Composition for functional layer of electrochemical element, functional layer for electrochemical element, laminate for electrochemical element, and electrochemical element

Abstract

The present invention provides a composition for a functional layer comprising a particulate polymer having a core-shell structure. Furthermore, in the particulate polymer, the coating rate of the shell part on the outer surface of the core part is 1-90%, the swelling degree of the polymer A of the core part in an electrolyte solution is 0.1-less than 5, the polymer A contains an unsaturated carboxylic acid ester monomer unit having 6 or less carbon atoms, and the volume average particle diameter is 0.1-10 [mu] m.

Description

Technical Field

[0001] The present invention relates to a composition for a functional layer of an electrochemical element, a functional layer for an electrochemical element, a laminate for an electrochemical element, and an electrochemical element. Background Art

[0002] Electrochemical elements such as lithium ion secondary batteries and electric double layer capacitors have characteristics of being small, light, having a high energy density, and being capable of repeated charge and discharge, and are used in a wide range of applications. Moreover, an electrochemical element generally includes constituent members such as a positive electrode, a negative electrode, and a spacer that separates the positive electrode and the negative electrode to prevent a short circuit between the positive electrode and the negative electrode.

[0003] Here, in an electrochemical element such as a lithium ion secondary battery, constituent members having a porous film layer for improving heat resistance and strength, an adhesive layer for bonding battery members to each other, etc. (hereinafter, these are collectively referred to as "functional layers") are used. Specifically, an electrode formed by further forming a functional layer on an electrode substrate in which an electrode composite material layer is provided on a current collector, and a spacer formed by forming a functional layer on a spacer substrate are used as battery members. Moreover, in recent years, for the purpose of further improving the performance of electrochemical elements such as lithium ion secondary batteries, further improvement of the functional layer has been studied.

[0004] For example, Patent Document 1 discloses a composition for a functional layer of a non-aqueous secondary battery, which contains particulate polymers having a core-shell structure in which the polymer in the core part and the polymer in the shell part have a prescribed glass transition temperature and electrolyte swelling degree, respectively. According to Patent Document 1, the functional layer formed using this composition for a functional layer of a non-aqueous secondary battery can not only provide high anti-adhesion properties to battery members, but also exhibit excellent adhesiveness both before and after immersion in an electrolyte.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent No. 6504168. Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] Here, for the functional layer, it is preferable that the adhesive strength is also high after immersion in an electrolyte. In addition, from the viewpoint of improving electrochemical characteristics, it is preferable that the resistance of the electrochemical element having the functional layer is low.

[0010] However, there is room for improvement in achieving both high adhesive strength after immersion in an electrolyte and low resistance of the electrochemical element having the functional layer, for the functional layer formed using the composition for a functional layer of the above-mentioned prior art.

[0011] Accordingly, an object of the present invention is to provide a composition for an electrochemical element functional layer that can form a functional layer for an electrochemical element capable of achieving both high adhesion strength after electrolyte impregnation and low resistance of the electrochemical element.

[0012] In addition, an object of the present invention is to provide a functional layer for an electrochemical element that can achieve both high adhesion strength after electrolyte impregnation and low resistance of the electrochemical element.

[0013] Furthermore, an object of the present invention is to provide a laminate for an electrochemical element that can reduce the resistance of the electrochemical element.

[0014] Furthermore, an object of the present invention is to provide an electrochemical element having low resistance and excellent electrochemical properties such as cycle characteristics.

[0015] Means for Solving the Problems

[0016] The present inventors conducted in-depth research for the purpose of solving the above problems. Then, the present inventors newly found that by using a composition containing a particulate polymer having a specified core-shell structure and properties, a functional layer having high adhesion strength even after impregnation in an electrolyte can be obtained, and the electrochemical element having this functional layer has low resistance and exhibits excellent electrochemical properties, thereby completing the present invention.

[0017] That is, an object of the present invention is to advantageously solve the above problems. [1] The present invention is a composition for an electrochemical element functional layer, which contains a particulate polymer having a core-shell structure including a core part and a shell part covering a part of the outer surface of the core part, the coverage rate of the shell part on the outer surface of the core part is 1% or more and 90% or less, the swelling degree of the polymer A in the core part in the electrolyte is 0.1 times or more and less than 5 times, it contains an unsaturated carboxylic acid ester monomer unit having 6 or less carbon atoms, and the volume average particle diameter D50 is 0.1 μm or more and 10 μm or less.

[0018] If, like this, a composition for an electrochemical functional layer containing a particulate polymer having the above-specified core-shell structure and properties is used, a functional layer for an electrochemical element capable of achieving both high adhesion strength after electrolyte impregnation and low resistance of the electrochemical element can be formed.

[0019] In addition, in the present invention, the "coverage rate of the shell part on the outer surface of the core part", the "swelling degree in the electrolyte", and the "volume average particle diameter" can be measured by the methods described in the examples of this specification.

[0020] In addition, in the present invention, the polymer "comprising monomer units" means "the polymer obtained using the monomer contains structural units derived from the monomer". Further, in the present invention, the "content ratio (mass%)" of each monomer unit (each repeating unit) contained in the polymer can be determined using 1 H-NMR, 13 C-NMR and other nuclear magnetic resonance (NMR) methods.

[0021] [2] In the composition for an electrochemical element functional layer of [1] above, it is preferable that the volume average particle diameter D50 of the above granular polymer is 1.0 μm or more and 12 μm or less.

[0022] If the volume average particle diameter D50 of the granular polymer is 1.0 μm or more in this way, the deformability of the granular polymer during hot pressing or the like when manufacturing an electrochemical element can be sufficiently ensured. Therefore, the adhesion strength of the functional layer after electrolyte impregnation can be further improved. Further, if the volume average particle diameter D50 of the granular polymer is 12 μm or less, a decrease in electrolyte impregnation property can be suppressed. Therefore, the resistance of the electrochemical element can be further reduced, and electrochemical properties such as cycle characteristics can be further improved.

[0023] Further, in the present invention, the volume average particle diameter D50 of the granular polymer can be determined using the method described in the examples of this specification.

[0024] [3] In the composition for an electrochemical element functional layer of [1] or [2] above, it is preferable that the polymer A in the core part contains crosslinkable monomer units in a proportion of 0.1 mass% or more and 75 mass% or less.

[0025] If the crosslinkable monomer units contained in the polymer A in the core part are 0.1 mass% or more in this way, adhesion between the electrochemical element members adjacent to each other across the functional layer can be suppressed during the manufacturing process of the electrochemical element (that is, the anti-blocking property of the functional layer can be improved). Further, if the proportion of the crosslinkable monomer units contained in the polymer A in the core part is 75 mass% or less, the adhesion strength of the functional layer after electrolyte impregnation can be further improved.

[0026] [4] In the composition for an electrochemical element functional layer according to any one of [1] to [3] above, it is preferable that the polymer B in the shell part contains crosslinkable monomer units in a proportion of 0.1 mass% or more and 75 mass% or less.

[0027] If the proportion of the crosslinkable monomer units contained in the polymer B in the shell part is 0.1 mass% or more in this way, the anti-blocking property can be further improved. Further, if the proportion of the crosslinkable monomer units contained in the polymer B in the shell part is 75 mass% or less, the adhesion strength of the functional layer after electrolyte impregnation can be further improved.

[0028] In addition, an object of the present invention is to advantageously solve the above problems, [5] The present invention relates to a functional layer for an electrochemical element, which is formed by using the composition for an electrochemical element functional layer according to any one of the above [1] to [4].

[0029] The functional layer for an electrochemical element formed by using the above composition for an electrochemical element functional layer can achieve good balance between high adhesive strength after electrolyte impregnation and low resistance of the electrochemical element having the functional layer for an electrochemical element.

[0030] In addition, an object of the present invention is to advantageously solve the above problems, [6] The present invention relates to a laminate for an electrochemical element, which has a substrate and a functional layer on the substrate, and the functional layer is the functional layer for an electrochemical element according to the above [5].

[0031] In this way, the laminate for an electrochemical element having the above functional layer for an electrochemical element can reduce the resistance of the electrochemical element.

[0032] Furthermore, an object of the present invention is to advantageously solve the above problems, [7] The present invention relates to an electrochemical element, which has the laminate for an electrochemical element according to the above [6].

[0033] In this way, the electrochemical element having the above laminate for an electrochemical element has excellent electrochemical characteristics such as cycle characteristics due to its low resistance.

[0034] Advantages of the Invention

[0035] According to the present invention, it is possible to provide a composition for an electrochemical element functional layer, which can form a functional layer for an electrochemical element that can achieve good balance between high adhesive strength after electrolyte impregnation and low resistance of the electrochemical element.

[0036] In addition, according to the present invention, it is possible to provide a functional layer for an electrochemical element that can achieve good balance between high adhesive strength after electrolyte impregnation and low resistance of the electrochemical element.

[0037] Furthermore, according to the present invention, it is possible to provide a laminate for an electrochemical element that can reduce the resistance of the electrochemical element.

[0038] Furthermore, according to the present invention, it is possible to provide an electrochemical element having low resistance and excellent electrochemical characteristics such as cycle characteristics. Detailed Description of Embodiments

[0039] Hereinafter, embodiments of the present invention will be described in detail.

[0040] Here, the composition for the functional layer of the electrochemical element of the present invention (hereinafter also simply referred to as "the composition for the functional layer") is used as a material when forming the functional layer for the electrochemical element of the present invention (hereinafter also simply referred to as "the functional layer"). In addition, the functional layer of the present invention is formed using the composition for the functional layer of the present invention. In addition, the laminate for the electrochemical element of the present invention (hereinafter also simply referred to as "the laminate") has the functional layer of the present invention. Further, the functional layer formed using the composition for the functional layer of the present invention exhibits an adhesive ability for bonding electrochemical element members to each other, and furthermore, can also function as a porous film layer for improving the heat resistance and strength of electrochemical element members such as spacers and electrodes. Moreover, the electrochemical element of the present invention has the laminate for the electrochemical element of the present invention.

[0041] (Composition for the functional layer of the electrochemical element)

[0042] The composition for the functional layer of the electrochemical element of the present invention is a slurry composition in which at least a granular polymer, optionally a binder material for the functional layer, non-conductive particles (excluding those belonging to the granular polymer and the binder material for the functional layer), a water-soluble polymer, and / or other components are contained, and water or the like is used as a dispersion medium.

[0043] <Granular polymer>

[0044] In the present invention, the granular polymer functions to make the functional layer formed using the composition for the functional layer exhibit excellent adhesiveness.

[0045] Here, the granular polymer has a core-shell structure including a core part and a shell part covering a part of the outer surface of the core part, and the coverage rate of the shell part on the outer surface of the core part is 1% or more and 90% or less. Moreover, the polymer A of the core part is characterized in that the swelling degree in the electrolyte is 0.1 times or more and less than 5 times, contains an unsaturated carboxylic acid ester monomer unit having 6 or less carbon atoms, and the volume average particle diameter D50 is 0.1 μm or more and 10 μm or less.

[0046] The composition for the functional layer of the present invention can make the functional layer formed using the composition for the functional layer well balance the high adhesive strength after electrolyte impregnation and the low resistance of the electrochemical element having the functional layer by containing the granular polymer having the above-described specified structure and properties.

[0047] Here, the reason for obtaining the above-described excellent effects by using the granular polymer is not yet clear, but it is speculated as follows.

