JP2017027945A - Separator for power storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separator for a power storage device capable of suppressing deformation of a laminate of the separator and the electrode or a wound laminate in the power storage device.SOLUTION: The separator for a power storage device includes a base material having at least one porous film; and a polymer existing in at least one area of the base material, and with regard to a three point bending test, a relation represented by formula (f):Fsep-Fbase≥10 (f) is satisfied (in the formula, Fsepis a maximal value when plotting a load (N), for maintaining the push-in speed of an indenter to a laminated wound body 1 of the electrode and the separator for power storage device and a housing body 1 housing the electrolyte at 50 mm/min over time, and the Fbaseis the maximal value when plotting the load (N) for maintaining the push-in speed of the indenter to a laminated wound body 2 of the base material and the electrode and a housing body 2 housing the electrolyte at 50 mm/min over time).SELECTED DRAWING: None

Description

  The present invention relates to an electrical storage device separator.

  In recent years, non-aqueous electrolyte batteries represented by lithium ion batteries have been actively developed. Usually, in a nonaqueous electrolyte battery, a separator including a microporous membrane is provided between positive and negative electrodes. The separator has a function of preventing direct contact between the positive and negative electrodes and allowing ions to permeate through the electrolytic solution held in the micropores.

  In addition to the electrical characteristics and safety of nonaqueous electrolyte batteries, separators are also required to have improved adhesion to electrodes from the viewpoint of uniform charge / discharge current and suppression of lithium dendrite. In order to give the separator adhesiveness, various polymer coatings on the separator base material have been proposed (Patent Documents 1 to 9).

  In patent document 1, the adhesive polymer which has a core-shell type structure, and its swelling degree are examined.

  In patent document 2, the shape fluctuation | variation of the polymer particle contained in a polymer coating liquid and a particle size fluctuation | variation are examined.

  Regarding the selection of the adhesive polymer, Patent Document 3 describes the combined use of an acrylic polymer having a sulfonic acid group and an acrylic polymer having an epoxy group, and Patent Document 9 describes a styrene-butadiene rubber as the adhesive polymer. Has been.

  Regarding the thermal properties of the adhesive polymer, in Patent Document 4, the glass transition temperature of a thermoplastic polymer disposed on a substrate is examined, and in Patent Document 5, a polymer having a glass transition temperature of 10 ° C. to 100 ° C. Particles have been proposed, and Patent Document 7 proposes an adhesive polymer that develops adhesiveness at a temperature lower than the melting point of the polymer forming the separator substrate.

  Regarding the location of the adhesive polymer on the substrate, Patent Document 6 proposes to distribute the binder polymer evenly in the range of 1% to 80% of the substrate surface, and in Patent Document 8, It has been proposed to partially place a gel polymer on a substrate.

JP 2015-28843 A International Publication No. 2012/020737 International Publication No. 2012/043729 International Publication No. 2014/017651 International Publication No. 2013/151144 International Publication No. 2003/012896 JP 2011-023186 A JP-T-2006-525624 Special table 2008-521964

  However, when an adhesive layer is formed on the base material using the adhesive polymer described in Patent Documents 1 to 9, in the electricity storage device, an adhesive force is secured at the interface between the base material and the electrode. In this case, the rigidity of the adhesive layer in the substrate is insufficient, so that the rigidity of the separator / electrode laminate or the wound laminate is not increased, and the electricity storage device may be deformed.

  Therefore, the problem to be solved by the present invention is to provide a separator for an electricity storage device capable of suppressing deformation of a separator-electrode laminate or a wound laminate in an electricity storage device.

The present inventors have found that the above problem can be solved by allowing a polymer having rigidity even in an electrolytic solution to exist on the separator substrate, and have completed the present invention.
That is, the present invention is as follows.
[1]
A substrate comprising at least one porous membrane; and a polymer present in at least one region of at least one side of the substrate;
A separator for an electricity storage device including the following formula (f) for a three-point bending test:
Fsep _max −Fbase _max ≧ 10 (f)
{In the formula, Fsep _max is a load (N) for maintaining the pressing speed of the indenter with respect to the stacked body 1 of the electrode and the electricity storage device separator and the storage body 1 storing the electrolyte at 50 mm / min. Fbase _max is a pressing speed of the indenter with respect to the laminated body 2 of the base material and the electrode and the storage body 2 in which the electrolytic solution is stored 50 mm. / Maximum value when the load (N) to maintain at / min is plotted over time}
The said separator for electrical storage devices which satisfy | fills the relationship represented by these.
[2]
The separator for an electricity storage device according to [1], wherein the electrode is a positive electrode or a negative electrode.
[3]
The separator for an electricity storage device according to [2], which satisfies the relationship represented by the formula (f) regardless of whether the electrode is the positive electrode or the negative electrode.
[4]
Any of [1] to [3], wherein the indenter is pushed into the storage body 1 or the storage body 2 from a direction perpendicular to the winding direction of the stacked winding body 1 or the stacked winding body 2. The separator for electrical storage devices of Claim 1.
[5]
The separator for an electricity storage device according to any one of [1] to [4], wherein the size and material of the storage body 1 are the same as the size and material of the storage body 2.
[6]
Any one of [1] to [5], wherein an area ratio of a surface of the base material coated with the polymer after impregnating the electrolytic device with the separator for an electricity storage device is 5% to 80%. The separator for an electricity storage device according to item.
[7]
When the aluminum foil is pressed for 3 minutes under the conditions of a temperature of 25 ° C. and a pressure of 5 MPa on the outermost surface where the polymer of the electricity storage device separator exists, the electricity storage device separator and the aluminum foil The separator for electrical storage devices according to any one of [1] to [6], wherein the peel strength between the layers is 8 N / m (8 gf / cm) or less.
[8]
When the aluminum foil is pressed for 3 minutes under the conditions of a temperature of 80 ° C. and a pressure of 10 MPa on the outermost surface where the polymer of the electricity storage device separator exists, the electricity storage device separator and the aluminum foil The separator for electrical storage devices according to any one of [1] to [7], wherein a peel strength between the layers is 9.8 N / m (10 gf / cm) or more.
[9]
The separator for an electricity storage device according to any one of [1] to [8], wherein the polymer is a granular thermoplastic polymer.
[10]
Using the Voronoi polygonal area (Si) obtained by performing Voronoi division on the granular thermoplastic polymer, the following formula:
{Wherein Si is the actual value of the area of the Voronoi polygon, m is the average of the actual values of the area of the Voronoi polygon, and n is the total number of Voronoi polygons}
[9] The electricity storage device separator according to [9], wherein the dispersion (σ ² ) defined by is from 0.01 to 0.7.
[11]
The dispersion (σ ² ) is the electricity storage device separator according to [10], which is an average value of values calculated for 95 visual fields.
[12]
The coating liquid containing the polymer, coating area ratio with respect to the substrate of ^{5% ~70%, 0.05g / m} 2 ~1.0g / m 2 of coating basis weight, and 0.1μm~3μm coating The manufacturing method of the separator for electrical storage devices of any one of [1]-[8] including the process of apply | coating to the said at least 1 surface of the said base material on the conditions of work thickness.

  According to the present invention, since the rigidity of the adhesive part of the separator for an electricity storage device is ensured, the rigidity of the electricity storage device can be improved and deformation of the electricity storage device can be suppressed.

FIG. 1 shows an example of a photograph observing the surface of the polymer layer. FIG. 2 shows an example of a result of automatically specifying a thermoplastic polymer included in the observation visual field of FIG. 1 using image processing software. FIG. 3 shows an example of a result obtained by performing Voronoi division on the plurality of particles identified in FIG. 2 to obtain a Voronoi polygon. FIG. 4 shows an example of a result of automatically calculating the area of the Voronoi polygon obtained in FIG. 3 using image processing software. FIG. 5 shows an example of a method for setting one section composed of 19 views out of 95 views for observing the thermoplastic polymer particles arranged on the separator. FIG. 6 shows an example of a method for setting five sections including 95 visual fields for observing thermoplastic polymer particles arranged on a separator. 7A to 7E are schematic views showing a planar shape of a polymer layer formed on at least one surface of a substrate in the separator according to the embodiment of the present invention.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

  The electricity storage device separator (hereinafter referred to as “separator”) according to the present embodiment includes a base material including at least one porous film and a polymer present in at least one region of at least one surface of the base material. If desired, the separator may further include a porous layer including an inorganic filler and a resinous binder.

In the present embodiment, the separator is represented by the following formula (f) for a three-point bending test:
Fsep _max −Fbase _max ≧ 10 (f)
{In the formula, Fsep _max represents the load (N) for maintaining the pressing speed of the indenter at 50 mm / min with respect to the stacked winding body 1 of the electrode and the separator and the storage body 1 in which the electrolytic solution is stored. It is the maximum value when plotted, and Fbase _max is a load for maintaining the pressing speed of the indenter at 50 mm / min with respect to the laminated body 2 of the base material and the electrode and the storage body 2 in which the electrolytic solution is stored. (N) is the local maximum when plotted over time}
The relationship represented by is satisfied.

The value obtained by subtracting Fbase _max from Fsep _max in the formula (f) is the stacked winding body 1 obtained by winding the electrode and the separator and winding, and the storage body 1 storing the electrolytic solution, The storage body 1 in the case where the laminated winding body 2 obtained by winding the base material on the electrode instead of the separator and the storage body 2 storing the electrolytic solution are each subjected to a three-point bending test. The difference between the strength (N) and the strength (N) of the storage body 2 (hereinafter referred to as “rigidity difference”).

  Since the electricity storage device is modeled by the storage body 1 or 2 according to the configuration of the storage body 1 including the laminated winding body 1 and the electrolytic solution or the storage body 2 including the laminated winding body 2 and the electrolytic solution, the above-mentioned The higher the rigidity difference defined in, the higher the rigidity of the electricity storage device including the separator. When the stiffness difference is 10 N or more, the electricity storage device has sufficient rigidity to suppress deformation of the electricity storage device or interface separation between the separator and the electrode even if a shear stress is applied between the separator and the electrode in the electrolyte. Have From the viewpoint of the rigidity of the electricity storage device, a higher rigidity difference is preferable, and the upper limit value of the rigidity difference is determined according to the design of the electricity storage device and is not limited.

  On the other hand, when the difference in stiffness is less than 10 N for both the positive and negative electrodes, the electricity storage device including the separator cannot withstand the shear stress applied between the separator and the electrode in the electrolytic solution, and the electricity storage device is deformed. Cohesive failure of the polymer part existing between the two or separation of the interface between the separator and the electrode occurs.

  Therefore, when the difference in rigidity is 10 N or more, (i) suppress the generation of lithium dendrite and the wrinkle or delamination of the wound body in the electrolyte, thereby suppressing the increase in the thickness of the electricity storage device over time. Since the cycle characteristics of the electricity storage device can be improved, and / or (ii) the rapid charge / discharge of the electricity storage device can be achieved even if the coating area of the separator substrate surface coated with the polymer is low, The rate characteristics of the electricity storage device are improved. From the viewpoints of (i) and (ii), the rigidity difference is more preferably 12N or more, and further preferably 14N or more.

  The difference in rigidity is controlled to 10 N or more by making the adhesion and rigidity of the polymer existing in at least one region of at least one surface of the separator base material in the electrolyte solution compatible. Therefore, the strength (N) of the storage body 1 formed using the separator including the polymer in at least one region of at least one surface of the base material is the storage body 2 formed using the base material instead of the separator. The strength (N) is preferably 10N or more, more preferably 12N or more, and preferably 14N or more.

Fsep _max in the formula (f) is preferably formed by laminating and winding the electrode and the separator to form the laminated wound body 1, placing the laminated wound body 1 in the storage body 1, and supplying the electrolytic solution to the storage body 1. It is measured after pouring, and more preferably, it is measured after the container 1 is heat-pressed after the electrolyte is poured.

Fbase _max in the formula (f) is preferably formed by laminating the base material and the electrode to form the laminated wound body 2, placing the laminated wound body 2 in the storage body 2, and supplying the electrolytic solution to the storage body 2. More preferably, it is measured after heat-pressing the container 2 after pouring the electrolyte.

  From the viewpoint of ease and accuracy of the three-point bending test, the indenter is pushed into the storage body not from the direction perpendicular to the end face of the laminated winding body but from the direction perpendicular to the longitudinal direction of the laminated winding body. It is more preferable that it is pushed into the storage body from a direction perpendicular to the winding direction of the laminated winding body, and the tip of the indenter is pushed so that it can approach the center of the laminated winding body in the storage body. More preferably.

  In the three-point bending test, the electrode used is an electrode current collector such as an aluminum foil or copper foil; a positive electrode provided with a positive electrode active material on the positive electrode current collector as long as the housing can be subjected to the three-point bending test. And any of a negative electrode provided with a negative electrode active material on a negative electrode collector. From the viewpoints of (i) and (ii) above, the electrode is preferably a positive electrode or a negative electrode, and even if the electrode is either a positive electrode or a negative electrode, the rigidity difference is more preferably 10 N or more.

  The container used for the three-point bending test may be a pouch-type case obtained by laminating a plurality of polymer films, for example, polypropylene films, and one or more metal sheets, for example, aluminum sheets.

  The dimensions of the housing used for the three-point bending test are arbitrary as long as the laminated winding body obtained by laminating and winding the electrode and the separator or the base material and the electrolytic solution can be housed. May have the form and dimensions of Since both ends of the storage body are fixed at the time of the three-point bending test, it is preferable that the size of the storage body is close to the dimension of the laminated winding body, and the laminated winding body is from the pushing direction of the indenter during the three-point bending test. It is preferable that the laminated winding body is arranged in the storage body so that the center or the center of gravity of the laminated winding body coincides with the center or the center of gravity of the storage body when the storage body is observed.

In the present embodiment, both the storage body 1 that houses the laminated winding body 1 of electrodes and separators and the storage body 2 that houses the laminated winding body 2 of electrodes and substrates have arbitrary dimensions and materials. However, from the viewpoint of ease and accuracy of the three-point bending test, it is preferable that the size and material of the storage body 1 are the same as the size and material of the storage body 2.
From the viewpoint of the ease and accuracy of the three-point bending test, the electrolytic solution used for forming the storage body 1 and the electrolytic solution used for forming the storage body 2 are preferably the same.
From the viewpoint of the ease and accuracy of the three-point bending test, it is preferable that the heat press conditions of the storage body 1 and the heat press conditions of the storage body 2 are the same.
The method and conditions of the three-point bending test will be described in the examples.

  The separator can be used for manufacturing an electricity storage device. Each structure which concerns on a separator is demonstrated below.

[Polymer, polymer layer and adhesive layer]

The polymer is disposed in at least one region of at least one surface of a porous film or a porous film having a porous layer containing an inorganic filler and a resin binder on at least one surface (also collectively referred to as “substrate”). Is done. The polymer is preferably a thermoplastic polymer. In this specification, the term “thermoplastic polymer” is a thermoplastic polymer usually used as a binder for bonding a separator and an electrode, or is gelled by being hot-pressed in an electrolytic solution to exhibit adhesiveness. The polymer to be included.
The layer containing the polymer (hereinafter referred to as “polymer layer”) is formed on at least one surface of the substrate. The polymer layer should just be formed in the at least one part area | region of the at least single side | surface of a base material.
The polymer layer can be bonded to the electrode and the separator through a hot pressing process. That is, the polymer layer can function as an adhesive layer between the electrode and the separator.

  In order to improve the rigidity of the electricity storage device by controlling the difference in rigidity measured by the three-point bending test to 10 N or more, the adhesion of the polymer layer at the interface between the electrode and the separator and the rigidity of the polymer layer in the electrolyte It is required to balance both.

