JP2018005972A - Binder composition for power storage device, electrode mixture for power storage device, electrode for power storage device, and secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a binder composition for a power storage device, which has good flexibility and good adhesion, which enables the achievement of satisfactory suitability to coating in an electrode mixture for a power storage device, and which enables the materialization of good charge and discharge characteristics in a secondary battery.SOLUTION: A binder composition for a power storage device comprises: (Y)a fluorine-containing copolymer having e.g. (a)a unit based on chlorotrifluoroethylene, (b)a unit based on an alkyl vinyl ether, and (c)a unit based on vinyl ether having a hydroxy group or an epoxy group; and (Z)a fluorine copolymer having e.g. (s)a unit based on trifluoroethylene, and (t)a unit based on propylene and having a glass transition temperature of -60 to 20°C; and a liquid medium.SELECTED DRAWING: None

Description

  The present invention relates to a binder composition for an electricity storage device, an electrode mixture for an electricity storage device, an electrode for an electricity storage device, and a secondary battery.

An electricity storage device such as a secondary battery is usually composed of an electrode, a non-aqueous electrolyte, a separator and the like as main members. An electrode for an electricity storage device is generally produced by applying an electrode mixture for an electricity storage device containing an electrode active material, a conductive material, a binder and a liquid medium to the surface of the current collector and drying it.
A binder for an electricity storage device is usually used as a binder composition in which a polymer as a binder is dissolved or dispersed in water or an organic solvent, and an electrode active material and a conductive material are dispersed in the binder composition to form an electrode mixture. Prepare.

If the adhesion between the electrode active materials and the adhesion between the electrode active material layer and the current collector are insufficient, an electricity storage device with a large initial capacity cannot be obtained, and the obtained electricity storage device was repeatedly charged and discharged. In this case, the capacity of the battery is reduced due to the electrode active material dropping off from the electrode. For this reason, the outstanding binding property is requested | required of the binder for electrical storage devices used for an electrode mixture.
At the same time, even when the electrode active material is covered with the binder for the electricity storage device, it is required that the resistance of the electrode be kept low and good charge / discharge characteristics can be realized.
In addition, the electrode is required to have flexibility so that cracks do not occur on the electrode surface when an external force is applied to the electrode, such as an electrode winding process when manufacturing the battery.

  Patent Document 1 includes a mixture of an aqueous dispersion of a fluorine-containing copolymer having a hydrophilic group in a side chain and having a specific molecular weight range, and an aqueous dispersion containing polytetrafluoroethylene (PTFE). It has been shown that the binder is excellent in battery characteristics, and the electrode mixture is prepared by uniformly stirring the mixture, the electrode active material, and the conductive additive.

  Further, Patent Document 2 discloses a result of mixing an aqueous dispersion of an amorphous fluorine-containing copolymer such as a tetrafluoroethylene-propylene copolymer and a polytetrafluoroethylene (PTFE) aqueous dispersion. The dressing is described.

International Publication No. 2010/134465 JP 2009-146871 A

The binder described in Examples (Table 1) of Patent Document 1 is an aqueous dispersion (A) of a fluorinated copolymer having units (a), (b), and (c) in the present invention. (B) and a polytetrafluoroethylene (PTFE) aqueous dispersion (G), and according to the knowledge of the present inventors, the electrode produced using the binder is sufficiently flexible. I can not say.
Patent Documents 1 and 2 describe that an aqueous dispersion of a fluorine-containing copolymer and an aqueous dispersion of PTFE are mixed to form a binder. Therefore, when PTFE is subjected to shearing, the viscosity is likely to increase. Therefore, in an electrode mixture using such a binder, there is a problem that it is difficult to obtain good coatability.

  The present invention has a binder composition for an electricity storage device that has good flexibility and adhesion, can provide good coating properties in an electrode mixture for an electricity storage device, and can realize good charge / discharge characteristics in a secondary battery. And an electrode mixture for an electricity storage device, an electrode for an electricity storage device, and a secondary battery using the binder composition.

The present invention includes the following [1] to [10].
[1] Fluorine-containing copolymer having a unit (a) based on the following monomer (a), a unit (b) based on the following monomer (b), and a unit (c) based on the following monomer (c) It has one or more units (s) based on the monomer (s) selected from the group consisting of a coalescence (Y), tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, and has a glass transition temperature of −60 ° C. The binder composition for electrical storage devices containing the fluorine-containing copolymer (Z) which is -20 degreeC, and a liquid medium.
Monomer (a): One or more selected from tetrafluoroethylene and chlorotrifluoroethylene.
Monomer (b): one or more selected from the group consisting of a compound represented by the following formula (I) and a compound represented by the following (II).
_{CH 2 = CH- (CH 2)} n -O-R ··· (I)
_{CH 2 = CH- (CH 2)} n -OCO-R ··· (II)
[Wherein, n is 0 or 1, and R represents a saturated hydrocarbon group having 1 to 20 carbon atoms. ]
Monomer (c): One or more selected from the group consisting of compounds having an ethylenically unsaturated group and having a hydroxy group, an epoxy group or a carboxy group.

[2] The electricity storage device according to [1], wherein the glass transition temperature of the fluorine-containing copolymer (Y) is higher than the glass transition temperature of the fluorine-containing copolymer (Z), and the difference is 10 ° C. or more. Binder composition.
[3] The electricity storage according to [1] or [2], wherein the fluorine-containing copolymer (Z) further has one or more units (t) based on monomers selected from the following monomer group T: Binder composition for devices.
Monomer group T: ethylene, propylene, perfluoro (alkyl vinyl ether), 1,2-difluoroethylene, 1,1,2-trifluoroethylene, 3,3,3-trifluoro-1-propene, 1,3 , 3,3-tetrafluoropropene, and vinyl fluoride.

[4] The fluorine-containing copolymer (Z)
Tetrafluoroethylene / propylene copolymer,
Tetrafluoroethylene / propylene / vinylidene fluoride copolymer,
Vinylidene fluoride / hexafluoropropylene copolymer,
Tetrafluoroethylene / vinylidene fluoride / hexafluoropropylene copolymer,
Tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer,
Tetrafluoroethylene / propylene / 3,3,3-trifluoro-1-propene copolymer,
Tetrafluoroethylene / propylene / vinylidene fluoride / 3,3,3,3-trifluoro-1-propene copolymer,
Vinylidene fluoride / hexafluoropropylene / 3,3,3-trifluoro-1-propene copolymer,
Tetrafluoroethylene / vinylidene fluoride / hexafluoropropylene / 3,3,3-trifluoro-1-propene copolymer,
Vinylidene fluoride / perfluoro (alkyl vinyl ether) copolymer,
Ethylene / hexafluoropropylene copolymer,
Tetrafluoroethylene / propylene / 1,3,3,3-tetrafluoropropene copolymer,
Tetrafluoroethylene / propylene / 1,1,2-trifluoroethylene copolymer,
The binder for an electricity storage device according to [3], which is at least one selected from the group consisting of a tetrafluoroethylene / propylene / vinyl fluoride copolymer and a tetrafluoroethylene / propylene / 1,2-difluoroethylene copolymer. Composition.

  [5] Any one of [1] to [3], wherein the monomer (c) includes one or more selected from the group consisting of compounds represented by the following formulas (III) to (VI): 2. The binder composition for an electricity storage device according to 1.

[Wherein, n is 0 or 1, m is an integer of 0 to 2, R ¹ is a (m + 2) -valent saturated hydrocarbon group having 1 to 10 carbon atoms, or a carbon number having an etheric oxygen atom. Represents a (m + 2) -valent saturated hydrocarbon group having ² to 10 carbon atoms, and R ² is a divalent saturated hydrocarbon group having 1 to 8 carbon atoms or a divalent saturated hydrocarbon having 2 to 8 carbon atoms having an etheric oxygen atom. Represents a hydrocarbon group, and R ³ represents an alkylene group having 1 to 8 carbon atoms or an alkylene group having 2 to 8 carbon atoms having an etheric oxygen atom. ]

[6] The fluorine-containing copolymer (Y) further includes one or more units (d) based on the monomer (d) which is a macromonomer having a hydrophilic portion. ] The binder composition for electrical storage devices as described in any one of.
[7] The binder composition for an electricity storage device according to any one of [1] to [6], wherein the liquid medium is an aqueous medium.
[8] An electrode mixture for an electricity storage device comprising the binder composition for an electricity storage device described in any one of [1] to [7] and a battery active material.
[9] An electrode for an electricity storage device comprising a current collector and an electrode active material layer formed on the current collector using the electrode mixture for an electricity storage device described in [8].
[10] A secondary battery comprising the electrode for an electricity storage device according to [9] and an electrolytic solution.

The binder composition for an electricity storage device of the present invention has good flexibility and adhesiveness, provides good coating properties in an electrode mixture for an electricity storage device, and realizes good charge / discharge characteristics in a secondary battery. it can. Moreover, the reactivity in an electrode is restrained lower, the thermal runaway in a secondary battery is less likely to occur, and higher safety is obtained.
The electrode mixture for an electricity storage device of the present invention has excellent adhesion between electrode active materials and adhesion between the electrode active material and the current collector, excellent flexibility, good coating properties, and secondary properties. Good charge / discharge characteristics in the battery can be obtained. Moreover, the reactivity in an electrode is restrained lower, the thermal runaway in a secondary battery is less likely to occur, and higher safety is obtained.
The electrode for an electricity storage device of the present invention has good adhesion between the electrode active materials and adhesion between the electrode active material and the current collector, and also has excellent flexibility and good charge / discharge characteristics in the secondary battery. can get. Moreover, the reactivity in an electrode is restrained lower, the thermal runaway in a secondary battery is less likely to occur, and higher safety is obtained.
The secondary battery of the present invention has good adhesion between the electrode active materials and the adhesion between the electrode active material and the current collector, and also has excellent electrode flexibility and good charge / discharge characteristics. Moreover, the reactivity in an electrode is restrained lower, the thermal runaway in a secondary battery is less likely to occur, and higher safety is obtained.