[0048] That is, since the coverage rate of the shell part on the outer surface of the core part is 1% or more and 90% or less, when the functional layer formed from the composition for the functional layer is bonded to the electrochemical element member, the polymer of the shell part is interposed between the polymer of the core part and the electrochemical element member to form a gap. Further, it is presumed that since ions such as lithium ions that contribute to the electrochemical reaction pass through this gap, the resistance of the functional layer is reduced. In addition, it is presumed that due to the synergistic effects that the swelling degree of the polymer A of the core part in the electrolyte is 0.1 times or more and less than 5 times, it contains an unsaturated carboxylic acid ester monomer unit having 6 or less carbon atoms, and the volume average particle diameter is 0.1 μm or more and 10 μm or less, the polymer A of the core part also exhibits high adhesiveness to the electrochemical element member after being impregnated in the electrolyte.

[0049] For the above reasons, it is presumed that the functional layer using the composition for the functional layer of the present invention can achieve a good balance between the high adhesive strength after electrolyte impregnation and the low resistance of the electrochemical element having the functional layer.

[0050] [Structure of the particulate polymer]

[0051] The particulate polymer has a core-shell structure including a core part and a shell part that partially covers the outer surface of the core part.

[0052] In addition, even if the outer surface of the core part appears to be completely covered by the shell part in appearance, as long as there are pores connecting the inside and outside of the shell part, the shell part is a shell part that partially covers the outer surface of the core part. After bonding the electrochemical element members to each other with the functional layer formed from the composition for the functional layer, the particulate polymer may be particulate or may have any other shape.

[0053] -Coverage rate of the shell part on the outer surface of the core part-

[0054] In the present invention, the "coverage rate of the shell part on the outer surface of the core part" means the average ratio of the surface of the polymer A of the core part covered by the polymer B of the shell part.

[0055] Moreover, in the particulate polymer, the coverage rate of the shell part on the outer surface of the core part is 1% or more, preferably 10% or more, more preferably 15% or more, and 90% or less, preferably 80% or less, more preferably 60% or less. If the coverage rate of the shell part on the outer surface of the core part is above the above lower limit value, the anti-blocking property of the functional layer can be improved. In addition, if the coverage rate of the shell part on the outer surface of the core part is below the above upper limit value, the adhesive strength of the functional layer after electrolyte impregnation can be improved.

[0056] -Core part-

[0057] The core of the granular polymer is composed of Polymer A. As described in detail below, Polymer A has a swelling degree in the electrolyte within a specified range, contains an unsaturated carboxylic acid ester monomer unit having 6 or less carbon atoms, and has a volume average particle size D50 within a specified range.

[0058] = Swelling degree in the electrolyte =

[0059] The swelling degree of Polymer A in the electrolyte is 0.1 times or more, preferably 0.5 times or more, more preferably 0.8 times or more, less than 5 times, preferably 4.5 times or less, more preferably 4.0 times or less. If the swelling degree of Polymer A in the electrolyte is 0.1 times or more, the dissolution of the components in the electrolyte becomes less, so that the adhesion strength of the functional layer after electrolyte impregnation can be further improved. In addition, if the swelling degree of Polymer A in the electrolyte is less than 5 times, the resistance of the electrochemical element having the functional layer is further reduced, and the electrochemical characteristics such as the cycle characteristics can be further improved.

[0060] = Unsaturated carboxylic acid ester monomer unit =

[0061] The unsaturated carboxylic acid ester monomer unit contained in Polymer A has 6 or less carbon atoms, preferably 5 or less, preferably 1 or more, more preferably 3 or more. If the unsaturated carboxylic acid ester monomer unit contained in Polymer A has 6 or less carbon atoms, the polarity increase of the granular polymer can be suppressed. Therefore, the water absorption performance of the coating film of the functional layer composition during the formation of the functional layer can be reduced, and the anti-blocking property of the functional layer can be further improved. In addition, if the unsaturated carboxylic acid ester monomer unit contained in Polymer A has 1 or more carbon atoms, the residual monomers can be reduced, and the increase of low molecular weight components can be suppressed. Then, thereby, the resistance of the electrochemical element having the functional layer can be further reduced, and the electrical characteristics such as the cycle characteristics can be further improved.

[0062] Here, as the unsaturated carboxylic acid ester monomer capable of forming an unsaturated carboxylic acid ester monomer unit having 6 or less carbon atoms, for example, (meth)acrylate monomer units having 6 or less carbon atoms in the alkyl group can be mentioned. Specifically, for example, butyl acrylate such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate and tert-butyl acrylate, amyl acrylate, hexyl acrylate, heptyl acrylate and the like can be mentioned. In addition, in this specification, "(meth)acrylic acid" means acrylic acid or methacrylic acid.

[0063] The unsaturated carboxylic acid ester monomers having 6 or less carbon atoms can be used alone or in combination of two or more. Among them, from the viewpoint of further well balancing the improvement of the adhesion strength of the functional layer after electrolyte impregnation and the reduction of the resistance of the electrochemical element, n-butyl acrylate, hexyl acrylate and ethyl acrylate are preferred, and n-butyl acrylate is more preferred.

[0064] Moreover, when all the repeating units in Polymer A are taken as 100% by mass, the proportion of the unsaturated carboxylic acid ester monomer units having 6 or less carbon atoms in Polymer A in the core part is preferably 3% by mass or more, more preferably 5% by mass or more, still more preferably 7% by mass or more, preferably 99% by mass or less, more preferably 95% by mass or less, and still more preferably 90% by mass or less. If the proportion of the unsaturated carboxylic acid ester monomer units having 6 or less carbon atoms in Polymer A in the core part is within the above range, the adhesion strength of the functional layer after electrolyte impregnation can be further improved.

[0065] In addition to the above-mentioned unsaturated carboxylic acid ester monomer units having 6 or less carbon atoms, Polymer A can optionally contain monomer units other than the unsaturated carboxylic acid ester monomer units having 6 or less carbon atoms, such as crosslinkable monomer units, aromatic vinyl monomer units, acidic group-containing monomer units, amide group-containing monomer units (hereinafter these monomer units are also referred to as "other monomer units").

[0066] = Crosslinkable monomer units =

[0067] The crosslinkable monomer unit is a repeating unit derived from a crosslinkable monomer. The crosslinkable monomer is a monomer that can form a crosslinked structure during or after polymerization by heating or irradiation with energy rays. By including crosslinkable monomer units, it is easy to control the swelling degree of Polymer A in the core part in the electrolyte.

[0068] Examples of the crosslinkable monomer capable of forming crosslinkable monomer units include a crosslinkable monomer having a thermally crosslinkable crosslinkable group and having one ethylenic double bond in each molecule; a crosslinkable monomer having two or more ethylenic double bonds in each molecule.

[0069] Examples of the thermally crosslinkable crosslinkable group include an epoxy group, an N-hydroxymethylamide group, an oxetanyl group, an oxazolinyl group, and combinations thereof. Among these, from the viewpoints of easy crosslinking and easy adjustment of the crosslinking density, the epoxy group is more preferred.

[0070] Moreover, as examples of crosslinkable monomers having an epoxy group as a thermally crosslinkable crosslinking group and having an ethylenic double bond, there may be mentioned unsaturated glycidyl ethers such as vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, and o-allylphenyl glycidyl ether; monoxides of dienes or polyenes such as butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, and 1,2-epoxy-5,9-cyclododecadiene; alkenyl epoxides such as 3,4-epoxy-1-butene, 1,2-epoxy-5-hexene, and 1,2-epoxy-9-decene; and glycidyl esters of unsaturated carboxylic acids such as glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl 4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl 4-methyl-3-pentenoate, glycidyl 3-cyclohexenecarboxylate, and glycidyl 4-methyl-3-cyclohexenecarboxylate.

[0071] In addition, as examples of crosslinkable monomers having an N-hydroxymethylamide group as a thermally crosslinkable crosslinking group and having an ethylenic double bond, there may be mentioned (meth)acrylamides having a hydroxymethyl group such as N-hydroxymethyl(meth)acrylamide.

[0072] Furthermore, as examples of crosslinkable monomers having an oxetanyl group as a thermally crosslinkable crosslinking group and having an ethylenic double bond, there may be mentioned 3-((meth)acryloxymethyl)oxetane, 3-((meth)acryloxymethyl)-2-trifluoromethyloxetane, 3-((meth)acryloxymethyl)-2-phenyloxetane, 2-((meth)acryloxymethyl)oxetane, and 2-((meth)acryloxymethyl)-4-trifluoromethyloxetane.

[0073] In addition, as examples of crosslinkable monomers having an oxazolinyl group as a thermally crosslinkable crosslinking group and having an ethylenic double bond, there may be mentioned 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline.

[0074] Furthermore, examples of the crosslinkable monomer having two or more ethylenic double bonds in each molecule include butadiene, isoprene, allyl (meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipropylene glycol diallyl ether, polyethylene glycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyl ether, tetraallyloxyethane, trimethylolpropane-diallyl ether, allyl or vinyl ethers of polyfunctional alcohols other than those described above, triallylamine, methylenebisacrylamide, and divinylbenzene.

[0075] In addition, in the present invention, "(meth)acrylate" means acrylate and / or methacrylate.

[0076] The crosslinkable monomer may be used alone or in combination of two or more. Among these, a crosslinkable monomer having two or more ethylenic double bonds in each molecule is preferred, ethylene glycol dimethacrylate and allyl methacrylate are more preferred, and ethylene glycol dimethacrylate is further preferred. The crosslinkable monomer may be used alone or in combination of two or more in any ratio. Among them, a crosslinkable monomer having two or more ethylenic double bonds in each molecule is preferred, and ethylene glycol dimethacrylate is more preferred.

[0077] Moreover, when all the repeating units in the polymer A of the core part are taken as 100% by mass, the proportion of the crosslinkable monomer unit in the polymer A of the core part is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, further preferably 0.3% by mass or more, preferably 75% by mass or less, more preferably 70% by mass or less, and further preferably 65% by mass or less. If the proportion of the crosslinkable monomer unit in the polymer A of the core part is at least the above lower limit value, the anti-blocking property of the functional layer can be further improved. In addition, if the proportion of the crosslinkable monomer unit in the polymer A of the core part is at most the above upper limit value, the adhesion strength of the functional layer after electrolyte impregnation can be further improved.

[0078] = Aromatic vinyl monomer unit =

[0079] The aromatic vinyl monomer unit is a repeating unit derived from an aromatic vinyl monomer. By including the aromatic vinyl monomer unit, it is possible to easily control the swelling degree of the polymer A in the core part in the electrolyte and further improve the adhesion strength of the functional layer. Here, the aromatic vinyl monomer capable of forming the aromatic vinyl monomer unit is not particularly limited, and examples thereof include styrene, α-methylstyrene, styrenesulfonic acid, butoxystyrene, vinylnaphthalene, etc. Among them, styrene is preferred. The aromatic vinyl monomer may be used alone or in combination of two or more.

[0080] Moreover, when all the repeating units in the polymer A in the core part are taken as 100% by mass, the proportion of the aromatic vinyl monomer units in the polymer A in the core part is preferably 0% by mass or more, more preferably 3% by mass or more, further preferably 5% by mass or more, preferably 98% by mass or less, more preferably 95% by mass or less, and further preferably 90% by mass or less. If the proportion of the aromatic vinyl monomer units in the polymer A in the core part is within the above range, the adhesion strength of the functional layer after electrolyte impregnation and the reduction of the resistance of the electrochemical element can be better balanced.

[0081] = Acidic group-containing monomer unit =

[0082] The acidic group-containing monomer unit is a repeating unit derived from an acidic group-containing monomer. Examples of the acidic group-containing monomer that can form the acidic group-containing monomer unit include monomers having a carboxyl group, monomers having a sulfonic acid group, and monomers having a phosphoric acid group.

[0083] Examples of the carboxyl group-containing monomer include monocarboxylic acids and their derivatives, dicarboxylic acids and their acid anhydrides, and their derivatives.

[0084] Examples of the monocarboxylic acid include acrylic acid, methacrylic acid, crotonic acid, etc.