In order to ensure the adhesion of the polymer layer at the interface between the electrode and the separator, it is preferable that the polymer layer formed on the substrate has adhesiveness or an anchor effect.
Furthermore, in order to improve the rigidity of the adhesive layer in the electrolyte, at least one of the following 1-3 is required:
1. Use a polymer with high rigidity in the electrolyte;
2. 2. the polymer layer forms a continuous layer; and An adhesive layer containing a mixture of an inorganic filler and a polymer is formed.

[1. (Use a polymer with high rigidity in the electrolyte)
The polymer having high rigidity in the electrolytic solution may be a thermoplastic polymer as long as the difference in rigidity can be controlled to 10 N or more. Specific examples of the thermoplastic polymer include the following 1) to 4).
1) conjugated diene polymer,
2) Acrylic polymer,
3) polyvinyl alcohol resin, and 4) fluorine-containing resin.

The 1) conjugated diene polymer is a polymer containing a conjugated diene compound as a monomer unit. Examples of the conjugated diene compound include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, and substituted linear chains. Examples thereof include conjugated pentadienes, substituted and side chain conjugated hexadienes, and these may be used alone or in combination of two or more.
Moreover, the conjugated diene polymer may contain a (meth) acrylic compound or other monomer described later as a monomer unit. Specifically, for example, styrene-butadiene copolymer and its hydride, acrylonitrile-butadiene copolymer and its hydride, acrylonitrile-butadiene-styrene copolymer and its hydride, and the like.

The 2) acrylic polymer is a polymer containing a (meth) acrylic compound as a monomer unit. The (meth) acrylic compound indicates at least one selected from the group consisting of (meth) acrylic acid and (meth) acrylic acid ester.
An example of such a compound is a compound represented by the following formula (P1).
_{^{CH 2 = CR Y1 -COO-R}} Y2 (P1)
In formula (P1), R ^Y1 represents a hydrogen atom or a methyl group, and R ^Y2 represents a hydrogen atom or a monovalent hydrocarbon group. When R ^Y2 is a monovalent hydrocarbon group, it may have a substituent and may have a hetero atom in the chain. Examples of the monovalent hydrocarbon group include a linear alkyl group, a cycloalkyl group, and an aryl group which may be linear or branched. Examples of the substituent include a hydroxyl group and a phenyl group, and examples of the hetero atom include a halogen atom and an oxygen atom. A (meth) acrylic compound is used alone or in combination of two or more.
Examples of such (meth) acrylic compounds include (meth) acrylic acid, chain alkyl (meth) acrylate, cycloalkyl (meth) acrylate, (meth) acrylate having a hydroxyl group, and phenyl group-containing (meth) acrylate. Can be mentioned.

More specifically, the chain alkyl group which is one kind of R ^Y2 is a chain alkyl group having 1 to 3 carbon atoms, which is a methyl group, an ethyl group, an n-propyl group, or an isopropyl group; Examples thereof include chain alkyl groups having 4 or more carbon atoms, such as a butyl group, an isobutyl group, a t-butyl group, an n-hexyl group, a 2-ethylhexyl group, and a lauryl group. Moreover, as an aryl group which is 1 type of ^RY2, a phenyl group is mentioned, for example.
Specific examples of the (meth) acrylic acid ester monomer having R ^Y2 include, for example, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-hexyl acrylate, Chain alkyl groups such as 2-ethylhexyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate (Meth) acrylate having;
Examples include (meth) acrylates having an aromatic ring, such as phenyl (meth) acrylate and benzyl (meth) acrylate.

Among these, excessive swelling in the electrolytic solution is achieved by appropriately separating the solubility parameter (SP value) of the electrolytic solution and the SP value of the polymer from the viewpoint of improving adhesion with the electrode (electrode active material). In view of suppressing the balance between rigidity and resistance, a monomer having a chain alkyl group having 4 or more carbon atoms, more specifically, R ^Y2 is a chain alkyl group having 4 or more carbon atoms. (Meth) acrylate monomers are preferred. More specifically, at least one selected from the group consisting of butyl acrylate, butyl methacrylate, and 2-ethylhexyl acrylate is preferable. The upper limit of the number of carbon atoms in the chain alkyl group having 4 or more carbon atoms is not particularly limited, and may be 14, for example, but 7 is preferable. These (meth) acrylic acid ester monomers are used singly or in combination of two or more.

The (meth) acrylic acid ester monomer preferably includes a monomer having a cycloalkyl group as R ^Y2 instead of or in addition to the monomer having a chain alkyl group having 4 or more carbon atoms. Excessive swelling in the electrolytic solution can be suppressed by the presence of the umbrella-rich cycloalkyl group, and this also improves the adhesion to the electrode.
More specifically, examples of the monomer having such a cycloalkyl group include cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, and the like. 4-8 are preferable, as for the number of the carbon atoms which comprise the alicyclic ring of a cycloalkyl group, 6 and 7 are more preferable, and 6 is especially preferable. Further, the cycloalkyl group may or may not have a substituent. Examples of the substituent include a methyl group and a t-butyl group. Among these, at least one selected from the group consisting of cyclohexyl acrylate and cyclohexyl methacrylate is preferable in terms of good polymerization stability when preparing an acrylic polymer. These are used singly or in combination of two or more.

Moreover, it is preferable that an acryl-type polymer contains a crosslinkable monomer as a (meth) acrylic acid ester monomer instead of the above thing, or in addition, Preferably in addition to the above thing. Although it does not specifically limit as a crosslinkable monomer, For example, the monomer which has 2 or more of radically polymerizable double bonds, the monomer which has a functional group which gives a self-crosslinking structure during superposition | polymerization or after superposition | polymerization, etc. are mentioned. These are used singly or in combination of two or more.
Examples of the monomer having two or more radical polymerizable double bonds include divinylbenzene and polyfunctional (meth) acrylate. The polyfunctional (meth) acrylate may be at least one selected from the group consisting of bifunctional (meth) acrylate, trifunctional (meth) acrylate, and tetrafunctional (meth) acrylate. Specifically, for example, polyoxyethylene diacrylate, polyoxyethylene dimethacrylate, polyoxypropylene diacrylate, polyoxypropylene dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, butanediol diacrylate, butanediol Examples include dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, and pentaerythritol tetramethacrylate. These are used singly or in combination of two or more. Especially, at least 1 sort (s) selected from the group which consists of a trimethylol propane triacrylate and a trimethylol propane trimethacrylate from a viewpoint similar to the above is preferable.

Examples of the monomer having a functional group that gives a self-crosslinking structure during or after polymerization include a monomer having an epoxy group, a monomer having a methylol group, a monomer having an alkoxymethyl group, and a monomer having a hydrolyzable silyl group. It is done. As the monomer having an epoxy group, an ethylenically unsaturated monomer having an alkoxymethyl group is preferable. Specifically, examples thereof include glycidyl (meth) acrylate, 2,3-epoxycyclohexyl (meth) acrylate, and 3,4-epoxy. Examples include cyclohexyl (meth) acrylate and allyl glycidyl ether.
Examples of the monomer having a methylol group include N-methylol acrylamide, N-methylol methacrylamide, dimethylol acrylamide, dimethylol methacrylamide, and the like.
The monomer having an alkoxymethyl group is preferably an ethylenically unsaturated monomer having an alkoxymethyl group. Specifically, for example, N-methoxymethylacrylamide, N-methoxymethylmethacrylamide, N-butoxymethylacrylamide, N- Examples include butoxymethyl methacrylamide.
Examples of the monomer having a hydrolyzable silyl group include vinyl silane, γ-acryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ-methacryloxypropyltriethoxy. Silane etc. are mentioned.
These are used singly or in combination of two or more.

The acrylic polymer may further have a monomer other than those described above as a monomer unit in order to improve various qualities and physical properties. Examples of such a monomer include a monomer having a carboxyl group (excluding (meth) acrylic acid), a monomer having an amide group, a monomer having a cyano group, a monomer having a hydroxyl group, and an aromatic vinyl monomer. Is mentioned.
Furthermore, various vinyl monomers having functional groups such as sulfonic acid groups and phosphoric acid groups, and vinyl acetate, vinyl propionate, vinyl versatic acid, vinyl pyrrolidone, methyl vinyl ketone, butadiene, ethylene, propylene, vinyl chloride, chloride Vinylidene or the like can be used as necessary.
These are used singly or in combination of two or more. The other monomer may belong to two or more of the above monomers at the same time.

Examples of the monomer having an amide group include (meth) acrylamide.
The monomer having a cyano group is preferably an ethylenically unsaturated monomer having a cyano group, and specific examples include (meth) acrylonitrile.
As a monomer which has a hydroxyl group, 2-hydroxyethyl (meth) acrylate etc. are mentioned, for example.

  Examples of the aromatic vinyl monomer include styrene, vinyl toluene, α-methyl styrene, and the like. Styrene is preferred.

  The acrylic polymer is obtained, for example, by a usual emulsion polymerization method. There is no restriction | limiting in particular regarding the method of emulsion polymerization, A conventionally well-known method can be used.

  For example, in a dispersion system having the above-described monomer, surfactant, radical polymerization initiator, and other additive components used as necessary in an aqueous medium as a basic composition component, a monomer composition containing each of the above monomers. An acrylic polymer is obtained by polymerization. In the polymerization, a method of making the composition of the monomer composition to be supplied constant throughout the entire polymerization process, a method of changing the morphological composition of the particles of the resin dispersion produced by sequentially or continuously changing the polymerization process, etc. Various methods can be used as required.

The surfactant is a compound having at least one or more hydrophilic groups and one or more lipophilic groups in one molecule. Various surfactants include non-reactive surfactants and reactive surfactants, preferably reactive surfactants, more preferably anionic reactive surfactants, and more preferably sulfonic acid. It is a reactive surfactant having a group.
It is preferable to use 0.1 to 5 parts by mass of the surfactant based on 100 parts by mass of the monomer composition. Surfactant is used individually by 1 type or in combination of 2 or more types.

The radical polymerization initiator is one that initiates the addition polymerization of the monomer by radical decomposition with heat or a reducing substance, and any of inorganic initiators and organic initiators can be used. As the radical polymerization initiator, a water-soluble or oil-soluble polymerization initiator can be used.
The radical polymerization initiator is preferably used in an amount of 0.05 to 2 parts by mass with respect to 100 parts by mass of the monomer composition. A radical polymerization initiator can be used individually by 1 type or in combination of 2 or more types.

  As said 3) polyvinyl alcohol-type resin, polyvinyl alcohol, polyvinyl acetate, etc. are mentioned, for example.

  Examples of the above 4) fluorine-containing resin include polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, and ethylene-tetrafluoroethylene copolymer. Can be mentioned.

A polymer having high rigidity in an electrolytic solution is a polymer that can be dissolved or dispersed in a solvent (hereinafter referred to as “solvent-based polymer”) but can be dissolved or dispersed in water (hereinafter referred to as “water-based polymer”). Also good.
As the solvent-based polymer, among the thermoplastic polymers, a polymer having solubility in an organic solvent and / or a polymer having dispersibility in an organic solvent may be used.
The water-based polymer may be in the form of an aqueous dispersion (hereinafter referred to as “latex”) containing water and a granular polymer dispersed in water, or the polymer itself may have a portion having a high affinity for water. .
Among these, from the viewpoint of polymer coatability or electrical characteristics of the electricity storage device, an aqueous polymer is preferable, and latex is more preferable. The latex can be formed, for example, when the thermoplastic polymer is obtained by emulsion polymerization.

  As the polymer in the latex, it is preferable to use at least one selected from the group consisting of an acrylic polymer, a fluorine-containing resin, and a styrene-butadiene rubber.

  When the water-based polymer contains an acrylic polymer, in order to suppress the swelling of the water-based polymer in the electrolytic solution, that is, to moderately reduce the degree of swelling of the water-based polymer with respect to the electrolytic solution, it has been explained in 2) above. Among the (meth) acrylic compounds, it is preferable to use a monomer having an SP value that is appropriately separated from the solubility parameter (SP value) of the electrolytic solution.

The SP value of the electrolytic solution is arbitrarily determined according to a desired power storage device design.
For example, an electrolytic solution for a non-aqueous electrolyte secondary battery generally includes one or more carbonates as a non-aqueous solvent. Examples of the carbonate include ethylene carbonate (EC, SP value derived by the Hildebrand method (hereinafter referred to as “Hildebrand SP value”): 14.7), propylene carbonate (PC, Hildebrand SP value: 13.3). ), Dimethyl carbonate (DMC, Hildebrand SP value: 9.9), diethyl carbonate (DEC, Hildebrand SP value: 8.8), methyl ethyl carbonate (MEC), and the like.
The SP value of a mixture of two or more carbonates is the sum of the product (SP _n V _n ) of the SP value of each component and the volume ratio of each component. For example, the Hildebrand SP value of a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (EC volume / DEC volume = 2/3) is 11.6.

  In order to improve the rigidity of the acrylic polymer in the electrolytic solution, the amount of the functional group having the SP value that is the same as or close to the SP value of the functional group of the electrolytic solution component is decreased in the (meth) acrylic compound. It is also preferable.

  The monomer described above preferably has an appropriate degree of swelling in the electrolytic solution. When the degree of swelling of the monomer is too low, the affinity with the electrolytic solution deteriorates and the battery characteristics also deteriorate. On the other hand, if the degree of swelling of the monomer is too high, the polymer cannot maintain its strength in the electrolytic solution, so that the rigidity of the polymer in the electrolytic solution is reduced.

  The thermoplastic polymer contains a monomer having a difference between the Hildebrand SP value of the electrolyte and the Hildebrand SP value of the monomer (hereinafter referred to as “SP value difference”) in the range of 0.5 to 4.0. It is preferable. When the SP value difference is 0.5 or more, the affinity between the electrolytic solution and the polymer is appropriately maintained. Therefore, the polymer is appropriately swollen in the electrolytic solution, and the polymer rigidity can be prevented from being lowered. it can. On the other hand, when the SP value difference is 4.0 or less, the affinity between the electrolytic solution and the polymer is good, and the battery characteristics are good. The SP value difference is more preferably 1.0 to 3.5, still more preferably 1.5 to 3.2, and particularly preferably 1.8 to 3.0.

The amount of the monomer having an SP value difference in the range of 0.5 to 4.0 is preferably at least 30 parts by weight, more preferably at least 50 parts by weight with respect to 100 parts by weight of the polymer containing the monomer as a constituent unit. More preferably, it is 60 parts by mass or more.
The amount of the monomer having an SP value difference in the range of 1.8 to 3.0 is preferably at least 30 parts by mass, more preferably at least 40 parts by mass with respect to 100 parts by mass of the polymer containing the monomer as a constituent unit. More preferably, it is 50 parts by mass or more.
By adjusting the amount of the monomer having an SP value difference in the range of 0.5 to 4.0 or 1.8 to 3.0 to the above-mentioned mass ratio, maintaining the rigidity in the electrolyte and battery characteristics Can be compatible.
On the other hand, the amount of the monomer having an SP value difference of about 0 is preferably as small as possible, more preferably 20 parts by weight or less, more preferably 20 parts by weight or less, based on 100 parts by mass of the polymer containing the monomer having an SP value difference of about 0 The amount is preferably 15 parts by weight or less, particularly preferably 10 parts by weight or less.

  In order to improve the rigidity of the acrylic polymer in the electrolyte solution, it is also preferable to adjust the degree of crosslinking of the acrylic polymer to an appropriate range. If the degree of crosslinking is excessively increased, the strength of the acrylic polymer may decrease, so the gel fraction of the acrylic polymer is preferably 85% to 99%, more preferably 90% to 97%. preferable.

