Drying methods that can be used include heater-type, hot air-type, infrared radiation-type, and vacuum-type drying equipment.

[0062] In the present invention, by using a solution in which a polyether copolymer is dissolved and further containing a photoinitiator or a thermal polymerization initiator, a resin layer made of a crosslinked product of the polyether copolymer can be supported on the laminate by applying the solution to the laminate or immersing the laminate in the solution and then irradiating the laminate with active energy rays such as ultraviolet rays or by applying heat. An electrolyte salt or a crosslinking aid can also be added to the solution obtained by dissolving the polyether copolymer, if necessary.

[0063] Examples of the thermal polymerization initiator include radical initiators such as organic peroxides and azo compounds.

[0064] As the organic peroxide, those typically used for crosslinking purposes, such as ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, and peroxyesters, can be used. Specific examples include 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, benzoyl peroxide, and t-butylperoxy-2-ethylhexanoate.

[0065] Examples of azo compounds that can be used include azonitrile compounds, azoamide compounds, and azoamidine compounds that are typically used for crosslinking purposes. Specific examples include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2-azobis(2-methyl-N-phenylpropionamidine) dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis(2-methylpropane), and 2,2'-azobis[2-(hydroxymethyl)propionitrile].

[0066] The amount of the thermal polymerization initiator is preferably within a range of 0.01 to 10 parts by mass, more preferably 0.1 to 4.0 parts by mass, per 100 parts by mass of the polyether polymer.

[0067] Examples of photoinitiators that can be used in the present invention include alkylphenones, benzophenones, acylphosphine oxides, titanocenes, triazines, bisimidazoles, and oxime esters. Among these, alkylphenones, benzophenones, and acylphosphine oxides are preferred. Two or more photoinitiators can also be used in combination.

[0068] Specific examples of alkylphenone-based photoinitiators include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-[4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl]-2-methyl-propan-1-one, etc. 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexyl-phenyl-ketone, and 2-hydroxy-2-methyl-1-phenyl-propan-1-one are preferred.

[0069] Specific examples of benzophenone-based photoinitiators include benzophenone, 2-chlorobenzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(dimethylamino)benzophenone, methyl-2-benzoylbenzoate, etc. Benzophenone, 4,4'-bis(diethylamino)benzophenone, and 4,4'-bis(dimethylamino)benzophenone are preferred.

[0070] Specific examples of the acylphosphine oxide photopolymerization initiator include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, etc. Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide is preferred.

[0071] The amount of the photoreaction initiator is preferably within a range of 0.01 to 6.0 parts by mass, more preferably 0.1 to 4.0 parts by mass, per 100 parts by mass of the polyether polymer.

[0072] In the present invention, a crosslinking coagent may be used in combination with the photoinitiator. The crosslinking coagent is typically a polyfunctional compound (e.g., a compound containing at least two CH═CH—, CH═CH—CH═—, or CF═CF—). Specific examples of the crosslinking coagent include triallyl cyanurate, triallyl isocyanurate, triacryl formal, triallyl trimellitate, N,N′-m-phenylene bismaleimide, dipropargyl terephthalate, diallyl phthalate, tetraallyl terephthalamide, triallyl phosphate, hexafluorotriallyl isocyanurate, N-methyltetrafluorodiallyl isocyanurate, trimethylolpropane trimethacrylate, and trimethylolpropane triacrylate.

[0073] The amount of the crosslinking aid used in the present invention is preferably within a range of 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, per 100 parts by mass of the polyether copolymer.

[0074] The active energy rays used to crosslink the polyether copolymer used in the present invention may be ultraviolet light, visible light, electron beams, etc. Among these, ultraviolet light is particularly preferred in view of the cost of the equipment and ease of control.

[0075] When the crosslinking reaction is carried out by heat, it can be carried out by heating at a temperature setting of room temperature to about 200°C for about 10 minutes to 24 hours. When using ultraviolet light, a xenon lamp, a mercury lamp, a high-pressure mercury lamp, or a metal halide lamp can be used. For example, the electrolyte can be exposed to light with a wavelength of 365 nm and a light intensity of 1 to 50 mW / cm. 2 This can be done by irradiating with light at 4000 kJ / cm for 0.1 to 30 minutes.

