JP2013077498A - Negative electrode for lithium ion secondary battery and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode for a Li ion secondary battery which does not have wrinkles or the like during negative electrode manufacture, suppresses exfoliation of an active material due to expansion and contraction during charge and discharge, and has excellent cycle characteristics, and to provide a method of manufacturing the negative electrode for a Li ion secondary battery.SOLUTION: In a negative electrode for a Li ion secondary battery in which an active material containing Si is arranged on a current collector, a binder includes a polyimide resin containing Si of formula (1) [X represents a tetravalent organic group, Y represents a divalent organic group, n represents an integer of 1-10,000, T represents a functional group (Rto Rrepresent a C1-8 hydrocarbon group or an oxygen-containing hydrocarbon group, and m represents an integer of 1-8)] indicated by formula (2).

Description

  The present invention relates to a negative electrode for a lithium ion secondary battery in which an active material mixture layer containing a negative electrode active material containing silicon and a binder is disposed on the surface of a negative electrode current collector, and a method for producing the same.

A lithium ion secondary battery has an active material capable of inserting and extracting lithium (Li) in a positive electrode and a negative electrode, respectively. And it operate | moves because Li ion moves in the electrolyte solution provided between both electrodes.
Such lithium ion secondary batteries are small and have a large capacity, and are therefore used in a wide range of fields such as mobile phones and notebook computers.

In recent years, lithium ion secondary batteries using an active material containing silicon (Si) as a negative electrode active material have been proposed in order to increase the output of the lithium ion secondary battery.
However, the active material containing silicon has several times larger volume expansion / contraction due to charge / discharge than graphite conventionally used as the negative electrode active material. Therefore, the active materials are easily separated from each other, or the active material and the current collector are easily separated, and the active material is easily pulverized. Due to the influence of the detachment and pulverization, the current collecting property is lowered, and the charge / discharge cycle characteristics are deteriorated. There was a problem. In addition, volume expansion and contraction of the active material and the current collector due to temperature changes during battery use has also been a problem.

Moreover, a high-strength polyimide is suitably used for the negative electrode binder of the lithium ion secondary battery using an active material containing silicon. When the binder is polyimide, the negative electrode is usually produced by sintering (imidizing) the polyimide precursor.
However, the sintering process temperature is usually as high as 200 ° C. or more, and due to the difference in the coefficient of linear expansion between the current collector and the active material mixture layer, distortion occurs at the contact interface between the binder and the current collector, There was a problem that stress was generated and wrinkles and curls were easily generated in the obtained negative electrode.

  Therefore, in order to suppress the occurrence of such strains and stresses during the sintering process, Patent Document 1 discloses a technique using a thermoplastic polyimide having a linear expansion coefficient of 1 to 300 ppm / ° C. ing. However, the suppressive power was still not sufficient.

  Moreover, in order to improve the adhesiveness of an electrical power collector and an active material, patent document 2 uses the polyimide silica hybrid resin which made the silane-modified polyamic acid sol-gel hardening and spin-drying | dehydrating cyclization as a binder, and patent document 3 Then, a method using a siloxane-containing polyimide has been proposed. However, the polyimide resins described in these documents have a problem that it is difficult to control the linear expansion coefficient.

In relation to the present invention, Patent Document 4 describes an example in which a polyimide having an alkoxysilyl group at the terminal is used as an electrolyte membrane of a fuel cell.
However, Patent Document 4 mentions the importance of the adhesion strength of the terminal alkoxysilyl group with other substances, the importance of the linear expansion coefficient, the development to the binder for lithium ion secondary battery negative electrodes, and the like. Absent.

International Publication No. 2004/004031 Pamphlet JP 2011-86427 A JP 2010-238562 A International Publication No. 2008/123522 Pamphlet

  The present invention has been made in view of the above-described prior art, and the purpose thereof is charge / discharge without generation of wrinkles or curls during the production of a negative electrode even when a material containing silicon is used as a negative electrode active material. Negative electrode for lithium ion secondary battery that can suppress peeling of active materials or active material and current collector due to physical and temperature expansion and contraction at the time, and can obtain a lithium ion secondary battery with excellent cycle characteristics And a method of manufacturing the same.

