JPWO2008105036A1 - Lithium ion secondary battery electrode binder resin, composition and paste containing the same, and lithium ion secondary battery electrode using the same - Google Patents

Abstract

Summary: A resin for a binder of a lithium ion secondary battery that has excellent adhesion to electrode active material particles, adhesion to metal foil, and excellent retention of electrode active material particles with large volume expansion / contraction due to charge / discharge. It is disclosed. The resin for a lithium ion secondary battery electrode binder has as a main component at least one structural unit selected from structural units represented by any one of the following general formulas (1) to (3), and the general formula (1) The content (a) of the structural unit represented by the formula (2), the content (b) of the structural unit represented by the general formula (2), and the content (c) of the structural unit represented by the general formula (3) are as follows: The logarithmic viscosity at 30 ° C. is 0.02 to 2.0 dl / g.

Description

  The present invention relates to a resin for an electrode binder (binder) of a lithium ion secondary battery. More specifically, the present invention relates to a polyamide-imide resin for electrode binder having a specific structure and logarithmic viscosity. The present invention also relates to a paste for an electrode material of a lithium ion secondary battery containing active resin particles capable of occluding, storing and releasing such resin and lithium ions, and a lithium ion secondary battery electrode.

  In recent years, along with the downsizing and weight reduction of portable electronic devices typified by mobile phones, PDAs (personal digital assistants) or notebook computers, power storage devices such as lithium ion secondary batteries. However, there is a growing demand for downsizing, weight reduction, high energy density, and improvement of charge / discharge characteristics (capacity and charge / discharge cycle characteristics).

  Conventionally, graphite-based carbon materials have been mainly used as negative electrode active materials for lithium ion secondary batteries. However, in order to produce a lithium ion secondary battery with higher energy density, a negative electrode active material having a higher charge / discharge capacity is desired.

  In recent years, tin and silicon have attracted attention as novel negative electrode active material materials that can replace graphite-based carbon materials. When such tin, silicon, or an alloy or oxide thereof is used as the negative electrode active material for a lithium ion secondary battery, the reaction between the active material and lithium during charging is a so-called alloying reaction. For this reason, the expansion and contraction of the volume of the negative electrode active material due to charge / discharge becomes very large.

  On the other hand, regarding lithium ion secondary battery electrode materials, a paste comprising a polyamideimide resin composition (see, for example, Patent Document 1) in which carbon powder is dispersed in a polyamideimide resin solution, a polyamideimide resin solution, inorganic fine particles, and a color pigment. A resin composition (see, for example, Patent Document 3) including a binder component obtained by reacting a polyamideimide resin and a coupling agent has been proposed. However, the resins disclosed therein are insufficient in adhesiveness with active materials and metal foils. In particular, when a negative electrode active material having a large volume expansion / contraction due to charge / discharge such as tin or silicon was used, desorption of the active material occurred due to charge / discharge, and the cycle characteristics were insufficient.

On the other hand, tensile strength of 50 N / mm ² or more, elongation at break of 10% or more, strain energy density of 2.5 × 10 ⁻³ J / mm using an active material particle containing silicon and an electrode material containing a binder. ^A negative electrode for a lithium secondary battery having a mechanical property of ³ or more and an elastic modulus of 10000 N / mm ² or less has been proposed (see, for example, Patent Document 4). However, even with the resin disclosed herein, the adhesion to the electrode active material particles and the adhesion to the metal foil are insufficient, and the negative electrode active material having a large volume expansion / contraction due to charge / discharge is retained. Sex was insufficient.

JP 7-292245 A JP 7-331068 A JP 11-224671 A International Publication No. 2004/4031 Pamphlet

  In view of the above problems, the present invention is a lithium ion secondary that has excellent adhesion to electrode active material particles and adhesion to metal foil, and excellent retention of electrode active material particles with large volume expansion / contraction due to charge / discharge. It aims at providing resin for battery electrode binders.

  As a result of diligent research, the inventors of the present application show that a polyamide-based resin having a specific chemical structure is excellent in adhesion to electrode active material particles and adhesion to metal foil, and has a large volume expansion / contraction due to charge / discharge. The present invention has been completed by finding that it is excellent in retention of active material particles and exhibits excellent performance as a resin for a lithium ion secondary battery electrode binder.

That is, the present invention is as follows.
1. The content (a) of the structural unit represented by the general formula (1) having as a main component at least one structural unit selected from the structural units represented by any of the following general formulas (1) to (3), The content (b) of the structural unit represented by the general formula (2) and the content (c) of the structural unit represented by the general formula (3) have the relationship of the following formula (A), at 30 ° C. Resin for lithium ion secondary battery electrode binder having a logarithmic viscosity of 0.02 to 2.0 dl / g.
a / (a + b + c) ≦ 0.55 (molar ratio) (A)

(In the general formulas (1) to (3), R is a divalent aromatic group represented by the following general formula (4), and Ar ¹ is a divalent aromatic represented by the following general formula (5). Group Ar ² represents a trivalent aromatic group represented by the following general formula (6), and R, Ar ¹ and Ar ² in different structural units are independent of each other). )

(In the general formula (4), X represents a direct bond, —O—, —S—, —CO—, —SO ₂ —, —C (CH ₃ ) ₂ — or —C (CF ₃ ) ₂ —. P represents an integer of 0 to 3. In the general formula (5), Y represents a direct bond, —O—, —CO—, —SO ₂ —, —CH ₂ —, —C (CH ₃ ) ₂ —. Or -C (CF ₃ ) _2- , q is 0 or 1. In the general formula (6), Z is a direct bond, -O-, -CO-, -COO-, -OCO-,- SO _2- , -CH _2- , -C (CH ₃ ) ₂ -or -C (CF ₃ ) ₂ -is shown, r is 0 or 1. The above general formulas (4), (5) and (6) ), Each benzene ring is selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, a chlorine atom, a bromine atom, a nitro group, and a cyano group. Optionally having at least one substituent.

2. In the general formulas (1) to (3), R contains 4,4′-diaminodiphenyl ether residue and m-phenylenediamine residue, and 4,4′-diaminodiphenyl ether in the resin Residue content (x) and m-phenylenediamine residue content (y) are 1.5 ≦ x / y ≦ 4 (molar ratio)
2. The resin for a lithium ion secondary battery electrode binder according to 1 above.

3. 2. The resin for a lithium ion secondary battery electrode binder according to 1 above, wherein the content of each structural unit represented by any one of the general formulas (1) to (3) has a relationship represented by the following formula (B).
0.05 ≦ a / (a + b + c) ≦ 0.55 (molar ratio) (B)

4). 2. The resin for a lithium ion secondary battery electrode binder according to 1 above, which has a residual carboxyl group amount of 0.05 to 0.40 mmol / g.
5). 2. The resin for a lithium ion secondary battery electrode binder as described in 1 above, wherein the gel activity represented by the following formula (7) after heating in the air at 280 ° C. for 2 hours is 3.0% by weight or less.
Gelation activity (% by weight) = (N-methyl-2-pyrrolidone insoluble matter weight / sample weight) × 100 (7)
6). The resin composition for lithium ion secondary battery electrode binders containing 5-30 weight% of resin for lithium ion secondary battery electrode binders in any one of said 1-5, and a polar solvent.
7). The lithium ion secondary battery electrode binder resin according to any one of 1 to 5 above, a polar solvent and lithium ion secondary battery electrode active material particles, and a content of the lithium ion secondary battery electrode binder resin However, the paste for lithium ion secondary battery electrode material which is 1-20 weight part with respect to 100 weight part of content of lithium ion secondary battery electrode active material particle.
8). 8. The lithium ion secondary battery electrode material as described in 7 above, comprising lithium ion secondary battery negative electrode active material particles having a volume of 130 to 250 when lithium ions are fully charged with respect to the volume 100 before storage of lithium ions. For paste.
9. 9. A lithium ion secondary battery electrode comprising a current collector and the paste for a lithium ion secondary battery electrode material according to 7 or 8 applied on the current collector.
10. 10. The lithium ion secondary battery electrode according to 9, wherein the current collector is a metal foil.
11. 10. The lithium ion secondary battery electrode according to 9, wherein the paste is in a dried state.