[0085] Examples of the monocarboxylic acid derivative include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, etc.

[0086] Examples of the dicarboxylic acid include maleic acid, fumaric acid, itaconic acid, etc.

[0087] Examples of the dicarboxylic acid derivative include maleic acid monoesters such as methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloro maleic acid, dichloro maleic acid, fluoro maleic acid, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, fluoroalkyl maleate, etc.

[0088] Examples of the acid anhydride of the dicarboxylic acid include maleic anhydride, acrylic anhydride, methyl maleic anhydride, dimethyl maleic anhydride, etc.

[0089] In addition, as the carboxyl group-containing monomer, acid anhydrides that generate carboxyl groups by hydrolysis can also be used.

[0090] In addition, examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth)allyl sulfonic acid, 3-allyloxy-2-hydroxypropyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, etc.

[0091] In addition, in the present specification, "(meth)allyl" means allyl and / or methallyl.

[0092] Furthermore, examples of the monomer containing a phosphate group include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, ethyl-(meth)acryloyloxyethyl phosphate, etc. Among these, acrylic acid is preferred.

[0093] In addition, in the present invention, "(meth)acryloyl" means acryloyl and / or methacryloyl. The monomer containing an acidic group can be used alone or in combination of two or more.

[0094] Moreover, when all the repeating units in the polymer A of the core part are taken as 100% by mass, the proportion of the monomer unit containing an acidic group in the polymer A of the core part is preferably 0% by mass or more, more preferably 0.3% by mass or more, further preferably 0.5% by mass or more, preferably 20% by mass or less, more preferably 12% by mass or less, and further preferably 8% by mass or less. If the proportion of the monomer unit containing an acidic group in the polymer A of the core part is within the above range, the adhesion strength of the functional layer after electrolyte impregnation and the low resistance of the electrochemical element can be better balanced.

[0095] =Amide group-containing monomer unit=

[0096] The amide group-containing monomer unit is a repeating unit derived from an amide group-containing monomer. Examples of the amide group-containing monomer capable of forming an amide group-containing monomer unit include methacrylamide, acrylamide, dimethylacrylamide, diethylacrylamide, diacetoneacrylamide, hydroxyethylacrylamide, hydroxymethylacrylamide, hydroxypropylacrylamide, hydroxybutylacrylamide, etc. Among these, acrylamide and hydroxymethylacrylamide are preferred. The amide group-containing monomer can be used alone or in combination of two or more.

[0097] Moreover, when all the repeating units in the polymer A of the core part are taken as 100% by mass, the proportion of the amide group-containing monomer unit in the polymer A of the core part is preferably 0% by mass or more, more preferably 0.3% by mass or more, further preferably 0.5% by mass or more, preferably 20% by mass or less, more preferably 12% by mass or less, and further preferably 8% by mass or less. If the proportion of the amide group-containing monomer unit in the polymer A of the core part is within the above range, the adhesion strength of the functional layer after electrolyte impregnation and the low resistance of the electrochemical element can be better balanced.

[0098] =Volume average particle diameter D50 of the polymer A of the core part=

[0099] The volume-average particle diameter D50 of the polymer A in the core part is 0.1 μm or more, preferably 0.10 μm or more, more preferably 0.5 μm or more, further preferably 1 μm or more, still more preferably 3.5 μm or more, even more preferably 4.0 μm or more, and is 10 μm or less, preferably 9.5 μm or less, more preferably 9 μm or less. If the volume-average particle diameter D50 of the polymer A in the core part is at or above the above lower limit value, the deformability of the particulate polymer during hot pressing or the like when manufacturing an electrochemical element can be ensured. Therefore, the adhesion strength of the functional layer after electrolyte impregnation can be improved. In addition, an increase in the resistance of the electrochemical element can be suppressed, and electrochemical characteristics such as cycle characteristics can be improved. Further, if the volume-average particle diameter D50 of the polymer A in the core part is at or below the above upper limit value, the impregnation property of the electrolyte becomes high. Therefore, the resistance of the electrochemical element can be reduced, and electrochemical characteristics such as cycle characteristics can be improved.

[0100] -Shell part-

[0101] The shell part of the particulate polymer is composed of polymer B. Here, as long as the polymer B in the shell part can cover the outer surface of the core part with a coverage rate of the shell part on the outer surface of the core part being 1% or more and 90% or less, it can contain any monomer units. Examples of the monomer units that can be contained in the polymer B of the shell part include crosslinkable monomer units, aromatic vinyl monomer units, unsaturated carboxylic acid ester monomer units, acidic group-containing monomer units, cationic group-containing monomer units, and the like. Among them, from the viewpoint of further reducing the resistance of the electrochemical element, it is preferred that the polymer B contains crosslinkable monomer units.

[0102] In addition, the polymer B of the shell part is usually a polymer having a different composition from the polymer A of the above core part.

[0103] =Crosslinkable monomer units=

[0104] As the crosslinkable monomer of the crosslinkable monomer units of the polymer B capable of forming the shell part, the same crosslinkable monomers as those described in the item of "Core part" can be cited. The crosslinkable monomers can be used alone or in combination of two or more.

[0105] Moreover, when taking all the repeating units in the polymer B of the shell part as 100% by mass, the proportion of the crosslinkable monomer units in the polymer B of the shell part is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, further preferably 0.3% by mass or more, preferably 75% by mass or less, more preferably 70% by mass or less, further preferably 65% by mass or less. If the proportion of the crosslinkable monomer units in the polymer B of the shell part is at or above the above lower limit value, the anti-blocking property of the functional layer can be further improved. In addition, if the proportion of the crosslinkable monomer units in the polymer B of the shell part is at or below the above upper limit value, the resistance of the electrochemical element can be further reduced.

[0106] =Aromatic vinyl monomer unit=

[0107] As the aromatic vinyl monomer for the aromatic vinyl monomer unit of the polymer B capable of forming the shell part, the same aromatic vinyl monomers as those described in the item of "core part" can be cited. The aromatic vinyl monomers can be used alone or in combination of two or more.

[0108] Moreover, when taking all the repeating units in the polymer B of the shell part as 100% by mass, the proportion of the aromatic vinyl monomer unit in the polymer B of the shell part is preferably 1% by mass or more, more preferably 3% by mass or more, further preferably 8% by mass or more, preferably 99% by mass or less, more preferably 98% by mass or less, and further preferably 95% by mass or less.

[0109] =Unsaturated carboxylic acid ester monomer unit=

[0110] As the unsaturated carboxylic acid ester monomer for the unsaturated carboxylic acid ester monomer unit of the polymer B capable of forming the shell part, the same unsaturated carboxylic acid ester monomers as those described in the item of "core part" with 6 or less carbon atoms can be cited. The unsaturated carboxylic acid ester monomers can be used alone or in combination of two or more.

[0111] Moreover, when taking all the repeating units in the polymer B of the shell part as 100% by mass, the proportion of the unsaturated carboxylic acid ester monomer unit in the polymer B of the shell part is preferably 1% by mass or more, more preferably 3% by mass or more, further preferably 8% by mass or more, preferably 99% by mass or less, more preferably 98% by mass or less, and further preferably 95% by mass or less.

[0112] =Acid group-containing monomer unit=

[0113] As the acid group-containing monomer for the acid group-containing monomer unit of the polymer B capable of forming the shell part, the same acid group-containing monomers as those described in the item of "core part" can be cited. The acid group-containing monomers can be used alone or in combination of two or more.

[0114] Moreover, when taking all the repeating units in the polymer B of the shell part as 100% by mass, the proportion of the acid group-containing monomer unit in the polymer B of the shell part is preferably 0% by mass or more, more preferably 0.3% by mass or more, further preferably 0.5% by mass or more, preferably 20% by mass or less, more preferably 12% by mass or less, and further preferably 8% by mass or less.

[0115] =Cationic group-containing monomer unit=

[0116] The cationic group-containing monomer unit is a repeating unit derived from a cationic group-containing monomer. Examples of the cationic group-containing monomer capable of forming a cationic group-containing monomer unit include 3-(methacrylamido)propyltrimethylammonium methyl sulfate, dimethylaminopropylmethacrylamide, dimethylaminopropylacrylamide, dimethylaminopropyl methacrylate, dimethylaminopropyl acrylate, dimethylaminopropylacrylamide methyl chloride quaternary ammonium salt, dimethylaminoethyl acrylate benzyl chloride quaternary ammonium salt, and the like.

[0117] Moreover, when all the repeating units in the polymer B of the shell part are taken as 100% by mass, the proportion of the cationic group-containing monomer unit in the polymer B of the shell part can be 0% by mass, that is, it does not contain. When the polymer B contains a cationic group-containing monomer unit, it is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, preferably 60% by mass or less, more preferably 48% by mass or less, and further preferably 45% by mass or less. If the proportion of the cationic group-containing monomer unit in the polymer B of the shell part is within the above range, when manufacturing the granular polymer, the polymer B is likely to aggregate on the surface of the polymer A, and thus, the granular polymer can be easily manufactured.

[0118] - Volume average particle diameter D50 of the granular polymer

[0119] The granular polymer having the above-mentioned core part and shell part preferably has a volume average particle diameter D50 of 1.0 μm or more, more preferably 2.0 μm or more, further preferably 2.5 μm or more, particularly preferably 4.3 μm or more, preferably 12 μm or less, more preferably 11 μm or less, and further preferably 10 μm or less. If the volume average particle diameter D50 of the granular polymer is above the above lower limit value, the deformability of the granular polymer during hot pressing or the like when manufacturing the electrochemical element can be further ensured, and thus the adhesion strength of the functional layer after electrolyte impregnation can be further improved. In addition, if the volume average particle diameter D50 of the granular polymer is below the above upper limit value, the decrease in electrolyte impregnation property can be suppressed, and thus the resistance of the electrochemical element can be further reduced, and the electrochemical properties such as the cycle characteristics can be further improved.

[0120] In addition, the volume average particle diameter D50 of the granular polymer can be adjusted by, for example, changing the types and proportions of the monomers used in the manufacture of the granular polymer and / or changing the polymerization conditions of the granular polymer.

[0121] In addition, in the present invention, the "volume average particle diameter D50 of the granular polymer" can be measured by the method described in the examples of this specification.

[0122] - Ratio of the polymer A in the core part to the polymer B in the shell part in the granular polymer

[0123] The ratio of polymer A in the core part to polymer B in the shell part in the granular polymer is preferably 99:1 to 20:80 in terms of mass ratio (polymer A in the core part: polymer B in the shell part). If the ratio of polymer A in the core part to polymer B in the shell part in the granular polymer is within the above range, the balance between the improvement of the adhesion strength of the functional layer after electrolyte impregnation and the reduction of the resistance of the electrochemical element can be made better.

[0124] <<Manufacturing method of granular polymer>>

[0125] The manufacturing method of the granular polymer having the above core-shell structure is not particularly limited, and polymerization methods or coagulation methods can be mentioned. As polymerization methods, emulsion polymerization, suspension polymerization, etc. can be mentioned. As the coagulation method, from the aspect of being able to easily manufacture the desired granular polymer, the following method can be mentioned: after separately preparing polymer A in the core part and polymer B in the shell part, polymer B is coagulated on the surface of polymer A, thereby manufacturing the granular polymer. An example of manufacturing a granular polymer having a core-shell structure by the above coagulation method is shown below.

[0126] First, a monomer for forming polymer A in the core part, a polymerization initiator, and an optionally used dispersion stabilizer and / or molecular weight regulator are mixed to prepare monomer composition A. Then, the prepared monomer composition A is subjected to a polymerization reaction in an aqueous solvent such as water to obtain an aqueous dispersion containing polymer A. At this time, the polymerization temperature can be, for example, 60°C or higher and 100°C or lower.

