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

Abstract

The present invention provides a separator for power storage devices, the separator having excellent heat resistance and being capable of providing a power storage device with excellent charge and discharge cycle 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 loaded 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 to 40% by mole of a repeating unit that is derived from a monomer represented by formula (1), 98 to 60% by mole of a repeating unit that is derived from a monomer represented by formula (2), and 0 to 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 0.4 g / m2 to 3.0 g / m2; and the ratio between the Gurley values before and after loading of the resin layer is 200% or more.

Description

[Technical Field]

[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. [Background technology]

[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 composed of a pair of electrodes and a separator impregnated with an electrolyte solution, and are used in a variety of industrial and consumer electrical 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 prevention 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). [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 01 / 67536 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-152857 Summary of the Invention [Problem to be solved by the invention]

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

[0010] As a result of extensive investigations aimed at solving the above problems, the present inventors have 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 ratio of the Gurley values ​​before and after supporting the resin layer to 200% or more, the heat resistance of the separator can be improved and excellent charge-discharge cycle characteristics can be imparted to an electricity storage device. The present invention was completed based on this finding and through further investigations.

[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, 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): The weight of the resin layer is 0.4 g / m 2 More than 3.0g / m 2 or less, and the ratio of the Gurley value before and after the resin layer is supported is 200% or more. [ka] [In formula (1), R represents an alkyl group having 1 to 12 carbon atoms, or —CH2O(CR 1 R 2 R 3 ) R1 , 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 may differ between 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. [ka] [ka] [In formula (3), R 5 is a group having an ethylenically unsaturated group.] Item 2. The separator for an electricity storage device 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 resin, a cellulose resin, and a polyamide resin. Item 3. The separator for an electricity storage device according to Item 1 or 2, wherein the porous substrate has a film thickness of 3 μm or more and 40 μm or less. Item 4. A method for producing a separator for an electricity storage device according to any one of Items 1 to 3, comprising the step of applying a solution in which the polyether copolymer is dissolved in an aprotic organic 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 5. An electricity storage device comprising the electricity storage device separator according to any one of items 1 to 3. [Effects of the Invention]

[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. DETAILED DESCRIPTION OF THE INVENTION

[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. Separators for electricity storage devices> 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 0.4 g / m 2 More than 3.0g / m 2 The present invention is characterized in that the ratio of the Gurley values ​​before and after the support of the resin layer is 200% or more.

[0017] [ka]

[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 may differ between R 4is an alkyl group or an aryl group having 1 to 12 carbon atoms, and n is an integer of 0 to 12.

[0019] [ka]

[0020] [ka]

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

[0022] By virtue of these features, the separator of the present invention has excellent heat resistance and can impart excellent charge-discharge cycle 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 surface 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. The porous substrate and the ceramic layer are preferably adjacent to each other (surface-contacting). Furthermore, when a resin layer is provided on the porous substrate opposite the ceramic layer side, the resin layer and the porous substrate are preferably adjacent to each other (surface-contacting). Furthermore, when a resin layer is provided on the ceramic layer opposite the porous substrate side, the resin layer and the ceramic layer are preferably 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 ratio of the Gurley values ​​before and after the support of the resin layer on the separator is calculated by the following formula. Gurley value ratio (%) = {Gurley value of laminate after supporting resin layer / Gurley value of laminate before supporting resin layer} × 100

[0025] In the present invention, the Gurley value ratio is 200% or more, and from the viewpoint of more suitably exerting the effects of the present invention, it is preferably 300% or more, more preferably 350% or more, even more preferably 400% or more, and is preferably 10,000% or less, more preferably 8,000% or less, even more preferably 5,000% or less.

[0026] From the viewpoint of more suitably exerting the effects of the present invention, the membrane thickness (total thickness) of the separator of the present invention is preferably 3 μm or more, more preferably 5 μm or more, even more preferably 8 μm or more, and is preferably 40 μm or less, more preferably 25 μm or less, even more preferably 15 μm or less.

[0027] porous substrate The porous substrate is laminated with a ceramic layer to form a laminate. As described above, the porous substrate is preferably adjacent to (in contact with) the ceramic layer.

[0028] 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.

[0029] 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.

[0030] 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 have good electrical properties.

[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 ratio of the Gurley value is 200% or more. 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 300 seconds / 100 ml or more, and particularly preferably 400 seconds / 100 ml or more, and is also preferably 20,000 seconds / 100 ml or less, more preferably 16,000 seconds / 100 ml or less, and even more preferably 10,000 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 a 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 only, or two or more types.