  Resin for electrode binder of lithium ion secondary battery of the present invention has excellent adhesion to electrode active material particles, adhesion to metal foil, and retainability of electrode active material particles with large volume expansion / contraction due to charge / discharge Excellent. The lithium ion secondary battery electrode binder of the present invention can provide a lithium ion secondary battery electrode having a high capacity and excellent cycle characteristics.

<Resin for lithium ion secondary battery electrode binder>
The resin for a lithium ion secondary battery electrode binder of the present invention (hereinafter sometimes referred to as a resin) is at least one selected from the structural units represented by any one of the general formulas (1) to (3). The content of the structural unit represented by the general formula (1) (a), the content of the structural unit represented by the general formula (2) (b), and the general formula (3) The content (c) of the structural unit represented has the relationship of the following formula (A).
a / (a + b + c) ≦ 0.55 (molar ratio) (A)
That is, the main chain structure of the resin is based on a polyamide-imide resin containing an imide group and an amide group, but the structure is limited by the general formulas (4) to (6). This is a polyamide-imide resin having the following structure. Here, the main component in the present invention refers to a component exceeding 50 mol%. Preferably it is 80 mol% or more. Further, the polyamideimide resin refers to a polyamideimide resin or a precursor thereof.

  By using the polyamide-imide resin having the above specific structure as a binder for a lithium ion secondary battery electrode, adhesion with electrode active material particles that occlude, store, and release lithium ions, and current collection such as Cu foil Adhesiveness with metal foil for body is greatly improved. Moreover, it is excellent in the holding | maintenance property of negative electrode active material particle, and the detachment | desorption of electrode active material particle | grains by the expansion / contraction of the volume of the electrode active material particle produced with the occlusion / release of lithium ion can be suppressed.

  Moreover, content of the structural unit represented by General formula (1) is 55 mol% or less with respect to the content total of the structural unit represented by either of General formula (1)-(3). is required. By setting it as this range, solvent solubility required in order to set it as the resin composition for lithium ion secondary battery electrode binders is acquired.

  The first aspect of the resin of the present invention is an aspect where a / (a + b + c) = 0. That is, it is a polyamide-imide resin or a precursor thereof which does not have the structural unit represented by the general formula (1) but has the structural unit represented by the general formula (2) or (3) as a main component. Such a resin is obtained by polymerizing an aromatic tricarboxylic acid anhydride which is an acid component or its monochloride and an aromatic diamine component.

In the structural unit represented by the general formula (2) or (3), Ar ² represents a residue of an acid component. This acid component has a trivalent aromatic group represented by the following general formula (6). In addition, in different structural units contained in one molecule, Ar ² is independent from each other. Therefore, plural kinds of structural units containing different Ar ² may be contained in one molecule.

(In the general formula (6), Z represents a direct bond, —O—, —CO—, —COO—, —OCO—, —SO ₂ —, —CH ₂ —, —C (CH ₃ ) ₂ — or — C (CF ₃ ) ₂ —, where r represents 0 or 1. Each benzene ring is an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, a chlorine atom, a bromine atom, or a nitro group. And may optionally have at least one substituent selected from the group consisting of cyano groups.)

  As such an acid component, specifically, trimellitic acid monochloride, trimellitic anhydride, 3 ′, 4,4′-biphenyltricarboxylic acid monochloride anhydride, 3 ′, 4,4′-diphenylmethanetricarboxylic acid Examples include acid chloride anhydride, 3 ′, 4,4′-diphenylisopropane tricarboxylic acid chloride anhydride, and 3,4,4′-benzophenone tricarboxylic acid monochloride anhydride. These may be used alone or in combination of two or more. In the present invention, trimellitic acid monochloride or trimellitic acid anhydride is preferable and trimellitic acid monochloride is more preferable from the viewpoint of further improving the adhesion and retention with the electrode active material particles.

  In the structural unit represented by the general formula (2) or (3), R represents a residue of a diamine component. This diamine component has a divalent aromatic group represented by the following general formula (4). By using such a diamine component, it is possible to obtain a resin having excellent adhesion to the metal foil, adhesion to the electrode active material particles, and excellent retention of the electrode active material particles. In different structural units contained in one molecule, Rs are independent from each other. Therefore, a plurality of types of structural units containing different R may be contained in one molecule. R is not only independent between the structural unit represented by the general formula (2) and the structural unit represented by the general formula (3), but also the structural unit represented by the general formula (2). They are also independent from each other and between the structural units represented by the general formula (3). Further, when different types of structural units are contained in one molecule, the molecule may be a block copolymer, an alternating copolymer, or a random copolymer.

(In the general formula (4), X represents a direct bond, —O—, —S—, —CO—, —SO ₂ —, —C (CH ₃ ) ₂ — or —C (CF ₃ ) ₂ —. P represents an integer of 0 to 3. Each benzene ring is selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, a chlorine atom, a bromine atom, a nitro group, and a cyano group. (It may optionally have at least one selected substituent.)

  Examples of such a diamine component include m-phenylenediamine, p-phenylenediamine, oxydianiline, 2,2′-bis (4-aminophenyl) propane, and 2,2′-bis (4-aminophenyl) hexa. Fluoropropane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 3,4-diaminobiphenyl, 4,4'-diaminobenzophenone, 3,4-diaminodiphenyl ether 3,3′-diaminobenzophenone, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 2, 2-bis [4- (4-aminophenoxy) phenyl] propane, bis [4- 4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 4,4′-bis (4-aminophenoxy) biphenyl, 2,2-bis [4- (4-aminophenoxy) ) Phenyl] hexafluoropropane, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfide, and the like. These may be used alone or in combination of two or more.

  Among these, m-phenylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylpropane, 1,3-bis (4-aminophenoxy) benzene, 2,2-bis [4- (4 -Aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] sulfone, etc. are excellent in polymerization reactivity, solvent solubility of the resulting resin, adhesion to metal foil, electrode active material particles and This is preferable in that it can further improve the adhesion and the retention of the electrode active material particles. Furthermore, 4,4'-diaminodiphenyl ether and m-phenylenediamine are preferred.

  Furthermore, a structural unit in which R in the general formula (2) or (3) is a 4,4′-diaminodiphenyl ether residue and a structural unit that is an m-phenylenediamine residue are contained in one molecule. When the 4,4′-diaminodiphenyl ether residue content (x) and the m-phenylenediamine residue content (y) are 1.5 ≦ x / y ≦ 4 (molar ratio), retention of electrode active material particles It is preferable because the properties are further improved. Moreover, the sum of the structural unit which is a 4,4′-diaminodiphenyl ether residue and the structural unit which is an m-phenylenediamine residue is 50 of all the structural units represented by the general formula (2) and / or (3). It is preferable to exceed mol%. Since the polyamideimide resin composition having such a diamine residue has an excellent balance of mechanical properties such as strength and elongation, it can follow the volume change of the electrode active material particles during lithium ion storage and release. It is estimated that the retention of the electrode active material particles is further improved. Even if each molecule | numerator which comprises resin is a block copolymer of the structural unit containing 4,4'- diamino diphenyl ether residue as R, and the structural unit containing m-phenylenediamine residue, it is an alternating copolymer. It may be a random copolymer.

Therefore, as a first aspect of the resin of the present invention, that is, an aspect in which a / (a + b + c) = 0, Ar ² in the general formula (2) or (3) is a trimellitic acid monochloride residue. And a constituent unit in which R is a 4,4′-diaminodiphenyl ether residue and a constituent unit in which R is an m-phenylenediamine residue, and the content (x) of 4,4′-diaminodiphenyl ether residue and m-phenylene A resin having a diamine residue content (y) of 1.5 ≦ x / y ≦ 4 (molar ratio) is preferred.

  In addition, within the range which does not impair the effect of this invention, you may have structural units other than general formula (2)-(3) less than 50 mol%. For example, as an acid component, terephthalic acid, isophthalic acid, 4,4′-biphenyldicarboxylic acid, pyromellitic acid, 3,3′-benzophenone tetracarboxylic acid, 4,4′-benzophenone tetracarboxylic acid, 3,3′- Biphenylsulfonetetracarboxylic acid, 4,4'-biphenylsulfonetetracarboxylic acid, 3,3'-biphenyltetracarboxylic acid, 4,4'-biphenyltetracarboxylic acid, adipic acid, sebacic acid, maleic acid, fumaric acid, dimer Acid, stilbene dicarboxylic acid or acid anhydrides thereof, or acid chloride can be used. Moreover, you may copolymerize aliphatic diamine and naphthalene diamine, such as 1, 4- naphthalene diamine, 1, 5- naphthalene diamine, 2, 6- naphthalene diamine, 2, 7- naphthalene diamine, as a diamine component.