When the water-based polymer contains a fluorine-containing resin, among the fluorine-containing resins described in 4) above, a polyvinylidene fluoride or a copolymer containing vinylidene fluoride and hexafluoropropylene as a copolymerization component is preferable. Vinylidene fluoride-hexafluoro More preferred are propylene copolymers, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymers, and the like.
In order to improve the rigidity of the fluorine-containing resin in the electrolytic solution, the copolymerization ratio of hexafluoropropylene in the fluorine-containing resin is preferably in the range of 0.5 mol% to 15 mol%, for example. More preferably, it is in the range of mol% to 10 mol%. It is also preferable to increase the molecular weight of the fluorine-containing resin, and the weight average molecular weight (Mw) of the fluorine-containing resin is preferably 100,000 or more, more preferably 300,000 or more, and further preferably 500,000 or more. The degree of crystallinity of the fluororesin is preferably as high as possible, more preferably 15% or more, still more preferably 20% or more, and particularly preferably 25% or more.

  When the water-based polymer contains styrene-butadiene rubber, it is preferable to adjust the degree of crosslinking of the styrene-butadiene rubber within an appropriate range in order to improve the rigidity of the styrene-butadiene rubber in the electrolytic solution. If the degree of crosslinking is excessively increased, the strength of the styrene-butadiene rubber may decrease, so the gel fraction of the styrene-butadiene rubber is preferably 90% to 99%, and preferably 95% to 98%. Is more preferable.

  When a thermoplastic polymer is used as the polymer having high rigidity in the electrolytic solution, the glass transition temperature of the thermoplastic polymer (hereinafter also referred to as “Tg”) is not particularly limited, but may be −50 ° C. or higher. Preferably it is 20 degreeC or more, More preferably, it is 20 degreeC-120 degreeC, More preferably, it is 20 degreeC-100 degreeC. When the Tg of the thermoplastic polymer is 20 ° C. or higher, sticking of the outermost surface of the separator having the polymer layer can be suppressed, and the handling property tends to be improved. Further, when Tg is 120 ° C. or lower, the adhesion of the separator to the electrode (electrode active material) tends to be better.

Here, the glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC). Specifically, it is determined by the intersection of a straight line obtained by extending the base line on the low temperature side in the DSC curve to the high temperature side and the tangent at the inflection point of the stepped change portion of the glass transition.
“Glass transition” refers to a change in calorific value associated with a change in the state of the polymer that is a test piece in DSC on the endothermic side. Such a change in heat quantity is observed as a step-like change shape in the DSC curve. The “step change” refers to a portion of the DSC curve until the curve moves away from the previous low-temperature base line to a new high-temperature base line. Note that a combination of a step change and a peak is also included in the step change.
Further, the “inflection point” indicates a point at which the gradient of the step-like change portion of the DSC curve is maximized. Further, in the step-like change portion, when the upper side is the heat generation side, it can also be expressed as a point where the upward convex curve changes to the downward convex curve. “Peak” indicates a portion of the DSC curve from when the curve leaves the low-temperature side baseline until it returns to the same baseline again. “Baseline” refers to a DSC curve in a temperature region where no transition or reaction occurs in the test piece.

The Tg of the thermoplastic polymer can be adjusted as appropriate by changing, for example, the type of monomer used in the production of the thermoplastic polymer and the blending ratio of each monomer. The Tg of the thermoplastic polymer is derived from the homopolymer Tg generally indicated for each monomer used in its production (eg, as described in “A WILEY-INTERSCIENCE PUBLICATION”) and the blending ratio of the monomers. It can be estimated roughly. For example, thermoplastic polymers that incorporate a high proportion of monomers such as styrene, methyl methacrylate, and acrylonitrile that give a polymer with a Tg of about 100 ° C. have a high Tg. Further, for example, a thermoplastic polymer containing a high proportion of monomers such as butadiene giving a Tg polymer of about -80 ° C, n-butyl acrylate and 2-ethylhexyl acrylate giving a Tg polymer of about -50 ° C. Has a low Tg.
The Tg of the polymer can be estimated from the FOX formula (the following formula (2)). In addition, as a glass transition temperature of a thermoplastic polymer, what was measured by the method using said DSC is employ | adopted.
1 / Tg = W1 / Tg1 + W2 / Tg2 +... + Wi / Tgi +... Wn / Tgn (2)
{Wherein Tg (K) represents the Tg of the copolymer, Tgi (K) represents the Tg of the homopolymer of each monomer i, and Wi represents the mass fraction of each monomer}.

  The thermoplastic polymer-containing layer formed on the substrate preferably has at least two glass transition temperatures. Thereby, the balance of the adhesiveness to an electrode and handling property can be made compatible more favorably.

  When the thermoplastic polymer-containing layer has at least two glass transition temperatures, it is preferable that at least one of the glass transition temperatures is present in a region below 20 ° C. Thereby, it will become further excellent in adhesiveness with a base material. As a result, there is an effect that the separator is more excellent in adhesion with the electrode. From the same viewpoint, it is more preferable that at least one of the glass transition temperatures of the thermoplastic polymer to be used exists in a region of 15 ° C. or lower. More preferably, it exists in the region of -30 ° C or higher and 15 ° C or lower. The glass transition temperature existing in the region below 20 ° C is present only in the region of -30 ° C or higher and 15 ° C or lower from the viewpoint of further improving the adhesion between the thermoplastic polymer and the base material while maintaining the handling property better. It is preferable.

  When the thermoplastic polymer has at least two glass transition temperatures, it is preferable that at least one of the glass transition temperatures exists in a region of 20 ° C. or higher. Thereby, there exists an effect that it is further excellent in the adhesiveness and handling property of a separator and an electrode. Moreover, it is more preferable that at least one of the glass transition temperatures of the thermoplastic polymer to be used exists in a region of 20 ° C. or higher and 120 ° C. or lower. More preferably, it is 50 degreeC or more and 120 degrees C or less. When the glass transition temperature exists in the above range, it is possible to impart better handling properties. Furthermore, it is possible to further improve the adhesion between the electrode and the separator that are expressed by pressurization during battery production. The glass transition temperature that exists in the region of 20 ° C or higher exists only in the region of 20 ° C or higher and 120 ° C or lower in order to further improve the adhesion between the thermoplastic polymer and the base material while maintaining better handling properties. It is preferable that it exists only in the region of 50 ° C. or higher and 120 ° C. or lower.

The thermoplastic polymer having at least two glass transition temperatures can be achieved by, for example, a method of blending two or more thermoplastic polymers, a method of using a thermoplastic polymer having a core-shell structure, or the like. However, it is not limited to these methods. The core-shell structure is a polymer having a dual structure in which the polymer belonging to the central portion and the polymer belonging to the outer shell portion have different compositions.
In particular, in a polymer blend and a core-shell structure, the glass transition temperature of the entire thermoplastic polymer can be controlled by combining a polymer having a high glass transition temperature and a polymer having a low glass transition temperature. Moreover, a plurality of functions can be imparted to the entire thermoplastic polymer.

  For example, in the case of a blend, in particular, by blending two or more types of polymers existing in a region where the glass transition temperature is 20 ° C. or higher and polymers existing in a region where the glass transition temperature is lower than 20 ° C., stickiness resistance is obtained. And the paintability to the base material can be more satisfactorily achieved. As a mixing ratio in the case of blending, the ratio of the polymer existing in the region where the glass transition temperature is 20 ° C. or higher and the polymer existing in the region where the glass transition temperature is lower than 20 ° C. is 0.1: 99.9 to 99. Is preferably in the range of 9: 0.1, more preferably 5:95 to 95: 5, still more preferably 50:50 to 95: 5, and particularly preferably 60:40 to 90 :. 10.

In the case of the core-shell structure, the adhesiveness and compatibility with other materials (for example, a polyolefin microporous film) can be adjusted by changing the type of the outer shell polymer. Moreover, it can adjust to the polymer which improved the adhesiveness to the electrode after hot press, for example by changing the kind of polymer which belongs to a center part. Alternatively, viscoelasticity can be controlled by combining a highly viscous polymer and a highly elastic polymer.
The glass transition temperature of the shell of the thermoplastic polymer having a core-shell structure is not particularly limited, but is preferably less than 20 ° C, more preferably 15 ° C or less, and further preferably -30 ° C or more and 15 ° C or less. The glass transition temperature of the core of the thermoplastic polymer having a core-shell structure is not particularly limited, but is preferably 20 ° C or higher, more preferably 20 ° C or higher and 120 ° C or lower, and further preferably 50 ° C or higher and 120 ° C or lower.

The thermoplastic polymer may be granular, and more particularly may be a particle composed of one type of thermoplastic polymer or a mixture of a plurality of thermoplastic polymers, or may have the core-shell structure described above.
When the thermoplastic polymer is granular, the term “granular” refers to a state in which each polymer has a contour as measured by a scanning electron microscope (SEM). Therefore, the granular thermoplastic polymer may be, for example, a flat shape, a spherical shape, a polygonal shape, or the like.

  In order to ensure the adhesion and rigidity of the thermoplastic polymer in the electrolyte, and further improve the cycle characteristics or rate characteristics of the electricity storage device, the separator is impregnated with the electrolyte and then the substrate coated with the polymer is used. The surface area ratio is preferably 100% or less, 80% or less, 70% or less, 60% or less, or 50% or less, and the area ratio is 5% or more, 10% or more, 15% or more, or It is preferably 20% or more. This area ratio is measured by observing the outermost surface of the substrate with SEM (magnification 30000 times).

  FIG. 7 is a schematic diagram showing a planar shape of a polymer layer present on at least one surface of a substrate in a separator. The polymer layer on the substrate may have, for example, a planar shape indicated by black in FIG. The polymer layer exists in a planar shape such as a dot shape (FIG. 7A), a lattice shape (FIG. 7B), a linear shape (FIG. 7C), a stripe shape (FIG. 7D), a turtle shell pattern shape (FIG. 7E), and the like. Also good.

Voronoi polygons obtained by performing Voronoi division on granular thermoplastic polymer (hereinafter also referred to as "thermoplastic polymer particles") placed on the separator substrate in order to improve the high-temperature storage characteristics in addition to the rigidity of the electricity storage device The dispersion (σ ² ) of the area (s _i ) is preferably 0.01 or more and 0.7 or less.

  Voronoi division refers to dividing a plurality of points (mother points) arranged at arbitrary positions in a certain distance space according to which mother point is closer to other points in the same space. . A diagram including the region thus obtained is called a Voronoi diagram. In general, in the Voronoi diagram, the boundary lines of a plurality of regions become a part of the bisector of each generating point, and each region forms a polygon (Voronoi polygon).

When observing the separator surface with a specific visual field, one thermoplastic polymer particle is regarded as one circle having an average diameter (l) in the observation visual field. A perpendicular bisector is drawn between a plurality of adjacent thermoplastic polymer particles, and a polygon surrounded by the perpendicular bisector for each particle is referred to as a “Voronoi polygon”.
The variance (σ ² ) of the area (s _i ) of the Voronoi polygon is:
{Wherein s _i is the actual value of the area of the Voronoi polygon, m is the average value of the actual area of the Voronoi polygon, and n is the total number of Voronoi polygons}
Is a value calculated by. It is assumed that a region that is not closed when Voronoi division is performed in the observation field is not subject to calculation of the above formula. Examples of the non-closed region include a region obtained by performing Voronoi division on the particle when the particle is present at the boundary of the observation field and the entire particle is not observed.
Therefore, in an image obtained by photographing at least a part of the separator surface, it is preferable to confirm whether or not the entire particle is observed at the edge of the image.

In this embodiment, the dispersion (σ ² ) of the area (s _i ) of the Voronoi polygon is an index indicating the level of variation in the arrangement of the granular thermoplastic polymer on the substrate. This dispersion (σ ² ) is considered to represent the distribution or aggregation state of the coated surface of the granular thermoplastic polymer. When the dispersion (σ ² ) of the Voronoi polygonal area (s _i ) is 0.01 or more, it can be evaluated that the granular thermoplastic polymer is appropriately aggregated and disposed on the separator surface. Therefore, in this case, the adhesiveness between the electrode and the separator tends to be sufficient. If the dispersion (σ ² ) is 0.7 or less, it can be evaluated that the particulate thermoplastic polymer is not excessively aggregated on the separator surface. Therefore, in this case, the ion resistance on the separator surface is uniform, lithium ions do not concentrate on a specific region of the surface, and the generation of metallic lithium is suppressed, so the high-temperature storage characteristics of the electricity storage device tend to be excellent It is in. The value of this dispersion (σ ² ) is preferably 0.01 or more and 0.6 or less, more preferably 0.01 or more and 0.5 or less, and 0.1 or more and 0.4 or less. Is more preferable, and 0.1 to 0.35 is particularly preferable.

  The average particle diameter of the granular thermoplastic polymer is preferably 10 nm to 2,000 nm, more preferably 50 nm to 1,500 nm, still more preferably 100 nm to 1,000 nm, particularly preferably 130 nm to 800 nm, and particularly preferably 150 nm. It is -800 nm, Most preferably, it is 200-750 nm. Setting this average particle size to 10 nm or more ensures that the size of the granular thermoplastic polymer is such that it does not enter the pores of the substrate when a granular thermoplastic polymer is applied to the substrate including at least the porous film. Means that Therefore, in this case, it is preferable from the viewpoint of improving the adhesion between the electrode and the separator and the cycle characteristics of the electricity storage device. In addition, when the average particle size is 2,000 nm or less, a granular thermoplastic polymer in an amount necessary for achieving both the adhesion between the electrode and the separator and the cycle characteristics of the electricity storage device is applied onto the substrate. It is preferable from the viewpoint of working. The average particle diameter of the granular thermoplastic polymer can be measured according to the method described in the following examples.

In order to know the area density of the thermoplastic polymer particles and the dispersion (σ ² ) of the area (s _i ) of the Voronoi polygon obtained by performing Voronoi division on the thermoplastic polymer particles, the surface of the separator is observed. The observation means is appropriately selected depending on the size or distribution state of the thermoplastic polymer particles coated on the separator, and any method can be adopted. For example, an electron microscope, an atomic force microscope, an optical microscope, a differential interference microscope, or the like can be used. Among these, when dealing with the distribution state of the dispersed particles as in the present embodiment, it is preferable to use an electron microscope or an atomic force microscope.

  Within the observation field, an average observation field of the polymer layer coated on the separator surface should be ensured. Further, the projected area in the observation field should be adjusted as appropriate so that the average distribution state of the dispersed particles can be grasped. For example, the number of dispersed particles employed as a calculation target is preferably about 80 to 200 / field of view. This observation visual field can be obtained by observing the polymer layer with a preset observation means and magnification. For example, FIG. 1 is an example of a photograph in which the surface of the polymer layer is observed with a scanning electron microscope as the observation means and a magnification of 10,000. FIG. 1 clearly captures the state in which thermoplastic polymer particles having a particle diameter of about 500 nm are dispersed on the surface of the polymer layer. Thus, by grasping the state in which the thermoplastic polymer particles are dispersed on the surface of the polymer layer, the dispersion state of the thermoplastic polymer particles can be analyzed by Voronoi division.

  In observation using a scanning electron microscope, an appropriate magnification is set for analysis by Voronoi division according to the particle size of the thermoplastic polymer particles. Specifically, the magnification is set such that the number of thermoplastic polymer particles observed in one visual field is preferably 40 to 300, more preferably 60 to 240, and still more preferably 80 to 200. . Thus, analysis by Voronoi division can be performed appropriately. For example, if the particle size is about 500 nm, it is appropriate to set the magnification to 10,000 times. If the particle size is about 200 nm, setting the magnification to about 30,000 times is suitable for analysis by Voronoi division. Is appropriate.