[0034] In order to more effectively exert 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] The laminate of the porous substrate and the ceramic layer may be commercially available products, such as those manufactured by Celgard (registered trademark) by Celgard, those manufactured by UBE Corporation (registered trademark) by Seapore, and those manufactured by Toray Industries, Inc. (registered trademark).

[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] [ka]

[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 may differ between R 4is an alkyl group or an aryl group having 1 to 12 carbon atoms, and n is an integer of 0 to 12.], and The following general formula (2)

[0039] [ka]

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

[0041] [ka]

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

[0043] The compound of formula (1) can be obtained from a commercial product or easily synthesized by a general ether synthesis method from epihalohydrin and alcohol. Examples of commercially available compounds 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 commercially available 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] Compound (2) is a basic chemical product and is readily available commercially.

[0045] In the compound of formula (3), R 5 is a substituent containing an ethylenically unsaturated group. Examples of ethylenically unsaturated group-containing monomer components 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. Allyl glycidyl ether, glycidyl acrylate, and glycidyl methacrylate are preferred.

[0046] The polyether copolymer comprises a repeating unit derived from a monomer of formula (1): [ka] [wherein R is an alkyl group having 1 to 12 carbon atoms, or —CH2O(CR 1 R 2R 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 may differ between 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. (B): a repeating unit derived from a monomer of formula (2), and [ka] and (C): a repeating unit derived from a monomer of formula (3), [ka] [In the formula, R 5 is a substituent containing a group having an ethylenically unsaturated group. It consists of:

[0047] Here, the repeating units (A) and (C) may each be derived from two or more types of monomers.

[0048] In the polyether copolymer, the molar ratios of repeating units (A), (B), and (C) are (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%, and 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 increases and the oxyethylene chains crystallize, resulting in a significant deterioration in ionic conductivity. It is generally known that ionic conductivity can be improved by reducing the crystallinity of polyethylene oxide, and the polyether copolymer of the present invention is significantly superior in this respect.

[0049] 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 for 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.

[0050] 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.

[0051] Polyether copolymers can be synthesized as follows. Using a ring-opening polymerization catalyst, coordinated anionic initiators such as organoaluminum-based catalysts, organozinc-based catalysts, or organotin-phosphate ester condensate catalysts, or anionic initiators containing K+ as a counterion, such as potassium alkoxide, diphenylmethyl potassium, or potassium hydroxide, the monomers are reacted with stirring at a reaction temperature of 10 to 120°C in the presence or absence of a solvent to obtain polyether copolymers. From the viewpoints of the degree of polymerization and the properties of the resulting copolymers, coordinated anionic initiators are preferred, and organotin-phosphate ester condensate catalysts are particularly preferred due to their ease of handling.

[0052] 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.

[0053] In the separator of the present invention, the weight of the resin layer is 0.4 g / m 2 More than 3.0g / m 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 0.45 g / m 2 More preferably, 0.5 g / m 2 More preferably, 0.7 g / m 2 and preferably 2.5 g / m 2 or less, more preferably 2.2 g / m 2 or less, more preferably 2.0 g / m 2 The following is the result.

[0054] Method for manufacturing separator for power storage device 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 Gurley value ratio, the method in which a solution obtained by dissolving a polyether copolymer in water or an organic solvent is applied to a separator, and then dried to form a resin layer is preferred.

[0055] The organic solvent used in the present invention is not particularly limited, but it can dissolve the polyether copolymer and can be selected from aprotic organic solvents such as acetone, 2-butanone, toluene, xylene, THF, acetonitrile, methanol, isopropanol, N-methyl-2-pyrrolidone, etc. These solvents may be used alone or in combination of two or more.

[0056] The concentration of the polyether copolymer in the solution is not particularly limited, but is preferably 2% by mass to 40% by mass, more preferably 5% by mass to 40% by mass, and even more preferably 8% by mass to 30% by mass.

[0057] 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 water or an organic 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.

[0058] 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.

[0059] 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.

[0060] Examples of the thermal polymerization initiator include radical initiators such as organic peroxides and azo compounds.

[0061] Examples of organic peroxides that can be used include ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, and peroxyesters, which are typically used for crosslinking purposes. 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.

[0062] Azo compounds include azonitrile compounds, azoamide compounds, azoamidine compounds, and other compounds typically used for crosslinking. 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].

[0063] 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, relative to 100 parts by mass of the polyether polymer.

[0064] 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.

[0065] Specific examples of alkylphenone 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.