  Next, as a second aspect of the resin of the present invention, an aspect where 0 <a / (a + b + c) ≦ 0.55 will be described. That is, it is an aramid-amidoimide copolymer having the structural unit represented by the general formula (1). It is obtained by copolymerizing an aramid structure with the polyamideimide resin. It is known that a pre-aromatic polyamide has a characteristic curve in which, for example, a stress-strain curve in tensile properties increases in strength with elongation. It is considered that the retention of the electrode active material particles is further improved by copolymerizing the segment having such mechanical properties to the polyamideimide main chain. In this embodiment, each molecule constituting the resin always includes a different type of structural unit. However, the molecule may be a block copolymer, an alternating copolymer, a random copolymer, It may be a coalescence.

  In this embodiment, the structural unit represented by the general formula (2) or (3) is as described in the first embodiment.

In the aramid structural unit represented by the general formula (1), Ar ¹ represents a residue of an acid component. This acid component is an aromatic dicarboxylic acid or a dichloride thereof, and has a divalent aromatic residue represented by the following general formula (5). In addition, in different structural units contained in one molecule, Ar ¹ is independent from each other. Therefore, a plurality of types of structural units containing different Ar ¹ may be contained in one molecule.

(In the general formula (5), Y represents a direct bond, —O—, —CO—, —SO ₂ —, —CH ₂ —, —C (CH ₃ ) ₂ — or —C (CF ₃ ) ₂ —. Q represents 0 or 1. Each benzene ring is selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, a chlorine atom, a bromine atom, a nitro group, and a cyano group. Optionally having at least one substituent.

  As such an acid component, for example, isophthalic acid, terephthalic acid, diphenylmethane-4,4′-dicarboxylic acid, diphenylmethane-2,4-dicarboxylic acid, diphenylmethane-3,4-dicarboxylic acid, diphenylmethane-3,3′- Dicarboxylic acid, 2,2′-bis- (4-carboxyphenyl) propane, 2- (2-carboxyphenyl) -2- (4-carboxyphenyl) propane, 2- (3-carboxyphenyl) -2- (4 -Carboxyphenyl) propane, diphenyl ether-4,4'-dicarboxylic acid, diphenyl ether-2,4-dicarboxylic acid, diphenyl ether-3,4-dicarboxylic acid, diphenyl ether-3,3'-dicarboxylic acid, diphenylsulfone-4,4 '-Dicarboxylic acid, diphenylsulfone-2,4-dicarboxylic acid Diphenylsulfone-3,4-dicarboxylic acid, diphenylsulfone-3,3′-dicarboxylic acid, benzophenone-4,4′-dicarboxylic acid, benzophenone-2,4-dicarboxylic acid, benzophenone-3,4-dicarboxylic acid, Examples thereof include benzophenone-3,3′-dicarboxylic acid or dichlorides thereof. These may be used alone or in combination of two or more. In addition, within the range which does not impair the effect of this invention, you may have less than 50 mol% of acid components which comprise residues other than General formula (5), for example, naphthalenedicarboxylic acid.

  It is these dichlorides that are advantageous for obtaining an aramid-amideimide copolymer, preferably terephthalic acid dichloride, isophthalic acid dichloride, 3,3′-biphenyldicarboxylic acid dichloride, 3,3′-diphenyl ether dicarboxylic acid. Acid dichloride, 3,3′-diphenylsulfide dicarboxylic acid dichloride, 3,3′-diphenylsulfone dicarboxylic acid dichloride, 3,3′-diphenylmethane dicarboxylic acid dichloride, 2-methyl-1,4-benzenedicarboxylic acid dichloride, 5- Methyl-1,3-benzenedicarboxylic acid dichloride, 2,5-dimethyl-1,4-benzenedicarboxylic acid dichloride, 4,6-dimethyl-1,3-benzenedicarboxylic acid dichloride, 3,3′-dimethyl-4, 4'-biphenyldicarboxylic acid dichloride, Examples include 2,2′-dimethyl-4,4′-biphenyldicarboxylic acid dichloride, 3,3 ′, 5,5′-tetramethyl-4,4′-biphenyldicarboxylic acid dichloride, and the like.

Y in the general formula (5) is preferably not a flexible group in terms of further improving the solvent solubility of the resulting resin and the adhesion to the electrode active material particles, and is preferably a direct bond, —SO ₂ —, —CH _2. —, —C (CH ₃ ) ₂ — or —C (CF ₃ ) ₂ — is preferred. Specifically, isophthalic acid dichloride or terephthalic acid dichloride is preferable, and terephthalic acid dichloride is more preferable.

  In the structural unit represented by the general formula (1), R represents a residue of a diamine component. Said 1st aspect WHEREIN: It describes as R in General formula (2) or (3). Also in this embodiment, a structural unit in which R in the general formulas (1) to (3) is a 4,4′-diaminodiphenyl ether residue and a structural unit in which an m-phenylenediamine residue is contained is contained in one molecule. When the 4,4′-diaminodiphenyl ether residue content (x) and m-phenylenediamine residue content (y) are 1.5 ≦ x / y ≦ 4 (molar ratio), the electrode active material particles This is preferable because the retentivity is more improved. In addition, the total constitution in which the sum of the constitutional unit which is a 4,4′-diaminodiphenyl ether residue and the constitutional unit which is an m-phenylenediamine residue is represented by any one of the general formulas (1) to (3) It is preferable to exceed 50 mol% of the unit. R may be a block copolymer of a structural unit containing a 4,4′-diaminodiphenyl ether residue and a structural unit containing an m-phenylenediamine residue, an alternating copolymer, a random copolymer, It may be a polymer.

In the present invention, in the aramid-amideimide copolymer, the content (a) of the structural unit represented by the general formula (1), the content (b) of the structural unit represented by the general formula (2), It is preferable that the content (c) of the structural unit represented by the formula (3) has the relationship of the following formula (B).
0.05 ≦ a / (a + b + c) ≦ 0.55 (molar ratio) (B)
By making content of the structural unit represented by General formula (1) into 5 mol% or more with respect to the content total of the structural unit represented by either of General formula (1)-(3), The retention of the electrode active material fine particles is improved.

<Logarithmic viscosity (ηinh)>
The logarithmic viscosity of the resin for the lithium ion secondary battery electrode binder of the present invention is 0 because it exhibits solution viscosity when dissolved in a solvent and mechanical properties (toughness) as a binder (binder). It should be 2 to 2.0 dl / g. Further, from the viewpoint of solution viscosity when dissolved in a solvent, 0.4 dl / g or more is more preferable, and 1.3 dl / g or less is more preferable.

  The logarithmic viscosity of the resin in the present invention was measured by dissolving 0.25 g of resin in 50 ml of N-methyl-2-pyrrolidone according to JIS K7367-1 (2002) and using an Ubbelohde viscosity tube at 30 ° C. Say things. Specifically, the measurement is performed as follows.

Weigh about 0.25 g of resin with a balance (accuracy: 0.1 mg) so that it does not absorb water (this value is x (g)), transfer to a 50 ml volumetric flask, and add 40 ml of N-methyl-2-pyrrolidone solvent. In addition, shake and stir until the resin is dissolved (at this time, the temperature of the solution must not be heated to 30 ° C. or higher to dissolve). After dissolution is completed, the solution is fixedly dissolved in 50 ml to prepare a N-methyl-2-pyrrolidone solution having a resin concentration of C (g / dl).
C (g / dl) = x (g) / 50 (ml)
The Ubbelohde viscometer is fixed in a thermostat controlled at 30 ° C. ± 0.05 ° C., and the flow time (t) of the prepared resin solution and the flow time (t0) of the solvent N-methyl-pyrrolidone are measured. The logarithmic viscosity represented by the formula is determined.
ηinh (dl / g) = ln (t / t0) / C

  In addition, the logarithmic viscosity of resin can be adjusted with the preparation amount ratio of the acid component used for superposition | polymerization, and a diamine component, for example. That is, by setting the molar ratio of acid monomer / diamine monomer to 100/100, the logarithmic viscosity can be increased, and by increasing the acid monomer / diamine monomer molar ratio to 101/100, etc. The logarithmic viscosity can be reduced.