  The thermoplastic polymer particles included in the observation field obtained by the above observation method are specified. For example, the thermoplastic polymer particles are identified from the observation field with the naked eye or using image processing software. FIG. 2 is an example showing a result of automatically specifying the thermoplastic polymer particles included in the observation visual field of FIG. 1 using image processing software. By identifying the thermoplastic polymer particles in a preset method and magnification field of view, the total number of particles, the diameter of each particle, and the projected area of each particle are calculated (see also FIG. 3 below). In that case, it is preferable to specify only particles that are entirely contained within the observation field.

  The above-defined Voronoi division can be performed on the thermoplastic polymer particles specified in a specific field of view on the separator surface. Specifically, the surface of the coated film after the thermoplastic polymer is coated on the separator surface is photographed to obtain an image. A Voronoi polygon can be drawn by performing the Voronoi division by regarding the thermoplastic polymer particles specified in the obtained image as a circle having an average diameter (l). For example, Voronoi polygons may be drawn manually or using image processing software. Then, the area of the drawn Voronoi polygon is calculated.

  For example, FIG. 3 is an example of a result obtained by performing Voronoi division on the plurality of thermoplastic polymer particles specified in FIG. 2 to obtain a Voronoi polygon. FIG. 4 shows the result of automatically calculating the number and area of Voronoi polygons corresponding to the closed region in the Voronoi polygon shown in FIG. 3 using image processing software.

By the above observation method and image processing method, the projected area in the viewing field is determined, and the total number of thermoplastic polymer particles, the projected area, and the Voronoi polygonal area in the viewing field are obtained. Then, according to the above definition, it can be calculated for the thermoplastic polymer particles in the visual field, the area density, and Voronoi dispersion polygonal area (s _i) a (sigma ^2).
However, the distribution of the thermoplastic polymer particles may vary depending on the observation field. Therefore, as the area density and the variance (σ ² ), it is preferable to employ an average value of values calculated for a plurality of observation fields. The number of fields of view is preferably 3 or more.

It is particularly preferable to employ an average value of values calculated for 95 visual fields determined as follows.
i) Each measurement field: an image taken with a scanning electron microscope ii) Field setting method:
a) Set the field of view of the starting point,
b) Nine visual fields consisting of regions sequentially adjacent in the horizontal direction with respect to the visual field of the starting point, nine visual fields consisting of regions adjacent in the vertical direction, and the visual field of the starting point 19 Set the field of view,
c) setting the area defined by the 19 fields of view as the starting section;
d) Set four sections consisting of regions that are sequentially adjacent to each other in the uniaxial direction at intervals of 10 mm with respect to the starting section.
e) For each of the four sections, set 19 fields of view at positions similar to 19 fields in the starting section, and f) All 95 fields in the four sections and the starting section (19 fields × 5 Section) is set as the measurement field of view.

  Each of the measurement visual fields is preferably a captured image that is captured by setting the magnification so that the number of thermoplastic polymer particles observed in one visual field is 80 to 200.

Hereinafter, a preferred method for setting 95 fields of view according to the present embodiment will be described with reference to the drawings.
i) As described above, it is preferable to employ an image captured by a scanning electron microscope with a magnification of 10,000 times as described above. For example, the image shown in FIG. FIG. 5 is a diagram schematically showing a part of an image of thermoplastic polymer particles on a base material, which is imaged with a scanning electron microscope with a magnification of 10,000 times.
In the image of FIG. 5, first, the visual field (10) of the starting point is set. Since one field of view is composed of images taken with a scanning electron microscope with a magnification of 10,000 times, the scale of one field of view is about 10 μm × 10 μm, and a field of view suitable for Voronoi division evaluation based on thermoplastic polymer particles is provided. Configure. Next, nine visual fields (1 to 9) that are sequentially adjacent to the starting visual field (10) in the lateral direction (X-axis direction) are set. Each of these visual fields (1 to 9) is made up of captured images having the same magnification as that of the starting visual field (10), and is sequentially set in one direction with a common side and one side. Next, nine visual fields (11 to 19) which are sequentially adjacent to the starting visual field (10) in the vertical direction are set. Each of these visual fields (11 to 19) is composed of the same region as the starting visual field (10), and is sequentially set in one direction while sharing one side with an adjacent region.

Subsequently, the region defined by the 19 fields of view is set as the starting section (I). Since the starting section (I) is composed of a square area having two sides, the upper side of the visual fields 1 to 10 and the right side of the visual fields 10 to 19 in FIG. 5, the scale of one section is about 100 μm × 100 μm. The dispersion calculated from the 19 fields of view constituting the section (I) can be evaluated as a value more accurately representing the state of the separator surface.
In this embodiment, in order to further accurately evaluate the state of the separator surface, the evaluation is performed by providing five sections equivalent to the above-described one section. Specifically, refer to FIG. FIG. 6 is an overall image of an image of the thermoplastic polymer particles on the substrate shown in FIG. In FIG. 6, four sections (II to V) that are sequentially adjacent to each other in the uniaxial direction at intervals of 10 mm are set with respect to the section (I) of the starting point. Each of these four sections consists of the same area as the starting section (I).
Next, for each of these four sections (II to V), 19 fields of view are set at positions similar to the 19 fields of view in the starting section (I). Then, all 95 fields (19 fields × 5 fields) in the four sections (II to V) and the field (I) of the starting point are set as observation fields of the thermoplastic polymer particles on the substrate.

The observation of the separator surface is preferably performed on a region of the separator surface that is not involved in ion conduction. For example, it is possible to observe a separator that has just been manufactured and is not yet incorporated into a storage element. When the electricity storage element is in use or after use, the so-called “ear” portion of the separator (a region near the outer edge of the separator and not involved in ion conduction) may be observed. This is a preferred aspect in the present embodiment.
As understood from the above evaluation method, when 95 visual fields are to be observed, a separator piece having a length of about 40 mm is to be measured, and therefore, the dispersion state of the thermoplastic polymer on the separator surface can be accurately evaluated.

The fact that thermoplastic polymer particles can be subjected to Voronoi division as described above means that in the polymer layer formed on the substrate, the thermoplastic polymer particles do not substantially overlap and exist as single layer particles. It shows that. For example, when thermoplastic polymers overlap in a polymer layer several times, the concept of area occupied by a single particle cannot be established, and Voronoi division cannot be performed.
The separator in the present embodiment is arranged such that the thermoplastic polymer particles in the polymer layer formed on the substrate do not substantially overlap, and the above-described area density and dispersion (σ ² ) However, it is preferable that each is adjusted to the above-mentioned range.

The means for adjusting the area density and dispersion (σ ² ) of the thermoplastic polymer to the above range is not limited, but for example, the thermoplastic polymer content in the coating liquid applied to the substrate, the coating It can be adjusted by changing the coating amount of the working liquid, the coating method, and the coating conditions. More specifically, the viscosity of the thermoplastic polymer solution is adjusted to be high, and the thermoplastic polymer is dispersed and arranged in the above range by applying a shearing force to the coated surface of the porous film. be able to.

  The presence form (pattern) of the polymer layer on the base material is not particularly limited, but it is preferable that the thermoplastic polymer particles exist in a mutually dispersed state over the entire surface of the base material so as to satisfy the above dispersion. . The thermoplastic polymer particles may form clusters in a part of the region, but it is necessary that the particles are dispersed to the extent that the dispersion range is satisfied as a whole. The polymer particles may be stacked in a part of the region, but it is necessary that the particles are dispersed to the extent that the dispersion range is satisfied as a whole.

When the polymer layer is present in a pattern on the substrate, the above-described area density and dispersion (σ ² ) are preferably evaluated using an image obtained by photographing a region where the polymer layer is present.

[2. (The polymer layer forms a continuous layer)
“The polymer layer forms a continuous layer” means that one or more interfaces are not formed in the polymer layer itself. When the polymer on the substrate forms a continuous layer, the rigidity of the adhesive layer itself composed of the continuous layer is increased, so that the rigidity of the electricity storage device is easily increased.

  Examples of the polymer for forming the continuous layer include polyethylene oxide (PEO), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polyether urethane (PEU), and polyethyl acrylate. (PEA), PVDF-hexafluoropropylene (HFP) copolymer, or a combination thereof.

  In order to form the polymer layer as a continuous layer, it is preferable to dissolve the polymer in a good solvent to obtain a coating solution, and to apply the coating solution to the substrate. At this time, in order to ensure the permeability of the separator, the ratio of the coating area of the polymer layer to the base material is adjusted, or the polymer layer formed by coating may be made porous by using solvent phase separation or the like. More preferred.

  In order to adjust the coating area ratio of the polymer layer to the substrate to such an extent that the permeability of the separator is ensured, it is preferable to obtain a coating solution by dispersing or dissolving the polymer in a volatile solvent such as acetone. In that case, the polymer concentration in the coating solution is preferably less than 30% by mass, more preferably less than 15% by mass, and even more preferably less than 10% by mass. After forming the polymer layer by applying the coating liquid to the substrate, the volatile solvent such as acetone is preferably removed from the polymer layer by drying.

  When the polymer layer on the substrate is made porous by solvent phase separation or the like, the permeability of the separator can be ensured even if the coating area ratio of the coating liquid containing the polymer is 100%. Specifically, the polymer is dissolved in a good solvent to prepare a coating solution. This coating solution is applied onto a substrate and immersed in an appropriate coagulation solution. This solidifies the polymer while inducing a phase separation phenomenon. In this solidification step, the polymer layer (continuous layer) has a porous structure. Thereafter, the coagulating liquid is removed by washing with water and dried.

  As the coating solution, for example, a good solvent that dissolves polyvinylidene fluoride resin may be used. As the good solvent, for example, polar amide solvents such as N-methylpyrrolidone, dimethylacetamide, dimethylformamide, and dimethylformamide can be suitably used. From the viewpoint of forming a good porous structure, it is preferable to mix a phase separation agent that induces phase separation in the polar amide solvent in addition to the good solvent. Examples of the phase separation agent include water, methanol, ethanol, propyl alcohol, butyl alcohol, butanediol, ethylene glycol, propylene glycol, and tripropylene glycol. The phase separation agent is preferably added in a range that can ensure a viscosity suitable for coating. As the solvent, it is preferable to use a mixed solvent of 60% by weight or more of a good solvent and 40% by weight or less of a phase separation agent from the viewpoint of forming an appropriate porous structure.

  As the coagulation liquid, water, a mixed solvent of water and a good solvent, or a mixed solvent of water, a good solvent, and a phase separation agent can be used. In particular, a mixed solvent of water, a good solvent, and a phase separation agent is preferable.

  In order to form the polymer layer as a continuous layer, it is also preferable that the adhesive layer is formed into a continuous layer using a film-forming aid. Specifically, the adhesive layer formed of latex can form a continuous layer by including a film-forming aid in the latex. Examples of the film-forming aid include glycol compounds and acetate compounds.

  In order to form a continuous layer using a water-based polymer, it is also preferable to use a plurality of water-based polymers that are easily fused to each other. By using a plurality of water-based polymers that are easily fused to each other, the mobility of the surface of the continuous layer can be increased, and the degree of swelling of the continuous layer with respect to the electrolyte can be adjusted within an appropriate range.

[3. (Forming an adhesive layer containing a mixture of inorganic filler and polymer)
By applying a mixture of an inorganic filler and a polymer as a binder for an inorganic filler to a substrate, a composite of the inorganic filler and the polymer can be formed in a coating layer (adhesive layer) formed on the substrate. it can. By combining the inorganic filler and the polymer, the rigidity of the adhesive layer is improved.

  As the binder for inorganic filler, the polymer described in 1 or 2 above may be used. If desired, the coating solution may further contain a dispersant, water, an organic solvent, and the like.

The inorganic filler is not particularly limited, but preferably has high heat resistance and electrical insulation and is electrochemically stable in the range of use of the lithium ion secondary battery.
As an inorganic filler, an aluminum compound, a magnesium compound, and another compound are mentioned, for example.
Examples of the aluminum compound include aluminum oxide, aluminum silicate, aluminum hydroxide, aluminum hydroxide oxide, sodium aluminate, aluminum sulfate, aluminum phosphate, and hydrotalcite.
Examples of the magnesium compound include magnesium sulfate and magnesium hydroxide.
Examples of other compounds include oxide ceramics, nitride ceramics, clay minerals, silicon carbide, calcium carbonate, barium titanate, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, silica sand, Glass fiber etc. are mentioned. Examples of oxide ceramics include silica, titania, zirconia, magnesia, ceria, yttria, zinc oxide, iron oxide, and the like. Examples of nitride ceramics include silicon nitride, titanium nitride, and boron nitride. Examples of the clay mineral include talc, montmorillonite, sericite, mica, amicite, bentonite and the like.
These may be used alone or in combination.

  Among these, at least one selected from the group consisting of aluminum oxide, aluminum hydroxide oxide, and aluminum silicate is preferable from the viewpoint of electrochemical stability and heat resistance. Specific examples of aluminum oxide include alumina. Specific examples of the aluminum hydroxide oxide include boehmite. Specific examples of aluminum silicate include kaolinite, dickite, nacrite, halloysite, and pyrophyllite.

  As the aluminum oxide, alumina is more preferable from the viewpoint of electrochemical stability. By adopting particles mainly composed of alumina as the inorganic filler constituting the porous layer, it is possible to realize a very lightweight porous layer while maintaining high permeability. Furthermore, even when the porous layer thickness is thinner, thermal shrinkage of the porous film at a high temperature is suppressed, and excellent heat resistance tends to be exhibited. Alumina has many crystal forms such as α-alumina, β-alumina, γ-alumina, and θ-alumina, and any of them can be suitably used. Of these, α-alumina is most preferred because it is thermally and chemically stable.

  As the aluminum hydroxide oxide, boehmite is more preferable from the viewpoint of preventing internal short circuit due to generation of lithium dendrite. By adopting particles mainly composed of boehmite as the inorganic filler constituting the porous layer, a very lightweight porous layer can be realized while maintaining high permeability. Furthermore, even when the porous layer thickness is thinner, thermal shrinkage of the porous film at a high temperature is suppressed, and excellent heat resistance tends to be exhibited. Synthetic boehmite that can reduce ionic impurities that adversely affect the characteristics of the storage element is more preferable.

  Among aluminum silicates, kaolinite (hereinafter, also referred to as kaolin) mainly composed of kaolin mineral is preferable from the viewpoints of lightness and air permeability. Kaolin includes wet kaolin and calcined kaolin obtained by calcining it. Of these, calcined kaolin is particularly preferred from the viewpoint of electrochemical stability, since impurities are removed in addition to the release of crystal water during the calcining treatment. By adopting particles mainly composed of calcined kaolin as the inorganic filler constituting the porous layer, it is possible to realize a very lightweight porous layer while maintaining high permeability. Furthermore, even when the porous layer thickness is thinner, thermal shrinkage of the porous film at a high temperature is suppressed, and excellent heat resistance tends to be exhibited.

  The average particle size of the inorganic filler is preferably 0.1 μm or more and 10.0 μm or less, more preferably 0.2 μm or more and 5.0 μm or less, and further preferably 0.4 μm or more and 3.0 μm or less. preferable. Adjusting the average particle size of the inorganic filler to the above range is preferable from the viewpoint of increasing the air permeability and suppressing thermal shrinkage at high temperatures.