  In order to solve the above-mentioned problems, the present inventors have made extensive studies. As a result, when a polyimide resin having a silicon-containing group at the end, which is represented by the formula (1) described later, is used as a binder, there is no generation of wrinkles or curls during negative electrode preparation, It was found that a lithium ion secondary battery with excellent cycle characteristics can be obtained by suppressing separation of active materials or between active materials and current collectors due to thermal expansion and contraction, and the present invention was completed based on this finding. It came to do.

  Thus, according to the present invention, there are provided the following negative electrodes for lithium ion secondary batteries [1] to [3] and a method for producing a negative electrode for lithium ion secondary batteries [4].

[1] A negative electrode for a lithium ion secondary battery in which an active material mixture layer containing a negative electrode active material containing silicon and a binder is disposed on the surface of a negative electrode current collector,
The negative electrode for a lithium ion secondary battery, wherein the binder comprises a silicon-containing polyimide resin represented by the following formula (1).

[Wherein, X represents a tetravalent organic group, Y represents a divalent organic group, and n represents an integer of 1 to 10,000. T is the formula (2)

(In the formula, R _{1 to} R ₃ each independently represent a hydrocarbon group having 1 to 8 carbon atoms or an oxygen-containing hydrocarbon group having 1 to 8 carbon atoms, and m represents an integer of 1 to 8). Represents a silicon-containing group represented by ]

[2] The negative electrode for a lithium ion secondary battery according to [1], wherein the silicon-containing polyimide resin has a linear expansion coefficient of 2 to 30 ppm / ° C.
[3] The silicon-containing polyimide resin is obtained by imidizing a silicon-containing polyimide precursor resin represented by the following formula (3): [1] or [2] Negative electrode for lithium ion secondary battery.

(In the formula, T, X, Y and n represent the same meaning as described above. R represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms.)
[4] After applying a negative electrode mixture slurry containing a negative electrode active material containing silicon and a silicon-containing polyimide precursor resin represented by the following formula (3) on the surface of the negative electrode current collector, 30 to 130 The method for producing a negative electrode for a lithium ion secondary battery according to [1] or [2], further comprising a step of imidizing the silicon-containing polyimide precursor resin after performing preliminary drying at 0 ° C. and rolling. .

(In the formula, T, X, Y, n and R represent the same meaning as described above.)

The negative electrode for a lithium ion secondary battery of the present invention does not generate wrinkles or curls at the time of production, and the active material and the current collector, or the active materials are not separated or the active material is not pulverized. Therefore, a lithium ion secondary battery that is excellent in charge and discharge cycle characteristics and does not have a reduced current collecting property can be suitably produced.
According to the method for producing a negative electrode for a lithium ion secondary battery of the present invention, the negative electrode for a lithium ion secondary battery of the present invention can be efficiently produced.

  Hereinafter, the present invention will be described in detail by dividing it into 1) a negative electrode for a lithium ion secondary battery and 2) a method for producing a negative electrode for a lithium ion secondary battery.

1) Negative electrode for lithium ion secondary battery The negative electrode for lithium ion secondary battery of the present invention has an active material mixture layer containing a negative electrode active material containing silicon (Si) and a binder on the surface of the negative electrode current collector. It is the arrange | positioned negative electrode for lithium ion secondary batteries, Comprising: The said binder comprises the silicon containing polyimide resin represented by the said Formula (1), It is characterized by the above-mentioned.

<Silicon-containing negative electrode active material>
The negative electrode active material containing silicon (Si) used in the present invention (hereinafter sometimes simply referred to as “negative electrode active material”) is not particularly limited as long as it is a negative electrode active material containing Si. For example, Si simple substance; Si compound such as Si-containing oxide (silicon oxide, etc.), Si-containing nitride (silicon nitride, etc.); and Si-containing alloy (silicon and one or more other elements) Solid solutions, intermetallic compounds of silicon and one or more other elements, eutectic alloys of silicon and one or more other elements, etc.).
You may use these individually by 1 type or in combination of 2 or more types.

  The negative electrode active material may contain other active materials in addition to Si alone, Si compounds, and Si-containing alloys. Examples of other active materials include graphite, Sn, Al, Ag, Zn, Ge, Cd, and Pd. Other active materials may be used singly or in combination of two or more.

  The average particle diameter of the negative electrode active material is usually 0.01 to 100 μm, preferably 1 to 10 μm. Note that the negative electrode active material may be crystalline or amorphous.