<Residual carboxyl group amount>
The resin of the present invention preferably has a residual carboxyl group amount of 0.05 to 0.40 mmol / g. When the residual carboxyl group amount is 0.05 mmol / g or more, the adhesion with the metal foil and the electrode active material particles is further improved. This is presumably due to the improved flexibility of the resin main chain due to the residual carboxyl group. Moreover, from a viewpoint of the storage stability of the resin composition for lithium ion secondary battery electrode binders, 0.40 mmol / g or less is preferable and 0.25 mmol / g or less is more preferable. If it is 0.40 mmol / g or less, the resin composition for a lithium ion secondary battery electrode binder is excellent in storage stability at room temperature and excellent in handleability. Therefore, it is preferable to contain the structural unit represented by the general formula (3) so that the residual carboxyl group amount of the resin falls within this range.

The measurement of the amount of residual carboxyl groups of the resin in the present invention is performed by the following method.
(1) Reagent A. DMF (dimethylformamide): solvent special grade reagent Bromothymol blue indicator (0.3% by weight): 0.15 g of bromothymol blue is dissolved in 50 ml of methanol.
C. N / 50 sodium methylate solution: 0.5 g of metallic sodium is dissolved in 1 liter of methanol.
The titer of the N / 50 sodium methylate solution is determined by the following method.
In a 200 ml Erlenmeyer flask containing 50 ml of distilled water, 20 ml of N / 50 sodium methylate solution is collected with a whole pipette, and titrated with 0.1N HCl standard solution (commercially available) using phenolphthalein as an indicator.
Titer (F) = 0.25 × f × S
f: 0.1N HCl standard solution titer,
S: Titration value of 0.1N HCl standard solution (ml)

(2) Measurement About 0.2 g of resin is precisely weighed (this value is expressed as wg) and dissolved in 20 ml of special grade DMF (N, N-dimethylformamide) in a 50 ml Erlenmeyer flask. Next, 4 drops of bromthymol blue indicator (0.3% by weight) is dropped, and titrated with a N / 50 sodium methylate solution from a microburette. Titration was performed until the yellow color of the indicator changed (yellow) → (yellow green) → (emerald green) completely (this value is defined as Sml).
Separately, a blank titration value for a pure solvent containing no resin is obtained (this value is defined as Bml). The amount of residual carboxyl groups is determined by the following formula.
Residual carboxyl group amount (mmol / g) = (F × (1/50) × (SB)) / resin sampling weight (wg)
F: titer of N / 50 sodium methylate solution S: titration of sample (ml)
B: Blank titration (ml) (titration with a pure solvent that does not dissolve the resin)

  The residual carboxyl group amount of the resin can be adjusted by adjusting the degree of polymerization (logarithmic viscosity) or imide ring closure rate of the resin. That is, the amount of residual carboxyl groups can be increased by reducing the logarithmic viscosity of the resin in the range of 0.2 to 2.0 dl / g, or by shortening the heat treatment time in the heated imide ring closure. The amount of residual carboxyl groups can be reduced by increasing the logarithmic viscosity of the resin in the range of 0.2 to 2.0 dl / g, or by increasing the heat treatment time in the heated imide ring closure. In the case of a resin having a logarithmic viscosity of 0.2 to 2.0 dl / g, the residual carboxyl group amount can be easily adjusted to the above range if the imide ring closure rate is 80 to 90%.

<Gerization activity>
In the resin of the present invention, the gelation activity represented by the formula (7) is preferably 3.0% by weight or less because the adhesion with the metal foil and the electrode active material particles is further improved. By using a resin having such a gelling activity, in the solvent drying process after the paste is applied to the current collector metal foil, the gelling reaction due to the heating of the resin is suppressed, so that the adhesion is improved. It is considered a thing. In order to obtain a resin having such a gelling activity, the production method described below is effective.

The gelation activity of the resin in the present invention is determined by the following measurement method.
(1) The resin powder is sieved and a 100 mesh ON, 24 mesh PASS product is collected. Here, the sieve is a Tyler sieve (JIS Z 8801 1956), the opening of a 100 mesh (nominal) sieve is 0.147 mm, and the same is the 24 mesh sieve. The screen is 0.701 mm.
(2) Weigh about 3 g of the screened resin powder, spread evenly on an aluminum cup (diameter 50 mm), place in a hot air dryer (TEMPERATURE CHAMBER MODEL HPS-222 / TABAI ESPEC CORP), 2 Heat treatment for hours. n = 3 processes are performed.
(3) About 0.5 g of the resin powder after the heat treatment is precisely weighed (heat treatment sample weight), put into a 100 ml volumetric flask, and further N-methyl-2-pyrrolidone is added for about 8 minutes.
(4) The resin flask is dissolved by immersing the measuring flask in a hot water bath whose temperature is adjusted to 80 ° C. for 1 hour. During dissolution (4 times / hour), shake the volumetric flask to promote dissolution.
(5) After immersion for 1 hour, add N-methyl-2-pyrrolidone to make up to 100 ml. Next, the measuring flask is immersed in an ultrasonic cleaner (BRANSONIC 220 / BRANSONIC CLEANINNG EQUIPMENT COMPANY) soaked in water for 15 minutes to complete the dissolution.
(6) Filter through a precisely weighed 100 mesh stainless steel wire mesh.
(7) After filtration, the wire mesh is washed with a washing bottle containing N-methyl-2-pyrrolidone, and then washed with ion-exchanged water.
(8) The filtered wire mesh is dried again at 280 ° C. for 2 hours, then placed in a desiccator, cooled and precisely weighed, and the weight of N-methyl-2-pyrrolidone insoluble matter is precisely weighed.
(9) The gelation activity (gel content) is calculated from the weight of the heat-treated sample and the N-methyl-2-pyrrolidone insoluble matter by the following formula.
Gelation activity (% by weight) = N-methyl-2-pyrrolidone insoluble matter weight / heat-treated sample weight × 100

<Method for producing resin for lithium ion secondary battery electrode binder>
The resin of the present invention includes, for example, (i) an acid chloride method using an aromatic diamine and trimellitic anhydride monochloride, and (ii) an isocyanate method in which an aromatic diisocyanate derived from an aromatic diamine and trimellitic anhydride are reacted. (Iii) It can be produced by a direct polymerization method in which an aromatic diamine and trimellitic anhydride are reacted by heating to high temperature in the presence of a dehydration catalyst. Further, for example, those in which the ratio of the cyclic imide bond to the amide bond is increased (Japanese Patent Publication No. 45-38574), or those in which the ratio of the amide bond to the cyclic imide bond is increased (Japanese Patent Laid-Open No. 61-195127). Publication). In order to obtain a resin having a gelation activity of 3.0% by weight or less, it is preferable to use an acid chloride method that is advantageous for polymerizing a resin having excellent linearity. The reactions themselves used in these methods are well known, and those skilled in the art can easily set reaction conditions, and the production methods are also specifically described in the following examples.

Hereinafter, a specific example will be described.
First, the first embodiment of the resin of the present invention, that is, a method for producing a polyamideimide resin in which a / (a + b + c) = 0 is described with reference to an example. For example, after reacting the aromatic diamine containing 4,4′-diaminodiphenyl ether and m-phenylenediamine with the aromatic tricarboxylic acid anhydride monochloride by a so-called acid chloride method to obtain a polyamic acid, By pouring into a poor solvent such as water or acetone during high-speed stirring, the polyamic acid is isolated, and the resulting polyamic acid is heated to imide cyclization at a temperature of 150 ° C. to 250 ° C. and a pressure of less than 30 torr. A polyamide-imide resin can be obtained.

  Next, a second embodiment of the resin of the present invention, that is, a method for producing an aramid-polyamideimide resin satisfying 0 <a / (a + b + c) ≦ 0.55 will be described with an example. For example, it can be produced by the same method as in the first embodiment, using aromatic tricarboxylic acid anhydride monochloride and aromatic dicarboxylic acid dichloride. Further, for example, the aromatic diamine is dissolved in an organic solvent, and first, an aromatic dicarboxylic acid dichloride is reacted to produce an amino-terminated aramid polymer having an aramid constituent unit of the general formula (1), and then aromatic You may copolymerize the amide imide corresponding to General formula (2) or (3) by making tricarboxylic-acid chloride anhydride react. This method is preferable because a resin having low gelation activity can be obtained.