[0066] 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.

[0067] 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.

[0068] 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, relative to 100 parts by mass of the polyether polymer.

[0069] In the present invention, a crosslinking coagent may be used in combination with the photoreaction initiator. The crosslinking coagent is usually 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, triacrylformal, 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.

[0070] 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, relative to 100 parts by mass of the polyether copolymer.

[0071] 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.

[0072] 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 400 W for 0.1 to 30 minutes.

[0073] The crosslinking reaction may be carried out after the separator is coated with a solution obtained by dissolving a polyether copolymer containing a photoinitiator or a thermal polymerization initiator, or after the separator is immersed in the solution, and before, during, or after the separator is dried.

[0074] <2. Energy storage devices> The electricity storage device of the present invention uses 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).

[0075] positive electrode The positive electrode has a positive electrode composition containing a positive electrode active material and a binder on a current collector.

[0076] 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.

[0077] As the positive electrode active material, metal oxides, metal sulfides, or specific polymers can be used depending on the type of battery desired.

[0078] For example, in the case of a lithium battery that utilizes the dissolution and deposition 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.

[0079] In the case of a lithium-ion battery using doping and undoping of lithium ions, a lithium composite oxide represented by LixMO2 (where M represents one or more transition metals, x varies depending on the charge and discharge state of the battery, and is usually 0.05 or more and 1.10 or less), or a lithium composite phosphate represented by LixMPO4 (where M represents one or more transition metals, x varies depending on the charge and discharge state of the battery, and is usually 0.05 or more and 1.10 or less) can be used. As the transition metal M constituting this lithium composite oxide or lithium phosphate, Co, Ni, Mn, Al, Fe, etc. are preferable. Specific examples of such lithium composite oxides include LiCoO2, LiNiO2, LiNi y Co z Mn 1-y-z O2 (where 0 < y, z < 1), LiNi y Co z [[ID=IO]]Al[[ID=II]] 1-y-z O2 (where 0 < y, z < 1), LiMn2O4, LiFePO4, etc. can be mentioned. <00004-44> The lithium composite oxide can generate a high voltage and becomes a positive electrode active material excellent in energy density. A plurality of these positive electrode active materials may be used in combination as the positive electrode active material. Further, when forming the positive electrode active material using the above positive electrode active material, a known binder or the like can be added.

[0081] As the binder used in the positive electrode electrode composition, for example, one or more compounds selected from fluorine-based binders, acrylic rubbers, modified acrylic rubbers, styrene-butadiene rubbers, acrylic polymers, and vinyl polymers can be used. Further, since an acrylic polymer has oxidation resistance, sufficient adhesion in a small amount, and flexibility can be obtained for the electrode plate, it is preferable to use an acrylic polymer. Particularly, since it does not dissolve organic active materials, an aqueous binder that dissolves in water is preferable. These binders are added to the positive electrode current collector at a ratio of preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass as the positive electrode electrode composition.

[0082] In addition to the above, the 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 (e.g., acetylene black, ketjen black, carbon fiber, and graphite), conductive polymers, and metal powders, with conductive carbon being particularly preferred. Any solvent that can dissolve the positive electrode active material and binder can be used as the solvent, and water, N-methyl-2-pyrrolidone, and the like are preferred. 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.

[0083] negative electrode The negative electrode has a negative electrode composition containing a negative electrode active material and a binder on a current collector.

[0084] 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.

[0085] For example, in the case of a lithium battery that utilizes the dissolution and deposition of lithium, metallic lithium, a lithium alloy that can absorb and release lithium, or the like can be used as the negative electrode active material.

[0086] When a lithium-ion battery is fabricated 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, and other carbon fibers, pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke), glassy carbons, fired organic polymer compounds (phenolic resin, furan resin, etc., fired 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.

[0087] The binder used in the negative electrode composition may 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. 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 in water are particularly preferred because they do not dissolve organic active materials. These binders are added to the negative electrode current collector in an amount of preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, of the negative electrode composition.

[0088] In addition to the above, the negative electrode composition for the negative electrode may contain a conductive additive, a solvent, a thickener, etc. Examples of the conductive additive 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 that can dissolve the negative 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, or alkali metal salts thereof, and polyethylene oxide.