  The particle size distribution of the inorganic filler is preferably as follows. The minimum particle size is preferably 0.02 μm or more, more preferably 0.05 μm or more, and further preferably 0.1 μm or more. The maximum particle size is preferably 20 μm or less, more preferably 10 μm or less, and even more preferably 7 μm or less. The ratio of the maximum particle size / average particle size is preferably 50 or less, more preferably 30 or less, and still more preferably 20 or less. Adjusting the particle size distribution of the inorganic filler to the above range is preferable from the viewpoint of suppressing thermal shrinkage at high temperatures. The particle size distribution of the inorganic filler may further have one or more particle size peaks between the maximum particle size and the minimum particle size. As a method for adjusting the particle size distribution of the inorganic filler, for example, a method of pulverizing the inorganic filler using a ball mill, a bead mill, a jet mill or the like to adjust the particle size distribution to a desired particle size distribution, a blend after adjusting fillers having a plurality of particle size distributions And the like.

  Examples of the shape of the inorganic filler include a plate shape, a scale shape, a polyhedron, a needle shape, a columnar shape, a spherical shape, a spindle shape, and a lump shape. A plurality of inorganic fillers having the above shapes may be used in combination. Among these, from the viewpoint of improving permeability, one or more shapes selected from the group consisting of a plate shape, a scale shape, and a polyhedron are preferable.

  From the viewpoint of rigidity, the smaller the aspect ratio of the inorganic filler, the better. Specifically, the aspect ratio of the inorganic filler is preferably 5.0 or less, more preferably 4.0 or less, and still more preferably 3.0 or less. The aspect ratio can be calculated from the major axis / minor axis by measuring the major axis and minor axis of a particle from an SEM image or the like. When five or more particles are confirmed in the SEM image, the aspect ratio may be an average value of major axis / minor axis calculated for the five particles.

  The weight ratio of the inorganic filler to the polymer in the coating solution can be arbitrarily determined according to the rigidity and battery characteristics required for the electricity storage device, but the inorganic filler: polymer = 95: 5 to 20:80 More preferably, it is 90: 10-30: 70, More preferably, it is 85: 15-40: 60.

  When the inorganic filler and the polymer are combined, the filler-rich portion is more likely to pass ionic components such as lithium ions in the adhesive layer than the binder-rich portion. Therefore, the area ratio of the substrate surface coated with the coating liquid is 100. %, Both the rigidity and electrical characteristics of the electricity storage device can be achieved.

  The thickness of the adhesive layer containing the mixture of the inorganic filler and the polymer is not limited, but is 0.1 μm to 10 μm from the viewpoint of compatibility between the adhesive property and the rigidity of the adhesive layer in the electrolytic solution. Preferably, it is 0.5 μm to 8 μm.

[Polymer coating method]
One aspect of the method for producing a separator includes a step of applying a coating liquid containing the polymer described above onto a substrate.

As coating conditions for the coating liquid containing the polymer, the coating area ratio of the polymer to the base material is preferably 5% to 70%, and the polymer coating weight is 0.05 g / m ² to 1. It is preferably 0.0 g / m ² and / or the polymer coating thickness is preferably 0.1 μm to 3 μm. When applying the coating liquid containing the granular thermoplastic polymer which can be used for the Voronoi division demonstrated above, it is preferable that coating thickness is 0.1 micrometer-0.8 micrometer.

  The method for coating the coating liquid on the polyolefin microporous membrane or the multilayer microporous membrane is not particularly limited, but for example, gravure coater method, small diameter gravure coater method, reverse roll coater method, transfer roll coater method, kiss coater method, Examples thereof include a dip coater method, a knife coater method, an air doctor coater method, a blade coater method, a rod coater method, a squeeze coater method, a cast coater method, a die coater method, a screen printing method, a spray coating method, and an ink jet coating method. Among these, the gravure coater method or the spray coating method is preferable from the viewpoint that the degree of freedom of the coating shape of the thermoplastic polymer is high and a preferable area ratio can be easily obtained.

  When a thermoplastic polymer is applied to a substrate including a porous film, if the coating liquid gets into the substrate, the adhesive resin fills the surface and the inside of the hole, resulting in reduced permeability. End up. Therefore, a poor solvent for the thermoplastic polymer is preferable as the medium for the coating liquid. When a poor solvent for a thermoplastic polymer is used as the medium for the coating liquid, the coating liquid does not enter the porous film, and the adhesive polymer is mainly present on the surface of the multilayer microporous film. From the viewpoint of suppressing the deterioration of the property. Such a medium is preferably water. Moreover, the medium that can be used in combination with water is not particularly limited, and examples thereof include ethanol and methanol.

  It is preferable to perform a surface treatment on the base material before coating, because the coating liquid can be easily applied and the adhesion between the base material and the adhesive polymer is improved. The surface treatment method is not particularly limited as long as the porous structure of the multilayer microporous membrane is not significantly impaired. For example, corona discharge treatment method, plasma treatment method, mechanical surface roughening method, solvent treatment method, acid treatment method And an ultraviolet oxidation method.

  The method for removing the solvent from the coating film after coating is not limited as long as it does not adversely affect the polyolefin microporous film or the multilayer microporous film. For example, a method of drying a polyolefin microporous film or multilayer microporous film while fixing it at a temperature below its melting point, a method of drying under reduced pressure at a low temperature, or immersing in a poor solvent for the adhesive polymer to solidify the adhesive polymer A method of extracting a solvent at the same time may be used.

[Porous layer containing inorganic filler and resin binder]
The separator may further include a porous layer including an inorganic filler and a resin binder. The position where the separator includes the filler porous layer may be on one side or both sides of the substrate.

  In order to form the porous layer, the inorganic filler described in 3 above may be used.

  The proportion of the inorganic filler in the filler porous layer can be appropriately determined from the viewpoints of the binding properties of the inorganic filler, the permeability of the separator, the heat resistance, etc., but is 50% by mass or more and less than 100% by mass. More preferably, it is 70 mass% or more and 99.99 mass% or less, More preferably, it is 80 mass% or more and 99.9 mass% or less, Most preferably, it is 90 mass% or more and 99 mass% or less.

  The type of the resin binder is not particularly limited, but when the separator has a filler porous layer, it is insoluble in the electrolyte solution of the lithium ion secondary battery and is electrochemical in the range of use of the lithium ion secondary battery. It is preferable to use a stable resin binder.

  Specific examples of the resin binder include, for example, polyolefins such as polyethylene and polypropylene; fluorine-containing resins such as polyvinylidene fluoride and polytetrafluoroethylene; vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, and ethylene-tetrafluoroethylene copolymer. Fluorine-containing rubber such as styrene-butadiene copolymer and its hydride, acrylonitrile-butadiene copolymer and its hydride, acrylonitrile-butadiene-styrene copolymer and its hydride, methacrylate ester-acrylate copolymer, styrene-acrylate copolymer Acrylonitrile-acrylic acid ester copolymer, ethylene propylene rubber, polyvinyl alcohol, polyvinyl acetate, etc. Cellulose derivatives such as ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose; melting point and / or glass transition temperature of polyphenylene ether, polysulfone, polyether sulfone, polyphenylene sulfide, polyetherimide, polyamideimide, polyamide, polyester, etc. Examples thereof include a resin having a temperature of ° C or higher.

  As the resin binder, a resin latex binder is preferable. When a resin latex binder is used, when a filler porous layer containing an inorganic filler and a binder is laminated on at least one side of the substrate, a part or all of the resin binder is dissolved in a solvent, and then the obtained solution is used. Compared to the case where the resin binder is bonded to the porous film by laminating on at least one side of the base material and removing the solvent by dipping in a poor solvent or drying, a high output characteristic is obtained with less susceptibility to ion permeability. It tends to be easy. In addition, even when the temperature rises rapidly during abnormal heat generation, smooth shutdown characteristics are exhibited and high safety tends to be easily obtained.

  The resin latex binder is obtained by emulsion polymerization of an aliphatic conjugated diene monomer, an unsaturated carboxylic acid monomer, and other monomers copolymerizable with these from the viewpoint of improving electrochemical stability and binding properties. Are preferred. There is no restriction | limiting in particular as a method of emulsion polymerization, A conventionally well-known method can be used. The addition method of the monomer and other components is not particularly limited, and any of a batch addition method, a divided addition method, and a continuous addition method can be adopted, and one-stage polymerization, two-stage polymerization, or multi-stage polymerization is possible. Any of these can be adopted.

  The average particle size of the resin binder is preferably 50 to 500 nm, more preferably 60 to 460 nm, and still more preferably 80 to 250 nm. When the average particle diameter of the resin binder is 50 nm or more, when a filler porous layer containing an inorganic filler and a binder is laminated on at least one surface of the polyolefin porous film, the ion permeability is hardly lowered and high output characteristics are easily obtained. In addition, even when the temperature rises rapidly during abnormal heat generation, smooth shutdown characteristics are exhibited and high safety is easily obtained. When the average particle size of the resin binder is 500 nm or less, good binding properties are exhibited, and when a multilayer porous film is formed, heat shrinkage tends to be good and safety tends to be excellent.

  The average particle diameter of the resin binder can be controlled by adjusting the polymerization time, polymerization temperature, raw material composition ratio, raw material charging order, pH, and the like.

  The layer thickness of the filler porous layer is preferably 1 μm or more from the viewpoint of improving heat resistance and insulation, and is preferably 50 μm or less from the viewpoint of increasing the capacity and permeability of the battery.

Layer density of the filler porous layer is preferably from 0.5 to 2.0 g / cm ^3, more preferably 0.7~1.5cm ^3. When the layer density of the filler porous layer is 0.5 g / cm ³ or more, the thermal contraction rate at high temperature tends to be good, and when it is 2.0 g / cm ³ or less, the air permeability tends to decrease. It is in.

  Examples of the method for forming the filler porous layer include a method of forming a filler porous layer by applying a coating liquid containing an inorganic filler and a resin binder on at least one surface of a substrate. The coating liquid may further contain a solvent, a dispersant, and the like in order to stabilize dispersion and improve coating properties. The method for applying the coating liquid to the substrate is not particularly limited as long as the required layer thickness or coating area can be realized.

[Base material]
The at least one porous film contained in the substrate is not particularly limited, and may be, for example, a polyolefin microporous film formed from a polyolefin resin composition containing polyolefin.

  In the present embodiment, the content of the polyolefin resin in the polyolefin microporous membrane is not particularly limited, but based on the total mass of all the components constituting the porous membrane from the viewpoint of shutdown performance when used as a separator substrate. Thus, it is preferably 50% or more and 100% or less, more preferably 60% or more and 100% or less, and further preferably 70% or more and 100% or less.

  The polyolefin resin is not particularly limited, and may be a polyolefin resin used for normal extrusion, injection, inflation, blow molding, and the like, and includes ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and Homopolymers and copolymers such as 1-octene, multistage polymers and the like can be used. Moreover, these polyolefin can also be used individually or in mixture.

  Typical examples of polyolefin resins include low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ultra high molecular weight polyethylene, isotactic polypropylene, atactic polypropylene, ethylene-propylene random copolymer, polybutene, ethylene propylene. Rubber and the like. When a polyolefin microporous membrane is used as a separator substrate, a resin mainly composed of high-density polyethylene is preferable because it has a low melting point and high strength.

  In order to improve the heat resistance of the polyolefin microporous membrane, it is more preferable to use a porous membrane made of a resin composition containing polypropylene and a polyolefin resin other than polypropylene.

  The three-dimensional structure of polypropylene is not limited, and any of isotactic polypropylene, syndiotactic polypropylene and atactic polypropylene may be used.

  The ratio of polypropylene to the total polyolefin in the polyolefin resin composition is preferably 1 to 35% by mass, more preferably 3 to 20% by mass from the viewpoint of achieving both heat resistance and a good shutdown function. More preferably, it is 4-10 mass%.

  Examples of polyolefin resins other than polypropylene include, but are not limited to, homopolymers or copolymers of olefin hydrocarbons such as ethylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene. It is done. Specifically, examples of the polyolefin resin other than polypropylene include polyethylene, polybutene, and ethylene-propylene random copolymer.

From the viewpoint of shutdown characteristics in which the pores of the polyolefin microporous membrane are blocked by heat melting, polyolefins other than polypropylene, such as low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, ultrahigh molecular weight polyethylene, etc. Is preferably used. Among these, from the viewpoint of strength, it is more preferable to use polyethylene having a density measured according to JIS K 7112 of 0.93 g / cm ³ or more.

  The viscosity average molecular weight of the polyolefin resin constituting the polyolefin microporous membrane is not particularly limited, but is preferably 30,000 or more and 12 million or less, more preferably 50,000 or more and less than 2 million, and still more preferably 100,000 or more. Less than one million. A viscosity average molecular weight of 30,000 or more is preferable because the melt tension during melt molding increases, moldability is improved, and the strength tends to increase due to entanglement between polymers. On the other hand, when the viscosity average molecular weight is 12 million or less, it is easy to uniformly melt and knead, and it tends to be excellent in sheet formability, particularly thickness stability, which is preferable. Furthermore, when the viscosity average molecular weight is less than 1,000,000, it is preferable because the pores are likely to be blocked when the temperature rises and a good shutdown function tends to be obtained.

  For example, instead of using a polyolefin having a viscosity average molecular weight of less than 1 million alone, a mixture of a polyolefin having a viscosity average molecular weight of 2 million and a polyolefin having a viscosity average molecular weight of 270,000, the mixture having a viscosity average molecular weight of less than 1 million It may be used.

  The polyolefin microporous membrane may contain any additive. Although it does not specifically limit as an additive, For example, Polymers other than polyolefin; Inorganic particle | grains; Antioxidants, such as a phenol type, a phosphorus type, and a sulfur type; Metal soaps, such as a calcium stearate and a zinc stearate; Ultraviolet absorber; Examples thereof include a light stabilizer; an antistatic agent; an antifogging agent; and a coloring pigment.

  The puncture strength of the polyolefin microporous membrane is not particularly limited, but is preferably 200 g / 20 μm or more, more preferably 300 g / 20 μm or more, preferably 2000 g / 20 μm or less, more preferably 1000 g / 20 μm or less. It is preferable that the puncture strength is 200 g / 20 μm or more from the viewpoint of suppressing film breakage due to the dropped active material or the like during battery winding, and from the viewpoint of suppressing the concern of short-circuiting due to expansion and contraction of the electrode accompanying charge / discharge. . On the other hand, it is preferable that the puncture strength is 2000 g / 20 μm or less from the viewpoint of reducing width shrinkage due to orientation relaxation during heating.

  The puncture strength can be adjusted by adjusting the draw ratio and / or the draw temperature of the polyolefin microporous membrane. The puncture strength is measured by the method described in the examples.

  The porosity of the polyolefin microporous membrane is not particularly limited, but is preferably 20% or more, more preferably 35% or more, preferably 90% or less, preferably 80% or less. A porosity of 20% or more is preferable from the viewpoint of ensuring the permeability of the separator. On the other hand, a porosity of 90% or less is preferable from the viewpoint of ensuring puncture strength. The porosity can be adjusted by changing the draw ratio of the polyolefin microporous membrane. The porosity is measured by the method described in the examples.

  The film thickness of the polyolefin microporous membrane is preferably 2 μm or more, more preferably 5 μm or more, preferably 100 μm or less, more preferably 60 μm or less, and even more preferably 50 μm or less. The film thickness of 2 μm or more is preferable from the viewpoint of improving mechanical strength. On the other hand, it is preferable to set the film thickness to 100 μm or less because the occupied volume of the separator in the battery is reduced, which tends to be advantageous in increasing the capacity of the battery.

  The air permeability of the polyolefin microporous membrane is preferably 10 seconds / 100 cc or more, more preferably 50 seconds / 100 cc or more, preferably 1000 seconds / 100 cc or less, more preferably 500 seconds / 100 cc or less. The air permeability is preferably 10 seconds / 100 cc or more from the viewpoint of suppressing self-discharge of the electricity storage device. On the other hand, it is preferable that the air permeability is 1000 seconds / 100 cc or less from the viewpoint of obtaining good charge / discharge characteristics. The air permeability can be adjusted by changing the stretching temperature and / or stretching ratio of the polyolefin microporous membrane. The air permeability is measured by the method described in the examples.