In the present invention, the “monomer” is a compound having a polymerizable carbon-carbon double bond.
In the present invention, the “unit based on a monomer” is a structural unit composed of monomer molecules formed by polymerization of monomers, and a part of the monomer molecules disappears by decomposition. You may do it.
In the present specification, unless otherwise specified, a monomer and a unit based on the monomer are represented by the same reference numeral. For example, “unit (a)” represents “unit based on monomer (a)”.
In the present invention, the number average molecular weight of the fluorinated copolymer is a value obtained by gel permeation chromatography (GPC) using a solvent soluble in the fluorinated copolymer and obtained as a polystyrene equivalent value.

  In the present invention, examples of the electricity storage device include a lithium ion primary battery, a lithium ion secondary battery, a lithium polymer battery, an electric double layer capacitor, and a lithium ion capacitor. As an electricity storage device, it is particularly preferable to use it for a lithium ion secondary battery because it can more effectively express adhesiveness, electrolytic solution resistance, charge / discharge characteristics, and the like.

<Binder composition for electricity storage device>
The binder composition for an electricity storage device of the present invention (hereinafter sometimes simply referred to as a binder composition) includes a fluorinated copolymer (Y) and a fluorinated copolymer (Z).
<Fluorine-containing copolymer (Y)>
The fluorine-containing copolymer (Y) comprises a unit (a) based on the monomer (a), a unit (b) based on the monomer (b), and a unit (c) based on the monomer (c). Have. Furthermore, you may have the unit (d) based on a monomer (d).
[Monomer (a)]
The monomer (a) is at least one selected from tetrafluoroethylene (TFE) and chlorotrifluoroethylene (CTFE).

[Monomer (b)]
The monomer (b) is at least one selected from the group consisting of a compound represented by the following formula (I) and a compound represented by the following (II).
_{CH 2 = CH- (CH 2)} n -O-R ··· (I)
_{CH 2 = CH- (CH 2)} n -OCO-R ··· (II)
In the formulas (I) and (II), n is 0 or 1, and R represents a saturated hydrocarbon group having 1 to 20 carbon atoms.
The saturated hydrocarbon group as R may contain a linear, branched or ring structure. R does not have a fluorine atom.

The saturated hydrocarbon group as R has 1 to 20 carbon atoms, preferably 2 to 15 and more preferably 2 to 10 in that good adhesion can be easily obtained.
Specific examples of the monomer (b) include vinyl ethers such as ethyl vinyl ether (EVE), propyl vinyl ether, butyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexyl vinyl ether (CHVE); ethyl allyl ether, propyl allyl ether, butyl allyl ether, Examples include allyl ethers such as cyclohexyl allyl ether; vinyl esters such as butanoic acid vinyl ester and octanoic acid vinyl ester; and allyl esters such as butanoic acid allyl ester and octanoic acid allyl ester.

[Monomer (c)]
The monomer (c) is at least one selected from the group consisting of compounds having an ethylenically unsaturated group and having a hydroxy group, an epoxy group or a carboxy group. The monomer (c) has at least one of a hydroxy group, an epoxy group or a carboxy group, and may have two or more of these. Units based on the monomer (c) contribute to the improvement of adhesion.
Examples of the compound having an ethylenically unsaturated group and a hydroxy group (hereinafter also referred to as a monomer (ci)) include a vinyl ether having a hydroxy group, a vinyl ester having a hydroxy group, an allyl ether having a hydroxy group, and One or more selected from the group consisting of allyl esters having a hydroxy group are preferred. Examples thereof include compounds represented by the following formula (III) or (IV).
As a compound having an ethylenically unsaturated group and an epoxy group (hereinafter also referred to as a monomer (c-ii)), a vinyl ether having an epoxy group, a vinyl ester having an epoxy group, an allyl ether having an epoxy group, and One or more selected from the group consisting of allyl esters having an epoxy group are preferred. Examples thereof include compounds represented by the following formula (V) or (VI).

In the formulas (III) to (VI), n is 0 or 1.
In formula (III) and (IV), m is an integer of 0-2. When m is 2, two R ² existing in one molecule may be the same or different from each other.

In the formulas (III) and (IV), R ¹ is an (m + 2) -valent saturated hydrocarbon group having 1 to 10 carbon atoms or an (m + 2) -valent saturated hydrocarbon having 2 to 10 carbon atoms having an etheric oxygen atom. Represents a group. The saturated hydrocarbon group may contain a linear, branched or ring structure.
The saturated hydrocarbon group as divalent (m = 0) R ¹ is, for example, a linear alkylene group having 1 or 2 carbon atoms, or a saturated hydrocarbon group having 2 to 6 carbon atoms having 1 to 3 etheric oxygen atoms. Hydrogen group (however, the number of etheric oxygen atoms contained when the saturated hydrocarbon group has 2 carbon atoms is 1 and the number of etheric oxygen atoms contained when the saturated hydrocarbon group has 3 carbon atoms) Is one or two).
Specific examples include an alkylene group, a cycloalkylene group, and an alkylene group containing a cycloalkylene group. The alkylene group may be linear or branched. As the cycloalkylene group, a cycloalkylene group having 5 to 8 carbon atoms is preferable, and a cyclohexylene group is particularly preferable. As alkylene radicals containing from cycloalkylene group, for example _{-CH 2 -C 6 H 4 -CH 2} - , and the like.
Examples of the trivalent (m = 1) or tetravalent (m = 2) saturated hydrocarbon group as R ¹ include groups in which m hydrogen atoms have been removed from the divalent saturated hydrocarbon group.

In the formulas (III) and (IV), R ² represents a divalent saturated hydrocarbon group having 1 to 8 carbon atoms or a divalent saturated hydrocarbon group having 2 to 8 carbon atoms having an etheric oxygen atom. The saturated hydrocarbon group may contain a linear, branched or ring structure. Examples of R ² include the same as the divalent saturated hydrocarbon group for R ¹ .
In particular, in formula (III), R ¹ is a linear alkylene group having 1 or 2 carbon atoms, or an alkylene group having 2 to 6 carbon atoms having 1 to 3 etheric oxygen atoms (however, the number of etheric oxygen atoms is 3 or less).
In particular, in formula (IV), R ³ is preferably an alkylene group having 1 to 4 carbon atoms.

In the formulas (V) and (VI), R ³ represents an alkylene group having 1 to 8 carbon atoms or an alkylene group having 2 to 8 carbon atoms having an etheric oxygen atom. It may be linear or branched. R ³ is preferably an alkylene group having 1 to 4 carbon atoms.

As a specific example of the monomer (ci),
2-hydroxyethyl vinyl ether (HEVE), 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 4-hydroxybutyl vinyl ether (HBVE), 4-hydroxy-2-methylbutyl vinyl ether, Hydroxyalkyl vinyl ethers such as 5-hydroxypentyl vinyl ether and 6-hydroxyhexyl vinyl ether;
Monovinyl ethers of alicyclic diols such as cyclohexanedimethanol monovinyl ether (CHMVE);
Polyethylene glycol monovinyl ethers such as diethylene glycol monovinyl ether (DEGV), triethylene glycol monovinyl ether, tetraethylene glycol monovinyl ether;
Hydroxyalkyl allyl ethers such as hydroxyethyl allyl ether, hydroxybutyl allyl ether, 2-hydroxyethyl allyl ether, 4-hydroxybutyl allyl ether, glycerol monoallyl ether;
Hydroxyalkyl vinyl esters such as hydroxyethyl vinyl ester and hydroxybutyl vinyl ester;
Hydroxyalkyl allyl esters such as hydroxyethyl allyl ester and hydroxybutyl allyl ester;
And (meth) acrylic acid hydroxyalkyl esters such as hydroxyethyl (meth) acrylate.
Specific examples of the monomer (c-ii) include allyl glycidyl ether, glycidyl vinyl ether, allyl-3,4-epoxybutyl ether, allyl-5,6-epoxyhexyl ether, and the like.

Examples of the compound having an ethylenically unsaturated group and a carboxy group (hereinafter also referred to as a monomer (c-iii)) include:
3-butenoic acid, 4-pentenoic acid, 2-hexenoic acid, 3-hexenoic acid, 5-hexenoic acid, 2-heptenoic acid, 3-heptenoic acid, 6-heptenoic acid, 3-octenoic acid, 7-octenoic acid, Unsaturated carboxylic acids such as 2-nonenoic acid, 3-nonenoic acid, 8-nonenoic acid, 9-decenoic acid or 10-undecenoic acid, acrylic acid, methacrylic acid, vinylacetic acid, crotonic acid, cinnamic acid;
Saturated carboxylic acid vinyl ethers such as vinyloxyvaleric acid, 3-vinyloxypropionic acid, 3- (2-vinyloxybutoxycarbonyl) propionic acid, 3- (2-vinyloxyethoxycarbonyl) propionic acid;
Saturated carboxylic acid allyl ethers such as allyloxyvaleric acid, 3-allyloxypropionic acid, 3- (2-allyloxybutoxycarbonyl) propionic acid, 3- (2-allyloxyethoxycarbonyl) propionic acid;
Saturated polycarboxylic acid monovinyl esters such as monovinyl adipate, monovinyl succinate, vinyl phthalate, vinyl pyromellitic acid;
Unsaturated dicarboxylic acids such as itaconic acid, maleic acid, fumaric acid, maleic anhydride, itaconic anhydride, or intramolecular acid anhydrides thereof;
Examples thereof include unsaturated carboxylic acid monoesters such as itaconic acid monoester, maleic acid monoester and fumaric acid monoester.
Among the examples of the monomer (c-iii), crotonic acid, itaconic acid, maleic acid, maleic acid monoester, fumaric acid are available in terms of copolymerization with other fluorine-based monomers and availability. Acid, fumaric acid monoester, 3-allyloxypropionic acid, or 10-undecylene (undecenic) acid is preferred.

  The monomer (c) preferably contains at least one selected from the group consisting of the monomer (ci) and the monomer (c-ii). The total amount of the monomer (ci) and the monomer (c-ii) is preferably 50% by mass or more, more preferably 70% by mass or more based on the total amount of the monomer (c). It may be 100% by mass.