<binder>
The binder used in the present invention contains a silicon-containing polyimide resin represented by the above formula (1) having a silicon-containing group at the terminal (hereinafter sometimes referred to as “silicon-containing polyimide resin (1)”). It is. The binder has a role of binding the negative electrode active materials or the negative electrode active material and the current collector to form a conductive network and maintaining the structure.

  The content of the silicon-containing polyimide resin (1) is usually 90% by weight or more, preferably 95% by weight or more, more preferably 98% by weight or more with respect to the whole binder.

In the formula (1), T represents a silicon-containing group represented by the formula (2).
In said formula (2), R < ₁ > -R < ₃ > represents a C1-C8 hydrocarbon group or a C1-C8 oxygen containing hydrocarbon group each independently.

Examples of the hydrocarbon group having 1 to 8 carbon atoms of R _{1 to} R ₃ include methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, n- C1-C8 alkyl groups such as pentyl group, isopentyl group, n-hexyl group, n-octyl group; C3-C8 cycloalkyl groups such as cyclopentyl group, cyclohexyl group; vinyl group, allyl group An alkenyl group having 2 to 8 carbon atoms; a cycloalkenyl group such as cyclohexenyl group; an alkynyl group having 2 to 8 carbon atoms such as ethynyl group and 1-propynyl group; a carbon number such as phenyl group and tolyl group An aryl group having 6 to 8 carbon atoms; an aralkyl group having 7 or 8 carbon atoms such as a benzyl group and a phenethyl group;

Examples of the oxygen-containing hydrocarbon group having 1 to 8 carbon atoms include an alkoxy group having 1 to 8 carbon atoms such as a methoxy group, an ethoxy group, and a propoxy group; a total carbon number of 2 to 8 such as a methoxymethyl group and a methoxyethyl group Alkoxyalkyl group; acetyl group, benzoyl group and the like. And an acyl group having 2 to 8 carbon atoms; an alkoxycarbonyl group having 2 to 8 carbon atoms such as a methoxycarbonyl group; an acyloxy group having 2 to 8 carbon atoms such as an acetoxy group and a benzoyloxy group;
Of _these, the hydrocarbon group having 1 to 8 carbon atoms of R 1 to R _3, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms is preferable, a methyl group, an ethyl group, a methoxy group An ethoxy group is more preferable, and a methyl group and an ethyl group are particularly preferable.
m is an integer of 1-8, preferably an integer of 1-5, more preferably an integer of 1-4.

  Specific examples of T include groups in which m is 1, such as trimethoxysilylmethyl group, triethoxysilylmethyl group, methyldiethoxysilylmethyl group, dimethylethoxysilylmethyl group; 1-trimethoxysilylethyl group, 2- M such as trimethoxysilylethyl group, 1- (triethoxysilyl) ethyl group, 2- (triethoxysilyl) ethyl group, 2- (dimethoxymethylsilyl) ethyl group, 2- (diethoxymethylsilyl) ethyl group, etc. 2 groups; 3- (trimethoxysilyl) propyl group, 3- (dimethoxymethylsilyl) propyl group, 3- (dimethylmethoxysilyl) propyl group, 3- (triethoxysilyl) propyl group, 3- (methyldi-) Groups in which m is 3, such as ethoxysilyl) propyl group and 3- (dimethylethoxysilyl) propyl group; 4- (trimethyl Xylyl) butyl group, 4- (dimethoxymethylsilyl) butyl group, 4- (methoxydimethylsilyl) butyl group, 4- (triethoxysilyl) butyl group, 4- (diethoxymethylsilyl) butyl group, 4- (ethoxy A group in which m is 4, such as a dimethyl) silylbutyl group;

In formula (1), X represents a tetravalent organic group. As the tetravalent organic group, those having a cyclic structure are preferable. Here, examples of the ring having a cyclic structure include an aromatic ring and an aliphatic ring, and an aromatic ring is preferable.
Specific examples of X include a tetravalent organic group derived from an acid anhydride exemplified as a compound represented by the formula (4) described later. An example is shown below.

  Y represents a divalent organic group. As the divalent organic group, those having a cyclic structure are preferable. Here, examples of the ring having a cyclic structure include an aromatic ring and a heterocyclic ring, but an aromatic ring is preferable. Specifically, a divalent organic group derived from diamines exemplified as a compound represented by the formula (5) described later can be given. An example is shown below.