  The average pore diameter of the polyolefin microporous membrane is preferably 0.15 μm or less, more preferably 0.1 μm or less, and the lower limit is preferably 0.01 μm or more. An average pore size of 0.15 μm or less is preferable from the viewpoint of suppressing self-discharge of the power storage device and suppressing a decrease in capacity when the separator for power storage device is used. The average pore diameter can be adjusted by changing the draw ratio when producing a polyolefin microporous membrane.

  The short temperature, which is an index of heat resistance of the polyolefin microporous membrane, is preferably 140 ° C. or higher, more preferably 150 ° C. or higher, more preferably 160 ° C. or higher, from the viewpoint of the safety of the electricity storage device.

  The method for producing the polyolefin microporous membrane is not particularly limited, and a known production method can be adopted. For example, a method in which a polyolefin resin composition and a plasticizer are melt-kneaded and formed into a sheet shape, optionally stretched and then made porous by extracting the plasticizer, and a polyolefin resin composition is melt-kneaded to obtain a high draw rate. After extruding at a ratio, the polyolefin crystal interface is peeled off by heat treatment and stretching, the polyolefin resin composition and the inorganic filler are melt-kneaded and molded on a sheet, and then the polyolefin and inorganic filler are stretched And a method of making the structure porous by removing the solvent at the same time as solidifying the polyolefin by dissolving it in a poor solvent for the polyolefin after dissolving the polyolefin resin composition.

[Separator for electricity storage devices]
A separator is excellent in adhesiveness with an electrode active material by providing a polymer layer on a base material.

  When the aluminum foil is pressed for 3 minutes under the conditions of a temperature of 25 ° C. and a pressure of 5 MPa against the separator outermost surface where the polymer is present on the separator substrate, the peel strength between the separator and the aluminum foil ( (Hereinafter also referred to as “room temperature peel strength”) is preferably 8 N / m (8 gf / cm) or less, more preferably 7 gf / cm or less, and even more preferably 6 gf / cm or less.

  Since the aluminum foil is used as an electrode current collector, the adhesion and blocking resistance of the separator to the electrode at room temperature can be easily confirmed by measuring the room temperature peel strength. When the room temperature peel strength exceeds 8 gf / cm, the separator is sticky, and the slit property or winding property of the separator is impaired.

  When the aluminum foil is pressed for 3 minutes under conditions of a temperature of 80 ° C. and a pressure of 10 MPa against the separator outermost surface where the polymer is present on the separator substrate, the peel strength between the separator and the aluminum foil (Hereinafter also referred to as “heat peel strength”) is preferably 9.8 N / m (10 gf / cm) or more, more preferably 15 gf / cm or more, and further preferably 20 gf / cm or more. .

  Since the aluminum foil is used as an electrode current collector, the adhesion of the separator to the electrode during heating can be easily confirmed by measuring the heat peel strength. When the heat peel strength is less than 10 gf / cm, the electrode and the separator are peeled off during the assembly process or use of the electricity storage device, which causes the performance of the electricity storage device to deteriorate.

  The room temperature peel strength and the heat peel strength are measured by the methods described in the examples.

  The thickness of the separator is preferably 2 μm or more, more preferably 5 μm or more from the viewpoint of securing the rigidity of the electricity storage device and the strength of the separator, and preferably 100 μm or less, more preferably 50 μm or less from the viewpoint of charge / discharge characteristics of the electricity storage device. Preferably, it is 30 μm or less. When a polymer is present on the separator substrate, the thickness obtained by measuring the separator portion where the polymer is present is the thickness of the separator.

  The air permeability of the separator is preferably equal to or higher than the air permeability of the base material including at least one porous film in order to obtain good charge / discharge characteristics of the electricity storage device. The air permeability of the separator is adjusted by the stretching temperature or stretching ratio when producing the polyolefin microporous membrane as the substrate, the area ratio of the polymer present on the substrate, or the presence form.

  The short-circuit temperature, which is an indicator of the heat resistance of the separator, is preferably 140 ° C. or higher, more preferably 150 ° C. or higher, and further preferably 160 ° C. or higher from the viewpoint of the safety of the electricity storage device.

[Power storage device]
By adhering the separator according to this embodiment to the electrode, a laminate in which the separator and the electrode are laminated can be obtained.

  The laminate is excellent not only in handling properties during winding and rate characteristics and cycle characteristics of the electricity storage device, but also in adhesion and permeability. Therefore, a laminated body can be used suitably for electrical storage devices, such as batteries, such as a nonaqueous electrolyte secondary battery, a capacitor, and a capacitor, for example.

  Although the manufacturing method of a laminated body is not specifically limited, For example, the separator and electrode which concern on this embodiment may be overlapped, and the process of heating and / or pressing as needed may be included. Heating and / or pressing can be performed when the electrode and the separator are stacked. You may heat and / or press with respect to the winding body obtained by winding an electrode and a separator in a circular shape or a flat spiral shape.

  A vertically long separator having a width of 10 to 500 mm (preferably 80 to 500 mm) and a length of 200 to 4000 m (preferably 1000 to 4000 m) can be prepared and overlapped with the electrode.

  The laminate can also be produced by laminating in the order of positive electrode-separator-negative electrode-separator or negative electrode-separator-positive electrode-separator, and pressurizing and optionally heating.

  The pressure during pressurization is preferably 1 MPa to 30 MPa. The pressing time is preferably 5 seconds to 30 minutes. The heating temperature is preferably 40 ° C to 120 ° C. The heating time is preferably 5 seconds to 30 minutes. Furthermore, the pressure may be applied after heating, the pressure may be applied, the heat may be applied after the pressurization, or the pressurization and the heating may be performed simultaneously. Among these, it is preferable to perform pressurization and heating simultaneously.

  When the storage device is a secondary battery, the laminate is wound into a circular or flat spiral shape to obtain a wound body, and the wound body is stored in a storage body such as a can or a pouch-type case, and A secondary battery can be obtained by injecting an electrolyte and further heating and / or pressing as desired.

  When manufacturing a non-aqueous electrolyte secondary battery using the separator according to this embodiment, a known positive electrode, negative electrode, and non-aqueous electrolyte may be used.

As the cathode material is not particularly limited, for _example, LiCoO 2, LiNiO _2, spinel-type LiMnO _4, lithium-containing composite oxides such as olivine type LiFePO ₄ and the like.

  The negative electrode material is not particularly limited, and examples thereof include carbon materials such as graphite, non-graphitizable carbonaceous, graphitizable carbonaceous, and composite carbon bodies; silicon, tin, metallic lithium, various alloy materials, and the like. .

The nonaqueous electrolytic solution is not particularly limited, but an electrolytic solution in which an electrolyte is dissolved in an organic solvent can be used. Examples of the organic solvent include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. Examples of the electrolyte include lithium salts such as LiClO ₄ , LiBF ₄ , and LiPF ₆ .

  In this embodiment, the rigidity of an electrical storage device can be improved by improving the adhesiveness and rigidity of the adhesive part of the separator in electrolyte solution. Therefore, the separator according to the present embodiment is used for a laminate-type or pouch-type power storage device that is formed by performing hot pressing after the wound laminate and electrolyte are placed in a storage body. It is preferable.

  In addition, the measured value of various physical properties mentioned above is a value measured according to the measuring method in the Example mentioned later unless there is particular notice.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to an Example. The measurement methods and evaluation methods for various physical properties used in the following production examples, examples and comparative examples are as follows. Unless otherwise specified, various measurements and evaluations were performed under conditions of a room temperature of 23 ° C., 1 atm, and a relative humidity of 50%.

<Measurement method and evaluation method>
(1) Glass transition temperature of raw material polymer An appropriate amount of raw material polymer water dispersion (nonvolatile content: 38 to 42%, pH: 9.0) was taken in an aluminum dish and dried with a hot air dryer at 130 ° C for 30 minutes. About 17 mg of the dried film after drying was packed in an aluminum container for measurement, and a DSC curve and a DDSC curve were obtained in a DSC measuring apparatus (DSC 6220 manufactured by Shimadzu Corporation) under a nitrogen atmosphere. The measurement conditions were as follows.
(First stage temperature rise program)
Starting at 70 ° C., the temperature was raised at a rate of 15 ° C. per minute, and after reaching 110 ° C., the temperature was maintained for 5 minutes.
(Second stage temperature drop program)
The temperature was lowered from 110 ° C. at a rate of 40 ° C. per minute, and after reaching −50 ° C., the temperature was maintained for 5 minutes.
(Third-stage temperature rising program)
The temperature was raised from -50 ° C to 130 ° C at a rate of 15 ° C per minute. DSC and DDSC data were obtained at the third stage of temperature increase.
The intersection of the base line (the straight line obtained by extending the base line in the obtained DSC curve to the high temperature side) and the tangent at the inflection point (the point where the upward convex curve changes to the downward convex curve) is defined as the glass transition temperature ( Tg).

(2) Average particle diameter of raw material polymer The 50% particle diameter (nm) of the raw material polymer was measured as an average particle diameter by a light scattering method using a particle diameter measuring apparatus (trade name “MICROTRAC UPA150” manufactured by LEED & NORTHRUP).

(3) Gel fraction of raw material polymer (toluene insoluble content)
On a Teflon (registered trademark) plate, a raw material polymer coating liquid (nonvolatile content: 38 to 42%, pH: 9.0) is dropped with a dropper (diameter 5 mm or less), and dried for 30 minutes with a 130 ° C hot air dryer. did. After drying, about 0.5 g of the dried film was precisely weighed (a), taken into a 50 mL polyethylene container, 30 mL of toluene was poured into it, and shaken at room temperature for 3 hours. Thereafter, the content was filtered with 325 mesh, and the toluene insoluble matter remaining on the mesh was dried together with the mesh for 1 hour with a 130 ° C. hot air dryer. In addition, the dry weight of 325 mesh to be used was measured beforehand.

After evaporating toluene, the dry weight (b) of toluene-insoluble matter was obtained by subtracting the dry weight of 325 mesh previously measured from the dry weight of toluene-insoluble matter and the weight of 325 mesh. The gel fraction (toluene insoluble matter) was calculated by the following formula.
Gel fraction of raw material polymer (toluene insoluble content) = (b) / (a) × 100 [%]

(4) Swelling degree of raw material polymer to electrolyte (electrolyte solvent swelling degree)
The raw material polymer or raw material polymer dispersion was allowed to stand in an oven at 130 ° C. for 1 hour, and then the dried polymer was cut out to a weight of 0.5 g, and ethylene carbonate: ethyl methyl carbonate = 1: 2 (volume ratio) ) In a 50 mL vial with 10 g of the mixed solvent. After the sample in the vial was infiltrated for 3 hours, the sample was taken out, washed with the above mixed solvent, and the weight (Wa) was measured. After the sample was left in an oven at 150 ° C. for 1 hour, the weight (Wb) was measured, and the degree of swelling of the polymer with respect to the electrolytic solution was measured by the following formula.
Swelling degree of thermoplastic polymer to electrolyte (times) = (Wa−Wb) ÷ (Wb)

(5) Strength of raw material polymer after impregnation with electrolyte solution The raw material polymer was dried at 60 ° C. overnight to obtain a dried polymer product. After impregnating 1.0 g of the dried polymer in 10 ml of electrolyte for 24 hours, the strength of the raw material polymer after impregnation with the electrolyte was evaluated based on the following evaluation criteria.
<Evaluation criteria>
S: Even if pushed in with tweezers, the shape is maintained (not cut).
A: When it is pushed in with tweezers, it finally cuts.
B: Cut when the tweezers are pushed.
C: The polymer itself is not self-supporting and is difficult to grasp with tweezers.

(6) Weight average molecular weight (hereinafter also referred to as “Mw”)
The weight average molecular weight of the polymer was calculated as a polystyrene equivalent value by gel permeation chromatography (GPC) using a calibration curve of a polystyrene standard sample.

(7) Viscosity average molecular weight (hereinafter also referred to as “Mv”)
Based on ASRM-D4020, the intrinsic viscosity [η] at 135 ° C. in a decalin solvent was determined, and Mv of polyethylene was calculated by the following equation.
[Η] = 0.00068 × Mv ^0.67
Moreover, Mv of polypropylene was calculated by the following formula.
[Η] = 1.10 × Mv ^0.80

(8) Basis weight of substrate (polyolefin microporous membrane) A 10 cm x 10 cm square sample was cut out from the polyolefin microporous membrane, and the weight was measured with an electronic balance AEL-200 manufactured by Shimadzu Corporation. It is multiplied by the obtained weight 100 at 1 m ² per layer of basis weight (g / ^{m 2)} was calculated.

(9) Film thickness of microporous polyolefin membrane (μm)
A 10 cm x 10 cm square sample was cut out from the polyolefin microporous membrane, nine locations (3 points x 3 points) were selected in a lattice shape, and room temperature 23 ± 2 using a microthickness meter (Toyo Seiki Seisakusho Type KBM). The film thickness was measured at ° C. The average value of the nine measured values obtained was calculated as the film thickness of the polyolefin microporous membrane.

(10) Porosity of polyolefin microporous membrane (%)
A sample of 10 cm × 10 cm square was cut out from the polyolefin microporous membrane, the volume (cm ³ ) and mass (g) of the sample were determined, and the membrane density was assumed to be 0.95 (g / cm ³ ). The rate was calculated.
Porosity = (1−mass / volume / 0.95) × 100

(11) Air permeability of polyolefin microporous membrane (sec / 100cc)
In accordance with JIS P-8117, using a Gurley type air permeability meter G-B2 (trademark, inner cylinder mass: 567 g) manufactured by Toyo Seiki Seisakusho Co., Ltd., an area of 645 mm ² (a circle having a diameter of 28.6 mm) The time (seconds) through which 100 cc of air passes was measured as the air permeability (seconds / 100 cc) of the polyolefin microporous membrane having

(12) Puncture strength of polyolefin microporous membrane (g)
Using a handy compression tester KES-G5 (trademark) manufactured by Kato Tech, a polyolefin microporous membrane was fixed with a sample holder having a diameter of 11.3 mm at the opening. Next, the central portion of the fixed polyolefin microporous membrane is subjected to a puncture test under the conditions of a radius of curvature of the needle tip of 0.5 mm, a puncture speed of 2 mm / second, and a temperature of 25 ° C. (G) was obtained.