[0127] In addition, a monomer for forming polymer B in the shell part, a polymerization initiator, and an optionally used dispersion stabilizer are mixed to prepare monomer composition B. Then, the monomer composition B for the shell part is subjected to a polymerization reaction in an aqueous solvent such as water to obtain an aqueous dispersion containing polymer B. At this time, the polymerization temperature can be, for example, 60°C or higher and 100°C or lower.

[0128] In addition, as the above polymerization initiator, ammonium persulfate can be used, for example. In addition, as the above molecular weight regulator, thiols such as tert-dodecyl mercaptan, n-dodecyl mercaptan, octyl mercaptan, etc.; halogenated hydrocarbons such as carbon tetrachloride, dichloromethane, dibromomethane, etc.; α-methylstyrene dimer; sulfur-containing compounds such as tetraethyl thiuram disulfide, dipentamethylene thiuram disulfide, diisopropyl xanthogen disulfide, etc. can be mentioned. These can be used alone or in combination of two or more. Among them, thiols are preferred, and tert-dodecyl mercaptan is more preferred. In addition, as the above dispersion stabilizer, sodium dodecylbenzenesulfonate can be used, for example.

[0129] In addition, the proportion of each monomer in each of monomer composition A and monomer composition B is generally the same as the proportion of each monomer unit contained in polymer A in the core part and polymer B in the shell part of the granular polymer.

[0130] Next, after adding a coagulant to the aqueous dispersion of polymer A, the aqueous dispersion of polymer B is further added to react polymer A with polymer B. Then, an additional reagent such as ethylenediaminetetraacetic acid is added. At this time, the reaction temperature is preferably 20 °C or higher, more preferably 30 °C or higher, still more preferably 40 °C or higher, preferably 100 °C or lower, more preferably 90 °C or lower, still more preferably 80 °C or lower. If the reaction temperature is within the above range, it is possible to more easily produce the desired granular polymer. In addition, if the reaction temperature is 40 °C or higher, polymer B is more likely to coagulate on the surface of polymer A, and thus, it is possible to more easily produce the desired granular polymer.

[0131] Here, as the above-mentioned coagulant, magnesium sulfate can be preferably used, for example.

[0132] In addition, in the present invention, since the polymer A in the core part of the granular polymer contains an unsaturated carboxylate monomer unit, it generally exhibits anionic properties. Therefore, when the polymer B in the shell part contains a cationic group-containing monomer unit, it is possible to make polymer B coagulate well on the surface of polymer A without using the above-mentioned coagulant.

[0133] <Binder material for functional layer>

[0134] As the binder material for the functional layer that can be optionally used, known binder materials that are water-insoluble and can be dispersed in a dispersion medium such as water can be cited, such as thermoplastic elastomers. Moreover, as the thermoplastic elastomer, conjugated diene-based polymers and acrylic polymers are preferred, and acrylic polymers are more preferred.

[0135] Herein, the conjugated diene polymer refers to a polymer containing conjugated diene monomer units. As specific examples of the conjugated diene polymer, polymers containing aromatic vinyl monomer units and aliphatic conjugated diene monomer units such as styrene-butadiene copolymer (SBR), acrylic rubber (NBR) (a polymer containing acrylonitrile units and butadiene units), etc. can be cited. In addition, the acrylic polymer refers to a polymer containing (meth)acrylate monomer units. Herein, as the (meth)acrylate monomer capable of forming the (meth)acrylate monomer unit, the same (meth)acrylate monomer as that used for preparing the particulate polymer can be used. In addition, these binder materials for the functional layer can be used alone or in combination of two or more. However, when using the binder material for the functional layer, the polymer as the binder material for the functional layer is a polymer different from the above-described particulate polymer having a core-shell structure composed of a specified polymer.

[0136] Moreover, the volume average particle diameter D50 of the binder material for the functional layer is preferably 0.1 μm or more and 0.5 μm or less. If the volume average particle diameter D50 of the binder material for the functional layer is 0.1 μm or more, the dispersibility of the binder material for the functional layer can be improved. In addition, if the volume average particle diameter D50 of the binder material for the functional layer is 0.5 μm or less, the adhesiveness of the binder material for the functional layer can be improved.

[0137] The volume average particle diameter D50 of the binder material for the functional layer can be measured by the method described in the examples.

[0138] The amount of the binder material for the functional layer in the functional layer composition is not particularly limited, and is preferably 1 part by mass or more, more preferably 2 parts by mass or more, further preferably 5 parts by mass or more, preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and further preferably 40 parts by mass or less, relative to 100 parts by mass of the particulate polymer. If the amount of the binder material for the functional layer in the functional layer composition is the above lower limit value or more, the adhesiveness of the binder material for the functional layer can be further improved, thereby sufficiently preventing the particulate polymer from falling off the functional layer before heating or before immersion in the electrolyte. In addition, if the amount of the binder material for the functional layer in the functional layer composition is the above upper limit value or less, the decrease in the ionic conductivity of the functional layer and the decrease in the electrochemical characteristics of the electrochemical element can be suppressed.

[0139] As a manufacturing method of the binder material for the functional layer, solution polymerization method, suspension polymerization method, emulsion polymerization method, etc. can be cited. Among them, since polymerization can be carried out in water and the aqueous dispersion containing the particulate binder material for the functional layer can be directly and appropriately used as the material for the functional layer composition, emulsion polymerization method and suspension polymerization method are preferred.

[0140] <<Non-conductive Particles>>

[0141] As non-conductive particles that can be used arbitrarily, there is no particular limitation, and known non-conductive particles that can be used in electrochemical elements can be cited.

[0142] Specifically, as non-conductive particles, both inorganic fine particles and organic fine particles other than the above-mentioned particulate polymers and binder materials for functional layers can be used, but inorganic fine particles are usually used. Among them, as the material of the non-conductive particles, a material that stably exists and is electrochemically stable in the use environment of the electrochemical element is preferred. From this point of view, if preferred examples of the material of the non-conductive particles are cited, they can be: oxide particles such as alumina, hydrated alumina (boehmite), silica, magnesia (magnesite), calcium oxide, titania, BaTiO3, ZrO, alumina-silica composite oxide; nitride particles such as aluminum nitride and boron nitride; covalent crystal particles such as silicon and diamond; sparingly soluble ionic crystal particles such as barium sulfate, calcium fluoride, and barium fluoride; clay fine particles such as talc and montmorillonite. In addition, element substitution, surface treatment, solid solution formation, etc. can be performed on these particles as needed.

[0143] In addition, the above non-conductive particles can be used alone or in combination of two or more.

[0144] The amount of the non-conductive particles in the composition for the functional layer is not particularly limited, and is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, further preferably 50 parts by mass or more, preferably 99 parts by mass or less, more preferably 98 parts by mass or less, and further preferably 95 parts by mass or less relative to 100 parts by mass of the particulate polymer.

[0145] <<Water-soluble Polymer>>

[0146] The arbitrarily used water-soluble polymer is a component that imparts viscosity to the composition for the functional layer. In addition, generally, the water-soluble polymer has adhesiveness and electrolyte resistance, and therefore, it can play a role in assisting the adhesion of each component in the functional layer and the components of the electrochemical element to each other in the electrochemical element.

[0147] Here, in the present invention, a substance being "water-soluble" means that when 0.5 g of the substance is dissolved in 100 g of water at 25°C, the insoluble component is less than 1.0 mass%. In addition, for a substance whose solubility changes according to the pH of water, if it meets the above "water-soluble" at at least any one pH, then the substance is "water-soluble".

[0148] Moreover, as the water-soluble polymer, natural polymers, semi-synthetic polymers, and synthetic polymers can be cited, for example.

[0149] - Natural polymers -

[0150] As natural polymers, for example, polysaccharides and proteins derived from plants or animals, as well as their fermentation products using microorganisms, etc., and their heat treatment products can be cited.

[0151] Moreover, these natural polymers can be classified into plant-based natural polymers, animal-based natural polymers, and natural polymers produced by microorganisms, etc.

[0152] As plant-based natural polymers, for example, gum arabic, tragacanth gum, galactan, guar gum, carob gum, karaya gum, carrageenan, pectin, olive (Kannnan), quince seeds (quince), alginate (brown algae extract), starch (from rice, corn, potato, wheat, etc.), glycyrrhizin can be cited. As animal-based natural polymers, collagen, casein, albumin, gelatin can be cited. As natural polymers produced by microorganisms, xanthan gum, dextran, succinoglycan, pullulan can be cited.

[0153] - Semi-synthetic polymers -

[0154] As semi-synthetic polymers, cellulose-based semi-synthetic polymers can be cited. Moreover, cellulose-based semi-synthetic polymers can be classified into non-ionic cellulose-based semi-synthetic polymers, anionic cellulose-based semi-synthetic polymers, and cationic cellulose-based semi-synthetic polymers.

[0155] As non-ionic cellulose-based semi-synthetic polymers, for example: alkyl celluloses such as methyl cellulose, methyl ethyl cellulose, ethyl cellulose, microcrystalline cellulose; hydroxyalkyl celluloses such as hydroxyethyl cellulose, hydroxybutyl methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose stearoxy ether, carboxymethyl hydroxyethyl cellulose, alkyl hydroxyethyl cellulose, nonylphenol polyether-based hydroxyethyl cellulose.

[0156] As anionic cellulose-based semi-synthetic polymers, the substituted products obtained by substituting various derivative groups for the above non-ionic cellulose-based semi-synthetic polymers and their salts (sodium salts, ammonium salts, etc.) can be cited. Specifically, sodium cellulose sulfate, methyl cellulose, methyl ethyl cellulose, ethyl cellulose, carboxymethyl cellulose (CMC) and their salts can be cited.

[0157] As cationic cellulose-based semi-synthetic polymers, for example: low-nitrogen hydroxyethyl cellulose dimethyldiallylammonium chloride (polyquaternium-4), O-[2-hydroxy-3-(trimethylammonium)propyl] hydroxyethyl cellulose chloride (polyquaternium-10), O-[2-hydroxy-3-(lauryldimethylammonium)propyl] hydroxyethyl cellulose chloride (polyquaternium-24).

[0158] - Synthetic polymers -

[0159] Examples of synthetic polymers include polyacrylates such as sodium polyacrylate, polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, copolymers of acrylic acid or acrylate and vinyl alcohol, complete or partial saponified products of copolymers of maleic anhydride, maleic acid or fumaric acid and vinyl acetate, modified polyvinyl alcohol, modified polyacrylic acid, polyethylene glycol, polycarboxylic acid, ethylene-vinyl alcohol copolymer, vinyl acetate polymer, acrylamide polymer into which a carboxyl group has been introduced, and the like.

[0160] The amount of the water-soluble polymer in the composition for the functional layer is not particularly limited. Relative to 100 parts by mass of the granular polymer, it is preferably 0.01 part by mass or more, more preferably 0.05 part by mass or more, further preferably 0.1 part by mass or more, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 5 parts by mass or less.

[0161] <Other components>

[0162] Other components that can be arbitrarily used are not particularly limited as long as they do not affect the electrochemical reaction, and known components can be used. Examples of other components include known additives such as viscosity modifiers. These other components can be used alone or in combination of two or more.

[0163] <Preparation method of the composition for the functional layer of the electrochemical element>

[0164] The preparation method of the composition for the functional layer is not particularly limited. Generally, the above-mentioned granular polymer having a core-shell structure, water as a dispersion medium, and, if necessary, a binder material for the functional layer, non-conductive particles, water-soluble polymer, and / or other components are mixed to prepare the composition for the functional layer. When mixing, general stirring containers, ball mills, sand mills, bead mills, pigment dispersers, ultrasonic dispersers, grinders, homogenizers, planetary mixers, Filmix, etc. can be used. The mixing conditions are not particularly limited, and generally, it can be carried out within the range of room temperature to 80°C for 10 minutes to several hours.