[0089] Electrode (positive and negative electrodes) manufacturing method The electrodes (positive and negative electrodes) for an electricity storage device of the present invention can be obtained by forming an electrode (positive and negative electrode) composition on a current collector. Specific examples include a method in which a sheet-shaped electricity storage device electrode composition is laminated on a current collector (kneading sheet molding method); a method in which a paste-like electricity storage device electrode composition is applied to a current collector and dried (wet molding method); and a method in which composite particles of an electricity storage device electrode composition are prepared, and sheet-molded and roll-pressed onto a current collector (dry molding method). Among these, the wet molding method and dry molding method are preferred, and the wet molding method is more preferred.

[0090] 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.

[0091] 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, a nitroso group, a carbonyl group, a carboxyl group, or a cyano group. X1, X2, and X3 may be the same or different.

[0092] The metal cations may be transition metal cations. Preferably, metal cations selected from Mn, Fe, Co, Ni, Cu, Zn, and Ag are used. Also, 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, in a lithium ion capacitor, a Li salt compound is preferably used as the electrolyte salt compound.

[0093] The Li salt compound may be a Li salt compound having a wide potential window, such as those commonly used in lithium ion capacitors. Examples include, but are not limited to, LiBF, LiPF, LiClO, LiCFSO, LiN(CFSO), LiN(CFS0), and LiN[CFSC(CFS0)]. These compounds may be used alone or in combination.

[0094] Furthermore, a room temperature molten salt can be used as the electrolyte salt or the electrolyte solution.

[0095] Room temperature molten salt refers to 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.

[0096] 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.

[0097] 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.

[0098] These room-temperature molten salts having cations may be used alone or in combination of two or more.

[0099] 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 it exceeds 3.0 mol / L, the solubility decreases and crystals may precipitate.

[0100] 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, propyl nitrile, anisole, acetate esters, and propionate esters. These organic solvents may be used alone or in combination.

[0101] Method for manufacturing an 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, with the separator interposed therebetween, and injecting an electrolyte solution. [Example]

[0102] 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.

[0103] [Synthesis Example (Production of a Polyether Copolymerization Catalyst)] 10 g of tributyltin chloride and 35 g of tributylphosphate were placed in a three-necked flask equipped with a stirrer, thermometer, and distillation apparatus, and heated at 250°C for 20 minutes with stirring under a nitrogen stream to remove the distillate and obtain a solid condensation product as the residue, which was used as a polymerization catalyst in the following polymerization examples.

[0104] The monomer equivalent composition of polyether copolymer is 1 It was determined by 1 H NMR spectroscopy. The molecular weight of the polyether copolymer was measured by gel permeation chromatography (GPC), and the weight-average molecular weight was calculated in terms of standard polystyrene. GPC measurements were performed at 60°C using Shimadzu RID-6A and Showa Denko Showdex KD-807, KD-806, KD-806M, and KD-803 columns, and DMF as the solvent.

[0105] [Polymerization Example 1] The inside of a 3 L glass four-neck flask was purged with nitrogen, and 1 g of the condensation product shown in the catalyst synthesis example as a polymerization catalyst and glycidyl ether compound (a) adjusted to a water content of 10 ppm or less were added: [ka] 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 atmospheric pressure for 24 hours and then at 45°C under reduced pressure for 10 hours, yielding 280 g of polymer. The weight-average molecular weight of the resulting polyether copolymer was 1 million, and the composition analysis (composed of monomers) showed 72 mol% ethylene oxide, 23 mol% compound (a), and 5 mol% allyl glycidyl ether.

[0106] [Example 1] Negative electrode 1 / separator 1 (with ceramic layer, resin layer with a basis weight of 0.5 g / m on the porous substrate surface) 2 ) / Positive electrode 1 <Preparation of negative electrode 1> A mixture of 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 was stirred for 1 hour using a stainless steel ball mill, and then coated onto a copper current collector using a bar coater with a 50 μm gap. The mixture was dried at 80°C in a vacuum for 12 hours or more and then roll-pressed to form a negative electrode sheet.

[0107] <Preparation of positive electrode 1> The positive electrode active material is 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 a positive electrode sheet.

[0108] <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.

[0109] <Preparation of Separator 1> A solution prepared by dissolving 20 parts by mass of polyether copolymer 1 obtained in Polymerization Example 1 in 180 parts by mass of acetonitrile on a ceramic (alumina)-coated polyethylene porous substrate (total thickness 9 μm) with a film thickness of 2 μm was applied to the surface (porous substrate surface) that was not ceramic-coated, with a weight of approximately 0.5 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.

[0110] 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.