(13) Average pore diameter of microporous polyolefin membrane (μm)
It is known that the fluid inside the capillary follows the Knudsen flow when the mean free path of the fluid is larger than the pore size of the capillary, and follows the Poiseuille flow when it is smaller. Is assumed to follow the Knudsen flow, and the water flow in the measurement of water permeability of the polyolefin microporous membrane follows the Poiseuille flow.
The average pore diameter d (μm) is the air permeation rate constant R _gas (m ³ / (m ² · sec · Pa)), the water permeation rate constant R _liq (m ³ / (m ² · sec · Pa)), From the air molecular velocity ν (m / sec), water viscosity η (Pa · sec), standard pressure Ps (= 101325 Pa), porosity ε (%), and film thickness L (μm), the following formula is used. It was.
d = 2ν × (R _liq / R _gas ) × (16η / 3Ps) × 10 ⁶
Here, R _gas was calculated | required using the following Formula from the air permeability obtained by said (9).
R _gas = 0.0001 / (air permeability × (6.424 × 10 ⁻⁴ ) × (0.01276 × 101325))
R _liq was obtained from the water permeability (cm ³ / (cm ² · sec · Pa)) using the following equation.
R _liq = water permeability / 100
The water permeability was measured by setting a polyolefin microporous membrane previously immersed in ethanol in a stainless steel liquid-permeable cell having a diameter of 41 mm, washing the ethanol of the membrane with water, and then supplying water at a differential pressure of about 50000 Pa. The amount of water permeation per unit time, unit pressure, and unit area was calculated by measuring the amount of water permeation (cm ³ ) after passing through for 120 seconds.
Ν is a gas constant R (= 8.314), an absolute temperature T (K), a circumference ratio π, and an average molecular weight M of air (= 2.896 × 10 ⁻² kg / mol), using the following formula. I was asked.
ν = ((8R × T) / (π × M)) ^1/2

(14) Adhesiveness of substrate or separator to electrode (simple adhesion test)
A base material or a separator and a positive electrode current collector as an adherend (aluminum foil manufactured by Fuji Processed Paper Co., Ltd., thickness: 20 μm) were each cut to 30 mm × 150 mm and overlaid to obtain a laminated body. A sample was obtained by being sandwiched between Teflon (registered trademark) sheets (Naflon (trademark) PTFE sheet TOMBO-No. 9000 manufactured by NICHIAS Corporation). About each obtained sample, the press body for a test was obtained by pressing in the lamination direction over 3 minutes on the conditions of temperature 80 degreeC and pressure 10MPa.

The peel strength between the base material or separator of each of the obtained test press bodies and the positive electrode current collector was measured according to JIS K6854-2 using an autograph AG-IS type (trademark) manufactured by Shimadzu Corporation. And measured at a tensile speed of 200 mm / min. Based on the peel strength value, the adhesion to the electrode was evaluated according to the following evaluation criteria.
<Evaluation criteria>
A (good): 9.8 N / m (10 gf / cm) or more B (allowable): 5 N / m or more and less than 9.8 N / m C (defect): less than 5 N / m

(15) Handling property of substrate or separator (blocking resistance)
A test press body was obtained in the same manner as in the above (12) except that pressing was performed for 3 minutes under the conditions of a temperature of 25 ° C. and a pressure of 5 MPa. The peel strength between the base material or separator of the test press body and the positive electrode current collector was measured using a Shimadzu Corporation Autograph AG-IS type (trademark) according to JIS K6854-2 and a tensile speed of 200 mm. Measured at / min. Based on the peel strength value, handling properties were evaluated according to the following evaluation criteria.
<Evaluation criteria>
A (good): less than 8 N / m (8 gf / cm) B (allowable): 8 N / m or more and less than 12 N / m C (defect): 12 N / m or more

(16) Peel strength test of inorganic filler coating layer in electrolyte solution A polyolefin microporous film coated with an inorganic filler layer is cut out to 76 mm × 26 mm, a sample is prepared, and the sample before ultrasonic treatment is prepared. The mass (D) was weighed. This sample was put in a 50 mL vial containing 10 g of a mixed solvent of ethylene carbonate: diethyl carbonate = 2: 3 (volume ratio) at 25 ° C., and an ultrasonic cleaner (model US-102 manufactured by SND Corporation). Was subjected to ultrasonic treatment at an oscillation frequency of 38 kHz for 10 minutes. Thereafter, the sample was cut out, washed with ethanol, dried at room temperature, and the mass (E) of the sample after sonication was weighed.
The polyolefin microporous membrane used as the substrate was cut into 76 mm × 26 mm, and the mass (F) of the cut out polyolefin microporous membrane was weighed.
The residual ratio of the porous layer in the electrolytic solution after the ultrasonic treatment was calculated from the following formula.
Residual rate (%) = {(E−F) / (D−F)} × 100

(17) Adhesive force between raw material polymer and substrate (binding property with substrate)
A tape having a width of 12 mm and a length of 100 mm (manufactured by 3M) was applied to the raw material polymer coating layer of the separator. The force when peeling the tape from the sample at a speed of 50 mm / min was measured using a 90 ° peel strength measuring device (product name: IP-5N, manufactured by IMADA). Based on the obtained measurement results, the adhesive strength was evaluated according to the following evaluation criteria.
A (good): 59 N / m (6 gf / mm) or more B (allowable): 40 N / m or more and less than 59 N / m C (defect): less than 40 N / m

(18) Observation method of polymer layer (Voronoi division)
i) Evaluation using 3 fields of view Using a scanning electron microscope S-4800 (manufactured by Hitachi High-Technologies Corporation), the surface of the polymer layer on the separator is 3 times at 10,000 or 30,000 times depending on the particle size of the polymer particles. I took a picture with two fields of view. Area density, dispersion (σ ² ) of Voronoi polygon area (s _i ), and projected area (c _i ) and area of Voronoi polygon (s _i ) for the granular thermoplastic polymer included in these three fields of view (C _i / s _i ) was obtained as an average value of three fields of view. Here, area density, Voronoi polygon area (s _i ) variance (σ ² ), and ratio (c _i / s _i ) are image processing software “A image kun” (registered trademark; manufactured by Asahi Kasei Engineering Corporation). ) Automatically calculated. Further, when Voronoi division was performed in the observation field of view, the region that was not closed was not considered as an object for calculating the area of the Voronoi polygon.

ii) Evaluation using 95 visual fields Using a scanning electron microscope S-4800 (manufactured by Hitachi High-Technologies Corporation), the surface of the polymer layer on the separator is photographed at a magnification of 10,000 or 30,000, depending on the particle size of the polymer particles. I took a picture. 5 sections and 95 visual fields were set using the obtained images as shown in FIGS. The area density, the Voronoi polygon area density, the Voronoi polygon area (s _i ) variance (σ ² ), and the projected area (c _i ) and Voronoi for the granular thermoplastic polymer included in these 95 fields of view A ratio (c _i / s _i ) to the polygonal area (s _i ) was obtained as an average value of 95 fields in the same manner as i).

(19) Rate characteristics a. Preparation of positive electrode 90.4% by mass of nickel / manganese / cobalt composite oxide (NMC) (Ni: Mn: Co = 1: 1: 1 (element ratio), density 4.70 g / cm ³ ) as a positive electrode active material, 1.6% by mass of graphite powder (KS6) (density 2.26 g / cm ³ , number average particle diameter 6.5 μm) and acetylene black powder (AB) (density 1.95 g / cm ³ , number average) as conductive aids 3.8% by mass of particle diameter 48 nm) and polyvinylidene fluoride (PVDF) (density 1.75 g / cm ³ ) as a binder at a ratio of 4.2% by mass, and these are mixed with N-methylpyrrolidone (NMP). A slurry was prepared by dispersing in the slurry. By applying this slurry to one side of an aluminum foil (thickness 20 μm), which is a positive electrode current collector, using a die coater, drying at 130 ° C. for 3 minutes, and then compression molding using a roll press machine, A positive electrode was produced. The coating amount of the positive electrode active material at this time was 109 g / m ² .

b. Graphite powder A as prepared negative active material of the negative electrode (density 2.23 g / cm ^3, number average particle diameter 12.7 [mu] m) 87.6% by weight and graphite powder B (density 2.27 g / cm ^3, number average particle diameter 6.5 μm) is 9.7% by mass, and the ammonium salt of carboxymethyl cellulose as a binder is 1.4% by mass (in terms of solid content) (solid content concentration is 1.83% by mass aqueous solution) and the diene rubber latex is 1.7% by mass ( (Solid content conversion) (solid content concentration 40 mass% aqueous solution) was dispersed in purified water to prepare a slurry. This slurry was applied to one side of a 12 μm thick copper foil serving as a negative electrode current collector with a die coater, dried at 120 ° C. for 3 minutes, and then compression molded with a roll press to produce a negative electrode. The negative electrode active material coating amount at this time was 5.2 g / m ² .

c. Preparation of non-aqueous electrolyte solution By dissolving LiPF ₆ as a solute in a mixed solvent of ethylene carbonate: ethyl methyl carbonate = 1: 2 (volume ratio) to a concentration of 1.0 mol / L, a non-aqueous electrolyte solution was prepared. Prepared.

d. Battery assembly A separator or a microporous polyolefin membrane (base material itself) was cut into a circle of 24 mmφ, and a positive electrode and a negative electrode were cut into a circle of 16 mmφ. The negative electrode, the separator (or base material), and the positive electrode were stacked in this order and pressed or heat-pressed so that the positive electrode and the active material surface of the negative electrode were opposed to each other, and were accommodated in a stainless steel container with a lid. The container and the lid were insulated, and the container was in contact with the negative electrode copper foil and the lid was in contact with the positive electrode aluminum foil. A battery was assembled by injecting 0.4 ml of the non-aqueous electrolyte into the container and sealing it.

e. Evaluation of rate characteristics d. After charging the simple battery assembled in step 3 at 25 ° C. to a battery voltage of 4.2 V at a current value of 3 mA (about 0.5 C), the current value starts to be reduced from 3 mA so as to maintain 4.2 V. The first charge after the battery was made was performed for a total of about 6 hours. Thereafter, the battery was discharged to a battery voltage of 3.0 V at a current value of 3 mA.
Next, after charging to a battery voltage of 4.2 V at a current value of 6 mA (about 1.0 C) at 25 ° C., the current value starts to be reduced from 6 mA so as to hold 4.2 V, so that a total of about 3 Charged for hours. Thereafter, the discharge capacity when discharging to a battery voltage of 3.0 V at a current value of 6 mA was defined as 1 C discharge capacity (mAh).
Next, after charging to a battery voltage of 4.2 V at a current value of 6 mA (about 1.0 C) at 25 ° C., the current value starts to be reduced from 6 mA so as to hold 4.2 V, so that a total of about 3 Charged for hours. Thereafter, the discharge capacity when discharged to a battery voltage of 3.0 V at a current value of 12 mA (about 2.0 C) was defined as 2 C discharge capacity (mAh).
Then, the ratio of the 2C discharge capacity to the 1C discharge capacity was calculated, and this value was used as the rate characteristic.
Rate characteristic (%) = (2C discharge capacity / 1C discharge capacity) × 100
<Evaluation criteria for rate characteristics (%)>
S (remarkably good): Rate characteristics of over 90% A (good): Rate characteristics of over 85% and 90% or less B (allowable): Rate characteristics of over 80% and up to 85% C (defect): Rates of 80% or less Characteristic

(20) Cycle characteristics The cycle characteristics were evaluated using simple batteries assembled as in the above (17) a to d except that the separators obtained in Examples and Comparative Examples were used.
The above battery was charged at a constant current of 1/3 C to a voltage of 4.2 V, then charged at a constant voltage of 4.2 V for 8 hours, and then discharged to a final voltage of 3.0 V at a current of 1/3 C. Went. Next, after constant current charging to a voltage of 4.2 V with a current value of 1 C, 4.2 V constant voltage charging was performed for 3 hours, and further discharging was performed to a final voltage of 3.0 V with a current of 1 C. Finally, after constant current charging to 4.2 V with a current value of 1 C, 4.2 V constant voltage charging was performed for 3 hours as a pretreatment. 1C represents a current value for discharging the reference capacity of the battery in one hour.
The battery subjected to the above pretreatment was discharged to a discharge end voltage of 3 V with a discharge current of 1 A under a temperature of 25 ° C., and then charged to a charge end voltage of 4.2 V with a charge current of 1 A. Charging / discharging was repeated with this as one cycle. Then, using the capacity retention after 200 cycles with respect to the initial capacity (capacity in the first cycle), the cycle characteristics were evaluated according to the following criteria.
<Evaluation criteria for cycle characteristics>
S (remarkably good): 90% to 100% capacity retention rate A (good): 85% to less than 90% capacity retention rate B (allowable): 80% to less than 85% capacity retention rate C (defect) : 70% or more and less than 80% capacity retention ratio D (Remarkably poor): Less than 70% capacity retention ratio

(21) High-temperature storage characteristics High-temperature storage specific evaluation was performed using simple batteries assembled as in the above (17) a to d except that the separators obtained in Examples and Comparative Examples were used.
A method in which the battery is charged to a battery voltage of 4.2 V at a current value of 3 mA (about 0.5 C) at 25 ° C., and the current value starts to be reduced from 3 mA so as to maintain 4.2 V after reaching the battery voltage. The battery was charged for a total of 6 hours. Thereafter, the battery was discharged to a battery voltage of 3.0 V at a current value of 3 mA.
Next, in a 25 ° C. atmosphere, the battery voltage is charged to 4.2 V at a current value of 6 mA (about 1.0 C), and after reaching the voltage value, the current value starts to be reduced from 6 mA so as to maintain 4.2 V. The battery was charged for 3 hours. The discharge capacity when discharging to a battery voltage of 3.0 V at a current value of 6 mA was defined as A (mAh).
Next, in a 25 ° C. atmosphere, the battery voltage is charged to 4.2 V at a current value of 6 mA (about 1.0 C), and after reaching the voltage value, the current value starts to be reduced from 6 mA so as to maintain 4.2 V. The battery was charged for 3 hours. The cell held in a charged state was held in a 60 ° C. atmosphere for 7 days. Thereafter, the cell was taken out and discharged to a battery voltage of 3.0 V at a current value of 6 mA in an atmosphere of 25 ° C. Next, in a 25 ° C. atmosphere, the battery voltage is charged to 4.2 V at a current value of 6 mA (about 1.0 C), and after reaching the voltage value, the current value starts to be reduced from 6 mA so as to maintain 4.2 V. The battery was charged for 3 hours. Furthermore, the discharge capacity when discharging to a battery voltage of 3.0 V at a current value of 6 mA was defined as B (mAh).
Then, using the ratio of B to A, the high temperature storage characteristics were evaluated according to the following criteria.
<Evaluation criteria for high-temperature storage characteristics>
A (good): The ratio of the discharge capacity B to the discharge capacity A is 70% or more.
B (allowable): The ratio of the discharge capacity B to the discharge capacity A is less than 70%.

(22) Three-point bending strength test (cell rigidity difference)
(22-1) Rigidity difference when using positive electrode (22-1a) Preparation of first press body Aluminum laminate (Showon Denko Packaging Co., Ltd .: St ON25 / AL40 / OPP40) is cut to a width of 60 mm and a length of 80 mm Then, three sides were sealed with a heat sealer to obtain a storage body.
Positive electrode (manufactured by Enertech, positive electrode material: LiCoO ₂ , conductive auxiliary agent: acetylene black, binder: PVDF, LiCoO ₂ / acetylene black / PVDF (weight ratio) = 95/2/3, L / W: 36 mg / cm on both sides ² , density: 3.9 g / cc, Al current collector thickness: 15 μm, positive electrode thickness after pressing: 107 μm), and separators prepared in Examples or Comparative Examples, respectively, 30 mm in width and length The first laminate was obtained by cutting to 180 mm and stacking the cut positive electrode and separator.
The first laminated body was wound so that the length was about 27 mm and the width was 30 mm under the condition that the number of windings was 3 times, thereby obtaining a first wound body.
The first wound body is put in the above-prepared storage body, and a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (EC volume / DEC volume = 2/3, LiPF ₆ concentration: 1M as an electrolytic solution). , 0.5 ml of Hildebrand SP value as a mixture) was added, sealed with a heat sealer, and allowed to stand for 12 hours to obtain a first pressed body.
The first pressed body was pressed for 30 minutes under the conditions of a temperature of 80 ° C. and a pressure of 1 MPa to obtain a first pressed body. The first wound body in the first press body had a dimension of 30 mm × 27 mm.