[0076] The crosslinking reaction may be carried out after applying a solution obtained by dissolving a polyether copolymer containing a photoreaction initiator or a thermal polymerization initiator to a separator or after immersing the separator in the solution, and before, during, or after drying the separator.

[0077] <2. Electricity storage device> The electricity storage device of the present invention is formed using the aforementioned "1. Separator for electricity storage device", and specifically has a positive electrode, a negative electrode, the separator for electricity storage device interposed between the positive electrode and the negative electrode, and an electrolyte (solution).

[0078] Positive Electrode The positive electrode has a positive electrode composition containing a positive electrode active material and a binder on a current collector.

[0079] The material of the current collector used in the electrode for the electricity storage device of the present invention can be, for example, metal, carbon, conductive polymer, etc., and metal is preferably used. As the metal for the current collector, aluminum, platinum, nickel, tantalum, titanium, stainless steel, copper, other alloys, etc. are usually used. Among these, copper, aluminum, or an aluminum alloy is preferably used in terms of conductivity and voltage resistance, and a metal foil such as aluminum foil is preferably used as the current collector for the positive electrode.

[0080] As the positive electrode active material, metal oxides, metal sulfides, or specific polymers can be used depending on the type of battery desired.

[0081] For example, in the case of a lithium battery utilizing the dissolution and precipitation of lithium, metal sulfides or oxides that do not contain lithium, such as TiS2, MoS2, NbS2, and V2O5, as well as polymers such as polyacetylene and polypyrrole, can also be used.

[0082] When a lithium ion battery is produced using the doping and dedoping of lithium ions, a lithium composite oxide represented by LixMO2 (wherein M represents one or more transition metals, and x varies depending on the charge / discharge state of the battery, but is usually 0.05 or more and 1.10 or less) or a lithium composite phosphate represented by LixMPO4 (wherein M represents one or more transition metals, and x varies depending on the charge / discharge state of the battery, but is usually 0.05 or more and 1.10 or less) can be used. The transition metal M constituting this lithium composite oxide or lithium phosphate is preferably Co, Ni, Mn, Al, Fe, or the like. Specific examples of such lithium composite oxides include LiCoO2, LiNiO2, and LiNiO4. y Co z Mn 1-y-z O2 (wherein 0<y, z<1), LiNi y Co z Al 1-y-z O2 (wherein 0<y, z<1), LiMn2O4, LiFePO4, etc. can be mentioned.

[0083] Lithium composite oxides can generate high voltage and serve as positive electrode active materials with excellent energy density. A combination of these positive electrode active materials may be used as the positive electrode active material. When forming a positive electrode active material using such positive electrode active materials, known binders may be added.

[0084] The binder used in the positive electrode composition can be, for example, one or more compounds selected from fluorine-based binders, acrylic rubber, modified acrylic rubber, styrene-butadiene rubber, acrylic polymers, and vinyl polymers. Furthermore, acrylic polymers are preferred because they are oxidation-resistant, provide sufficient adhesion with a small amount, and provide flexibility to the electrode plate. Aqueous binders that dissolve or disperse in water are particularly preferred because they do not dissolve organic active materials. These binders are added to the positive electrode current collector in a ratio of preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, of the positive electrode composition.

[0085] In addition to the above, the positive electrode composition for the positive electrode may contain a conductive aid, a solvent, and a thickener. Examples of conductive aids include carbon compounds such as conductive carbons such as acetylene black, ketjen black, carbon fiber, and graphite, as well as conductive polymers and metal powders, with conductive carbon being particularly preferred. Any solvent that can dissolve or disperse the positive electrode active material and binder can be used as the solvent, and preferred examples include water and N-methyl-2-pyrrolidone. Examples of thickeners that can be used include carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, and alkali metal salts thereof, and polyethylene oxide.

[0086] Negative Electrode The negative electrode has a negative electrode composition containing a negative electrode active material and a binder on a current collector.

[0087] The material of the current collector used in the electrode for the electricity storage device of the present invention can be, for example, metal, carbon, conductive polymer, etc., and metal is preferably used. As the metal for the current collector, aluminum, platinum, nickel, tantalum, titanium, stainless steel, copper, other alloys, etc. are usually used. Among these, copper, aluminum, or an aluminum alloy is preferably used in terms of conductivity and voltage resistance, and a metal foil such as copper foil is preferably used as the current collector for the negative electrode.