  In addition, a diamine corresponding to 100.01 to 101 mol% is first reacted in an organic solvent with respect to terephthalic acid chloride or isophthalic acid chloride in such an amount that the content of the aramid structural unit of the formula (1) is in a desired range. To produce an amino-terminated aramid polymer having a degree of polymerization equivalent to 100 and having an aramid structural unit of the general formula (1), and then reacting tricarboxylic acid chloride anhydride after adding the remaining diamine A manufacturing method is more preferable. By this method, a resin having a lower gelation activity can be obtained.

  Examples of the organic solvent used when polymerizing the resin of the present invention include polar solvents such as N, N-dimethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, and cresol. N, N-dimethylacetamide and N-methyl-2-pyrrolidone are preferable. In order to obtain a resin having excellent linearity, the polymerization reaction is preferably performed at a monomer concentration of 5 to 40% by weight, and more preferably 10 to 30% by weight. The reaction temperature is preferably 60 ° C. or lower, more preferably less than 40 ° C.

  When the polyamic acid solution is dropped into the poor solvent, the viscosity of the polyamic acid solution is preferably adjusted to about 10 Pa · s. For this purpose, it is preferable to adjust the monomer concentration during the polymerization reaction to usually 5 to 80% by weight, preferably about 5 to 40% by weight.

  When reaction by-products such as hydrogen chloride are mixed in the resulting polyamic acid, the reaction by-products can be removed by conventional means. For example, after collecting the precipitated polyamic acid, the reaction by-product can be easily removed by immersing the collected precipitate in water (for example, distilled water) and stirring.

  The precipitated polyamic acid is isolated by filtration, a poor solvent (dehydration) or the like. This polyamic acid is dried by a conventional method, and is closed by heating at a temperature of 150 to 370 ° C. for 0.1 to 100 hours in a vacuum or in an inert gas atmosphere such as nitrogen gas or in an air atmosphere, Converted to polyamide-imide resin. Alternatively, it can be converted to a polyamideimide resin by chemical ring closure using acetic anhydride or the like. Specifically, for example, the following is performed under an air atmosphere. The polyamic acid is dried in a hot air dryer at 150 ° C. for 5 hours, then at 200 ° C. for 2 hours, and then at 220 ° C. for 4 hours to obtain a polyamideimide resin.

  In order to adjust the residual carboxyl group of the resin, the heating conditions in the heated imide ring closure may be adjusted. For example, a resin having a residual carboxyl group amount of 0.10 to 0.40 mmol / g can be obtained by drying at 150 ° C. for 5 hours, followed by 200 ° C. for 2 hours and then 240 ° C. for 4 hours. In the second stage heated imide ring closing process, it is preferable to heat and close the ring particularly under a vacuum or an inert gas. By doing so, a resin having excellent linearity and low gelation activity can be obtained.

  In terms of industrial production, chemical ring closure and heating in an inert gas atmosphere are possible, but vacuum drying is preferred. That is, it is preferable to carry out the heat ring-closing imidization by vacuum drying at a temperature of 150 ° C. or more and 250 ° C. or less and less than 30 torr.

Further, thermal characteristics such as Tg and Tm can be measured using DSC (differential scanning calorimeter, DSC-7 / PerkinElmer). The content ratio of the structural unit represented by any one of the general formulas (1) to (3) contained in the resin can be determined using the IR spectrum, proton NMR spectrum, and the like of the resin. Proton NMR, dissolving the resin into a solvent of _{DMSO-d 6} (dimethylsulfoxide -d ₆ (deuteration ratio 99.95% or ^{higher)), 270MHz 1 HNM (JEOL} / GX-270 / FT spectrometer) protons, such as It can be measured using NMR.

<Resin composition for lithium ion secondary battery electrode binder>
The resin composition for a lithium ion secondary battery electrode binder of the present invention (hereinafter sometimes referred to as varnish) contains the resin for a lithium ion secondary battery electrode binder of the present invention and a polar solvent. The resin has solvent solubility and can be dissolved in a polar solvent to obtain a uniform varnish. As the polar solvent, an aprotic polar solvent having a boiling point of 160 ° C. or higher is preferable, and specifically, N-methyl-2-pyrrolidone, N, N-dimethylacetamide and the like are preferably used.

  The content of the resin in the varnish of the present invention is preferably 5% by weight or more, and more preferably 10% by weight or more from the viewpoint of varnish handling properties. Moreover, 30 weight% or less is preferable and 20 weight% or less is more preferable. The content of the polar solvent is not particularly limited as long as the resin can be dissolved, but is preferably 70% by weight or more and 95% by weight or less.

  Further, the varnish of the present invention includes a surfactant, a dispersant, an antistatic agent, a leveling agent, an antifoaming agent and an epoxy resin, a phenol resin, a melamine resin, a polyfunctional isocyanate and other crosslinking agents, depending on the purpose of use. You may contain polyester, an acrylic resin, etc. In addition, amide solvents such as dimethylformamide, sulfur solvents such as dimethyl sulfoxide and sulfolane, nitro solvents such as nitromethane and nitroethane, ether solvents such as diglyme and tetrahydrofuran, cyclohexanone, as long as the characteristics as varnish are not impaired It may contain a ketone solvent such as methyl ethyl ketone, a nitrile solvent such as acetonitrile or propionitrile, γ-butyrolactone, tetramethylurea, or the like.

  The method for producing the varnish of the present invention is not particularly limited. It can be manufactured by adding the resin of the present invention to a polar solvent and stirring, but it can be appropriately combined with an emperor-type disperser such as a dissolver, three rolls, sand mill, ball mill, etc. according to the viscosity and concentration of the resin. Can be manufactured.

<Paste for lithium ion secondary battery electrode>
The lithium ion secondary battery electrode paste of the present invention is a resin for a lithium ion secondary battery electrode binder of the present invention, a polar solvent and lithium ion secondary battery electrode active material particles (hereinafter referred to as electrode active material particles). Contain). Moreover, you may contain electrically conductive agent powder (acetylene black, carbon black, etc.) as needed.

  The lithium ion secondary battery electrode active material particles can occlude and release lithium ions, and examples thereof include carbon-based powders (graphite, coke powder, etc.), metal powders such as silicon, and metal compound powders. Two or more types may be used.

  In the present invention, it is preferable to use lithium ion secondary battery electrode active material particles having a volume of 130 or more and 250 or less when the lithium ion is fully charged when the volume before storage of lithium ions is 100. When these electrode active material particles having a large volume change are used, conventionally known binders cannot follow the volume change of the electrode active material particles, and the electrode active material particles are peeled off. It was insufficient. If the resin of the present invention is used, the volume change of the electrode active material particles can be followed and the retainability is excellent, so that the effect of the present invention is remarkably exhibited. In addition, the ratio of the volume before lithium ion occlusion and when the lithium ion is fully charged refers to the electrode volume expansion change rate measured by the following method.

First, 89 parts by weight of electrode active material particles, 4 parts by weight of a conductive agent (acetylene black), and the structure of the first aspect of the present invention as a binder resin, represented by the general formulas (2) and (3) Ar ² is composed of trimellitic anhydride monochloride residue, and R represented by the general formula (4) is composed of 30 mol% of m-PDA residue and 70 mol% of DDE residue. In a nitrogen stream using N-methyl-2-pyrrolidone so that the polyamide-imide resin (ηinh 0.75, residual carboxyl group amount 0.18 mmol / g, gelation activity 1.0% by weight) is 7 parts by weight. An electrode material paste is prepared by mixing for 30 minutes in a mortar. This is applied onto a 35 μm thick copper foil and dried with a dryer at 90 ° C. to remove the solvent. Next, the paste is similarly applied to the back surface of the copper foil, dried to form electrodes on both sides, and then pressed to form an electrode having a thickness of 75 μm, a width (w) of the electrode agent coating portion of 10 mm, and a length (l) of 20 mm. Is made. Here, 40 μm obtained by subtracting 35 μm of the copper foil thickness from the total electrode thickness of 75 μm is defined as the electrode thickness (t0) before charging and discharging.