The monomer (c) preferably contains one or more selected from the group consisting of compounds represented by formulas (III) to (VI).
Among these, HEVE, HBVE, CHMVE, DEGV, allyl glycidyl ether, 3-allyloxy-1,2-propanediol, 5- (2-propenyloxy) -1-pentanol, 6- (2-propenyloxy)- 1-hexanol, 2- (2-propenyloxy) -1,4-butanediol, 4- (2-propenyloxy) -1,2-butanediol, 2- [2- (3-butenyl) ethyl] oxirane, At least one selected from the group consisting of 2- [3- (2-butenyl) propyl] oxirane and 2- [4- (2-butenyl) butyl] oxirane is preferred. HBVE, CHMVE, allyl glycidyl ether, and 3 -At least one selected from the group consisting of allyloxy-1,2-propanediol is more preferable. , HBVE, CHMVE is most preferable.

[Monomer (d)]
The fluorine-containing copolymer (Y) may optionally have a unit (d) based on the monomer (d) which is one or more kinds of macromonomers having a hydrophilic portion. The unit (d) contributes to the improvement of the dispersion stability of the fluorinated copolymer (Y) in the aqueous dispersion medium. It also contributes to improved adhesion and charge / discharge characteristics.
In the present invention, the “macromonomer” means a low molecular weight polymer or oligomer having a radical polymerizable unsaturated group at one end. The molecular weight or average molecular weight of the macromonomer is preferably 300 to 10,000. In the present specification, the molecular weight of the macromonomer means a formula weight obtained based on the chemical formula. In the case of a mixture of molecules having different molecular weights, such as a mixture of molecules having different ether chain lengths, it is represented by an average molecular weight which is an average value of molecular weights (formula weight).
The “hydrophilic part” means a part having a hydrophilic group, a part having a hydrophilic bond, or a part composed of a combination thereof.
Those corresponding to any of the monomers (a) to (c) are not included in the monomer (d).

The macromonomer preferably has a radically polymerizable unsaturated group at one end and a polyether chain or a polyester chain.
The radically polymerizable unsaturated group is a group having at least one ethylenically unsaturated group. For example, vinyl group, vinyl ether group, vinyl ester group, allyl group, allyl ether group, allyl ester group, acryloyl group, methacryloyl group, and the like can be mentioned. A vinyl group and a vinyl ether group are preferred because the synthesis of the fluorine-containing copolymer is easy.

Examples of hydrophilic groups include ionic (anionic or cationic) hydrophilic groups, nonionic hydrophilic groups, amphoteric hydrophilic groups, and combinations thereof.
The anionic hydrophilic ^{_{group, -SO 3 - NH + 4,}} -SO 3 - Na + and the like.
The cationic hydrophilic _groups, ^-NH 3 ₊ CH 3 COO ^-, and the like.
Examples of the nonionic hydrophilic group include — (CH ₂ CH ₂ O) _p H (p is 1 to 50).
The hydrophilic group of the ^{_{amphoteric, -N + (CH 3) 2}} CH 2 COO - , and the like.
From the viewpoint of dispersion stability of the binder composition, a portion having a nonionic or amphoteric hydrophilic group and a portion having another hydrophilic group are combined, or a portion having a hydrophilic group and a hydrophilic bond It is preferable to combine with the site | part which has.

As a preferable structure of the macromonomer having a hydrophilic part as the monomer (d), for example,
(1) CH ₂ = CHO (CH ₂ ) _a [O (CH ₂ ) _b ] _c OR ¹¹ (a is an integer of 1 to 10, b is an integer of 1 to 4, c is an integer of 2 to 20, R ¹¹ Is a hydrogen atom or a lower alkyl group);
_{(2) CH 2 = CHCH 2} O (CH 2) d [O (CH 2) e] f OR 2 (d is an integer of from 1 to 10, e is an integer from 1 to 4, f is 2 to 20 integer, R ² is a hydrogen atom or a lower alkyl group).
_{(3) CH 2 = CHO (} CH 2) g (OCH 2 CH 2) h (OCH 2 CH (CH 3)) k OR 3 (g is an integer of from 1 to 10, h is 2 to 20 integer, k is An integer of 0 to 20, R ³ is a hydrogen atom or a lower alkyl group, and the oxyethylene unit and the oxypropylene unit may be arranged in any of block or random type);
_{(4) CH 2 = CHCH 2} O (CH 2) m1 (OCH 2 CH 2) n1 OCH 2 CH (CH 3)) p OR 4 ((m1) is an integer of from 1 to 10, (n1) is 2 to 20 , P is an integer of 0 to 20, R ⁴ is a hydrogen atom or a lower alkyl group, and the oxyethylene unit and the oxypropylene unit may be arranged in either block or random form).
_{(5) CH 2 = CHO (} CH 2) q O (CO (CH 2) r O) s H (q is an integer of from 1 to 10, r is an integer of 1 to 10, s is an integer from 1 to 30), etc. Is mentioned.
1-30 are preferable and, as for carbon number of the lower alkyl group in said (1)-(5), 1-20 are more preferable.

(6) In addition, where one end group is a radically polymerizable unsaturated group, the other end group _{- (CH 2 CH 2 O)} p H a (p 1-50), these are 1,4 cyclohexylene group (hereinafter, -cycloC ₆ H ₁₀ -. where the it is described) macromonomers of which is bonded via one or more containing linking groups are also preferred. Specific examples include the following. (N2) represents the number of added moles of an oxyethylene group and is an integer of 2 to 40.
_{CH 2 = CHOCH 2 -cycloC 6 H} 10 -CH 2 O (CH 2 CH 2 O) n2 H,
_{CH 2 = CHCH 2 OCH 2 -cycloC} 6 H 10 -CH 2 O (CH 2 CH 2 O) n2 H,
_{CH 2 = CHO-cycloC 6 H} 10 -C (CH 3) 2 -cycloC 6 H 10 -O (CH 2 CH 2 O) n2 H,
_{CH 2 = CHCH 2 O-cycloC} 6 H 10 -C (CH 3) 2 -cycloC 6 H 10 -O (CH 2 CH 2 O) n2 H,
_{CH 2 = CHO-cycloC 6 H} 10 -CH 2 O- (CH 2 CH 2 O) n2 -H,
_{CH 2 = CHCH 2 O-cycloC} 6 H 10 -CH 2 O- (CH 2 CH 2 O) n2 -H.

As the monomer (d), one having a vinyl ether structure at one end is preferable because of excellent copolymerizability with a fluoroolefin. In particular, it is preferable that the polyether chain portion is composed of an oxyethylene unit or an oxyethylene unit and an oxypropylene unit because of excellent hydrophilicity.
Moreover, if there are two or more oxyethylene units, various properties such as stability are improved. Moreover, when there are too many oxyalkylene units, the water resistance, weather resistance, etc. of a coating film will worsen. The number of oxyalkylene units in one molecule is preferably 2 or more and 100 or less, and more preferably 2 or more and 75 or less.
Such a macromonomer having a hydrophilic moiety can be produced by a method such as polymerizing formaldehyde or diol with a vinyl ether or allyl ether having a hydroxyl group, or ring-opening polymerization of a compound having an alkylene oxide or a lactone ring.

(7) The macromonomer having a hydrophilic moiety has a chain obtained by radical polymerization of a hydrophilic ethylenically unsaturated monomer, and has a radical polymerizable unsaturated group such as a vinyloxy group or an allyloxy group at the terminal. It may be a macromonomer.
Macromonomers having such a hydrophilic moiety are described by Yamashita et al. In Polym. Bull. , 5.335 (1981).

The macromonomer having a hydrophilic site as the monomer (d) is also available as a commercial product, and examples thereof include the following products.
(I) Product name: Ramter PD-104, polyoxyalkylene alkenyl ether ammonium sulfate, manufactured by Kao Corporation.
(Ii) Product name: Ramter PD-420, etc., polyoxyalkylene alkenyl ether, manufactured by Kao Corporation.
(Iii) Daiichi Kogyo Seiyaku Co., Ltd., product name: QUALON KH-10, etc., (polyoxyethylene-1- (allyloxymethyl) alkyl ether ammonium sulfate.
(Iv) Product name: Aqualon HS-10, etc., manufactured by Daiichi Kogyo Seiyaku Co., Ltd., polyoxyethylene nonylpropenyl phenyl ether ammonium sulfate.
(V) Daiichi Kogyo Seiyaku Co., Ltd., product name: Aqualon RN-20, etc., polyoxyethylene nonylpropenyl phenyl ether.
(Vi) manufactured by Nippon Emulsifier Co., Ltd., product names: Antox-MS-60, 2-sodium sulfoethyl methacrylate.
(Vii) manufactured by Nippon Emulsifier Co., Ltd., product name: Antox SAD, alkyl allyl succinate sulfonate Na salt.
(Viii) Nippon Emulsifier Co., Ltd., product name: Antox MS-2N, 2-sodium sulfoethyl methacrylate.
(Ix) Nippon Emulsifier Co., Ltd., product name: Antox LMA-10, etc., alkoxy polyethylene glycol methacrylate.
(X) Nippon Emulsifier Co., Ltd., product name: Antox EMH-20, etc., alkoxy polyethylene glycol maleate.
(Xi) Sanyo Kasei Co., Ltd., product name: Eleminol JS-20.
(Xii) manufactured by Sanyo Chemical Co., Ltd., product name: Eleminol RS-3000.

In particular, as the monomer (d), the radical polymerizable unsaturated group and — (CH ₂ CH ₂ O) _p H (p is from 1 to 50) in the above point (6) because of excellent copolymerizability with the fluoroolefin. Are preferably linked via a linking group containing a 1,4-cyclohexylene group. As the radical polymerizable unsaturated group, a vinyl ether group is preferable.