[0088] For example, in the case of a lithium battery that utilizes the dissolution and deposition of lithium, metallic lithium, a lithium alloy capable of absorbing and releasing lithium, or the like can be used as the negative electrode active material.

[0089] When a lithium-ion battery is produced using doping and dedoping of lithium ions, non-graphitizable carbon or graphite-based carbon materials can be used. More specifically, carbon materials such as graphite, mesocarbon microbeads, mesophase carbon fiber, pyrolytic carbon, cokes (pitch coke, needle coke, petroleum coke), glassy carbon, organic polymer compound calcined bodies (phenolic resin, furan resin, etc., calcined at an appropriate temperature and carbonized), and activated carbon can be used. When forming a negative electrode from such materials, known binders can be added.

[0090] The binder used in the negative electrode composition can be, for example, one or more compounds selected from fluorine-based binders, acrylic rubber, modified acrylic rubber, styrene-butadiene rubber, acrylic polymers, and vinyl polymers. Furthermore, acrylic polymers are preferred because they are resistant to reduction, provide sufficient adhesion with a small amount, and provide flexibility to the electrode plate. Aqueous binders that dissolve or disperse in water are particularly preferred because they do not dissolve organic active materials. These binders are added to the negative electrode current collector in a ratio of preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, of the negative electrode composition.

[0091] In addition to the above, the negative electrode composition for the negative electrode may contain a conductive aid, a solvent, a thickener, etc. Examples of conductive aids include carbon compounds such as conductive carbons such as acetylene black, ketjen black, carbon fiber, and graphite, conductive polymers, and metal powders, with conductive carbon being particularly preferred. Any solvent can be used as the solvent as long as it can dissolve or disperse the negative electrode active material and binder, and preferred examples include water and N-methyl-2-pyrrolidone. Furthermore, examples of thickeners that can be used include carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, and the like, or alkali metal salts thereof, and polyethylene oxide.

[0092] Electrode (Positive Electrode / Negative Electrode) Manufacturing Method The electrodes (positive electrode / negative electrode) for a storage battery device of the present invention are obtained by forming an electrode (positive electrode / negative electrode) composition on a current collector. Specific examples include a method of laminating a sheet-shaped electrode composition for a storage battery device on a current collector (kneading sheet molding method); a method of applying a paste-like electrode composition for a storage battery device on a current collector and drying it (wet molding method); and a method of preparing composite particles of the electrode composition for a storage battery device, forming a sheet on a current collector, and roll-pressing the sheet (dry molding method). Among these, the wet molding method and dry molding method are preferred, and the wet molding method is more preferred.

[0093] Electrolyte (Solution) The electrolyte solution is obtained by dissolving an electrolyte salt in an aprotic organic solvent, and a room temperature molten salt (ionic liquid) can also be used.

[0094] In the present invention, the following electrolyte salt compounds are preferably used: a cation selected from metal cations, ammonium ions, amidinium ions, and guanidium ions, and a chloride ion, bromide ion, iodide ion, perchlorate ion, thiocyanate ion, tetrafluoroborate ion, nitrate ion, AsF6 - , PF6 - , stearyl sulfonate ion, octylsulfonate ion, dodecylbenzenesulfonate ion, naphthalenesulfonate ion, dodecylnaphthalenesulfonate ion, 7,7,8,8-tetracyano-p-quinodimethane ion, X1SO3 - , [(X1SO2)(X2SO2)N] - , [(X1SO2)(X2SO2)(X3SO2)C] - , and [(X1SO2)(X2SO2)YC] - and an anion selected from the group consisting of: wherein X1, X2, X3, and Y are electron-withdrawing groups. Preferably, X1, X2, and X3 are each independently a perfluoroalkyl group having 1 to 6 carbon atoms or a perfluoroaryl group having 6 to 18 carbon atoms, and Y is a nitro group, nitroso group, carbonyl group, carboxyl group, or cyano group. X1, X2, and X3 may be the same or different.

[0095] The metal cations may be transition metal cations. Preferably, metal cations selected from Mn, Fe, Co, Ni, Cu, Zn, and Ag are used. Furthermore, favorable results can be obtained by using metal cations selected from Li, Na, K, Rb, Cs, Mg, Ca, and Ba. Two or more of the above-mentioned compounds can be used in combination as the electrolyte salt compound. In particular, Li salt compounds are preferably used as the electrolyte salt compound in lithium ion capacitors.