Next, the electrode thus fabricated is charged and discharged. The electrolyte is ethylene carbonate and dimethyl carbonate (1: 1 by volume) each containing 1 mol / liter of LiPF _6, and a metal lithium foil is used for the counter electrode and the reference electrode. Evaluation is made with a tripolar cell using Denko Co., Ltd./HJ201 etc.

The battery is charged to 0 V (vs. Li ⁺ / Li) at a constant current of a current density of 30 mA / g. After the charge, the battery is discharged to 1.5 V (vs. Li ⁺ / Li) at the same current density as the charge. Here again, the battery is charged to 0 V (vs. Li ⁺ / Li) with a constant current of 30 mA / g. This state is defined as a state in which lithium ions are fully charged. Thereafter, the tripolar cell is disassembled in an Ar (argon) glove box, and the thickness (t1) of the main electrode is measured using a micrometer.
The rate of change in electrode volume expansion is obtained from the following equation from t1 and t0.
Electrode volume expansion change rate = (t1 × w × l) / (t0 × w × l) × 100 = t1 / t0 × 100

  When measured by the above method, for example, the volume when the lithium ions of the silicon powder are substantially fully charged is 180 with respect to the volume 100 before the lithium ions are occluded. Moreover, the volume when the lithium ion of tin is substantially fully charged is 152 with respect to the volume 100 before the storage of lithium ions, and the volume when the lithium ion of graphite is substantially fully charged is It is 108 with respect to the volume 100 before lithium ion occlusion.

  Examples of lithium ion electrode active material particles having a volume of 130 to 250 when the lithium ion is substantially fully charged when the volume before storage of lithium ions is 100 are, for example, silicon, tin, and compounds thereof Can be mentioned. Since the reaction between these and lithium is a so-called alloying reaction, the volume change due to charge / discharge becomes very large.

  Specifically, such negative electrode active material particles include tin (Sn), lead (Pb), aluminum (Al), indium (In), silicon (Si), zinc (Zn), antimony (Sb), bismuth. (Bi), cadmium (Cd), magnesium (Mg), boron (B), gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr), yttrium (Y) or hafnium (Hf) as a simple substance, an alloy, and a compound thereof. These may be crystalline or amorphous.

Alternatively, specific examples of such alloys or compounds include LiAl, AlSb, CuMgSb, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , _{NiSi 2, CaSi 2, CrSi 2} , Cu 5 Si, FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, SiO v ( 0 <v ≦ 2), SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSiO, or LiSnO.

  Among these, silicon, tin, a silicon compound, or a tin compound is preferable because the lithium ion occlusion reaction is particularly active.

Examples of the positive electrode active material particles include lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), and spinel type lithium manganate (LiMn ₂ O ₂ ).

  In the paste for a lithium ion secondary battery electrode material of the present invention, the content of the lithium ion secondary battery electrode binder resin is preferably 1 part by weight or more with respect to 100 parts by weight of the electrode active material particles. More preferred are parts by weight. Moreover, 20 weight part or less is preferable from a viewpoint of charging / discharging characteristics, and 15 weight part or less is more preferable. If it is this range, the adhesiveness of an electrode active material and adhesiveness with metal foil will improve more, and the bending resistance of the film obtained from a paste will improve.

  The solution viscosity of the paste for a lithium ion secondary battery electrode material of the present invention is usually 0.2 to 50 Pa · s, more preferably 5 to 30 Pa · s. The solution viscosity is measured at 25 ° C. by measuring 1 ml of the paste using an E-type viscometer manufactured by Tokimec. Viscosity standard calibration solution JS15H manufactured by Showa Shell Co., Ltd. is used for viscosity calibration.

  The method for producing the paste for lithium ion secondary battery electrode material of the present invention is not particularly limited, and may be produced by appropriately combining conventionally known methods using a dissolver, three rolls, sand mill, ball mill, or the like. . For example, it can be produced by adding electrode active material particles to the varnish of the present invention and kneading several times with three rolls.

<Lithium ion secondary battery electrode>
The lithium ion secondary battery electrode of the present invention can be obtained by applying the paste for a lithium ion secondary battery electrode material of the present invention to a current collector metal foil such as a copper foil and drying it as necessary. Examples of the application method include a doctor blade method. The coating thickness depends on the shape of the lithium ion secondary battery, the particle diameter of the electrode active material particles, and the thickness of the current collector metal foil, but is usually about 2 to 300 μm in a dry state. Moreover, a positive electrode and a negative electrode can be obtained according to the kind of electrode active material particle. In addition, the lithium ion secondary battery electrode of this invention can be manufactured by a well-known method except using the lithium ion secondary battery electrode material paste of this invention mentioned above as a paste.

  Examples are given below to describe the present invention in more detail, but the present invention is not limited to these examples. In addition, the characteristic of Table 1 in a present Example was evaluated with the following method.

1. Glass transition temperature (Tg)
According to JIS K7121-1987, it measured with DSC (differential scanning calorimeter, DSC-7 / PerkinElmer) at the temperature increase rate of 10 degree-C / min.

2. Adhesiveness (1) Bendability: With the surface of the electrode obtained in each of the examples and comparative examples dried, the surface of the electrode is wound around a stainless steel rod having a diameter of 10 mm, bent, and the active material is detached or removed from the metal foil. The state of peeling was visually observed. The evaluation criteria are as follows.
<Adhesiveness of active material particles>
○: No cracking ○ to Δ: Some cracks Δ: There are many cracks Δ- ×: Cracking <Adhesiveness with copper foil>
○: No dropout △: With dropout △ ～ ×: Many dropouts

(2) Tape peelability: JIS K5600-5-6, mechanical properties of the fifth part coating film--Solving the electrode solvent obtained in each Example and Comparative Example in accordance with Section 6 Crosscutting Method Cellophane tape (registered trademark) (cellophane tape No. 29, Nitto Denko Co., Ltd.) is pasted on the surface and the cellophane tape (registered trademark) is peeled off, and the active material layer is peeled off and the state of the coating film is visually observed. did. The evaluation criteria are as follows.
○: Excellent: Cu foil substrate is not visible after tape peeling.
(Triangle | delta): Good: An active material layer remains in Cu foil after tape peeling.
X: Defect: After peeling off the tape, a slight amount of active material layer remains on the Cu foil.
XX: Bad: After peeling off the tape, it becomes a Cu foil substrate.

3. ηinh (logarithmic viscosity)
The logarithmic viscosity was measured according to JIS K7367-1 (2002). In detail, it measured as follows.
About 0.25 g of polyamideimide resin was weighed with a balance (accuracy 0.1 mg) so as not to absorb water (this value is x (g)), transferred to a 50 ml volumetric flask, and N-methyl-2-pyrrolidone. 40 ml of solvent was added, and the mixture was shaken and stirred until the resin was dissolved (at this time, the temperature of the solution should not be dissolved by heating to 30 ° C. or higher). After the dissolution was completed, the solution was fixed to 50 ml to prepare an N-methyl-2-pyrrolidone solution having a resin concentration C (g / dl).
C (g / dl) = x (g) / 50 (ml)
The Ubbelohde viscometer is fixed in a thermostat controlled at 30 ° C. ± 0.05 ° C., and measures the flow time (t) of the prepared resin solution and the flow time (t0) of the solvent N-methyl-2-pyrrolidone. The logarithmic viscosity represented by the following formula was determined.
ηinh (dl / g) = ln (t / t0) / C

4). Residual carboxyl group content The residual carboxyl group content was measured by the following method.
(1) Reagent A. DMF (dimethylformamide): solvent special grade reagent Bromthymol blue indicator (0.3 wt%): 0.15 g of bromothymol blue was dissolved in 50 ml of methanol.
C. N / 50 sodium methylate solution: 0.5 g of metallic sodium was dissolved in 1 liter of methanol.
The titer of the N / 50 sodium methylate solution was determined by the following method. In a 200 ml Erlenmeyer flask containing 50 ml of distilled water, 20 ml of N / 50 sodium methylate solution was collected with a whole pipette and titrated with 0.1N HCl standard solution (commercially available) using phenolphthalein as an indicator.
Titer (F) = 0.25 × f × S
f: 0.1N HCl standard solution titer,
S: 0.1N HCl standard solution (ml)

(2) Measurement About 0.2 g of polyamide-imide resin was precisely weighed (this value is expressed as wg), and dissolved in 20 ml of special grade DMF (dimethylformamide) in a 50 ml Erlenmeyer flask. Next, 4 drops of bromthymol blue indicator (0.3% by weight) was dropped, and titrated with a N / 50 sodium methylate solution from a microburette. Titration was performed until the yellow color of the indicator changed (yellow) → (yellow green) → (emerald green) completely (this value is defined as Sml).