[Other monomers]
The fluorine-containing copolymer (Y) does not correspond to any of the monomers (a) to (d) in addition to the units (a) to (c) or the units (a) to (d), and You may have the unit (other unit (e)) based on the other monomer (e) copolymerizable with these.
Examples of other monomers (e) include olefins such as ethylene and propylene, vinyl compounds such as aromatic vinyl compounds such as styrene and vinyltoluene, acryloyl compounds such as butyl acrylate, and ethyl methacrylate. And methacryloyl compounds. In particular, olefins are preferred.
The total of the units (a) to (c) is preferably 70 to 100 mol%, more preferably 80 to 100 mol%, and more preferably 90 to 100 mol% with respect to all units constituting the fluorinated copolymer (Y). Is more preferable.
When the fluorinated copolymer (Y) has the unit (d), the total of the units (a) to (d) is 70 to 100 mol% with respect to all the units constituting the fluorinated copolymer (Y). Is preferable, 80-100 mol% is more preferable, and 90-100 mol% is further more preferable.

[Content of each unit]
In the fluorinated copolymer (Y), the content of the unit (a) is preferably 20 to 80 mol%, more preferably 30 to 70 mol%, based on the total of all units. When it is at least the lower limit of the above range, good dispersion stability is easily obtained. Good adhesiveness is easy to be obtained if it is below the upper limit. When two types of units are included as the unit (a), the total content thereof is the “content of the unit (a)”.
The content of the unit (b) is preferably 1 to 70 mol%, more preferably 5 to 60 mol%, still more preferably 10 to 50 mol% with respect to the total of all units. When it is at least the lower limit of the above range, good adhesion is easily obtained. When it is at most the upper limit value, a coating film with good flexibility is easily obtained. When the unit (b) contains two or more types of units, the total content thereof is “content of unit (b)”. The same applies to other units.
The content of the unit (c) is preferably from 0.1 to 40 mol%, more preferably from 1 to 20 mol%, based on the total of all units. It is excellent in the chemical stability of an aqueous dispersion as it is more than the lower limit of the said range. Good adhesiveness is easy to be obtained if it is below the upper limit.
When the fluorine-containing copolymer (Y) has a unit (d), the content of the unit (d) is preferably 0.1 to 25 mol% with respect to the total of all units, 0.3 to 20 mol% is more preferable. When it is at least the lower limit of the above range, good dispersion stability in the aqueous dispersion medium is easily obtained, and when it is at most the upper limit, good adhesion is easily obtained.

  The number average molecular weight of the fluorinated copolymer (Y) is preferably from 20,000 to 1,000,000, more preferably from 20,000 to 800,000, and even more preferably from 20,000 to 700,000. When it is at least the lower limit of the above range, good adhesion is easily obtained, and when it is at most the upper limit, good dispersion stability is easily obtained.

<Method for producing fluorinated copolymer (Y)>
The fluorine-containing copolymer (Y) can be produced by copolymerizing the monomers (a), (b), (c), and optional monomers (d), (e).
Examples of the polymerization method include an emulsion polymerization method, a solution polymerization method, a suspension polymerization method, and a bulk polymerization method. This can be done by applying a known method.

The emulsion polymerization method is preferred in that a fluorine-containing copolymer (Y) having a high molecular weight (for example, a number average molecular weight of 20,000 or more) is easily obtained.
In the emulsion polymerization method, a step of polymerizing (emulsion polymerization) a monomer component containing the monomers (a) to (c) in the presence of an aqueous medium and a radical polymerization initiator, more preferably an emulsifier (hereinafter referred to as emulsion polymerization). The latex of the fluorine-containing copolymer (Y) is obtained through the emulsion polymerization step.
As the emulsion polymerization method, a known method can be appropriately used in the production of the fluorine-containing copolymer (Y).
The latex obtained in the emulsion polymerization step can be used as it is as the binder composition of the present invention.

The fluorine-containing copolymer (Y) may be synthesized by a polymerization method other than the emulsion polymerization method.
For example, in the case of a solution polymerization method, a fluorine-containing copolymer can be produced by using a solvent that dissolves a monomer to be polymerized, instead of the aqueous medium and the emulsifier in the emulsion polymerization step.
Examples of the solvent used in the solution polymerization method include methyl ethyl ketone and xylene.

<Fluorine-containing copolymer (Z)>
The fluorine-containing copolymer (Z) is a monomer selected from the group consisting of tetrafluoroethylene (also referred to as TFE), hexafluoropropylene (also referred to as HFP), and vinylidene fluoride (also referred to as VdF). It is a copolymer having one or more units (s) based on s). The fluorine-containing copolymer (Z) contributes to the flexibility of the binder for an electricity storage device.
Hereinafter, tetrafluoroethylene is referred to as TFE, and units based on tetrafluoroethylene may be referred to as TFE units. The same applies to other monomers.
The fluorine-containing copolymer (Z) may be a copolymer comprising only two or three of TFE units, HFP units, and VdF units, and is selected from the group consisting of TFE, HFP, and VdF. The copolymer which consists of a unit based on 1 or more types of monomers (s) and a unit based on 1 or more types of the other monomer copolymerizable with this monomer (s) may be sufficient. The fluorine-containing copolymer (Z) is preferably an amorphous polymer.

As a unit based on another monomer copolymerizable with the monomer (s), one or more units (t) based on a monomer selected from the following monomer group T are preferable.
The monomer group T is ethylene (also referred to as E), propylene (also referred to as P), perfluoro (alkyl vinyl ether) (also referred to as PAVE), 1,2-difluoroethylene (also referred to as DiFE), 1, 1,2-trifluoroethylene (also referred to as TrFE), 3,3,3-trifluoro-1-propene (also referred to as TFP), 1,3,3,3-tetrafluoropropene (also referred to as TeFP) And vinyl fluoride (also referred to as VF).
Examples of PAVE include perfluoro (methyl vinyl ether) (also referred to as PMVE) and perfluoro (propyl vinyl ether) (also referred to as PPVE).

The fluorine-containing copolymer (Z) may have a unit (u) based on another monomer (u) copolymerizable with the monomer (s) other than the unit (t). Of all the units constituting the fluorinated copolymer (Z), the unit (u) is preferably 20 mol% or less, more preferably 5 mol% or less, and most preferably zero.
The fluorinated copolymer (Z) preferably does not contain the unit (c) based on the monomer (c). Moreover, it is preferable not to contain the unit (b) based on the said monomer (b).

It is preferably composed of 100 mol% of units constituting the fluorinated copolymer (Z), units (s) and units (t). However, it is allowed to contain other units such as impurities within a range that does not affect the characteristics.
Specific examples of the fluorine-containing copolymer (Z) comprising the unit (s) and the unit (t) are given below.
TFE / P copolymer (meaning a copolymer comprising a structural unit based on TFE and a structural unit based on P. The same shall apply hereinafter), TFE / P / VdF copolymer, VdF / HFP copolymer, TFE / VdF / HFP copolymer,
TFE / PAVE copolymer, TFE / P and TFP copolymer, TFE / P / VdF / TFP copolymer,
VdF / HFP and TFP copolymer, TFE / VdF, HFP and TFP copolymer,
TFE / PMVE and PPVE copolymer, VdF / PAVE copolymer, E / HFP copolymer,
TFE / P / TeFP copolymer, TFE / P / TrFE copolymer, TFE / P / VF copolymer,
Examples include TFE / P / DiFE copolymer.

The composition of the fluorine-containing copolymer (Z) composed of the unit (s) and the unit (t) is excellent in adhesion to the current collector and is easy to obtain good alkali resistance and voltage resistance. The range of is preferable.
In the TFE / P copolymer, TFE / P (meaning unit based on TFE / molar ratio of units based on P. The unit is mol%, and the total is 100 mol%. The same shall apply hereinafter) is 30. -80 / 70-20 are preferable, 40-70 / 60-30 are more preferable, and 60-50 / 40-50 (mol%) are the most preferable.
In the TFE / P / VdF copolymer, TFE / P / VdF = 30-60 / 60-20 / 0.05-40 (mol%),
In the VdF / HFP copolymer, VdF / HFP = 1/99 to 95/5 (mol%),
In the TFE / VdF / HFP copolymer, TFE / VdF / HFP = 20 to 40/1 to 40/20 to 40 (mol%),
In the TFE / PAVE copolymer, TFE / PAVE = 40/60 to 70/30,
In the TFE / P / TFP copolymer, TFE / P / TFP = 40-60 / 60-40 / 0.05-20 (mol%),
In the TFE / P / VdF / TFP copolymer, TFE / P / VdF / TFP = 30-60 / 60-20 / 0.05-40 / 0.05-20 (mol)%,
In the VdF / HFP / TFP copolymer, VdF / HFP / TFP = 1 to 95/99 to 5 / 0.05 to 20 (mol%),
In the TFE / VdF / HFP / TFP copolymer, TFE / VdF / HFP / TFP = 30-60 / 0.05-40 / 60-20 / 0.05-20 (mol%),
In the TFE / PMVE / PPVE copolymer, TFE / PMVE / PPVE = 40 to 70/3 to 57/3 to 57 (mol%),
In the VdF / PAVE copolymer, VdF / PAVE = 3/97 to 95/5 (mol%),
In the E / HFP copolymer, E / HFP = 40/60 to 60/40 (mol%),
In the TFE / P / TeFP copolymer, TFE / P / TeFP = 30-60 / 60-20 / 0.05-40 (mol%),
In the TFE / P / TrFE copolymer, TFE / P / TrFE = 30 to 60/60 to 20 / 0.05 to 40 (mol%),
In the TFE / P / VF copolymer, TFE / P / VF = 30 to 60/60 to 20 / 0.05 to 40 (mol%),
In the TFE / P / DiFE copolymer, TFE / P / DiFE = 30 to 60/60 to 20 / 0.05 to 40 (mol%) is preferable.

The fluorine content of the fluorine-containing copolymer (Z) is preferably 50% by mass or more, and more preferably 53% by mass or more. The upper limit is preferably 74% by mass or less, and more preferably 70% by mass or less. If the fluorine content of the fluorine-containing copolymer (Z) is too low, the alkali resistance and voltage resistance are likely to be insufficient. If it is too high, flexibility tends to be insufficient.
The fluorine content of the fluorine-containing copolymer (Z) is obtained by fluorine content analysis, and indicates the ratio of the mass of fluorine atoms to the total mass of all atoms constituting the fluorine-containing copolymer.
The number average molecular weight of the fluoropolymer (Z) is preferably 10,000 to 1,000,000, more preferably 20,000 to 500,000, still more preferably 20,000 to 300,000, and even more preferably 50,000 to 300,000. When it is at least the lower limit of the above range, excellent adhesion can be easily obtained, and when it is at most the upper limit, excellent flexibility is easily obtained.