[0096] The Li salt compound may be a Li salt compound having a wide potential window, such as those commonly used in lithium ion capacitors, such as LiBF, LiPF, LiClO, LiCFSO, LiN(CFSO), LiN(CFSO), and LiN[CFSC(CFSO)]. 2 These may be used alone or in combination of two or more.

[0097] Furthermore, a room temperature molten salt can be used as the electrolyte salt or the electrolyte solution.

[0098] A room-temperature molten salt is a salt that is at least partially liquid at room temperature, and room temperature refers to the temperature range in which a power supply is expected to operate normally. The temperature range in which a power supply is expected to operate normally has an upper limit of about 120°C, or in some cases about 60°C, and a lower limit of about -40°C, or in some cases about -20°C.

[0099] Room-temperature molten salts are also called ionic liquids, and known examples include pyridine-based, aliphatic amine-based, and alicyclic amine-based quaternary ammonium organic cations. Examples of quaternary ammonium organic cations include imidazolium ions such as dialkylimidazolium and trialkylimidazolium ions, tetraalkylammonium ions, alkylpyridinium ions, pyrazolium ions, pyrrolidinium ions, and piperidinium ions. Imidazolium cations are particularly preferred.

[0100] Examples of imidazolium cations include, but are not limited to, a 1,3-dimethylimidazolium ion, a 1-ethyl-3-methylimidazolium ion, a 1-methyl-3-ethylimidazolium ion, a 1-methyl-3-butylimidazolium ion, a 1-butyl-3-methylimidazolium ion, a 1,2,3-trimethylimidazolium ion, a 1,2-dimethyl-3-ethylimidazolium ion, a 1,2-dimethyl-3-propylimidazolium ion, and a 1-butyl-2,3-dimethylimidazolium ion.

[0101] These room-temperature molten salts having cations may be used alone or in combination of two or more.

[0102] In the present invention, the content of the electrolyte salt is preferably 0.1 to 3.0 mol / L, and particularly preferably 1.0 to 2.0 mol / L. If the content of the electrolyte salt is less than 0.1 mol / L, the resistance of the electrolyte solution increases and the large current / low temperature discharge characteristics deteriorate, while if the content exceeds 3.0 mol / L, the solubility decreases and crystals may precipitate.

[0103] The aprotic organic solvent used in the electrolyte solution of the present invention is not particularly limited. Specific examples of the aprotic organic solvent include propylene carbonate, ethylene carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, dipropyl carbonate, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propylnitrile, anisole, acetate esters, and propionate esters. These organic solvents may be used alone or in combination of two or more.

[0104] Manufacturing Method of Electricity Storage Device The electricity storage device of the present invention can be produced by stacking a positive electrode and a negative electrode, which are electrodes formed by forming the electrode composition on a current collector, via the separator described above, and injecting an electrolyte solution.

[0105] Specific embodiments for carrying out the present invention will be described below with reference to examples, but the present invention is not limited to the following examples as long as they do not deviate from the gist of the present invention.

[0106] Synthesis Example (Production of a Catalyst for Polyether Copolymerization) 10 g of tributyltin chloride and 35 g of tributylphosphate were placed in a three-necked flask equipped with a stirrer, a thermometer, and a distillation apparatus, and heated at 250° C. for 20 minutes with stirring under a nitrogen stream to remove the distillate, thereby obtaining a solid condensation product as a residue, which was used as a polymerization catalyst in the following polymerization examples.

[0107] The monomer equivalent composition of polyether copolymer is 1 The molecular weight of the polyether copolymer was determined by H NMR spectroscopy. Gel permeation chromatography (GPC) was performed to measure the molecular weight of the polyether copolymer, and the weight average molecular weight was calculated in terms of standard polystyrene. The GPC measurement was performed at 60°C using a Shimadzu RID-6A column and Showa Denko Showdex KD-807, KD-806, KD-806M, and KD-803 columns, and DMF as a solvent.