In addition, you may use these groups individually by 1 type or in combination of 2 or more types.
n is an integer of 1 to 10,000, preferably 10 to 10,000, and more preferably 10 to 5,000.

As the silicon-containing polyimide resin (1) used in the present invention, the polyimide precursor resin represented by the formula (3) having a Si-containing group at the terminal (hereinafter referred to as “polyimide precursor resin (3)”). Is preferably obtained by imidization.
By using the polyimide precursor resin (3), the negative electrode for a lithium ion secondary battery of the present invention can be more easily formed.

In said Formula (3), T, X, Y, and n represent the same meaning as the above.
R represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms.
Examples of the hydrocarbon group having 1 to 8 carbon atoms of R include the same groups as those exemplified as the hydrocarbon group having 1 to 8 carbon atoms of R _{1 to} R ₃ .

Examples of the method for imidizing the polyimide precursor resin (3) include known thermal imidization methods and chemical imidization methods.
The thermal imidization method is a method in which the polyimide precursor resin (3) is heated to a temperature causing a dehydration ring-closing reaction, specifically 130 to 450 ° C, preferably 300 to 400 ° C. As a method for heating, either a method of raising the temperature up to the maximum temperature in one step or a method of raising the temperature in multiple steps may be used.
The heating time is usually several minutes to 1 day, preferably 30 minutes to several hours, depending on the reaction scale and the like.
The heating may be performed in the air, but is preferably performed in a vacuum or in an inert gas atmosphere such as nitrogen or helium.

The chemical imidization method is a method in which the polyimide precursor resin (3) is immersed in a solution containing a chemical imidization agent, dehydrated and closed, and then dried.
A conventionally well-known thing can be used as a chemical imidating agent. For example, an aliphatic acid anhydride or an aromatic acid anhydride may be used as a dehydrating agent, and a tertiary amine such as triethylamine may be used as a catalyst. As described in JP-A-4-339835, an imida- Ru, benzimidazole, or substituted derivatives thereof may be used.

The progress of imidization can be confirmed by analyzing the IR spectrum or the like. Specifically, when a polyimide precursor resin solution (reaction mixture) is applied on a glass substrate and pre-dried and then the IR spectrum is confirmed, it is confirmed that a spectrum around 1780 cm ⁻¹ peculiar to an imide bond cannot be seen. be able to.

The linear expansion coefficient of the resulting silicon-containing polyimide resin (1) is preferably 2 to 30 ppm / ° C, more preferably 2 to 25 ppm / ° C, and particularly preferably 2 to 20 ppm / ° C.
By using such a silicon-containing polyimide resin (1), it is possible to obtain a lithium ion secondary battery excellent in charge / discharge cycle characteristics in which current collecting performance does not decrease.

  The polyimide precursor resin (3) is represented by, for example, the Si-containing terminal modifier (Si-containing terminal modifier (2a)) represented by the formula (2a) and the formula (4) as shown in the following formula. By mixing and stirring a tetracarboxylic dianhydride (tetracarboxylic dianhydride (4)) and a diamine compound (diamine compound (5)) represented by formula (5) in a solvent Can be obtained.

In the formula, R _{1 to} R ₃ , R, X, Y, m, and n represent the same meaning as described above.

Specific examples of the Si-containing terminal modifier represented by the formula (2a) include aminomethyltrimethoxysilane, aminomethyltriethoxysilane, aminomethylmethyldiethoxysilane, aminomethyldimethylethoxysilane, aminomethylmethyldimethoxy. Aminomethylsilanes such as silane; 2-aminoethylsilanes such as 1- (aminoethyl) triethoxysilane, 2- (aminoethyl) triethoxysilane, 2- (aminoethyl) dimethoxymethylsilane; 3-aminopropyl 3-aminopropyl such as trimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyldimethylmethoxysilane, 3-aminopropyldimethylethoxysilane Pyrsilanes; 4-aminobutyltrimethoxysilane, 4-aminobutylmethyldimethoxysilane, 4-aminobutyldimethylmethoxysilane, 4-aminobutyltriethoxysilane, 4-aminobutylmethyldiethoxysilane, 4-aminobutyldimethylethoxy 4-aminobutylsilanes such as silane; and the like.
These compounds can be used alone or in combination of two or more.