<Method for producing fluorine-containing copolymer (Z)>
The fluorine-containing copolymer (Z) can be produced by copolymerizing the monomer (s) and arbitrary monomers (t) and (u).
Examples of the polymerization method include an emulsion polymerization method, a solution polymerization method, a suspension polymerization method, and a bulk polymerization method. An emulsion polymerization method in which a monomer is polymerized in the presence of an aqueous medium and an emulsifier is preferred because the number average molecular weight and copolymer composition of the fluorinated copolymer can be easily adjusted and the productivity is excellent.
In the emulsion polymerization method, a fluorine-containing copolymer is passed through a step (emulsion polymerization step) of polymerizing (emulsion polymerization) a monomer component containing the monomer (s) in the presence of an aqueous medium, an emulsifier and a radical polymerization initiator. A coalesced latex is obtained. A pH adjusting agent may be added in the emulsion polymerization step.

[emulsifier]
As the emulsifier, a known emulsifier used in the emulsion polymerization method can be appropriately used. From the viewpoint of excellent mechanical and chemical stability of the latex, an ionic emulsifier is preferable, and an anionic emulsifier is more preferable.
As the anionic emulsifier, those known in the emulsion polymerization method can be used. Specific examples include hydrocarbon emulsifiers such as sodium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium alkyl sulfonate, sodium alkyl benzene sulfonate, sodium dialkyl ester sulfonate succinate, sodium alkyl diphenyl ether disulfonate; ammonium perfluorooctanoate, Fluorine-containing alkyl carboxylates such as ammonium perfluorohexanoate; compounds represented by the following formula (VII) (hereinafter referred to as compound (VII)) and the like.

_{F (CF 2) p O (} CF (X) CF 2 O) q CF (X) COOA ··· (VII).
In formula (VII), X represents a fluorine atom or perfluoroalkyl group having 1 to 3 carbon atoms, A represents a hydrogen atom, an alkali metal atom or an NH _4,, p represents an integer of 1 to 10, q Represents an integer of 0 or 1-3.
X is preferably a fluorine atom or a trifluoromethyl group. A is preferably Na or NH ₄ . p is preferably 1 to 5. q is preferably 1 to 2.

<Binder composition for electricity storage device>
The binder composition for an electricity storage device includes a fluorinated copolymer (Y), a fluorinated copolymer (Z), and a liquid medium.
The binder composition is preferably a latex in which the fluorine-containing copolymer (Y) and the fluorine-containing copolymer (Z) are dispersed in a liquid medium. Latex is a dispersion of a fluorine-containing copolymer (Y) and a fluorine-containing copolymer (Z), but a part of the fluorine-containing copolymer (Y) and / or the fluorine-containing copolymer (Z) is liquid. It may be dissolved in the medium.

Examples of the liquid medium include an aqueous medium and an organic solvent. The aqueous medium is water alone or a mixture of water and a water-soluble organic solvent. It is preferable to use ion-exchanged water.
As the water-soluble organic solvent, a known compound that can be dissolved in water at an arbitrary ratio can be appropriately used. As the water-soluble organic solvent, alcohols are preferable, and examples thereof include tert-butanol, propylene glycol, dipropylene glycol, dipropylene glycol monomethyl ether, and tripropylene glycol. Of these, tert-butanol, propylene glycol, dipropylene glycol, and dipropylene glycol monomethyl ether are preferred.
Organic solvents are dichlorodifluoromethane, trichlorofluoromethane, chlorodifluoromethane, dichloropentafluoropropane (HCFC-225), CF ₃ CH ₂ CF ₂ H (HFC-245fa), CF ₃ CF ₂ CH ₂ CF ₂ H (HFC) -365M fc), perfluorohexane, perfluorooctane, perfluoro (2 - butyl tetrahydrofuran), perfluoro _{(tributylamine), CF 3 CF 2 CF 2} CF 2 CF 2 CF 2 H, CF 3 CF 2 OCF 2 CF 2 H, CF _{3 CH 2 OCH 2 CF 3,} CF 3 CF 2 OCF 2 CF 2 OCF 2 CF 3 and the like.
An aqueous solvent is preferable in terms of easy high molecular weight.

The fluorine-containing copolymer (Y) and the fluorine-containing copolymer (Z) contained in the binder composition for an electricity storage device have different glass transition temperatures. Specifically, the glass transition temperature of the fluorine-containing copolymer (Y) is higher than the glass transition temperature of the fluorine-containing copolymer (Z), and the difference is 10 ° C. or more. The difference in glass transition temperature is more preferably 20 ° C. or higher, and is preferably larger in the range of 150 ° C. or lower.
If the difference in glass transition temperature between the fluorinated copolymer (Y) and the fluorinated copolymer (Z) is not less than the lower limit of the above range, the effect of improving flexibility can be sufficiently obtained and is not more than the upper limit. Good coatability is easily obtained.

10-150 degreeC is preferable, as for the glass transition temperature of a fluorine-containing copolymer (Y), 10-80 degreeC is more preferable, and 30-60 degreeC is further more preferable. The glass transition temperature of the fluorinated copolymer (Y) can be adjusted by the type and composition of the monomer constituting the copolymer. For example, as a method for increasing the glass transition temperature, there is a method using a monomer having a rigid structure in the side chain. As a method of reducing, there is a method using a monomer having a long-chain hydrocarbon group in the side chain.
When the glass transition temperature of the fluorinated copolymer (Y) is at least the lower limit of the above range, good coatability is easily obtained. Good adhesiveness is easy to be obtained if it is below the upper limit.

The glass transition temperature of the fluorinated copolymer (Z) is preferably -60 ° C to 20 ° C, more preferably -40 ° C to 10 ° C, and further preferably -20 ° C to 0 ° C.
The glass transition temperature of the fluorinated copolymer (Z) can be adjusted by the type and composition of the monomer constituting the copolymer. For example, a method for increasing the glass transition temperature includes a method for increasing the proportion of tetrafluoroethylene, and a method for decreasing the method includes a method for increasing the proportion of vinylidene fluoride or perfluoro (alkyl vinyl ether).
When the glass transition temperature of the fluorinated copolymer (Z) is at least the lower limit of the above range, good coatability is easily obtained, and when it is at most the upper limit, good flexibility is easily obtained.

The content ratio of the fluorine-containing copolymer (Y) and the fluorine-containing copolymer (Z) contained in the binder composition for an electricity storage device is not particularly limited, and the proportion of the fluorine-containing copolymer (Y) increases. When the adhesiveness is improved and the proportion of the fluorine-containing copolymer (Z) is increased, the flexibility is improved.
For example, the mass ratio represented by the fluorine-containing copolymer (Y) / the fluorine-containing copolymer (Z) is preferably 1/99 to 99/1, more preferably 10/90 to 90/10, and 10/90. -70/30 is more preferable, and 30 / 70-60 / 40 is particularly preferable in terms of the balance between adhesion and flexibility.

  The total content (solid content concentration) of the fluorine-containing copolymer (Y) and the fluorine-containing copolymer (Z) in the binder composition is more preferably 5 to 70% by mass with respect to the total amount of the binder composition. 10 to 60% by mass is more preferable, and 15 to 55% by mass is particularly preferable. When the electrode mixture is prepared using the binder composition as being above the lower limit of the above range, a good viscosity of the electrode mixture is easily obtained, and a thick coating is performed on the current collector. Can do. When it is below the upper limit of the above range, when preparing an electrode mixture by dispersing an electrode active material or the like in the binder composition, it is easy to obtain good dispersion stability, and good coating properties of the electrode mixture Is easy to obtain.

  The binder composition may contain other components other than the fluorine-containing copolymer (Y), the fluorine-containing copolymer (Z), and the liquid medium. Examples of the other components include emulsifiers and initiators used in the production of the fluorinated copolymer (Y) or the fluorinated copolymer (Z). The total content of the fluorine-containing copolymer (Y), the fluorine-containing copolymer (Z), and other components other than the liquid medium is preferably 10% by mass or less, and preferably 1% by mass with respect to the total amount of the binder composition. % Or less is more preferable.

  The binder composition of the present invention shows excellent flexibility when the fluorine-containing copolymer (Z) is used alone as a binder component, as shown in the examples described later, and the fluorine-containing copolymer ( Y) is inferior in flexibility to that, but by using both in a mixed manner, it is possible to improve adhesion while suppressing deterioration in flexibility and without impairing charge / discharge identification. In particular, when the fluorine-containing copolymer (Y) and the fluorine-containing copolymer (Z) are mixed, it is a surprising synergistic effect that the adhesion is improved as compared with the case where each of them is used alone.

<Electrode mixture for electricity storage devices>
The electrode mixture for an electricity storage device of the present invention (in the present specification, sometimes simply referred to as an electrode mixture) contains the binder composition of the present invention and an electrode active material. A conductive material may be contained as necessary, and other components other than these may be contained.
The electrode active material used by this invention is not specifically limited, A well-known thing can be used suitably.
As the positive electrode active material, metal oxides such as MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ ; metal sulfides such as TiS ₂ , MoS ₂ , FeS; Co such as LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ And lithium composite metal oxides containing transition metals such as Ni, Mn, Fe and Ti; compounds obtained by substituting a part of transition metal elements in these compounds with other metal elements; and the like. Further, a conductive polymer material such as polyacetylene or poly-p-phenylene can be used. Moreover, what coat | covered the carbon material and the inorganic compound to some or the whole surface of these surfaces can also be used.