[0108] [Polymerization Example 1] The inside of a 3 L four-necked glass flask was purged with nitrogen, and 1 g of the condensation product shown in the catalyst synthesis example as a polymerization catalyst and a glycidyl ether compound (a) adjusted to a water content of 10 ppm or less: 158 g of ethylene oxide, 22 g of allyl glycidyl ether, and 1,000 g of n-hexane as a solvent were charged, and 125 g of ethylene oxide was gradually added while monitoring the polymerization rate of compound (a) by gas chromatography. The polymerization temperature was 20°C, and the reaction was carried out for 10 hours. The polymerization reaction was terminated by adding 1 mL of methanol. The polymer was removed by decantation and then dried at 40°C under normal pressure for 24 hours and then at 45°C under reduced pressure for 10 hours to obtain 280 g of polymer. The weight-average molecular weight of the obtained polyether copolymer was 1,000,000, and the composition analysis results calculated as monomers were 72 mol% ethylene oxide, 23 mol% compound (a), and 5 mol% allyl glycidyl ether. The water content was 2.5% by mass.

[0109] [Example 1] Negative electrode 1 / separator 1 (with ceramic layer, resin layer with a basis weight of 0.25 g / m on the porous substrate surface) 2 ) / Positive electrode 1 Preparation of lithium ion battery 1 configured <Preparation of negative electrode 1> 90 parts by mass of graphite powder (porous structure material), 10 parts by mass of polyvinylidene fluoride, and 100 parts by mass of N-methyl-2-pyrrolidone as a solvent were stirred for 1 hour using a stainless steel ball mill, and then coated on a copper current collector using a bar coater with a gap of 50 μm. The coated material was dried at 80° C. in a vacuum for 12 hours or more and then roll-pressed to obtain negative electrode sheet 1.

[0110] <Preparation of Positive Electrode 1> The positive electrode active material was a 10 μm LiNi 0.80 Co 0.15 Al 0.05 90 parts by mass of this positive electrode active material was mixed with 3 parts by mass of spherical carbon particles produced by thermal decomposition of acetylene as a conductive additive, 7 parts by mass of polyvinylidene fluoride as a binder, and 50 parts by mass of N-methyl-2-pyrrolidone as a solvent, and the mixture was stirred for 1 hour using a stainless steel ball mill, and then applied to an aluminum current collector using a bar coater with a 100 μm gap. The mixture was dried at 80° C. in a vacuum for 12 hours or more and then roll-pressed to form positive electrode sheet 1.

[0111] <Preparation of Electrolyte Solution> A non-aqueous electrolyte solution was prepared by mixing 50 parts by mass of ethylene carbonate (EC), 50 parts by mass of dimethyl carbonate (DMC), and 20 parts by mass of LiPF6 as an electrolyte salt.

[0112] <Dehydration of Polyether Copolymer> The polyether copolymer obtained in Polymerization Example 1 above was pulverized into pieces of approximately 2 to 3 m square, and then dehydrated at 45°C under reduced pressure for 10 hours to obtain a dehydrated polyether copolymer. The water content in the obtained dehydrated polyether copolymer was 1.5% by mass.

[0113] <Preparation of Separator 1> A solution prepared by dissolving 20 parts by mass of dehydrated polyether copolymer in 180 parts by mass of acetonitrile was applied to a ceramic (alumina)-coated polyethylene porous substrate (total thickness 9 μm) with a film thickness of 2 μm, and the surface (porous substrate surface) that was not ceramic-coated was coated with a film weight of 0.25 g / m after drying.2 The mixture was dried at 60° C. for 10 minutes in a normal pressure dryer to prepare a separator 1 in which a resin layer was supported on a polyethylene porous substrate.

[0114] Finally, one negative electrode sheet and one positive electrode sheet were pressure-bonded via the separator 1 to form a laminate. The laminate was then housed in an aluminum laminate, and a non-aqueous electrolyte solution was injected to produce a lithium ion battery 1.

[0115] [Comparative Example 1] Negative electrode 1 / separator 2 (with ceramic layer, resin layer with a basis weight of 1.3 g / m on the porous substrate surface) 2 ) / Preparation of a lithium ion battery 2 configured with a positive electrode 1

[0116] <Preparation of Separator 2> Separator 2 was prepared in the same manner as in the preparation of separator 1, except that the basis weight of the dehydrated polyether copolymer was set to 1.3 g / m2.