  Examples of the tetracarboxylic dianhydride (4) include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, pyromellitic anhydride, 1,2,3,4-benzenetetracarboxylic acid. Anhydride, 1,4,5,8-naphthalenetetracarboxylic acid anhydride, 2,3,6,7-naphthalenetetracarboxylic acid anhydride, 2,2 ', 3,3'-biphenyltetracarboxylic acid dianhydride 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 2,3,3 ′, 4′-benzophenonetetracarboxylic Acid dianhydride, 3,3 ′, 4,4′-diphenyl ether tetracarboxylic dianhydride, 2,3,3 ′, 4′-diphenyl ether tetracarboxylic dianhydride, 3,3 ′, 4,4 ′ -Diphenyls Hongtetracarboxylic dianhydride, 2,3,3 ′, 4′-diphenylsulfonetetracarboxylic dianhydride, 2,2-bis (3,3 ′, 4,4′-tetracarboxyphenyl) tetrafluoropropane Dianhydride, 2,2′-bis (3,4-dicarboxyphenoxyphenyl) sulfone dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis ( 3,4-dicarboxyphenyl) propane dianhydride, cyclopentanetetracarboxylic anhydride, butane-1,2,3,4-tetracarboxylic acid, 2,3,5-tricarboxycyclopentylacetic anhydride, etc. It is done.

Among these, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid is preferable from the viewpoint of obtaining a preferable linear expansion coefficient and excellent heat resistance. It is preferable to use acid dianhydride or pyromellitic acid anhydride.
In addition, these compounds can be used individually by 1 type or in combination of 2 or more types.

  Examples of the diamine compound (5) include 4,4′-diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, and 3,3′-diamino. Diphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3, 3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 2,2- Di (3-amino Enyl) propane, 2,2-di (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2,2-di (3-aminophenyl) -1, 1,1,3,3,3-hexafluoropropane, 2,2-di (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 1,1-di (3-aminophenyl) -1-phenylethane, 1,1-di (4 -Aminophenyl) -1-phenylethane, 1- (3-aminophenyl) -1- (4-aminophenyl) -1-phenylethane, 1,3-bis (3-aminophenoxy) benzene, 1,3- Bis (4-aminophenoxy) benze 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminobenzoyl) benzene, 1,3-bis (4-aminobenzoyl) ) Benzene, 1,4-bis (3-aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 1,3-bis (3-amino-α, α-dimethylbenzyl) benzene, 1, 3-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (4-amino-α, α- Dimethylbenzyl) benzene, 1,3-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,3-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene 1,4-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 2,6-bis (3- Aminophenoxy) benzonitrile, 2,6-bis (3-aminophenoxy) pyridine, 4,4′-bis (3-aminophenoxy) biphenyl, 4,4′-bis (4-aminophenoxy) biphenyl, bis [4 -(3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl ] Sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone Bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2- Bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2 -Bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1, 3-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (4-aminopheno) B) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethyl Benzyl] benzene, 1,4-bis [4- (3-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] Benzene, 4,4′-bis [4- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4 ′ -Bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] diphenylsulfone, 4,4′-bis [4- (4-aminophenoxy) phenoxy] diphenylsulfone 3,3′-diamino-4,4′-diphenoxybenzophenone, 3,3′-diamino-4,4′-dibiphenoxybenzophenone, 3,3′-diamino-4-phenoxybenzophenone, 3,3 ′ -Diamino-4-biphenoxybenzophenone, 5-amino-2- (p-aminophenyl) benzoxazole, 2,2'-di (p-aminophenyl) -6,6'-bisbenzoxazole, 2- (4 -Aminophenyl) -6-aminobenzoxazole, N- (4-aminophenyl) -4-aminobenzamide, N, N'-bis (4-aminophenyl) terephthalamide, 4-aminophenyl-4-aminobenzoate, 2,2′-dimethylbiphenyl-4,4′-diamine and the like can be mentioned.

Among these, 4,4′-diaminodiphenyl ether and p-phenylenediamine are preferable from the viewpoint of cost, and 2,2′-di (p-aminophenyl) -6,6 from the viewpoint of dispersibility of the active material. 6'-bisbenzoxazole and 2- (4-aminophenyl) -6-aminobenzoxazole are preferred.
In addition, these compounds can be used individually by 1 type or in combination of 2 or more types.