[0165] (Functional layer for the electrochemical element)

[0166] The functional layer for an electrochemical element of the present invention is a functional layer formed using the above-described composition for a functional layer. The functional layer of the present invention can be obtained by, for example, applying the above-described composition for a functional layer onto the surface of an arbitrary substrate to form a coating film and then drying the coating film. That is, the functional layer of the present invention is formed from the dried product of the above-described composition for a functional layer and generally contains the above-described particulate polymer, an arbitrary binder material for a functional layer, non-conductive particles, a water-soluble polymer, and / or other components. In addition, each component contained in the functional layer is the same as those contained in the above-described composition for a functional layer, and the preferred ratios of existence of these respective components are the same as the preferred ratios of existence of the components in the composition for a functional layer.

[0167] (Laminated body for an electrochemical element)

[0168] The laminated body for an electrochemical element has a substrate and a functional layer on the substrate, and the functional layer is a functional layer formed using the above-described composition for a functional layer. Since the laminated body for an electrochemical element of the present invention has a functional layer formed using the above-described composition for a functional layer, the resistance of the electrochemical element can be reduced.

[0169] <Substrate>

[0170] The substrate can be appropriately selected according to the type of the electrochemical element component using the laminated body of the present invention. For example, when the laminated body of the present invention is used as a spacer, a spacer substrate is used as the substrate. In addition, for example, when the laminated body of the present invention is used as an electrode, an electrode substrate is used as the substrate.

[0171] <<Spacer substrate>>

[0172] As the spacer substrate, there is no particular limitation, and known spacer substrates such as an organic spacer substrate can be cited. The organic spacer substrate is a porous member made of an organic material. As an example of the organic spacer substrate, a microporous membrane or non-woven fabric containing a polyolefin resin such as polyethylene, polypropylene, polybutene, polyvinyl chloride, or an aromatic polyamide resin can be cited.

[0173] In addition, the thickness of the spacer substrate can be any thickness, preferably 5 μm or more and 30 μm or less, more preferably 5 μm or more and 20 μm or less, and further preferably 5 μm or more and 18 μm or less.

[0174] <<Electrode substrate>>

[0175] As the electrode substrate (positive electrode substrate and negative electrode substrate), there is no particular limitation, and an electrode substrate having an electrode composite layer formed on a current collector can be cited.

[0176] Here, for the current collector, the electrode active materials (positive electrode active material, negative electrode active material) and the binder materials for the electrode composite layers (binder material for the positive electrode composite layer, binder material for the negative electrode composite layer) in the electrode composite layer, and the method of forming the electrode composite layer on the current collector, those known ones can be used, and those described in, for example, Japanese Unexamined Patent Application Publication No. 2013-145763 can be used.

[0177] <<Manufacturing method of the laminate>>

[0178] The manufacturing method of the laminate of the present invention is not particularly limited, and a method of forming a functional layer on a release sheet and transferring the functional layer to a substrate can also be used, for example. However, from the viewpoint of improving the manufacturing efficiency without performing a transfer operation, the laminate is preferably manufactured through a step of supplying the composition for the functional layer to the substrate (supply step) and a step of drying the composition for the functional layer supplied to the substrate (drying step).

[0179] <<Supply step>>

[0180] In the supply step, the above-described composition for the functional layer of the present invention is supplied to the substrate, and a film of the composition for the functional layer is formed on the substrate. The method of supplying the composition for the functional layer to the substrate is not particularly limited. The composition for the functional layer can be coated on the surface of the substrate, or the substrate can be immersed in the composition for the functional layer. Moreover, from the viewpoint of easily controlling the thickness of the functional layer to be manufactured, it is preferable to coat the composition for the functional layer on the surface of the substrate.

[0181] As a method of coating the composition for the functional layer on the surface of the substrate, there is no particular limitation, and examples thereof include a doctor blade method, a reverse roll method, a direct roll method, a gravure coating method, a bar coating method, an extrusion method, a brush coating method, etc.

[0182] In addition, in the supply step, a film of the composition for the functional layer can be formed only on one surface of the substrate, or films of the composition for the functional layer can be formed on both surfaces of the substrate.

[0183] <<Drying step>>

[0184] In the drying step, the film of the composition for the functional layer formed on the substrate in the supply step is dried to remove the dispersion medium and form a functional layer.

[0185] As a method of drying the film of the composition for the functional layer, there is no particular limitation, and known methods can be used. Examples thereof include drying using warm air, hot air, low-humidity air, vacuum drying, and drying methods using irradiation with infrared rays, electron beams, etc. The drying conditions are not particularly limited. The drying temperature is preferably 50 to 150 °C, and the drying time is preferably 1 to 30 minutes.

[0186] In addition, when manufacturing the laminate of the present invention, after performing a supply process and a drying process on one surface of the substrate to form a functional layer, a supply process and a drying process may be performed on the other surface of the substrate to form a functional layer.

[0187] (Electrochemical element)

[0188] The electrochemical element of the present invention has the above-described laminate for an electrochemical element. The electrochemical element of the present invention can, for example, have an electrode and a spacer, and at least one of the electrode and the spacer has the above-described laminate of the present invention. Since such an electrochemical element uses the above-described laminate of the present invention as at least one of the electrode and the spacer, it has a low resistance and excellent electrochemical characteristics such as cycle characteristics.

[0189] In addition, the electrochemical element of the present invention only needs to have at least the laminate of the present invention. Therefore, as long as the effects of the present invention are not significantly impaired, it may also have constituent elements other than the laminate of the present invention.

[0190] Moreover, the electrochemical element of the present invention is not particularly limited. For example, it is a lithium ion secondary battery or an electric double layer capacitor, and preferably a lithium ion secondary battery.

[0191] Hereinafter, while taking a lithium ion secondary battery as an example of the electrochemical element of the present invention, a case where the above-described laminate of the present invention is used as a spacer of the lithium ion secondary battery will be described, but the electrochemical element of the present invention is not limited thereto.

[0192] A lithium ion secondary battery as an example of the electrochemical element of the present invention has a positive electrode, a negative electrode, a spacer, and an electrolytic solution, and the spacer is the above-described laminate.

[0193] <Positive electrode and negative electrode>

[0194] As the positive electrode and the negative electrode, electrodes formed from known electrode substrates (positive electrode substrate and negative electrode substrate) described in the item of "substrate" can be used.

[0195] <Electrolytic solution>

[0196] As the electrolyte, an organic electrolyte in which a supporting electrolyte is dissolved in an organic solvent is generally used. As the supporting electrolyte, a lithium salt can be used in, for example, a lithium ion secondary battery. Examples of the lithium salt include LiPF6, LiAsF6, LiBF4, LiSbF6, LiAlCl4, LiClO4, CF3SO3Li, C4F9SO3Li, CF3COOLi, (CF3CO)2NLi, (CF3SO2)2NLi, (C2F5SO2)NLi, etc. Among them, LiPF6, LiClO4, and CF3SO3Li are preferred because they are highly soluble in the solvent and exhibit a high degree of dissociation. In addition, the electrolyte can be used alone or in combination of two or more. Generally, there is a tendency that the higher the degree of dissociation of the supporting electrolyte used, the higher the lithium ion conductivity. Therefore, the lithium ion conductivity can be adjusted according to the type of the supporting electrolyte.

[0197] As the organic solvent used in the electrolyte, there is no particular limitation as long as it can dissolve the supporting electrolyte. In, for example, a lithium ion secondary battery, the following can be preferably used: carbonate esters such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), ethyl methyl carbonate (EMC), vinylene carbonate; esters such as γ-butyrolactone, methyl formate; ethers such as 1,2-dimethoxyethane, tetrahydrofuran; sulfur-containing compound classes such as sulfolane, dimethyl sulfoxide, etc.

[0198] In addition, a mixed solution of these organic solvents can also be used. Among them, carbonate esters are preferred because of their high dielectric constant and wide stable potential region. Generally, there is a tendency that the lower the viscosity of the organic solvent used, the higher the lithium ion conductivity. Therefore, the lithium ion conductivity can be adjusted by the type of the organic solvent.

[0199] In addition, the concentration of the electrolyte in the electrolyte can be appropriately adjusted. In addition, known additives can also be added to the electrolyte.

[0200] <Manufacturing method of an electrochemical element>

[0201] The manufacturing method of the electrochemical element of the present invention is not particularly limited. For example, a lithium ion secondary battery as an example of the electrochemical element of the present invention above can be manufactured by the following method: overlapping a positive electrode and a negative electrode with a spacer (the laminate of the present invention), winding, folding, etc. as needed, and then putting it into a battery container, injecting an electrolyte into the battery container, and sealing it. Here, an overcurrent prevention element such as a porous metal mesh, a fuse, a PTC element, a guide plate, etc. can be put into the battery container as needed to prevent the pressure inside the battery from rising and overcharging / discharging. The shape of the battery can be any of, for example, coin type, button type, sheet type, cylindrical type, square type, flat type, etc.

[0202] Example

[0203] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In addition, in the following description, unless otherwise specified, "%" and "parts" indicating amounts are based on mass.

[0204] In addition, unless otherwise specified, in a polymer produced by copolymerizing a plurality of monomers, the proportion of the structural unit formed by polymerizing a certain monomer in the above polymer generally coincides with the ratio (feed ratio) of the certain monomer in all the monomers used for the polymerization of the polymer.

[0205] In the examples and comparative examples, the measurement and evaluation of various properties were carried out as follows.

[0206] <Volume average particle diameter D50 of polymer A>

[0207] As a measurement sample, polymer A prepared in the examples and comparative examples was used. Weigh 0.1 g equivalent of the measurement sample, take it into a beaker, and add 0.1 mL of an aqueous solution of alkylbenzene sulfonic acid (manufactured by Fujifilm Corporation, "DRIWEL") as a dispersant. In the above beaker, further add 10 - 30 mL of a diluent (manufactured by Beckman Coulter, "ISOTON II"), and disperse it with a 20 W (watt) ultrasonic disperser for 3 minutes. Then, using a particle size analyzer (manufactured by Beckman Coulter, "Multisizer"), under the conditions of a pore size of 20 μm, a medium of Isoton II, and a measurement of 100,000 particle counts, the volume-based average particle diameter (volume average particle diameter D50) of the measurement sample was measured.

[0208] <Volume average particle diameter D50 of granular polymer>

[0209] As a measurement sample, the granular polymer prepared in the examples and comparative examples was used instead of polymer A prepared in the examples and comparative examples. Except for this, it was carried out in the same manner as the method described in the above <Volume average particle diameter D50 of polymer A>, and the volume average particle diameter D50 of the granular polymer was measured using "Multisizer" manufactured by Beckman Coulter.

[0210] In addition, for the granular polymers prepared in Examples 12 - 16 and Comparative Example 6, not only was it measured using the above particle size analyzer, but also the volume average particle diameter D50 of the granular polymer was measured using a laser diffraction / scattering particle size distribution measuring device (manufactured by Beckman Coulter, "LS13320XR").

[0211] <Volume average particle diameter D50 of the binder material for the functional layer>

[0212] As the test sample, the binder material for the functional layer prepared in the examples was used instead of the polymer A prepared in the examples and comparative examples. Except for this, the measurement was carried out in the same manner as the method described in the above <Volume average particle diameter D50 of granular polymer A>, and the volume average particle diameter D50 of the binder material for the functional layer was measured.

[0213] <Coating rate of the shell part on the outer surface of the core part>

[0214] For the coating rate of the shell part on the outer surface of the core part, it was confirmed using a scanning electron microscope. Specifically, an aqueous dispersion of the granular polymer was dropped on an aluminum foil and dried in a forced-air dryer set at 25°C for 3 hours to prepare a sample for observation.