[0111] [Example 2] Negative electrode 1 / separator 2 (with ceramic layer, resin layer with a basis weight of 1.0 g / m on the porous substrate surface) 2 ) / Positive electrode 1 <Preparation of separator 2> The coating weight of the polyether copolymer applied in the process of producing the separator 1 is 1.0 g / m 2 Separator 2 was produced in the same manner except for the above.

[0112] Finally, lithium ion battery 2 was fabricated in the same manner as lithium battery 1, except that separator 2 was used instead of the separator used in the fabrication process of lithium battery 1.

[0113] [Example 3] Negative electrode 1 / separator 3 (with ceramic layer, resin layer with a basis weight of 1.5 g / m on the porous substrate surface) 2 ) / Positive electrode 1 <Preparation of Separator 3> The weight of the polyether copolymer applied in the process of producing the separator 1 is 1.5 g / m 2 Separator 3 was produced in the same manner except for the above.

[0114] 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.

[0115] [Example 4] Negative electrode 1 / separator 4 (with ceramic layer, resin layer coating amount on ceramic layer surface: 1.5 g / m 2 ) / Positive electrode 1 <Preparation of Separator 4> Separator 4 was produced in the same manner as separator 1, except that the surface to be coated with the polyether copolymer was changed to the ceramic-coated surface.

[0116] 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.

[0117] [Example 5] Negative electrode 1 / separator 5 (with ceramic layer, resin layer with a basis weight of 1.5 g / m on the porous substrate surface) 2, resin layer is UV cross-linked) / Positive electrode 1 (Li-ion battery 5) <Preparation of electrolyte solution> A non-aqueous electrolyte solution was prepared by mixing 15 parts by mass of ethylene carbonate (EC), 15 parts by mass of propylene carbonate (PC), 50 parts by mass of diethyl carbonate, and 20 parts by mass of LiBF4 as an electrolyte salt.

[0118] <Preparation of Separator 5> A solution prepared by dissolving 20 parts by mass of polyether copolymer 1 obtained in Polymerization Example 1 and 0.4 parts by mass of a photoreaction initiator, benzophenone, in 180 parts by mass was applied to the non-ceramic coated surface (porous substrate surface) of a 2 μm thick ceramic (alumina) coated polyethylene porous substrate (total thickness 9 μm). The solution had a basis weight of 1.5 g / m after drying. 2 The coating was applied so that the coating was uniform, and the coating was dried in a normal pressure dryer at 60°C for 10 hours. Next, with the surface covered with a laminate film, the coating was irradiated with a high-pressure mercury lamp (30 mW / cm) manufactured by GS Yuasa Corporation. 2 The film was then exposed to UV light for 30 seconds to crosslink the film, producing a separator with a crosslinked polyether copolymer supported on the polyethylene porous membrane.

[0119] Finally, one negative electrode sheet and one positive electrode sheet were pressure-bonded via separator 5 to form a laminate. The laminate was then housed in an aluminum laminate, and a non-aqueous electrolyte solution was injected to produce lithium ion battery 5.

[0120] Comparative Example 1: Preparation of a lithium-ion battery 6 configured with a negative electrode 1 / separator 6 (with ceramic layer, without resin layer) / positive electrode 1 <Preparation of Separator 6> Separator 6 was produced in the same manner as separator 1, except that the polyether copolymer to be coated was not coated.

[0121] Finally, a lithium ion battery 6 was fabricated in the same manner as in the fabrication process of the lithium battery 1, except that the separator 4 was used instead.

[0122] Comparative Example 2: Negative electrode 1 / separator 7 (no ceramic layer, resin layer with a basis weight of 0.5 g / m on the porous substrate surface) 2 ) / Positive electrode 1 <Production of Separator 7> A porous polyethylene substrate (thickness: 9 μm) that was not ceramic-coated was used as the separator 7 in the process of producing the separator 1 .

[0123] Finally, a lithium ion battery 7 was fabricated in the same manner as in the fabrication process of the lithium battery 1, except that a separator 7 was used instead of the separator used in the fabrication process of the lithium battery 1.

[0124] Comparative Example 3: Negative electrode 1 / separator 8 (with ceramic layer, resin layer with a basis weight of 5.0 g / m on the porous substrate surface) 2 ) / Positive electrode 1 <Preparation of separator 8> The coating weight of the polyether copolymer applied in the process of producing the separator 1 is 5.0 g / m 2 Separator 8 was produced in the same manner except for the above.

[0125] Finally, lithium ion battery 8 was fabricated in the same manner as lithium battery 1, except that separator 7 was used instead of the separator used in the fabrication process of lithium battery 1.