(22-1b) Preparation of second press body Positive electrode (manufactured by Enertech, positive electrode material: LiCoO ₂ , conductive auxiliary agent: acetylene black, binder: PVDF, LiCoO ₂ / acetylene black / PVDF (weight ratio) = 95/2 / 3, L / W: 36 mg / cm ² on both sides, density: 3.9 g / cc, Al current collector thickness: 15 μm, positive electrode thickness after pressing: 107 μm), used in Examples or Comparative Examples The polyolefin microporous membrane was cut into a width of 30 mm and a length of 180 mm, respectively, and the cut positive electrode and the polyolefin microporous membrane were stacked to obtain the second laminate (21-1a). ), A second press body was obtained. The second wound body in the second press body had a dimension of 30 mm × 27 mm.

(22-1c) Rigidity difference between first press body and second press body Digital force gauge “DS2-50N” (product name, manufactured by Imada Co., Ltd.) provided with a piercing jig (A type A-4) The pedestal having two support bases was attached to an electric measurement stand “MX2-500N” (product name, manufactured by Imada Co., Ltd.).
The distance between the two support bases was adjusted to 15 mm.
The first press body and the second press body are respectively pierced in the winding direction of the winding body with 27 mm sides of the winding body arranged in a direction parallel to the direction connecting the two support bases. It was set on two support bases so that the direction would be vertical and the tip of the piercing jig and the center of the wound body could be in contact.
The individually set first press body and second press body are subjected to a three-point bending strength test at an indentation speed of 50 mm / min.
Rigidity difference = F _{first press body max−} F _{second press body max}
{In the formula, F _{first press body max} is the maximum when the load (N) necessary for maintaining the indentation speed of the piercing jig to the first press body at 50 mm / min is plotted over time. The F _{second press body max} is a value when the load (N) necessary for maintaining the indentation speed of the piercing jig to the second press body at 50 mm / min is plotted over time. Is the local maximum}
Thus, the difference in rigidity between the first press body and the second press body was calculated.

(22-2) Rigidity difference when using negative electrode Negative electrode as electrode (manufactured by Enertech, negative electrode material: graphite, conductive auxiliary agent: acetylene black, binder: SB latex, graphite / acetylene black / SB latex (weight ratio) = 95 / 2/3, L / W: 18 mg / cm ² on both sides, density: 1.5 g / cc, Cu current collector thickness: 10 μm, negative electrode thickness after pressing: 140 μm) Similar to 21-1), the stiffness difference was calculated.

<Manufacture of raw material polymer>
[Manufacture of raw material polymers (low Tg) 1A, 2A and 4A having a low glass transition temperature and raw polymer (high Tg) 1B, 2B and 4B to 6B having a high glass transition temperature]
In a reaction vessel equipped with a stirrer, reflux condenser, dropping tank and thermometer, 70.4 parts by mass of ion-exchanged water and “AQUALON KH1025” (registered trademark, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., 25% by mass aqueous solution) 0.5 part by mass and 0.5 part by mass of “ADEKA rear soap SR1025” (registered trademark, manufactured by ADEKA Corporation, 25% by mass aqueous solution), and the temperature inside the reaction vessel was raised to 80 ° C., While maintaining the temperature at 80 ° C., 7.5 parts by mass of ammonium persulfate (2% by mass aqueous solution) was added.

  5 minutes after adding the ammonium persulfate aqueous solution, dropping the emulsion prepared in the emulsion vessel by mixing the monomers and other raw materials listed in the “Emulsion” column of Table 1 with a homomixer for 5 minutes from the dropping tank. The entire amount was added dropwise over 150 minutes.

  After completion of the dropwise addition of the emulsion, the internal temperature of the reaction vessel was maintained at 80 ° C. for 90 minutes and then cooled to room temperature to obtain an emulsion. A latex containing 40% by mass of the starting polymer was obtained by adding an aqueous ammonium hydroxide solution (25% by mass aqueous solution) to the obtained emulsion and adjusting the pH to 9.0.

[Provision of Low Tg Raw Material Polymer 3A, High Tg Raw Material Polymer 3B, and Raw Material Polymer 7]
SB latex A shown in Table 1 (Tg: −8 ° C., particle size: 300 nm, toluene insoluble content: 96%, swelling degree: 1.2 times), SB latex B (Tg: 33 ° C., particle size: 300 nm, Toluene-insoluble content: 95%, swelling degree: 1.4 times), and water-based PVDF (Mw: 500,000, HPF ratio: 3 mol%) are prepared, and low Tg raw material polymer 3A and high Tg raw material polymer 3B, respectively. In addition, it was used as raw material polymer 7.

  About the raw material polymers 1A-4A, 1B-6B and 7, the physical property was evaluated by the said method. The evaluation results are shown in Table 1.

Explanation of abbreviations in Table 1 MMA: methyl methacrylate CHMA: cyclohexyl methacrylate IBXA: isobornyl acrylate BMA: butyl methacrylate BA: n-butyl acrylate EHA: 2-ethylhexyl acrylate MAA: methacrylic acid AA: acrylic acid HEMA: 2-hydroxyethyl methacrylate AM: acrylamide GMA: glycidyl methacrylate NaSS: p-sodium styrenesulfonate A-TMPT: trimethylolpropane triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
KH1025: Aqualon KH1025 (registered trademark, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
SR1025: Adekaria soap SR1025 (registered trademark, manufactured by ADEKA Corporation)
APS: ammonium persulfate SB: styrene-butadiene copolymer PVDF: polyvinylidene fluoride HEP: hexafluoropropylene

<Manufacture of base material>
[Production Example B1]
(Manufacture of base material B1-1)
45 parts by mass of a homopolymer high-density polyethylene having an Mv of 700,000,
45 parts by mass of a homopolymer high-density polyethylene having an Mv of 300,000,
5 parts by mass of a homopolymer polypropylene having an Mv of 400,000
Dry blended using a tumbler blender.

  1 part by mass of tetrakis- [methylene- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane as an antioxidant was added to 99 parts by mass of the obtained polyolefin mixture, and again a tumbler blender. Was used for dry blending to obtain a mixture.

The obtained mixture was supplied to the twin screw extruder by a feeder under a nitrogen atmosphere.
Further, liquid paraffin (kinematic viscosity at 37.78 ° C .: 7.59 × 10 ⁻⁵ m ² / s) was injected into the extruder cylinder by a plunger pump.

  The operating conditions of the feeder and the pump were adjusted so that the ratio of liquid paraffin in the total mixture to be extruded was 65 parts by mass and the polymer concentration was 35 parts by mass.

  Next, they are melt-kneaded while being heated to 230 ° C. in a twin-screw extruder, and the obtained melt-kneaded product is extruded through a T-die onto a cooling roll controlled at a surface temperature of 80 ° C. A sheet-like molded product was obtained by bringing into contact with a cooling roll and molding by cooling.

  This sheet was stretched by a simultaneous biaxial stretching machine at a temperature of 112 ° C. and a magnification of 7 × 6.4. Thereafter, the stretched product was immersed in methylene chloride, and the liquid paraffin was extracted and dried, and then dried, and further stretched twice in the transverse direction at a temperature of 130 ° C. using a tenter stretching machine.

  Thereafter, the stretched sheet was relaxed by about 10% in the width direction and subjected to heat treatment to obtain a base material B1-1 which was a polyolefin resin porous film.

(Manufacture of base material B1-2)
Except for adjusting the thickness of the melt-kneaded material coming out of the T-die, the temperature of the simultaneous biaxial stretching machine was 110 ° C., the temperature of the tenter stretching machine was 132 ° C., and the stretching ratio was 2.1 times. Substrate B1-2 was produced in the same manner as in Example 1.

[Production Example B2]
(Manufacture of base material B2-1)
Aluminum hydroxide oxide (average particle size 1.0 μm) 96.0 parts by mass, acrylic latex (solid content concentration 40%, average particle size 145 nm, minimum film formation temperature 0 ° C. or less) 4.0 parts by mass, and polycarboxylic acid A coating solution was prepared by uniformly dispersing 1.0 part by mass of an aqueous ammonium solution (SN Dispersant 5468 manufactured by San Nopco) in 100 parts by mass of water. Subsequently, the coating solution was applied to the surface of the polyolefin resin porous membrane (base material B1-1) using a gravure coater. Then, it dries at 60 degreeC, water is removed, and base material B2- in which aluminum hydroxide (porous layer of an inorganic filler) is formed with a thickness of 2 μm on the polyolefin resin porous film (base material B1-1). 1 was obtained.

(Manufacture of base material B2-2)
Other than using the raw material polymer 4A shown in Table 1 (low swelling and high strength) instead of acrylic latex (solid content concentration 40%, average particle size 145 nm, minimum film forming temperature 0 ° C. or less) In the same manner as in the production of the substrate B2-1, a substrate B2-2 in which aluminum hydroxide (a porous layer of an inorganic filler) is formed with a thickness of 2 μm on a polyolefin resin porous film (substrate B1-1). Obtained.

  About each of the obtained base material, various physical properties were measured by the said method. The measurement results are shown in Table 2.

(Manufacture of base material B2-3)
On the other surface of the polyolefin resin microporous membrane of the base B2-2, 2 μm of aluminum hydroxide (multi-layered inorganic filler) is formed in the same manner as the base B2-2, and both sides of the base B1-1 are formed. A base material B2-3 in which an aluminum hydroxide layer was formed to a thickness of 2 μm was obtained.

<Examples I-1 to I-17 and Examples I-19 to I-20, Comparative Examples I-1 to I-3>
According to the combination of the polyolefin microporous film and the raw material polymer described in Table 3 or 4, a separator for an electricity storage device was produced. Specifically, the raw material polymer described in Table 3 or 4 was uniformly dispersed in water at the concentration described in Table 3 or 4, to prepare a raw material polymer-containing coating solution. Next, the coating liquid is applied to the surface of one side of the polyolefin microporous membrane described in Table 3 or 4 under the coating conditions described in Table 3 or 4, and dried at 60 ° C. Water was removed. Furthermore, the coating liquid was similarly applied to the other surface of the polyolefin microporous membrane, and dried again to produce a power storage device separator having thermoplastic polymers on both surfaces of the polyolefin microporous membrane.

<Example I-18>
20 parts by mass of raw material polymer 2A and 80 parts by mass of raw material polymer 2B were mixed in water to obtain a polymer mixture having a polymer concentration of 10% by mass.
80 parts by mass of aluminum hydroxide oxide (average particle size 1.0 μm, aspect ratio 3.5) and 20 parts by mass of a polymer mixture are dispersed in water, and an aqueous solution of ammonium polycarboxylate (SN Dispersant 5468 manufactured by San Nopco) Further, an inorganic filler-containing polymer coating solution was obtained by addition.
On both surfaces of the polyolefin microporous membrane B1-1, an inorganic filler-containing polymer coating solution was applied using a gravure coater under the conditions of a coating area ratio of 100% and a coating thickness of 2 μm, and dried at 60 ° C. The separator of Example I-18 was obtained.

  Table 3 or 4 shows the physical properties and evaluation results of the separators obtained in Examples I-1 to I-20 and Comparative Examples I-1 to I-3.

  From the comparison between Examples and Comparative Examples shown in Tables 3 and 4, the separators of Comparative Examples I-1 to I-3 have a small difference in cell rigidity, despite having good adhesion to the electrodes. It can be seen that the cycle characteristics are poor.

<Examples II-1 to II-3, Comparative Examples II-1 to II-3>
According to the combination of the polyolefin microporous film and the raw material polymer shown in Table 5, a separator for an electricity storage device was produced. Specifically, the raw material polymer described in Table 5 was uniformly dispersed in water at the concentration shown in Table 5 to prepare a raw material polymer-containing coating solution. Subsequently, the coating liquid was applied on the surface of one side of the polyolefin microporous membrane described in Table 5 under the coating conditions described in Table 5, and dried at 60 ° C. to remove the water of the coating liquid. . Furthermore, the coating liquid was similarly applied to the other surface of the polyolefin microporous membrane, and dried again to produce a power storage device separator having thermoplastic polymers on both surfaces of the polyolefin microporous membrane.
About the produced electrical storage device separator, the physical-property measurement and evaluation were performed according to the said method, and especially evaluation by Voronoi division was performed. Table 5 shows the physical properties and evaluation results.

From the comparison of Examples II-1 to II-3 shown in Table 5, the dispersion (σ ² ) of the area (s _i ) of the Voronoi polygon obtained by performing the Voronoi division of the adhesive layer is approximately 0.7 or less. It can be seen that, in addition to good cell rigidity difference, good high-temperature storage characteristics can also be obtained.

Claims (12)

A substrate comprising at least one porous membrane; and a polymer present in at least one region of at least one side of the substrate;
A separator for an electricity storage device including the following formula (f) for a three-point bending test:
Fsep _max −Fbase _max ≧ 10 (f)
{In the formula, Fsep _max is a load (N) for maintaining the pressing speed of the indenter with respect to the stacked body 1 of the electrode and the electricity storage device separator and the storage body 1 storing the electrolyte at 50 mm / min. Fbase _max is a pressing speed of the indenter with respect to the laminated body 2 of the base material and the electrode and the storage body 2 in which the electrolytic solution is stored 50 mm. / Maximum value when the load (N) to maintain at / min is plotted over time}
The said separator for electrical storage devices which satisfy | fills the relationship represented by these.   The electricity storage device separator according to claim 1, wherein the electrode is a positive electrode or a negative electrode.   The separator for an electricity storage device according to claim 2, wherein the electrode satisfies the relationship represented by the formula (f) regardless of whether the electrode is the positive electrode or the negative electrode.   The said indenter is pushed into the said storage body 1 or the said storage body 2 from the direction perpendicular | vertical to the winding direction of the said laminated winding body 1 or the said laminated winding body 2, The any one of Claims 1-3 The separator for an electricity storage device according to item.   The separator for an electricity storage device according to any one of claims 1 to 4, wherein the size and material of the storage body 1 are the same as the size and material of the storage body 2.   The area ratio of the surface of the base material covered with the polymer after impregnating the electrolytic device with the electrolytic device separator is 5% to 80% according to any one of claims 1 to 5. The separator for electrical storage devices as described.   When the aluminum foil is pressed for 3 minutes under the conditions of a temperature of 25 ° C. and a pressure of 5 MPa on the outermost surface where the polymer of the electricity storage device separator exists, the electricity storage device separator and the aluminum foil The separator for electrical storage devices of any one of Claims 1-6 whose peeling strength between these is 8 N / m (8 gf / cm) or less.   When the aluminum foil is pressed for 3 minutes under the conditions of a temperature of 80 ° C. and a pressure of 10 MPa on the outermost surface where the polymer of the electricity storage device separator exists, the electricity storage device separator and the aluminum foil The separator for electrical storage devices of any one of Claims 1-7 whose peeling strength between these is 9.8 N / m (10 gf / cm) or more.   The said polymer is a separator for electrical storage devices of any one of Claims 1-8 which is a granular thermoplastic polymer. Using the Voronoi polygonal area (Si) obtained by performing Voronoi division on the granular thermoplastic polymer, the following formula:
{Wherein Si is the actual value of the area of the Voronoi polygon, m is the average of the actual values of the area of the Voronoi polygon, and n is the total number of Voronoi polygons}
The dispersion | distribution ((sigma) ² ) defined by these is the electrical storage device separator of Claim 9 which is 0.01 or more and 0.7 or less. The said dispersion | distribution ((sigma) ² ) is a separator for electrical storage devices of Claim 10 which is an average value of the value calculated about 95 visual fields. The coating liquid containing the polymer, coating area ratio with respect to the substrate of ^{5% ~70%, 0.05g / m} 2 ~1.0g / m 2 of coating basis weight, and 0.1μm~3μm coating The manufacturing method of the separator for electrical storage devices of any one of Claims 1-8 including the process of coating on the said at least 1 surface of the said base material on the conditions of work thickness.