[0215] Then, based on the sample images observed with a scanning electron microscope (SEM), the area of the entire granular polymer and the area of the polymer B of the shell part on the granular polymer were respectively determined, and the coating rate of the shell part on the outer surface of the core part was calculated based on the following formula.

[0216] Coating rate of the shell part on the outer surface of the core part (%) = (Area of the polymer B of the shell part on the granular polymer / Area of the granular polymer) × 100

[0217] In addition, in the sample images observed with a scanning electron microscope, the polymer having a particle diameter different from that of the granular polymer was identified as the polymer B of the shell part.

[0218] <Degree of swelling in the electrolyte>

[0219] The polymer A prepared in the examples and comparative examples was dispersed in ion-exchanged water to prepare an aqueous dispersion of polymer A. Then, the aqueous dispersion of polymer A was placed in a polytetrafluoroethylene petri dish. The aqueous dispersion of polymer A in the petri dish was dried at a temperature of 25°C for 48 hours to obtain a powdery sample. About 0.2 g of this sample was pressed at a temperature of 200°C and a pressure of 5 MPa for 2 minutes to obtain a test piece. The weight of this test piece was measured and denoted as W0.

[0220] Next, the above test piece was immersed in the electrolyte at a temperature of 60°C for 72 hours. In addition, as the electrolyte, an electrolyte in which LiPF6 as a supporting electrolyte was dissolved at a concentration of 1 mol / L with respect to a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and vinylene carbonate (VC) (volume mixing ratio: EC / DEC / VC = 68.5 / 30 / 1.5) was used.

[0221] After that, the test piece was taken out from the electrolytic solution, and the electrolytic solution adhering to the surface of the test piece was wiped off. Then, the weight of the test piece was measured and denoted as W1. Using the measured W0 and W1, the swelling degree S (times) of Polymer A in the electrolytic solution was calculated in the form of S (times) = W1 / W0.

[0222] <Adhesiveness after Immersion in Electrolytic Solution>

[0223] The spacers with functional layers prepared in the examples and comparative examples were cut into strips of 10 mm × 50 mm. Then, a laminate having a negative electrode and a spacer with a functional layer was prepared by arranging the spacer with the functional layer along the surface of the porous membrane of the negative electrode with the porous membrane, and this laminate was used as the test piece.

[0224] The above test piece and about 300 μl of the electrolytic solution were placed in a laminated packaging material. After 12 hours, the test piece together with the laminated packaging material was hot-pressed at a temperature of 40 °C and a load of 1.0 MPa for 20 minutes using a flat press to prepare a laminate having a negative electrode and a spacer with a functional layer. Here, as the electrolytic solution, an electrolytic solution in which LiPF6 as a supporting electrolyte was dissolved at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate (EC), diethyl carbonate (DEC), and vinylene carbonate (VC) (EC / DEC / VC (volume mixing ratio at 25 °C) = 68.5 / 30 / 1.5) was used.

[0225] After that, the test piece was taken out, and the electrolytic solution adhering to the surface was wiped off. Next, a transparent tape was pasted on the surface of the test piece on the current collector side of the negative electrode with the surface of the current collector side of the negative electrode facing down. At this time, as the transparent tape, the transparent tape specified in JIS Z1522 was used. In addition, the transparent tape was fixed to a horizontal test bench in advance. Then, one end of the spacer was stretched and peeled off vertically upward at a stretching speed of 50 mm / min, and the stress at this time was measured. This measurement was performed three times, and the average value of the stress was obtained as the peeling strength P, and the evaluation was carried out according to the following criteria. The greater the peeling strength P1, the higher the adhesion strength of the functional layer after immersion in the electrolytic solution.

[0226] A: The peeling strength P1 is 3.0 N / m or more

[0227] B: The peeling strength P1 is 2.0 N / m or more and less than 3.0 N / m

[0228] C: The peeling strength P1 is 0.5 N / m or more and less than 2.0 N / m

[0229] D: The peeling strength P1 is less than 0.5 N / m

[0230] <Adhesiveness (Anti-Adhesion) with Spacer>

[0231] The spacers with functional layers fabricated in the examples and comparative examples were cut into strips of 10 mm × 50 mm. Subsequently, a spacer identical to the spacer used in the spacer with the functional layer was provided on the functional layer side of the spacer with the functional layer (hereinafter, for ease of explanation, this spacer is referred to as "spacer A"), and a laminate was fabricated as a test piece.

[0232] This test piece was placed in a laminated packaging material, and the test piece together with the packaging material was hot-pressed at a temperature of 40 °C and a load of 6.0 MPa for 30 minutes using a flat press.

[0233] After that, the test piece was taken out. Subsequently, a transparent tape was adhered to the surface of this test piece with spacer A facing downwards. At this time, as the transparent tape, the transparent tape specified in JIS Z1522 was used. In addition, the transparent tape was fixed to a horizontal test bench in advance. Then, one end of the spacer with the functional layer was stretched and peeled vertically upwards at a stretching speed of 50 mm / minute, and the stress at this time was measured. This measurement was performed three times, and the average value of the stress was obtained as the peel strength P2, and evaluation was carried out according to the following criteria. The smaller the peel strength P2, the higher the adhesiveness between the functional layer and the spacer, and the more excellent the anti-blocking property.

[0234] A: Before the peel strength test, the spacer fell off.

[0235] B: The peel strength P2 is 0.0 N / m or more and less than 0.2 N / m

[0236] C: The peel strength P2 is 0.2 N / m or more and less than 0.5 N / m

[0237] D: The peel strength P2 is 0.5 N / m or more

[0238] <Cycling characteristics of secondary battery>

[0239] After injecting the electrolyte into the lithium-ion secondary batteries fabricated in the examples and comparative examples, they were left standing at a temperature of 25 °C for 5 hours. Subsequently, at a temperature of 25 °C, they were charged by a constant current method of 0.2C until the cell voltage reached 3.65 V. After that, an aging treatment was carried out at a temperature of 60 °C for 12 hours. Then, at a temperature of 25 °C, they were discharged by a constant current method of 0.2C until the cell voltage reached 3.00 V. After that, CC-CV charging was carried out by a constant current method of 0.2C (upper limit cell voltage 4.20 V), and CC discharge was carried out by a constant current method of 0.2C until 3.00 V. This 0.2C charge and discharge was repeatedly carried out 3 times.

[0240] Thereafter, in an environment at a temperature of 25 °C, charge and discharge operations are performed for 100 cycles at a charge and discharge rate of 1.0C with a battery cell voltage of 4.20 - 3.00V. At this time, the discharge capacity of the first cycle is defined as X1, and the discharge capacity of the 100th cycle is defined as X2.

[0241] Then, using the discharge capacity X1 and the discharge capacity X2, the capacity retention rate ΔCˊ = (X2 / X1) × 100 (%) is calculated and evaluated according to the following criteria. The larger the value of the capacity retention rate ΔCˊ, the better the cycle characteristics of the secondary battery after 100 cycles. In addition, it is speculated that the excellent cycle characteristics of the secondary battery after 100 cycles are because the functional layer of the secondary battery can retain the electrolyte well.

[0242] A: The capacity retention rate ΔCˊ is 95% or more

[0243] B: The capacity retention rate ΔCˊ is 92% or more and less than 95%

[0244] C: The capacity retention rate ΔCˊ is 90% or more and less than 92%

[0245] D: The capacity retention rate ΔCˊ is less than 90%

[0246] (Example 1)

[0247] <Preparation of Polymer A>

[0248] 80 parts of ion-exchanged water is supplied to a reactor equipped with a stirrer, the gas phase part is purged with nitrogen, and the temperature is raised to 80 °C.

[0249] On the other hand, in another container, 60 parts of ion-exchanged water, 0.2 parts of sodium dodecylbenzenesulfonate as a dispersion stabilizer, 40 parts of styrene as an aromatic vinyl monomer, 55.5 parts of n-butyl acrylate as an unsaturated carboxylic acid ester monomer having 4 carbon atoms, 0.5 parts of ethylene glycol dimethacrylate as a crosslinking monomer, 1 part of glycidyl methacrylate, 1 part of acrylic acid as an acidic group-containing monomer, 1 part of acrylamide as an amide group-containing monomer, and 1 part of hydroxymethylacrylamide are mixed to prepare a monomer composition A.

[0250] The prepared monomer composition A is added to the reactor heated to 80 °C over 1 minute and 30 seconds, and then 0.3 parts of ammonium persulfate as a polymerization initiator is supplied, and the reaction is carried out for 30 minutes. Thereafter, the monomer composition A is continuously added to the above reactor over 3 hours for polymerization. During the addition process, the reaction is carried out at 80 °C.

[0251] After the addition was completed, the mixture was further stirred at 80 °C for 2 hours, and then the reaction was terminated to obtain granular polymer A. The volume average particle diameter D50 of the obtained polymer A and the degree of swelling in the electrolyte were measured. The results are shown in Table 1.

[0252] <Preparation of Polymer B>

[0253] 80 parts of ion-exchanged water was supplied to a reactor equipped with a stirrer, the gas phase part was purged with nitrogen, and the temperature was raised to 80 °C.

[0254] On the other hand, in another container, 60 parts of ion-exchanged water, 0.5 part of sodium dodecylbenzenesulfonate as a dispersion stabilizer, 63.2 parts of styrene as an aromatic vinyl monomer, 33 parts of n-butyl acrylate as an unsaturated carboxylic acid ester having 4 carbon atoms, 0.8 part of ethylene glycol dimethacrylate as a crosslinkable monomer, and 3 parts of acrylic acid as an acidic group-containing monomer were mixed to prepare monomer composition B.

[0255] The prepared monomer composition B was added to the reactor heated to 80 °C over 1 minute and 30 seconds, and then 0.3 part of ammonium persulfate as a polymerization initiator was supplied, and the reaction was carried out for 30 minutes. Thereafter, monomer composition B was continuously added to the above reactor over 3 hours for polymerization. During the addition, the reaction was carried out at 80 °C.

[0256] After the addition was completed, the mixture was further stirred at 80 °C for 3 hours, and then the reaction was terminated to obtain granular polymer B.

[0257] <Preparation of Granular Polymer>

[0258] 40 parts of the above polymer A in terms of solid content was added to a reactor equipped with a stirrer, and further ion-exchanged water was added to make the solid content concentration of polymer A 15%. Further, 3 parts of magnesium sulfate as a coagulant in terms of solid content was added, and the temperature was raised to 60 °C.

[0259] 15 minutes after the start of heating, 60 parts of the above polymer B in terms of solid content was added, and the mixture was further maintained for 1 hour and 30 minutes. Thereafter, 7.2 parts of ethylenediaminetetraacetic acid was added, and the reaction was carried out at 60 °C for 2 hours to obtain an aqueous dispersion of the polymer.

[0260] Furthermore, while stirring the aqueous dispersion of the polymer, sulfuric acid was added dropwise at room temperature (25 °C) to adjust the pH to 7.0. Then, filtration separation was carried out, 200 parts of ion-exchanged water was added to 100 parts of the obtained solid content, and the washing treatment (washing, filtration, and dehydration) was repeated several times. Then, filtration separation was carried out, and further ion-exchanged water was added to obtain an aqueous dispersion of granular polymer.

[0261] Then, the obtained granular polymer was observed with a scanning electron microscope (SEM) to confirm that the granular polymer had a core-shell structure in which a part of the outer surface of polymer A was covered with polymer B. In addition, using the obtained granular polymer, the coverage rate of the shell portion on the outer surface of the core portion was determined. The results are shown in Table 1.