[0117] Finally, one sheet of the negative electrode and one sheet of the positive electrode were pressure-bonded via the separator 2 to form a laminate. The laminate was then housed in an aluminum laminate, and a non-aqueous electrolyte solution was injected to produce a lithium ion battery 2.

[0118] [Comparative Example 2] Negative electrode 1 / separator 3 (with ceramic layer, resin layer with a basis weight of 2.9 g / m on the porous substrate surface) 2 ) / Preparation of a lithium ion battery 3 configured with a positive electrode 1

[0119] <Preparation of Separator 3> Separator 3 was prepared in the same manner as in the preparation of separator 1, except that the basis weight of the dehydrated polyether copolymer was set to 2.9 g / m2.

[0120] Finally, a lithium ion battery 3 was fabricated in the same manner as in the fabrication process of the lithium battery 1, except that a separator 3 was used instead.

[0121] Comparative Example 3 Preparation of Lithium-ion Battery 4 Consisting of Negative Electrode 1 / Separator 4 (with Ceramic Layer, No Resin Layer) / Positive Electrode 1 <Preparation of Separator 4> Separator 4 was prepared in the same manner as in the preparation of separator 1, except that a separator not coated with the dehydrated polyether copolymer was used.

[0122] Finally, a lithium ion battery 4 was fabricated in the same manner as in the fabrication process of the lithium battery 1, except that a separator 4 was used instead of the separator used in the fabrication process of the lithium battery 1.

[0123] The separators produced in Example 1 and Comparative Examples 1 to 3 were measured by the Gurley value method shown below. The Gurley value of the separator before the resin layer was supported (Comparative Example 3) was used as the reference, and the increase rate of the Gurley value of Example 1 and Comparative Examples 1 to 2, which had a resin layer supported thereon, is shown in Table 1. In the table, the increase rate (%) of the Gurley value before and after the resin layer was supported can be calculated using the following formula: Increase rate (%) of Gurley value = {(Gurley value of separator after the resin layer was supported) - (Gurley value of separator before the resin layer was supported)} / Gurley value of separator before the resin layer was supported × 100

[0124] <Gurley Value> The Gurley value (seconds / 100 mL) was measured in accordance with JIS P8117 (ISO 5636 / 5).

[0125] The lithium ion batteries fabricated in Example 1 and Comparative Examples 1 to 3 were tested by the methods described below, and the results are shown in Table 1. Note that the rate characteristics of Comparative Example 3 were not measured.

[0126] <Charge-discharge cycle characteristics after overdischarge> Using lithium ion batteries 1 to 4 produced in the examples and comparative examples, a charge-discharge cycle test was performed once from 2.0 to 4.15 V at a 10-hour rate discharge (0.1 C) of the theoretical capacity, and then charging was performed using CC-CV, applying a constant current of 0.2 C up to 4.15 V and maintaining the constant voltage of 4.15 V until the current value reached 0.02 C. Thereafter, the battery was discharged to 2 V at 0.2 C, and then further discharged to 0 V at 0.06 C, and left at the open circuit voltage for 1 hour for 50 cycles. The discharge capacity (W n ) was calculated as the capacity retention rate relative to the initial discharge capacity (W0). Capacity retention rate [%] = (Wn / W0) × 100

[0127] <Rate characteristics> Using the lithium ion batteries 1 to 3 produced in Example 1, Comparative Example 1, and Comparative Example 2, charging was performed by CC-CV, applying a constant current of 0.2 C up to 4.15 V, and maintaining the voltage at 4.15 V until the current value reached 0.02 C. Discharging was performed at 0.1 C, 0.2 C, 0.3 C, 0.4 C, 0.5 C, 0.7 C, 1 C, 2 C, 3 C, and 4 C until the voltage reached 2 V. The discharge capacity (W 0.1 ) as the standard, the discharge capacity (W x The capacity retention rate of the battery was calculated. Capacity retention rate [%] = (W x / W 0.1 ) x 100

[0128]

[0129] From Table 1, it can be seen that the separator of the present invention in Example 1 is less likely to experience a decrease in capacity in the cycle test after overdischarge and also has good rate characteristics. Comparative Example 3, which does not use the polyether copolymer of the present invention, showed a significant decrease in capacity in the cycle test after overdischarge, and Comparative Examples 1 and 2, which used a high basis weight of the polyether copolymer, showed good results in the overdischarge test but a decrease in capacity retention in the rate characteristics.