Examples of the negative electrode active material include carbides of high molecular compounds such as coke, graphite, mesophase pitch spherules, phenol resin, polyparaphenylene, and carbonaceous materials such as vapor-generated carbon fibers and carbon fibers. In addition, metals such as Si, Sn, Sb, Al, Zn, and W that can be alloyed with lithium are also exemplified. For example, a general formula SiOx represented by silicon monoxide (x is 0.5 to 1.5). Is preferable). As the electrode active material, a material in which a conductive material is attached to the surface by a mechanical modification method or the like can also be used.
In the case of an electrode mixture for a lithium ion secondary battery, the electrode active material to be used is not limited as long as it can reversibly insert and release lithium ions by applying a potential in the electrolyte. Can do.

In particular, the electrode mixture used for the production of the positive electrode preferably contains a conductive material. By including a conductive material, the electrical contact between the electrode active materials can be improved, the electrical resistance in the active material layer can be lowered, and the discharge rate characteristics of the non-aqueous secondary battery can be improved.
Examples of the conductive material include conductive carbon such as acetylene black, ketjen black, carbon black, graphite, vapor grown carbon fiber, and carbon nanotube.
When the electrode mixture contains a conductive material, the effect of reducing electrical resistance is increased by adding a small amount of the conductive material, which is preferable.

As other components, known components in the electrode mixture can be used. Specific examples include water-soluble polymers such as carboxymethyl cellulose, polyvinyl alcohol, polyacrylic acid, and polymethacrylic acid.
The total proportion of the fluorine-containing copolymer (Y) and the fluorine-containing copolymer (Z) in the electrode mixture of the present invention is 0.1 to 20 parts by mass with respect to 100 parts by mass of the electrode active material. Is preferable, 0.5-10 mass parts is more preferable, and 1-8 mass parts is especially preferable.
Moreover, when an electrode mixture contains a electrically conductive material, the ratio of the electrically conductive material in an electrode mixture is more than 0 mass part with respect to 100 mass parts of an electrode active material, and 20 mass parts or less are preferable. 1-10 mass parts is more preferable, and 3-8 mass parts is especially preferable.
The solid concentration in the electrode mixture is preferably 30 to 95% by mass, more preferably 40 to 85% by mass, and particularly preferably 45 to 80% by mass with respect to 100% by mass of the electrode mixture.

<Electrode for power storage device>
The electrode for an electricity storage device of the present invention has a current collector and an electrode active material layer containing the binder for an energy storage device of the present invention and an electrode active material on the current collector.
The current collector is not particularly limited as long as it is made of a conductive material, and generally includes metal foils such as aluminum, nickel, stainless steel, and copper, metal nets, and metal porous bodies. Aluminum is preferably used as the positive electrode current collector, and copper is preferably used as the negative electrode current collector. The thickness of the current collector is preferably 1 to 100 μm.

As a method for producing an electrode for an electricity storage device, for example, the electrode mixture of the present invention is applied to at least one side, preferably both sides of a current collector, and the liquid medium in the electrode mixture is removed by drying, and an electrode active material layer Is obtained. If necessary, the electrode active material layer after drying may be pressed to have a desired thickness.
Various application methods can be used as a method of applying the electrode mixture to the current collector. Examples thereof include a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method. The coating temperature is not particularly limited, but usually a temperature around room temperature is preferable. Drying can be performed using various drying methods, for example, drying by warm air, hot air, low-humidity air, vacuum drying, drying by irradiation with (far) infrared rays, electron beams, or the like. The drying temperature is not particularly limited, but is usually room temperature to 200 ° C. in a heating vacuum dryer or the like. As a pressing method, a mold press, a roll press or the like can be used.

<Lithium ion secondary battery>
A lithium ion secondary battery as an electricity storage device includes the electrode for an electricity storage device of the present invention as at least one of a positive electrode and a negative electrode and an electrolyte. Furthermore, it is preferable to provide a separator.
The electrolytic solution includes an electrolyte and a solvent. Solvents include aprotic organic solvents such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), and methyl ethyl carbonate (MEC). Alkyl carbonates; esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; In particular, dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and methyl ethyl carbonate are preferable because high ion conductivity is easily obtained and the use temperature range is wide. These can be used alone or in admixture of two or more.
Examples of the electrolyte include lithium salts such as LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₅ , CF ₃ SO ₃ Li, and (CF ₃ SO ₂ ) ₂ NLi.

  Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to these examples. The tests and evaluations in the examples and comparative examples were performed by the following methods.

[Method for measuring composition of fluorine-containing copolymer]
The content of units based on each monomer (composition of the copolymer) relative to the total of all units of the fluorinated copolymer is measured by ¹⁹ F-NMR analysis, infrared absorption spectrum analysis, fluorine content analysis, etc. did.
As a measurement sample used for the analysis, a latex of a fluorine-containing copolymer was dried in an oven at 140 ° C. for 1 hour and then dried in a vacuum dryer for 24 hours.

[Number average molecular weight of fluorine-containing copolymer]
The latex of the fluorine-containing copolymer was dissolved in tetrahydrofuran and measured by GPC (model HLC-8320) manufactured by Tosoh Corporation.

[Coating properties of electrode mixture for electricity storage devices]
In each example, 50 circular samples having a diameter of 18 mm were cut out from an electrode (size: 150 mm × 250 mm) manufactured using a method of applying an electrode mixture onto a current collector with a doctor blade.
The thickness of each sample was measured and the average value was obtained. And the deviation from the average value of the thickness of 50 samples was evaluated in four steps (A to C and A are the best) according to the following criteria, and used as an index of coatability. The better the coatability, the more uniform the sample thickness.
A: The number of samples included in the thickness of ± 10% of the average thickness is 80% or more of the whole.
B: The number of samples included in the thickness of ± 10% of the average thickness is 60% or more and less than 80% of the total thickness.
C: The number of samples included in the thickness of ± 10% of the average thickness is less than 60% of the whole.

[Adhesion (peel strength)]
In each example, the manufactured electrode (positive electrode) was cut into a strip shape having a width of 2 cm and a length of 10 cm, and fixed with the coating surface of the electrode mixture facing up. Cellophane tape was affixed to the coating surface of the electrode mixture, and the strength (N) when the tape was peeled in the 90 ° C. direction at a speed of 10 mm / min was measured five times, and the average value was taken as the peel strength. It shows that it is excellent in the adhesiveness (binding property) by a binder, so that this value is large. That is, it shows that the adhesion between the electrode active materials bound by the binder and the adhesion between the electrode active materials and the current collector are excellent.

<Evaluation method of charge / discharge characteristics>
Evaluation of the charge / discharge characteristics of the secondary battery was performed by the following method.
[Evaluation of positive electrode]
(1) Manufacture of secondary batteries (positive electrode)
The positive electrode manufactured in each example was cut into a circular shape with a diameter of 18 mm, and a lithium metal foil having the same area and a polyethylene separator were laminated in a 2016 type coin cell in the order of the lithium metal foil, the separator, and the positive electrode. Produced. A coin-type non-aqueous electrolyte secondary battery was manufactured by adding a non-aqueous electrolyte and sealing it. As the non-aqueous electrolyte, a solution in which LiPF ₆ was dissolved in a solvent (a mixed solvent of ethyl methyl carbonate: ethylene carbonate = 1: 1 (volume ratio)) at a concentration of 1M was used.

(2) Evaluation of charge / discharge cycle characteristics of positive electrode For the coin-type non-aqueous electrolyte secondary battery manufactured in (1) above, at 25 ° C., a constant current corresponding to 0.2 C is 4.3 V (the voltage is a voltage relative to lithium). The battery was charged until the current value reached 0.02C at the charging upper limit voltage, and thereafter, a cycle of discharging to 3V with a constant current corresponding to 0.2C was performed. The capacity retention rate (unit:%) of the discharge capacity at the 100th cycle relative to the discharge capacity at the time of the first cycle discharge was determined and used as an index of the charge / discharge characteristics of the battery. The higher the capacity retention rate, the better.
Note that 1 C represents a current value for discharging the reference capacity of the battery in one hour, and 0.5 C represents a half current value.

(3) Evaluation of discharge rate characteristics of positive electrode Using a coin-type non-aqueous electrolyte secondary battery prepared in the same manner as in (1) above, at 25 ° C., a constant current corresponding to 0.2 C is 4.3 V (voltage) Represents a voltage with respect to lithium), and the battery was charged until the current value reached 0.02 C at the upper limit of charge voltage. Next, after discharging to 3 V with a constant current corresponding to 0.2 C, charging was performed in the same manner as described above, and discharging was performed to 3 V with a constant current corresponding to 3 C, thereby evaluating discharge rate characteristics. When the discharge capacity after 0.2C discharge was taken as 100%, the maintenance ratio of the discharge capacity after 3C discharge was calculated based on the following formula to obtain the initial discharge capacity ratio. A high initial discharge capacity ratio indicates that the resistance in the electrode is small and excellent.
Discharge capacity ratio (%) = (3C discharge capacity / 0.2C discharge capacity) × 100

(4) Evaluation of positive electrode reactivity The following charge / discharge cycle was implemented using the coin-type non-aqueous electrolyte secondary battery created similarly to said (1). In cycles 1 to 4, constant current charging was performed up to 4.2 V at a current corresponding to 0.5 C, and further, constant voltage charging was performed until the current value reached a current corresponding to 0.02 C at the charging lower limit voltage. Then, constant current discharge was performed to 3.0V with the electric current equivalent to 0.2C. In cycle 5, constant current charging was performed up to 4.3 V with a current corresponding to 0.5 C, and further constant voltage charging was performed until the current value reached a current corresponding to 0.02 C at the charging lower limit voltage. Thereafter, the obtained secondary battery in a charged state was decomposed in an argon atmosphere to obtain a charged positive electrode. The obtained positive electrode was washed three times with dimethyl carbonate (2 mL), vacuum-dried and then punched out to a diameter of 5 mm, placed in a sealed container made of SUS, and further sealed with 2 μL of the non-aqueous electrolyte of each example, An evaluation sample was used. About each obtained evaluation sample, it measured by the temperature range of 50-350 degreeC, and the temperature increase rate of 5 degree-C / min with the differential scanning calorimeter (DSC-6000 by SII nanotechnology company).
The positive electrode reactivity was evaluated by “exothermic peak temperature” and “exothermic amount at exothermic peak temperature”.
The “exothermic peak temperature” is the temperature showing the highest calorific value in the measured temperature range, and the calorific value at that temperature (a value obtained by correcting the calorific value at 60 ° C. to 0) is “the calorific value at the exothermic peak temperature”. (ΜW) ”. The lower the heat generation amount and the higher the heat generation peak temperature, the lower the reactivity of the positive electrode, indicating that the secondary battery is less prone to thermal runaway and has higher safety.