[0262] <Preparation of Binder Material for Functional Layer>

[0263] 70 parts of ion-exchanged water, 0.15 part of sodium lauryl sulfate as an emulsifier (manufactured by Kao Chemical Co., Ltd., "Emal (registered trademark) 2F"), and 0.3 part of ammonium persulfate as a polymerization initiator were supplied to a reactor equipped with a stirrer. The gas phase part was replaced with nitrogen, and the temperature was raised to 80°C.

[0264] On the other hand, in another container, 50 parts of ion-exchanged water, 0.5 part of sodium dodecylbenzenesulfonate as a dispersion stabilizer, 94 parts of n-butyl acrylate, 2 parts of methacrylic acid, 2 parts of acrylonitrile, 1 part of allyl methacrylate, and 1 part of allyl glycidyl ether were mixed to prepare a monomer composition.

[0265] This monomer composition was continuously added to the above-mentioned reactor equipped with a stirrer over 3 hours for polymerization. During the addition process, the reaction was carried out at 60°C. After the addition was completed, stirring was continued at 80°C for 2 hours to end the reaction, and an aqueous dispersion containing a binder material for the functional layer (acrylic polymer) was obtained. The volume average particle diameter D50 of the obtained binder material for the functional layer was 0.25 μm.

[0266] <Preparation of Composition for Functional Layer>

[0267] 0.5 part of sodium polyacrylate as a water-soluble polymer was added to 70 parts of alumina as a non-conductive particle (manufactured by Sumitomo Chemical Co., Ltd., "AKP3000", volume average particle diameter: 0.7 μm), and ion-exchanged water was added to make the solid content concentration 55%. It was mixed using a ball mill to obtain a pre-mixed slurry.

[0268] Furthermore, with respect to 70 parts of the above non-conductive particles, 5.0 parts of the binder material for the functional layer, 10 parts of the granular polymer having a core-shell structure, 1.5 parts of carboxymethyl cellulose as a viscosity regulator (thickener), and 0.2 part of sodium dodecylbenzenesulfonate as a dispersant (manufactured by Kao Chemical Co., Ltd., "NEOPELEX G-15") were added and mixed to make the solid content concentration 40%, obtaining a composition for the functional layer.

[0269] <Fabrication of Spacer with Functional Layer>

[0270] A polyethylene microporous film (thickness: 12 μm) was prepared as a spacer substrate. The functional layer composition obtained as described above was applied to one surface of the spacer substrate by a rod coating method to form a coating film. Next, the spacer substrate was dried at 50°C to dry the coating film to form a functional layer. The same operation as described above was performed on the other surface of the spacer substrate to prepare a spacer with a functional layer having a functional layer with a thickness of 2.0 μm on both sides of the spacer substrate.

[0271] <Production of positive electrode>

[0272] 100 parts of LiCoO2 (volume average particle size: 12 μm) as a positive electrode active material, 2 parts of acetylene black (made by Denka Co., Ltd., "HS-100") as a conductive material, 2 parts of polyvinylidene fluoride (made by Kureha Co., Ltd., "#7208") as a binder for a positive electrode composite material layer in terms of solid content, and N-methylpyrrolidone as a solvent were mixed to a total solid content concentration of 70%. The mixture was mixed with a planetary mixer to prepare a positive electrode slurry composition.

[0273] The above-mentioned positive electrode slurry composition is applied to an aluminum foil with a thickness of 20 μm as a current collector in a manner such that the film thickness after drying is about 150 μm with a notch wheel coater and dried. The drying is carried out by transporting the aluminum foil in an oven at 60 ° C for 2 minutes at a speed of 0.5 m / min. After that, the positive electrode raw material before pressing is obtained by heat treatment at 120 ° C for 2 minutes. The positive electrode raw material before pressing is rolled with a roller press to obtain a pressed positive electrode having a positive electrode composite material layer (thickness: 60 μm).

[0274] <Production of negative electrode>

[0275] In a 5MPa pressure-resistant container with a stirrer, 33 parts of 1,3-butadiene, 3.5 parts of itaconic acid, 63.5 parts of styrene, 0.4 parts of sodium dodecylbenzene sulfonate as an emulsifier, 150 parts of ion exchange water, and 0.5 parts of potassium persulfate as a polymerization initiator were placed, stirred thoroughly, and heated to 50°C to initiate polymerization. When the polymerization conversion rate reached 96%, the mixture was cooled and the reaction was terminated to obtain a mixture containing a binder material (SBR) for the negative electrode composite material layer. A 5% sodium hydroxide aqueous solution was added to the mixture containing the binder material for the negative electrode composite material layer, and after adjusting the pH to 8, the unreacted monomers were removed by heating and reduced pressure distillation. After that, it was cooled to below 30°C to obtain an aqueous dispersion containing the desired binder material for the negative electrode composite material layer.

[0276] Mix 80 parts of artificial graphite (volume average particle size: 15.6 μm) as the negative electrode active material (1) and 16 parts of silicon-based active material SiOx (volume average particle size: 4.9 μm) as the negative electrode active material (2). Mix a 2% aqueous solution of sodium carboxymethyl cellulose (manufactured by Nippon Paper Industries Co., Ltd., "MAC350HC") and ion-exchanged water, which are 2.5 parts in terms of the equivalent amount of solid components, and adjust the solid component concentration to 68%. Then, further mix at 25°C for 60 minutes. Furthermore, adjust the solid component concentration to 62% with ion-exchanged water and further mix at 25°C for 15 minutes to obtain a mixed solution. Put 1.5 parts of the aqueous dispersion containing the binder material for the negative electrode composite material layer and ion-exchanged water, which are in terms of the equivalent amount of solid components, into this mixed solution, adjust the final solid component concentration to 52%, and further mix for 10 minutes to obtain a mixed solution. Perform a defoaming treatment on this mixed solution under reduced pressure to obtain a negative electrode paste composition with good fluidity.

[0277] Coat the above negative electrode paste composition on a 20-μm-thick copper foil serving as a current collector with a film thickness of about 150 μm after drying using a chamfered wheel coater and dry it. This drying is carried out by transporting the copper foil at a speed of 0.5 m / minute in an oven at 60°C for 2 minutes. Then, perform a heat treatment at 120°C for 2 minutes to obtain a negative electrode raw material before pressing. Roll-press the negative electrode raw material before pressing with a roll press to obtain a pressed negative electrode having a negative electrode composite material layer (thickness: 80 μm).

[0278] <Fabrication of Lithium-Ion Secondary Battery>

[0279] Cut the pressed positive electrode fabricated as described above into 2.8 cm × 3.8 cm with the composite material layer side as the upper side, place it, and arrange the above spacer with a functional layer, which has been cut into 3.5 cm × 4.5 cm, on this positive electrode composite material layer. Furthermore, cut the pressed negative electrode fabricated as described above into 3.0 cm × 4.0 cm and arrange it on the spacer with a functional layer with the surface of the negative electrode composite material layer facing the spacer. At this time, arrange it with the surface of the spacer with a functional layer facing the positive electrode and the back surface of the spacer with a functional layer facing the negative electrode to obtain a laminate.

[0280] After pressing the laminate at 50 °C under 1 MPa to form a flat body, it is packaged with an aluminum packaging material used as the outer packaging of the battery, and an electrolytic solution [a solution in which LiPF6 as a supporting electrolyte is dissolved at a concentration of 1 mol / L in a mixed solvent of ethylene carbonate (EC) / diethyl carbonate (DEC) / vinyl carbonate (VC) (volume mixing ratio: EC / DEC / VC = 68.5 / 30 / 1.5)] is injected in a manner that no air remains. Then, the opening of the aluminum packaging material is heat-sealed at a temperature of 150 °C to fabricate a laminated lithium-ion secondary battery.

[0281] The obtained lithium-ion secondary battery is used to evaluate the cycle characteristics of the secondary battery. The results are shown in Table 1.

[0282] (Examples 2 and 3)

[0283] When preparing the monomer composition A, instead of n-butyl acrylate, 55.5 parts of ethyl acrylate as an unsaturated carboxylic acid ester monomer having 2 carbon atoms are used in Example 2, and 55.5 parts of hexyl acrylate as an unsaturated carboxylic acid ester monomer having 6 carbon atoms are used in Example 3. Except for this, it is carried out in the same manner as in Example 1 to prepare or fabricate Polymer A, Polymer B, granular polymer, composition for functional layer, spacer with functional layer, positive electrode, negative electrode, and lithium-ion secondary battery. Then, the measurement and evaluation are carried out in the same manner as in Example 1. The results are shown in Table 1.

[0284] (Examples 4 and 5)

[0285] When preparing the monomer composition A, the amounts of styrene and n-butyl acrylate are changed as shown in Table 1. Except for this, it is carried out in the same manner as in Example 1 to prepare or fabricate Polymer A, Polymer B, granular polymer, composition for functional layer, spacer with functional layer, positive electrode, negative electrode, and lithium-ion secondary battery. Then, the measurement and evaluation are carried out in the same manner as in Example 1. The results are shown in Table 1.

[0286] (Examples 6 and 7)

[0287] When preparing the monomer composition A, the amounts of styrene and n-butyl acrylate are changed as shown in Table 1, and furthermore, tert-dodecyl mercaptan as a molecular weight regulator is added in the amount shown in Table 1. Except for this, it is carried out in the same manner as in Example 1 to prepare or fabricate Polymer A, Polymer B, granular polymer, composition for functional layer, spacer with functional layer, positive electrode, negative electrode, and lithium-ion secondary battery. Then, the measurement and evaluation are carried out in the same manner as in Example 1. The results are shown in Table 1.

[0288] (Examples 8 to 11)

[0289] When preparing the granular polymer, the amounts of the solid components of polymer A and polymer B to be used were changed to the amounts shown in Table 2, and other than that, it was carried out in the same manner as in Example 1 to prepare or fabricate polymer A, polymer B, the granular polymer, the composition for the functional layer, the spacer with the functional layer, the positive electrode, the negative electrode, and the lithium ion secondary battery. Then, the measurement and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 2.

[0290] (Examples 12 to 19)

[0291] When preparing the granular polymer, the reaction temperatures of polymer A and polymer B were changed to those shown in Table 3, and other than that, it was carried out in the same manner as in Example 1 to prepare or fabricate polymer A, polymer B, the granular polymer, the composition for the functional layer, the spacer with the functional layer, the positive electrode, the negative electrode, and the lithium ion secondary battery. Then, the measurement and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 3.

[0292] (Examples 20 to 23)

[0293] When preparing monomer composition A, the amounts of styrene, n-butyl acrylate, and ethylene glycol dimethacrylate were changed to those shown in Table 4, and other than that, it was carried out in the same manner as in Example 1 to prepare or fabricate polymer A, polymer B, the granular polymer, the composition for the functional layer, the spacer with the functional layer, the positive electrode, the negative electrode, and the lithium ion secondary battery. Then, the measurement and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 4.

[0294] (Examples 24 to 27)

[0295] When preparing monomer composition B, the amounts of styrene, n-butyl acrylate, and ethylene glycol dimethacrylate were changed to those shown in Table 5, and other than that, it was carried out in the same manner as in Example 1 to prepare or fabricate polymer A, polymer B, the granular polymer, the composition for the functional layer, the spacer with the functional layer, the positive electrode, the negative electrode, and the lithium ion secondary battery. Then, the measurement and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 5.

[0296] (Example 28)

[0297] When preparing monomer composition B, coconut amine acetate was used as the dispersion stabilizer instead of sodium dodecylbenzenesulfonate. In addition, 3-(methacrylamido)propyltrimethylammonium methyl sulfate was used to replace acrylic acid. Furthermore, when preparing the granular polymer, magnesium sulfate was not added. Other than that, it was carried out in the same manner as in Example 1 to prepare or fabricate polymer A, polymer B, the granular polymer, the composition for the functional layer, the spacer with the functional layer, the positive electrode, the negative electrode, and the lithium ion secondary battery. Then, the measurement and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 5.