Separately, a blank titration value for a pure solvent containing no polymer was determined (this value is defined as Bml). The amount of residual carboxyl groups was determined by the following formula.
Residual carboxyl group amount (mmol / g) = (F × (1/50) × (SB)) / polyamideimide resin sampling weight (wg)
F: titer of N / 50 sodium methylate solution S: titration of sample (ml)
B: Blank titration (ml) (titration with pure solvent that does not dissolve polyamideimide resin)

Comparative Example 1
0.61 liter of dimethylacetamide (hereinafter referred to as DMAC, boiling point 165 ° C.) as a polymerization solvent and 1,6-hexamethylene dissolved in a 70 ° C. hot water bath as a diamine component in a reaction vessel (2000 ml glass four-necked flask) Diamine (hereinafter referred to as HMDA) 0.70 mol and 4,4′-diaminodiphenyl ether (hereinafter referred to as DDE) 0.30 mol were charged, and the solution was stirred to completely dissolve these diamine components. Subsequently, 0.70 mol of trimellitic anhydride monochloride (hereinafter referred to as TMAC) is gradually added so that the temperature of the polymerization reaction solution does not exceed 30 ° C., and after the addition is completed, the polymerization solution is heated to 30 ° C. The mixture was stirred and reacted for 1.0 hour to obtain a polymerization solution. The obtained polymerization solution was put into 1.7 liters of ion-exchanged water (hereinafter referred to as IW water) and filtered to obtain a polyamic acid powder. The obtained polyamic acid powder was dried in a hot air dryer at 150 ° C. for 5 hours, then at 200 ° C. for 2 hours, and then at 240 ° C. for 4 hours to obtain a polyamideimide resin powder. The obtained polyamideimide resin had a logarithmic viscosity of 0.45 dl / g, a residual carboxyl group amount of 0.26 mmol / g, and a gelation activity of 10% by weight.

  The obtained polyamideimide resin powder was dissolved in DMAC to prepare a polyamideimide resin solution (varnish) having a concentration of 10% by weight. The varnish is cooled to room temperature, 60 parts by weight of silicon powder (purity 99.9%) is added to 100 parts by weight of the varnish, and is completely uniform at room temperature for 30 minutes at 200 rpm using a motor and a stirring blade. The resulting slurry was kneaded with a three roll (EXACT model 50) to obtain a paste.

  This paste was applied to a copper foil (thickness 50 μm) so that the film thickness was about 25 μm, and dried in a vacuum dryer at 180 ° C. for 8 hours to obtain an electrode. 2. The adhesion was evaluated by the method described in 1. The evaluation results are shown in Table 1.

  In Comparative Example 1, since the structure of the molecule constituting the resin is outside the range defined in the present invention (70 mol% of the diamine component is HMDA), the adhesiveness, particularly the tape peelability was insufficient.

Comparative Examples 2-4
An amidoimide resin was prepared in the same procedure as in Comparative Example 1 except that the diamine component and acid component were changed to the types and amounts shown in Table 1. In addition, an electrode was prepared in the same procedure as in Comparative Example 1 using the electrode material paste shown in Table 1. Table 1 shows the evaluation results. Abbreviations in Table 1 are as follows.
DDM: 4,4′-diaminodiphenylmethane DMDA: 1,12-dodecamethylenediamine

  In Comparative Examples 2 to 4, since the structure of the molecules constituting the resin is outside the range defined by the present invention (the main component of the diamine component is DDM or DMDA), the adhesiveness, particularly the tape peelability, was insufficient. It was.

Comparative Example 5
A reaction vessel (2000 ml glass four-necked flask) was charged with 0.61 liter of DMAC as a polymerization solvent and 0.14 mol of m-PDA and 0.56 mol of DDE as diamine components, and the solution was stirred to completely remove these diamine components. Dissolved. Next, the temperature of the polymerization reaction liquid does not exceed 30 ° C. with 0.42 mol of acid component terephthalic acid chloride (hereinafter referred to as TPC) and 0.28 mol of TMAC so that the temperature of the polymerization reaction liquid does not exceed 30 ° C. Was added gradually. After the addition of the total amount of the acid component, the temperature of the polymerization solution was adjusted to 30 ° C. and stirred for 1.0 hour. The obtained polymerization solution was processed in the same procedure as in Comparative Example 1 to obtain an aramid-amidoimide copolymer powder. The logarithmic viscosity of the obtained aramid-amidoimide copolymer is 1.2 dl / g (however, since there is an insoluble content, the measured value after filtration), the residual carboxyl group amount is 0.22 mmol / g, and the gelation activity is It was 15% by weight. The obtained amideimide copolymer powder was dissolved in DMAC to prepare a 10 wt% amideimide copolymer solution (varnish). However, insoluble matter was visually observed in the solution. Using the obtained varnish, an electrode was produced in the same procedure as in Comparative Example 1. Table 1 shows the evaluation results.

  In Comparative Example 5, since the structure of the molecule constituting the resin is outside the range defined in the present invention (the structural unit of the general formula (1) is 60 mol%), the adhesiveness, particularly the tape peelability is insufficient. there were.

Example 1
In a reaction vessel (2000 ml glass four-necked flask), 0.61 liter of DMAC as a polymerization solvent and 0.28 mol of m-PDA and 0.42 mol of DDE were charged as a diamine component, and the solution was stirred to completely remove these diamine components. Dissolved. Next, 0.70 mol of TMAC is gradually added so that the temperature of the polymerization reaction solution does not exceed 30 ° C., and after the addition is completed, the polymerization solution is heated to 30 ° C. and stirred for 1.0 hour to react. Obtained. The obtained polymerization solution was put in 1.7 liters of IW water and filtered to obtain a polyamic acid powder. The obtained polyamic acid powder was dried in a vacuum dryer with a degree of vacuum of 30 torr at 150 ° C. for 5 hours, then at 200 ° C. for 2 hours, and then at 240 ° C. for 4 hours to obtain a polyamideimide resin powder. The properties of the obtained polyamideimide resin are shown in Table 1.

  The obtained polyamideimide resin powder was dissolved in DMAC to prepare a polyamideimide resin solution (varnish) having a concentration of 10% by weight. The varnish was cooled to room temperature, 90 parts by weight of silicon powder (purity 99.9%, average particle size 3 μm) was added to 100 parts by weight of varnish (10 parts by weight of resin), and 200 rpm using a motor and stirring blades. For 30 minutes at room temperature until completely uniform, and the resulting slurry was kneaded with three rolls (EXACT model 50) to obtain a paste.

  This paste was applied to a copper foil (thickness 50 μm) so as to have a film thickness of about 20 μm, and dried in a hot air dryer at 160 ° C. for 8 hours to obtain an electrode. When this electrode was immersed in an equal volume mixed solvent of ethylene carbonate and dimethyl carbonate, which is an electrolytic solution of a lithium ion battery, the coating film obtained from the paste was sufficiently durable. In addition, 2. Table 1 shows the evaluation results of the adhesion evaluation performed by the method described in 1. Bendability and tape peelability were also excellent.

Examples 2-13
A polyamideimide resin was prepared in the same procedure as in Example 1 except that the diamine component and acid component were changed to the types and amounts shown in Table 1. Moreover, the electrode was produced in the same procedure as Example 1 using the paste for electrode materials described in Table 1. Table 1 shows the evaluation measurement results. Abbreviations in Table 1 are as follows.
TPE-R: 1,3-bis (4-aminophenoxy) benzene PODA: 2,2-bis [4- (4-aminophenoxy) phenyl] propane SODA: bis [4- (4-aminophenoxy) phenyl] sulfone

Example 14
Using a diamine component and an acid component shown in Table 1, a polyamideimide resin (ηinh = 0.52 dl / g) having a low polymerization degree was obtained. Thereafter, this was further subjected to heat treatment in the atmosphere with a hot air dryer at 260 ° C. for 4 hours to obtain a polyamideimide resin having an increased molecular weight (→ ηinh = 0.79 dl / g). Moreover, the electrode was produced in the same procedure as Example 1 using the paste for electrode materials described in Table 1. Table 1 shows the evaluation results.