The main raw materials used in the production examples are as follows.
<Monomer (a)>
(A1): Chlorotrifluoroethylene (CTFE)
<Monomer (b)>
(B1): 2-ethylhexyl vinyl ether (b2): ethyl vinyl ether (EVE)
(B3): cyclohexyl vinyl ether (CHVE)
<Monomer (c)>
(C1): cyclohexanedimethanol monovinyl ether _{(CHMVE), CH 2 = CHOCH} 2 -cycloC 6 H 10 -CH 2 OH. “CycloC ₆ H ₁₀ ” represents “1,4-cyclohexylene” (hereinafter the same).
(C2): 4-hydroxybutyl vinyl ether (HBVE)
(C3): 10-Undecenoic acid <Monomer (d)>
_{(D1): CH 2 = CHOCH} 2 -cycloC 6 H 10 -CH 2 O (C 2 H 4 O) 15 H, average molecular weight 570, manufactured by Nippon Nyukazai Co..
<Emulsifier>
Nonionic emulsifier (1): DKS NL-100 (product name), manufactured by Daiichi Kogyo Seiyaku Co., Ltd., compound name: polyoxyethylene lauryl ether.
Anionic emulsifier (2): sodium lauryl sulfate.
<Polymerization initiator>
Initiator (1): ammonium persulfate (APS)
Initiator (2): t-butyl peroxypivalate

<Production Example 1: Production of fluorinated copolymer (Y1)>
In an autoclave with a stainless steel stirrer with an internal volume of 250 mL, 2.8 g of monomer (c1), 19 g of monomer (b1), 34 g of monomer (b3), 1.7 g of monomer (d1), ions 93 g of exchange water, 0.012 g of initiator (1), 5.2 g of nonionic emulsifier (1), and 0.1 g of anionic emulsifier (2) were charged and cooled with ice. Nitrogen gas was introduced, and the pressure in the autoclave was increased to about 0.34 MPa (3.5 kg / cm ² ) and degassed. After repeating this pressure degassing twice, 0.001 MPa (10 mmHg) After removing the dissolved air by degassing until 47 g, 47 g of monomer (a1) was charged and reacted at 50 ° C. for 24 hours.
After the reaction, the obtained aqueous dispersion was filtered through a 200-mesh nylon cloth to remove aggregates, and a fluorinated copolymer (Y1) latex was obtained. The content of the fluorinated copolymer (Y1) in the latex was 52% by mass.
The composition (content of each unit) of the obtained fluorine-containing copolymer, the measurement result of the number average molecular weight, and the amount of precipitate produced in the mechanical stability test of the latex are shown in Table 1 (hereinafter the same).

<Production Example 2: Production of fluorinated copolymer (Y2)>
In this example, the fluorine-containing copolymer was synthesized by a solution polymerization method without using the monomer (d).
A fluorinated copolymer (Y2) latex was produced in the same manner as in the production examples described in paragraphs [0078] to [0079] of Patent Document 1 (International Publication No. 2010/134465).
That is, 10.3 g of monomer (b2), 16.7 g of monomer (c1), 15.4 g of monomer (c2), 10% as other monomer (e1) in a pressure resistant polymerization tank having an internal volume of 250 mL. -4.9 g of undecenoic acid (hereinafter referred to as UDA), 67 g of methyl ethyl ketone (MEK) as an organic solvent, 0.6 g of initiator (2), and 2 g of Kyoward 500SH were cooled. KYOWARD 500SH is an acid adsorbent (hydrotalcite composed of a double salt of magnesium and aluminum) manufactured by Kyowa Chemical Industry Co., Ltd.
After deaeration in the same manner as in Production Example 1 to remove dissolved air, 52.2 g of monomer (a1) was charged and reacted at 50 ° C. for 24 hours.
After the reaction, 1.85 g of triethylamine was added to 167 g of the polymer solution thus obtained to neutralize it, and 145 g of ion-exchanged water was slowly added with stirring. Subsequently, MEK was distilled off under reduced pressure to obtain a fluorinated copolymer (Y2) latex. The content of the fluorinated copolymer (Y2) in the latex was 50% by mass.

<Production Example 3: Production of fluorinated copolymer (Z1)>
In this example, a redox polymerization initiator was used, and a fluorinated copolymer (Z1) was produced by the following procedure. TFE was used as the monomer (s), and P was used as the monomer (t).
That is, after degassing the inside of a stainless steel pressure-resistant reactor having an internal volume of 3200 mL equipped with an anchor blade for stirring, 1700 g of ion-exchange water, 17.7 g of sodium lauryl sulfate as an emulsifier, pH 60 g of disodium hydrogen phosphate 12 hydrate and 0.9 g of sodium hydroxide were added as regulators, and 8.4 g of ammonium persulfate (1 hour half-life temperature 82 ° C.) as an initiator. Further, 0.4 g of ethylenediaminetetraacetic acid disodium salt dihydrate (hereinafter referred to as EDTA) and 0.3 g of ferrous sulfate heptahydrate were dissolved in 200 g of ion-exchanged water as a redox catalyst. The aqueous solution was added to the reactor. At this time, the pH of the aqueous medium in the reactor was 9.2.
Then, a monomer mixed gas of TFE / P = 88/12 (molar ratio) was injected at 25 ° C. so that the internal pressure of the reactor was 2.50 MPaG. The anchor blade was rotated at 300 rpm, and sodium hydroxymethanesulfinate dihydrate (hereinafter referred to as Rongalite) adjusted to pH 10.0 with sodium hydroxide was added to the reactor to initiate the polymerization reaction.
The polymerization is continued while maintaining the polymerization temperature at 40 ° C., and the pressure in the reactor decreases with the progress of the polymerization. Therefore, when the internal pressure of the reactor drops to 2.49 MPaG, TFE / P = 56/44 (Molar ratio) monomer mixed gas was injected under its own pressure, and the internal pressure of the reactor was increased to 2.51 MPaG. This operation was repeated, and the internal pressure of the reactor was maintained at 2.49 to 2.51 MPaG, and the polymerization reaction was continued. When the total amount of the TFE / P monomer mixed gas injected reached 900 g, the internal pressure of the reactor was cooled to 10 ° C. to obtain a latex of a fluorinated copolymer (Z1). The polymerization time was 8 hours. The content of the fluorinated copolymer (Z1) in the latex was 34% by mass. The copolymer composition of the fluorine-containing copolymer (Z1) was a repeating unit based on TFE / a repeating unit based on P = 56/44 (molar ratio).
The fluorine content of the fluorine-containing copolymer (Z1) was 57% by mass.

<Reference Production Example 1: Production Example of PTFE Aqueous Dispersion>
A latex of polytetrafluoroethylene (PTFE) was produced in the same manner as in the production examples described in paragraphs [0084] to [0085] of Patent Document 1 (International Publication No. 2010/134465).
That is, 736 g of paraffin wax, 59 L of ultrapure water, and 15 g of ammonium perfluorooctanoate (APFO) as an emulsifier were charged in a 100 L pressure-resistant polymerization tank. After raising the temperature to 70 ° C., purging with nitrogen and then degassing, tetrafluoroethylene (TFE) was introduced to an internal pressure of 1.9 MPa while stirring. 1 L of 0.5 mass% disuccinic acid peroxide aqueous solution was injected into this to initiate polymerization. The polymerization was carried out for 45 minutes while maintaining the polymerization pressure at 1.9 MPa while supplying TFE, and then the temperature was raised to 90 ° C., and 1 L of a 2.5 mass% APFO aqueous solution was added and continued for 95 minutes. Aggregates and paraffin were removed from the obtained emulsion to obtain 25.1 kg of an aqueous dispersion having a polytetrafluoroethylene (PTFE) content of 26.0% by mass and an APFO content of 0.05% by mass.
To this aqueous dispersion, 0.2 kg of a nonionic surfactant mainly composed of polyoxyethylene (average degree of polymerization 9) lauryl ether was added and dissolved, and 0.3 kg of an anion exchange resin (Diaion WA—manufactured by Mitsubishi Chemical) was dissolved. 30) was dispersed and stirred for 24 hours, followed by filtration to remove the anion exchange resin. To the filtrate was added 0.04 kg of 28% by mass aqueous ammonia, concentrated at 80 ° C. for 10 hours by a phase separation method, and after removing the supernatant, 15 g of ammonium perfluorohexanoate (APFH) was newly added, 10.5 kg of an aqueous PTFE dispersion having a PTFE content of 59.7% by mass, an APFH content of 0.15% by mass, and an APFO content of 0.01% by mass was obtained. Water was added so that the PTFE content was 50% by mass and used in Reference Examples described later.

<Example 1: Production of positive electrode mixture 1 and positive electrode 1>
A positive electrode mixture was prepared using the fluorine-containing copolymer (Y1) latex obtained in Production Example 1 and the fluorine-containing copolymer (Z1) latex obtained in Production Example 3 as a binder composition.
That is, 100 parts by mass of LiNi _0.5 Mn _0.2 Co _0.3 O _{2 having} an average particle diameter of 10 μm as a positive electrode active material and 7 parts by mass of acetylene black as a conductive material are mixed, and the concentration is 1 mass as a viscosity modifier. % Of carboxymethylcellulose aqueous solution was added and kneaded, and the content ratio of the fluorinated copolymer (Y1) to the fluorinated copolymer (Z1) was fluorinated copolymer (Y1) / fluorinated. The fluorine-containing copolymer (Y1) so that the copolymer (Z1) = 50/50, that is, the fluorine-containing copolymer (Y1) is 1.5 parts by mass with respect to 100 parts by mass of the positive electrode active material. ) A latex is added, and a fluorine-containing copolymer (Z1) latex is added so that the fluorine-containing copolymer (Z1) is 1.5 parts by mass with respect to 100 parts by mass of the positive electrode active material. Got.
The obtained positive electrode mixture 1 was applied to an aluminum foil (current collector) having a thickness of 15 μm so that the thickness after drying was 60 μm with a doctor blade, and was dried in a vacuum dryer at 120 ° C. A positive electrode 1 was obtained.
The coatability and adhesion (peel strength) were evaluated by the above methods. The charge / discharge characteristics (charge / discharge cycle characteristics, discharge rate characteristics) were evaluated by the methods (1) to (3) above. The evaluation results are shown in Table 2 (hereinafter the same).