[0126] [Comparative Example 4] Separator 9 (with ceramic layer, resin layer with a basis weight of 0.3 g / m on the porous substrate surface) 2 ) <Production of Separator 9> The weight of the polyether copolymer applied in the process of producing the separator 1 is 0.3 g / m 2 Separator 9 was produced in the same manner except for the above.

[0127] For the separators produced in Examples 1 to 5 and Comparative Examples 1 to 4, the Gurley values ​​of the porous substrates before and after the resin layer was supported were measured by the <Gurley value> method shown below. The measurement results and the ratios of the Gurley values ​​are shown in Table 1. In the table, the ratios (%) of the Gurley values ​​before and after the resin layer was supported can be calculated by (Gurley value of laminate after the resin layer was supported / Gurley value of laminate before the resin layer was supported)×100.

[0128] <Gurley value> The Gurley value (seconds / 100 mL) was measured in accordance with JIS P8117 (ISO 5636 / 5).

[0129] The charge-discharge cycle characteristics after overdischarge were measured by the following method for each of the lithium ion batteries produced in Examples 1 to 5 and Comparative Examples 1 to 3. The measurement results are shown in Table 1.

[0130] <Charge / discharge cycle characteristics> After one charge-discharge cycle test at 2.7-4.1 V at a 10-hour rate discharge (1 / 10C) of the theoretical capacity, the discharge capacity (mAh / g) was measured after 30 charge-discharge cycle tests at 2.7-4.1 V at a 5-hour rate discharge (1 / 5C) of the theoretical capacity.

[0131] <Charge-discharge cycle characteristics after overdischarge> After one charge-discharge cycle test from 2.0 to 4.2 V at a 10-hour rate discharge (1 / 10 C) of the theoretical capacity, the battery was charged to 4.2 V, discharged at 1 / 5 C to 2 V, then discharged at 1 / 16 C to 0 V, and left at the open circuit voltage for 1 hour for 20 cycles. A cycle test was then conducted under the same conditions as the charge-discharge cycle test described above, and the measured discharge capacities (mAh / g) were compared.

[0132] [Table 1]

[0133] From Table 1, it can be seen that the separators of the present invention in Examples 1 to 5 are excellent because they show little deterioration in discharge capacity before and after cycling, and are less likely to experience capacity reduction in cycle tests after overdischarge, regardless of whether the resin layer is crosslinked or not. Comparative Example 3 showed relatively good results in cycle characteristics and overdischarge characteristics, but a decrease in initial capacity was observed.

[0134] The heat resistance of each of the separators used in Examples 1 to 5 and Comparative Examples 1 to 4 was evaluated by the following method.

[0135] <Separator heat resistance test> The test sample was cut into a square with sides of 6 cm, and placed on a hot plate set to 130°C. The test sample separator was sandwiched between 1 mm thick SUS plates, and a glass plate was placed as a weight to apply uniform pressure. After leaving it to stand for 10 minutes, the shape of the sample was confirmed. Those that could be used normally were rated as ◯, and those that curled and could not be used were rated as ×. The evaluation results are shown in Table 2.

[0136] [Table 2]

[0137] From Table 2, it can be seen that the separators of the present invention in Examples 1 to 5 are excellent because they have high heat resistance and are less likely to curl due to small expansion and contraction of the separator. The separators in Comparative Examples 1, 2, and 4 have low heat resistance, and Comparative Example 3 had no problems in the heat resistance test, but as shown in Table 1, the results were inferior to Examples 1 to 5 in terms of initial capacity.

Claims

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; 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): The weight of the resin layer is 0.4 g / m 2 3.0g / m or more 2 or less, and a ratio of the Gurley value before and after the resin layer is supported is 200% or more. 【Chemical 1】 [In formula (1), R represents an alkyl group having 1 to 12 carbon atoms, or —CH 2 O (CR 1 R 2 R 3 ) R 1 , R 2 , R 3 is a hydrogen atom or -CH 2 O (CH 2 CH 2 O)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. 【Chemistry 2】 【Chemistry 3】 [In formula (3), R 5 is a group having an ethylenically unsaturated group.

2. 2. The separator for an electricity 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 a polyolefin resin, a polyester resin, a cellulose resin, and a polyamide resin.

3. The separator for an electricity storage device according to claim 1 or 2, wherein the porous substrate has a film thickness of 3 μm or more and 40 μm or less.

4. 3. The method for producing the separator for an electricity storage device according to claim 1, further comprising the step of applying a solution in which the polyether copolymer is dissolved in an aprotic organic 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.

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

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