[0298] (Example 29)

[0299] In the <Preparation of Granular Polymer> step of Example 1, magnesium sulfate was not added, and the temperature increase temperature was changed from 60 °C to 30 °C. Other than this, it was carried out in the same manner as in Example 1 to prepare or produce Polymer A, Polymer B, granular polymer, composition for functional layer, spacer with functional layer, positive electrode, negative electrode, and lithium ion secondary battery. Then, the measurement and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 5.

[0300] (Example 30)

[0301] In the <Preparation of Granular Polymer> step of Example 29, the temperature increase temperature was changed from 30 °C to 25 °C. Other than this, it was carried out in the same manner as in Example 1 to prepare or produce Polymer A, Polymer B, granular polymer, composition for functional layer, spacer with functional layer, positive electrode, negative electrode, and lithium ion secondary battery. Then, the measurement and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 5.

[0302] (Example 31)

[0303] Suspension polymerization was carried out through the following steps.

[0304] [Preparation of Monomer Composition]

[0305] 40 parts of styrene as an aromatic vinyl monomer, 55.5 parts of butyl acrylate as an unsaturated carboxylic acid ester monomer having 4 carbon atoms, 0.5 part of ethylene glycol dimethacrylate as a crosslinking monomer, and 4 parts of glycidyl methacrylate were mixed to prepare a core monomer composition.

[0306] To this, 30 parts by mass of the pre-polymerized Polymer B of Example 1 in terms of solid content was further added relative to 100 parts by mass of the above monomers.

[0307] [Preparation of Colloidal Dispersion]

[0308] An aqueous solution in which 10.0 parts of magnesium chloride was dissolved in 200 parts of ion-exchanged water was prepared, and an aqueous solution in which 7.0 parts of sodium hydroxide was dissolved in 50 parts of ion-exchanged water was slowly added thereto with stirring to prepare a colloidal dispersion containing magnesium hydroxide as a metal hydroxide.

[0309] [Synthesis of Granular Polymer]

[0310] A granular polymer having a core part and a shell part is prepared by suspension polymerization. Specifically, the above monomer composition is put into the colloidal dispersion containing the above magnesium hydroxide, and after further stirring, 2.0 parts of tert-butyl peroxy-2-ethylhexanoate (manufactured by NOF Corporation, product name "PERBUTYL O") as a polymerization initiator is added to obtain a mixed solution. The obtained mixed solution is subjected to high-shear stirring at a rotation speed of 11,000 rpm for 1 minute using a pipeline type emulsifying and dispersing machine (manufactured by Taiheiyo Kiko Co., Ltd., product name "Cavitron") to form droplets of the monomer composition in the colloidal dispersion containing magnesium hydroxide. The colloidal dispersion containing magnesium hydroxide in which the droplets of the above monomer composition are formed is put into a reactor, heated to 90 °C, and subjected to a polymerization reaction for 5 hours to obtain an aqueous dispersion containing a granular polymer.

[0311] [Removal of colloid]

[0312] Here, the following operations are performed on the obtained aqueous dispersion containing the granular polymer to obtain a granular polymer in a dry state. First, while stirring the above aqueous dispersion containing the granular polymer, sulfuric acid is added dropwise at room temperature (25 °C) until the pH becomes 5.5 or less for pickling. Next, filtration separation is performed, 500 parts of ion-exchanged water is added to the obtained solid component to re-slurry it, and several water washing treatments (washing, filtration, and dehydration) are repeated. Then, filtration separation is performed, the obtained solid component is put into a container of a dryer, and dried at 25 °C for 1 minute to obtain a granular polymer having a core-shell structure in a dry state. Except for this, it is carried out in the same manner as in Example 1 to prepare or produce a composition for a functional layer, a spacer with a functional layer, a positive electrode, a negative electrode, and a lithium-ion secondary battery. Then, the measurement and evaluation are carried out in the same manner as in Example 1. In addition, the volume average particle diameter is measured according to the method described in the item of <Volume average particle diameter D50 of Polymer A>. The results are shown in Table 5.

[0313] (Comparative Example 1)

[0314] When preparing monomer composition A, ethylhexyl acrylate as an unsaturated carboxylic acid ester monomer having 8 carbon atoms is used instead of n-butyl acrylate. In addition, when preparing monomer composition B, 42 parts of styrene, 25 parts of ethylene dimethacrylate, 30 parts of butyl acrylate, and 3 parts of acrylic acid are used instead of the monomers used in Example 1.

[0315] Except for this, it is carried out in the same manner as in Example 1 to prepare or produce Polymer A, Polymer B, a granular polymer, a composition for a functional layer, a spacer with a functional layer, a positive electrode, a negative electrode, and a lithium-ion secondary battery. Then, the measurement and evaluation are carried out in the same manner as in Example 1. The results are shown in Table 6.

[0316] (Comparative Example 2 and Comparative Example 3)

[0317] When preparing monomer composition A, the monomers shown in Table 6 and tert-dodecyl mercaptan were used instead of the monomers used in Example 1. In addition, the same monomer composition B as in Comparative Example 1 was used.

[0318] Except for this, the procedures were carried out in the same manner as in Example 1 to prepare or produce Polymer A, Polymer B, granular polymer, functional layer composition, spacer with functional layer, positive electrode, negative electrode, and lithium-ion secondary battery. Then, the measurement and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 1. In addition, since Polymer A of Comparative Example 2 was completely dissolved in the electrolyte used for the measurement of the swelling degree, the numerical value of the swelling degree could not be determined in the same manner as in other Examples and Comparative Examples, and the numerical value of the swelling degree was marked as "0" in Table 6.

[0319] (Comparative Example 4 and Comparative Example 5)

[0320] When preparing monomer composition A, the amounts of styrene, n-butyl acrylate, and ethylene glycol dimethacrylate were changed as shown in Table 6.

[0321] In addition, when preparing the granular polymer, in Comparative Example 4, Polymer B was not used, and in Comparative Example 5, the solid content of Polymer A used was changed to 8 parts, and the solid content of Polymer B used was changed to 92 parts.

[0322] Except for this, the procedures were carried out in the same manner as in Example 1 to prepare or produce Polymer A, Polymer B, granular polymer, functional layer composition, spacer with functional layer, positive electrode, negative electrode, and lithium-ion secondary battery. Then, the measurement and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 6.

[0323] (Comparative Example 6)

[0324] When preparing the granular polymer, Polymer A prepared by the following method and Polymer B prepared in Comparative Example 1 were used, and the reaction temperature of Polymer A and Polymer B was changed to 40 °C.

[0325] Except for this, the procedures were carried out in the same manner as in Example 1 to prepare or produce Polymer B, granular polymer, functional layer composition, spacer with functional layer, positive electrode, negative electrode, and lithium-ion secondary battery. Then, the measurement and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 6.

[0326] <Preparation of Polymer A>

[0327] 350 parts of ion-exchanged water was supplied to a reactor equipped with a stirrer, the gas phase part was purged with nitrogen, and the temperature was raised to 60 °C.

[0328] In the above reaction vessel, 1.0 part of sodium dodecylbenzenesulfonate as a dispersion stabilizer, 41 parts of styrene, 35 parts of n-butyl acrylate, 20 parts of ethylene dimethacrylate, 1 part of glycidyl methacrylate, 1 part of acrylic acid, 1 part of acrylamide, and 1 part of hydroxyethyl acrylate were added to prepare monomer composition A.

[0329] Thereafter, 0.3 part of ammonium persulfate as a polymerization initiator was added to monomer composition A to initiate the reaction.

[0330] After 80 minutes of initiating the reaction, the temperature was raised to 80 °C, and stirring was continued for 2 hours, and then the reaction was terminated to obtain a granular polymer. The volume average particle diameter D50 of the obtained granular polymer was measured. The results are shown in Table 6.

[0331] (Comparative Example 7)

[0332] When preparing the granular polymer, the solid content of polymer A used was changed to 40 parts, the solid content of polymer B used was changed to 60 parts, and the reaction temperature of polymer A and polymer B was changed to 85 °C. Except for this, the preparation or production of polymer A, polymer B, granular polymer, functional layer composition, spacer with functional layer, positive electrode, negative electrode, and lithium ion secondary battery was carried out in the same manner as in Comparative Example 6. Then, the measurement and evaluation were carried out in the same manner as in Example 1. The results are shown in Table 6.

[0333] [Table 1]

[0334]

[0335] [Table 2]

[0336]

[0337] [Table 3]

[0338]

[0339] [Table 4]

[0340]

[0341] [Table 5]

[0342]

[0343] [Table 6]

[0344]

[0345] In addition, in Tables 1 to 6,

[0346] "ST" represents styrene,

[0347] "BA" represents n-butyl acrylate,

[0348] "HA" represents hexyl acrylate,

[0349] "EA" represents ethyl acrylate,

[0350] "AA" represents acrylic acid,

[0351] "AAm" represents acrylamide,

[0352] "HMAA" represents hydroxymethylacrylamide,

[0353] "2EHA" represents 2-ethylhexyl acrylate,

[0354] "EDMA" represents ethylene glycol dimethacrylate,

[0355] "GMA" represents glycidyl methacrylate,

[0356] "3(MAA)PTMAMS" represents 3-(methacrylamido)propyltrimethylammonium methyl sulfate.

[0357] As can be seen from Tables 1 to 5, in Examples 1 to 28 using a composition containing a particulate polymer having a specified core-shell structure and properties, a functional layer with high adhesive strength after electrolyte impregnation can be obtained, and the lithium ion secondary battery having this functional layer has excellent cycle characteristics.

[0358] Industrial applicability

[0359] According to the present invention, it is possible to provide a composition for an electrochemical element functional layer, which can form a functional layer for an electrochemical element that can well balance high adhesive strength after electrolyte impregnation and low resistance of the electrochemical element.

[0360] In addition, according to the present invention, it is possible to provide a functional layer for an electrochemical element that can well balance high adhesive strength after electrolyte impregnation and low resistance of the electrochemical element.

[0361] Furthermore, according to the present invention, it is possible to provide a laminate for an electrochemical element that can reduce the resistance of the electrochemical element.

[0362] Furthermore, according to the present invention, it is possible to provide an electrochemical element having low resistance and excellent electrochemical characteristics such as cycle characteristics.

Claims

1. A composition for an electrochemical element functional layer, comprising a particulate polymer, The particulate polymer has a core-shell structure including a core portion and a shell portion covering a portion of the outer surface of the core portion, The coverage rate of the shell portion on the outer surface of the core portion is 1% or more and 90% or less, The core polymer A has a swelling degree of 0.1 times or more and less than 5 times in the electrolyte, contains an unsaturated carboxylic acid ester monomer unit having 6 or less carbon atoms, and has a volume average particle size D50 of 0.1 μm or more and 10 μm or less.

2. The composition for an electrochemical element functional layer according to claim 1, wherein The volume average particle diameter D50 of the particulate polymer is 1.0 μm or more and 12 μm or less.

3. The composition for an electrochemical element functional layer according to claim 1, wherein The polymer A in the core portion contains a crosslinkable monomer unit in a ratio of 0.1% by mass or more and 75% by mass or less.

4. The composition for an electrochemical element functional layer according to claim 1, wherein The polymer B in the shell portion contains a crosslinkable monomer unit in a ratio of 0.1% by mass or more and 75% by mass or less. 5 . An electrochemical device functional layer formed using the composition for an electrochemical device functional layer according to claim 1 . 6 . A laminate for an electrochemical element, comprising a substrate and a functional layer on the substrate, wherein the functional layer is the functional layer for an electrochemical element according to claim 5 . 7 . An electrochemical element comprising the laminate for an electrochemical element according to claim 6 .

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