<Example 2: Production of positive electrode mixture 2 and positive electrode 2>
A positive electrode mixture 2 and a positive electrode 2 were produced in the same manner as in Example 1 except that the fluorinated copolymer (Y2) was used instead of the fluorinated copolymer (Y1), and evaluation was performed in the same manner.

<Example 3: Production of positive electrode mixture 3 and positive electrode 3>
The content ratio of the fluorine-containing copolymer (Y1) and the fluorine-containing copolymer (Z1) was set to be fluorine-containing copolymer (Y) / fluorine-containing copolymer (Z1) = about 33/67. That is, while adding the fluorine-containing copolymer (Y1) latex so that the fluorine-containing copolymer (Y1) becomes 1.0 part by mass with respect to 100 parts by mass of the positive electrode active material, In the same manner as in Example 1, except that the fluorinated copolymer (Z1) latex was added so that the fluorinated copolymer (Z1) was 2.0 parts by mass, the positive electrode mixture 3 and the positive electrode 3 Were manufactured and evaluated in the same manner.

<Comparative Example 1: Production of positive electrode mixture 4 and positive electrode 4>
Example 1 except that the fluorinated copolymer (Y) was not added and only the fluorinated copolymer (Z1) was added to 3.0 parts by mass with respect to 100 parts by mass of the positive electrode active material. Similarly, the positive electrode mixture 4 and the positive electrode 4 were produced and evaluated in the same manner.

<Comparative Example 2: Production of positive electrode mixture 5 and positive electrode 5>
Except that the fluorine-containing copolymer (Z1) was not added, and only the fluorine-containing copolymer (Y2) was added in an amount of 3.0 parts by mass with respect to 100 parts by mass of the positive electrode active material. Produced the positive electrode mixture 5 and the positive electrode 5 in the same manner as in Example 1 and evaluated them in the same manner.

<Reference Example 1>
Instead of the fluorine-containing copolymer (Z1), the polytetrafluoroethylene (PTFE) latex (PTFE content 50%) obtained in Reference Production Example 1 was used in a PTFE ratio of 1. A positive electrode mixture and a positive electrode were produced and evaluated in the same manner as in Example 2 except that the amount was 5 parts by mass.

<Reference Example 2>
Instead of the fluorinated copolymer (Y1), the polytetrafluoroethylene (PTFE) latex obtained in Reference Production Example 1 (PTFE content 50%) was obtained by adding 1. A positive electrode mixture and a positive electrode were produced and evaluated in the same manner as in Example 1 except that the amount was 5 parts by mass.

  The positive electrode reactivity was evaluated for Examples 1 and 3 and Comparative Example 1 by the method of (4) above. The evaluation results are shown in Table 3.

As shown in the results of Tables 1 and 2, Examples 1 to 3 in which the fluorine-containing copolymer (Y) and the fluorine-containing copolymer (Z) were mixed were used in the application of the electrode mixture for an electricity storage device. The workability was good, the electrode was excellent in flexibility and adhesion, and the charge / discharge characteristics in the secondary battery were also good.
In particular, when Example 2 is compared with Comparative Examples 1 and 2, Example 2 using a mixture of the fluorine-containing copolymer (Y2) and the fluorine-containing copolymer (Z1) is a comparison using each of them alone. Adhesion was improved as compared with Examples 1 and 2, and charge / discharge characteristics equal to or higher than that were obtained. Further, the flexibility of Example 2 is improved as compared with Comparative Example 2 in which the fluorine-containing copolymer (Y1) is used alone, and is almost equivalent to Comparative Example 1 in which the fluorine-containing copolymer (Z1) is used alone. there were. Moreover, the coating property did not deteriorate by mixing the fluorinated copolymer (Y) and the fluorinated copolymer (Z).
Moreover, when Example 1 and Example 2 are compared, Example 1 using the fluorine-containing copolymer (Y1) having the structural unit (d) is more adhesive and charge / discharge characteristics than Example 2. It turns out that it is excellent.

  In addition, as shown in the results of Reference Examples 1 and 2, the methods described in the Examples of Patent Documents 1 and 2 are inferior in the coating property of the electrode mixture, but in Examples 1 to 3 according to the present invention. Good coatability was obtained.

  Furthermore, as shown in the results of Table 3, Example 1 and Example 3 in which the fluorine-containing copolymer (Y) and the fluorine-containing copolymer (Z) were mixed and used were the fluorine-containing copolymer ( The positive electrode generates less heat than Comparative Example 1 using Z1) alone, and the reactivity of the positive electrode is kept lower, thermal runaway is less likely to occur, and a safer secondary battery is obtained. I understand.

Claims (10)

A fluorine-containing copolymer (Y) having a unit (a) based on the following monomer (a), a unit (b) based on the following monomer (b), and a unit (c) based on the following monomer (c) ),
It has one or more units (s) based on a monomer (s) selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride, and has a glass transition temperature of −60 ° C. to 20 ° C. The binder composition for electrical storage devices containing a fluorine-containing copolymer (Z) and a liquid medium.
Monomer (a): One or more selected from tetrafluoroethylene and chlorotrifluoroethylene.
Monomer (b): One or more selected from the group consisting of a compound represented by the following formula (I) and a compound represented by the following (II).
_{CH 2 = CH- (CH 2)} n -O-R ··· (I)
_{CH 2 = CH- (CH 2)} n -OCO-R ··· (II)
[Wherein, n is 0 or 1, and R represents a saturated hydrocarbon group having 1 to 20 carbon atoms. ]
Monomer (c): One or more selected from the group consisting of compounds having an ethylenically unsaturated group and having a hydroxy group, an epoxy group or a carboxy group.   The binder for electrical storage devices of Claim 1 whose glass transition temperature of the said fluorine-containing copolymer (Y) is higher than the glass transition temperature of the said fluorine-containing copolymer (Z), and the difference is 10 degreeC or more. Composition. The binder composition for an electricity storage device according to claim 1 or 2, wherein the fluorine-containing copolymer (Z) further has one or more units (t) based on a monomer selected from the following monomer group T. .
Monomer group T: ethylene, propylene, perfluoro (alkyl vinyl ether), 1,2-difluoroethylene, 1,1,2-trifluoroethylene, 3,3,3-trifluoro-1-propene, 1,3 , 3,3-tetrafluoropropene, and vinyl fluoride. The fluorine-containing copolymer (Z) is
Tetrafluoroethylene / propylene copolymer,
Tetrafluoroethylene / propylene / vinylidene fluoride copolymer,
Vinylidene fluoride / hexafluoropropylene copolymer,
Tetrafluoroethylene / vinylidene fluoride / hexafluoropropylene copolymer,
Tetrafluoroethylene / perfluoro (alkyl vinyl ether) copolymer,
Tetrafluoroethylene / propylene / 3,3,3-trifluoro-1-propene copolymer,
Tetrafluoroethylene / propylene / vinylidene fluoride / 3,3,3,3-trifluoro-1-propene copolymer,
Vinylidene fluoride / hexafluoropropylene / 3,3,3-trifluoro-1-propene copolymer,
Tetrafluoroethylene / vinylidene fluoride / hexafluoropropylene / 3,3,3-trifluoro-1-propene copolymer,
Vinylidene fluoride / perfluoro (alkyl vinyl ether) copolymer,
Ethylene / hexafluoropropylene copolymer,
Tetrafluoroethylene / propylene / 1,3,3,3-tetrafluoropropene copolymer,
Tetrafluoroethylene / propylene / 1,1,2-trifluoroethylene copolymer,
The binder for an electricity storage device according to claim 3, wherein the binder is one or more selected from the group consisting of a tetrafluoroethylene / propylene / vinyl fluoride copolymer and a tetrafluoroethylene / propylene / 1,2-difluoroethylene copolymer. Composition. The electrical storage device as described in any one of Claims 1-4 in which the said monomer (c) contains 1 or more types chosen from the group which consists of a compound represented by the following formula (III)-(VI). Binder composition.

[Wherein, n is 0 or 1, m is an integer of 0 to 2, R ¹ is a (m + 2) -valent saturated hydrocarbon group having 1 to 10 carbon atoms, or a carbon number having an etheric oxygen atom. Represents a (m + 2) -valent saturated hydrocarbon group having ² to 10 carbon atoms, and R ² is a divalent saturated hydrocarbon group having 1 to 8 carbon atoms or a divalent saturated hydrocarbon having 2 to 8 carbon atoms having an etheric oxygen atom. Represents a hydrocarbon group, and R ³ represents an alkylene group having 1 to 8 carbon atoms or an alkylene group having 2 to 8 carbon atoms having an etheric oxygen atom. ]   The fluorine-containing copolymer (Y) further includes one or more units (d) based on the monomer (d) which is a macromonomer having a hydrophilic portion. The binder composition for an electricity storage device according to item.   The binder composition for an electricity storage device according to any one of claims 1 to 6, wherein the liquid medium is an aqueous medium.   The electrode mixture for electrical storage devices containing the binder composition for electrical storage devices described in any one of Claims 1-7, and a battery active material.   The electrode for electrical storage devices which has an electrical power collector and the electrode active material layer formed using the electrode mixture for electrical storage devices described in Claim 8 on this electrical power collector.   A secondary battery comprising the electrode for an electricity storage device according to claim 9 and an electrolytic solution.