[0130] [Example 2] <Preparation of Separator 4> A solution of dehydrated polyether copolymer dissolved in acetone to a concentration of 1% by volume was applied to a ceramic (alumina)-coated polyethylene porous substrate (total thickness 9 μm) with a film thickness of 2 μm, and the solution was applied to the surface (porous substrate surface) that was not ceramic-coated, with a basis weight of 0.21 g / m after drying. 2 The mixture was dried at 60° C. for 10 minutes in a normal pressure dryer to prepare a separator 4 in which a resin layer was supported on a polyethylene porous substrate.

[0131] [Example 3] <Preparation of Separator 5> In the process of preparing separator 4, the weight of the dehydrated polyether copolymer was set to 0.35 g / m 2 Separator 5 was produced in the same manner as in Example 2, except that the coating was carried out so that the thickness of the coating film was as follows:

[0132] [Comparative Example 4] <Preparation of Separator 6> In the process of preparing Separator 4, the basis weight of the dehydrated polyether copolymer was 0.55 g / m 2 Separator 6 was produced in the same manner as in Example 2, except that the coating was carried out so that the thickness of the coating film was as follows:

[0133] [Comparative Example 5] <Preparation of Separator 7> In the process of preparing Separator 4, the weight of the dehydrated polyether copolymer was set to 0.75 g / m 2 Separator 6 was produced in the same manner as in Example 2, except that the coating was carried out so that the thickness of the coating film was as follows:

[0134] <Peeling test after thermoforming> The resin layer of the separator prepared in Examples 2 and 3 and Comparative Examples 4 and 5 was laminated so that it faced the ceramic layer of the ceramic-coated polyethylene porous substrate, sandwiched between SUS plates, and heat-treated at 40°C for 12 hours. The heat-treated laminate was cut into 1 cm x 10 cm strips, and 10 strips were prepared. One end of the strip was held and pulled, and the peeling state of the ceramic layer was visually observed. The evaluation criteria were as follows.

[0135] ◎: Peeling of the ceramic layer was observed on 0 strips. ◯: Peeling of the ceramic layer was observed on 1-2 strips. △: Peeling of the ceramic layer was observed on 3-4 strips. ×: Peeling of the ceramic layer was observed on 5 or more strips.

[0136]

[0137] From Table 2, it can be seen that the separator of the present invention has low tackiness even after thermoforming, and therefore has high releasability, and there is little concern that the ceramic layer laminated on the porous substrate will peel off. This means that even if the separator is rolled up and stored after applying the resin layer of the polyether copolymer of the present invention, it is unlikely to become a defective product during use.

Claims

1. A separator for an electrical storage device comprising a laminate of a porous substrate and a ceramic layer, and a resin layer supported on at least one surface of the laminate, wherein the resin layer is composed of a polyether copolymer and / or a crosslinked product thereof, and the polyether copolymer is composed of 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 basis weight of the resin layer is 0.10 g / m 2 0.40g / m or more 2 and the rate of increase in Gurley value before and after the support of the resin layer is 10% or more and 330% or less. [In formula (1), R represents an alkyl group having 1 to 12 carbon atoms, or —CH2O(CR 1 R 2 R 3 ) R 1 , R 2 , R 3 is a hydrogen atom or -CH2O(CH2CH2O)nR 4 and n and R 4 is R 1 , R 2 , R 3 R 4 is an alkyl group having 1 to 12 carbon atoms or an aryl group, and n is an integer from 0 to 12. [In formula (3), R 5 is a group having an ethylenically unsaturated group.

2. The separator for an electric storage device according to claim 1, wherein the porous substrate is a porous film made of at least one resin selected from the group consisting of polyolefin resin, polyester resin, cellulose resin, and polyamide resin.

3. A method for manufacturing a separator for an electrical storage device according to claim 1 or 2, comprising a step of applying a solution containing the polyether copolymer and a polar solvent to at least one surface of the laminate of the porous substrate and the ceramic layer, and drying the solution to form the resin layer.

4. An electricity storage device comprising the separator for an electricity storage device according to claim 1 or 2.

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