Example 15
A polyamideimide resin was prepared in the same procedure as in Example 1 except that the diamine component and acid component were changed to the types and amounts shown in Table 1. Moreover, the electrode was produced in the same procedure as Example 1 using the paste for electrode materials described in Table 1. Table 1 shows the evaluation results.

Example 16
A reaction vessel (2000 ml glass four-necked flask) was charged with 0.61 liter of DMAC as a polymerization solvent and 0.14 mol of m-PDA and 0.56 mol of DDE as diamine components, and the solution was stirred to completely remove these diamine components. Dissolved. Next, 0.14 mol of TPC and 0.56 mol of TMAC were gradually added as acid components so that the temperature of the polymerization reaction solution did not exceed 30 ° C. After the addition of the total amount of the acid component, the temperature of the polymerization solution was adjusted to 30 ° C. and stirred for 1.0 hour. The obtained polymerization solution was treated in the same procedure as in Example 1 to obtain an aramid-amidoimide copolymer powder. Moreover, the electrode was produced in the same procedure as Example 1 using the paste for electrode materials described in Table 1. Table 1 shows the evaluation results.

Examples 17-21
An amidoimide copolymer was prepared in the same procedure as in Example 1 except that the diamine component and acid component were changed to the types and amounts shown in Table 1. Moreover, the electrode was produced in the same procedure as Example 1 using the paste for electrode materials described in Table 1. Table 1 shows the evaluation results. Abbreviations in Table 1 are as follows.
IPC: Isophthalic acid dichloride

Example 22
30 parts by weight of 100 parts by weight of the polyamideimide resin solution (varnish) prepared in Example 2, 127.1 parts by weight of silicon (purity 99.9%), and 5.7 parts by weight of a conductive agent (acetylene black) in a mortar in a nitrogen stream. An electrode paste was prepared by mixing for a minute. This was coated on a 35 μm thick Cu foil, dried in a solvent at 90 ° C. in a dryer, coated on the back side, dried to form electrodes on both sides, and then pressed to a thickness of 75 μm, An electrode having a width of 10 mm and a length of 20 mm was produced.

Next, the adhesiveness after charging / discharging of the electrode produced in this way was evaluated. The electrolytes were ethylene carbonate and dimethyl carbonate (1: 1 by volume) each containing 1 mol / liter LiPF ₆ , using a metallic lithium foil for the counter electrode and the reference electrode, and Hokuto Denko Co., Ltd. for the charge / discharge device. Evaluation was carried out with a three-electrode cell using HJ201 manufactured by the company. The battery was charged to 0 V (vs. Li + / Li) at a constant current of 30 mA / g per active material. After the charge, the battery was discharged to 1.5 V (vs. Li + / Li) at the same current density as the charge. Here, after charging again to 0 V (vs. Li + / Li) at a constant current of 30 mA / g, the tripolar cell was disassembled in an Ar (argon) glove box. Here, when the external appearance observation of the electrode after the said charge / discharge was performed, peeling of the electrode active material particle was not seen. Moreover, the thickness change of the electrode was measured using the micrometer. Table 2 shows the evaluation results.

Examples 23-25
An electrode was prepared in the same procedure as in Example 22 except that the varnish and electrode active material particles shown in Table 2 were used, and the adhesion evaluation after charge / discharge was performed. The electrode active material particles were not peeled off from the charged / discharged electrode. Moreover, the thickness change of the electrode was measured using the micrometer. Table 2 shows the evaluation results.

Comparative Examples 6-8
An electrode was prepared in the same procedure as in Example 22 except that the varnish and electrode active material particles shown in Table 2 were used, and charge / discharge adhesion evaluation was performed. The electrode active material was peeled off from the charged / discharged electrode. Moreover, the thickness change of the electrode was measured using the micrometer. Table 2 shows the evaluation results.

  In Comparative Example 6, the resin itself is the resin of the present invention, but the paste composition is outside the scope of the present invention (the resin content exceeds 20 parts by weight with respect to 100 parts by weight of the electrode active material particles). Therefore, the charge / discharge test could not be performed. In Comparative Examples 7 and 8, since the resin was outside the scope of the present invention, the adhesiveness after charge / discharge was poor.

Claims (11)

The content (a) of the structural unit represented by the general formula (1) having as a main component at least one structural unit selected from the structural units represented by any of the following general formulas (1) to (3), The content (b) of the structural unit represented by the general formula (2) and the content (c) of the structural unit represented by the general formula (3) have the relationship of the following formula (A), at 30 ° C. Resin for lithium ion secondary battery electrode binder having a logarithmic viscosity of 0.02 to 2.0 dl / g.
a / (a + b + c) ≦ 0.55 (molar ratio) (A)

(In the general formulas (1) to (3), R is a divalent aromatic group represented by the following general formula (4), and Ar ¹ is a divalent aromatic represented by the following general formula (5). Group Ar ² represents a trivalent aromatic group represented by the following general formula (6), and R, Ar ¹ and Ar ² in different structural units are independent of each other). )

(In the general formula (4), X represents a direct bond, —O—, —S—, —CO—, —SO ₂ —, —C (CH ₃ ) ₂ — or —C (CF ₃ ) ₂ —. P represents an integer of 0 to 3. In the general formula (5), Y represents a direct bond, —O—, —CO—, —SO ₂ —, —CH ₂ —, —C (CH ₃ ) ₂ —. Or -C (CF ₃ ) _2- , q is 0 or 1. In the general formula (6), Z is a direct bond, -O-, -CO-, -COO-, -OCO-,- SO _2- , -CH _2- , -C (CH ₃ ) ₂ -or -C (CF ₃ ) ₂ -is shown, r is 0 or 1. The above general formulas (4), (5) and (6) ), Each benzene ring is selected from the group consisting of an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, a chlorine atom, a bromine atom, a nitro group, and a cyano group. Optionally having at least one substituent. In the general formulas (1) to (3), R contains 4,4′-diaminodiphenyl ether residue and m-phenylenediamine residue, and 4,4′-diaminodiphenyl ether in the resin Residue content (x) and m-phenylenediamine residue content (y) are 1.5 ≦ x / y ≦ 4 (molar ratio)
The resin for a lithium ion secondary battery electrode binder according to claim 1. The resin for a lithium ion secondary battery electrode binder according to claim 1, wherein the content of each structural unit represented by any one of the general formulas (1) to (3) has a relationship represented by the following formula (B).
0.05 ≦ a / (a + b + c) ≦ 0.55 (molar ratio) (B)   The resin for a lithium ion secondary battery electrode binder according to claim 1, having a residual carboxyl group amount of 0.05 to 0.40 mmol / g. The resin for a lithium ion secondary battery electrode binder according to claim 1, wherein the gel activity represented by the following formula (7) after heating in the air at 280 ° C for 2 hours is 3.0 wt% or less.
Gelation activity (% by weight) = (N-methyl-2-pyrrolidone insoluble matter weight / sample weight) × 100 (7)   The resin composition for lithium ion secondary battery electrode binders containing 5-30 weight% of resin for lithium ion secondary battery electrode binders in any one of Claims 1-5, and a polar solvent.   The lithium ion secondary battery electrode binder resin according to any one of claims 1 to 5, containing a polar solvent and lithium ion secondary battery electrode active material particles, and containing a lithium ion secondary battery electrode binder resin The paste for lithium ion secondary battery electrode materials whose quantity is 1-20 weight part with respect to 100 weight part of content of lithium ion secondary battery electrode active material particle.   The lithium ion secondary battery electrode according to claim 7, comprising lithium ion secondary battery negative electrode active material particles having a volume of 130 to 250 when the lithium ions are fully charged with respect to a volume 100 before lithium ion storage. Material paste.   A lithium ion secondary battery electrode comprising a current collector and a paste for a lithium ion secondary battery electrode material according to claim 7 or 8 applied on the current collector.   The lithium ion secondary battery electrode according to claim 9, wherein the current collector is a metal foil.   The lithium ion secondary battery electrode according to claim 9, wherein the paste is in a dried state.