  The mixing ratio of the Si-containing terminal modifier (2a), the tetracarboxylic dianhydride (4), and the diamine compound (5) is a mass ratio and is usually (Si-containing terminal modifier (2a)): (tetracarboxylic acid) The dianhydride (4)) :( diamine compound (5)) = 100: 80-100: 5-15, preferably 100: 90-100: 5-12.

The solvent used is not particularly limited as long as it is inert to the reaction, and examples thereof include amides such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam and the like. Solvents such as dimethyl sulfoxide, hexamethylphosphoroformamide, dimethyl sulfone, tetramethylene sulfone, dimethyltetramethylene sulfone; phenolic solvents such as cresol, phenol, xylenol; diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (Triglyme), diglyme solvents such as tetraglyme; lactone solvents such as γ-butyrolactone; ketone solvents such as isophorone, cyclohexanone and 3,3,5-trimethylcyclohexanone ; Pyridine, ethylene glycol, dioxane, and other solvents such as tetramethylurea; benzene, toluene, aromatic hydrocarbon solvents such as xylene; and the like. These solvents can be used alone or in combination of two or more.
The amount of the solvent used is a viscosity suitable for the negative electrode mixture slurry to be provided to the current collector in the subsequent negative electrode mixture layer formation, specifically, a value by a rotary viscometer at room temperature, It is desirable to select so as to be 0.5 to 10 Pa · s.

The reaction temperature is generally 0 to 100 ° C, preferably 10 to 50 ° C, more preferably 15 to 35 ° C.
Although depending on the reaction scale and the like, the reaction time is usually from several tens of minutes to several days, preferably from several hours to 48 hours.
The obtained polyimide precursor resin (3) can be subjected to the next imidization step as it is without being isolated.

<Active material mixture layer>
The active material mixture layer used in the present invention contains a negative electrode active material containing Si and a binder containing the silicon-containing polyimide resin (1), but preferably contains a conductive auxiliary material.
The conductive auxiliary material is not particularly limited, but it is preferable to use a conductive carbon material such as carbon black, acetylene black, ketjen black, carbon nanotube, or carbon nanofiber.
The blending ratio of the conductive auxiliary material is usually 1 to 20% by mass, preferably 4 to 6% by mass, when the total of the negative electrode active material, the binder and the conductive auxiliary material is 100% by mass. If the conductive auxiliary material is too small, a good conductive network cannot be formed. If the conductive auxiliary material is too large, the formability of the electrode is deteriorated and the energy density of the electrode is lowered.

<Negative electrode current collector>
In the present invention, conventionally known negative electrode current collectors can be used. Specifically, a porous or non-porous conductive substrate made of a conductive metal material such as stainless steel, titanium, nickel, aluminum, copper, or a conductive resin; mesh body, net body, punching sheet, lath body Porous conductive substrates such as fiber group molded products such as porous bodies, foams, and nonwoven fabrics; non-porous conductive substrates such as foils, sheets, and films; and the like.

The negative electrode for a lithium ion secondary battery of the present invention has an active material mixture layer containing a negative electrode active material and a binder containing a silicon-containing polyimide resin (1) disposed on the surface of the negative electrode current collector. Is.
There is no restriction | limiting in particular as a manufacturing method of the negative electrode for lithium ion secondary batteries of this invention, A conventionally well-known manufacturing method is mentioned. Especially, the manufacturing method of the negative electrode for lithium ion secondary batteries of this invention mentioned later is preferable.
According to the negative electrode for a lithium ion secondary battery of the present invention, even when a negative electrode active material containing Si is used, there is no generation of wrinkles or curls during the production of the negative electrode, and physical and temperature expansion and contraction during charge and discharge. Therefore, peeling of the active material and the current collector or between the active materials can be suppressed, and a lithium ion secondary battery excellent in cycle characteristics can be obtained.

2) Method for Producing Negative Electrode for Lithium Ion Secondary Battery The method for producing a negative electrode for lithium ion secondary battery according to the present invention comprises a negative electrode active material comprising the Si-containing negative electrode active material and the polyimide precursor resin (3). After the slurry is applied on the surface of the negative electrode current collector, it is preliminarily dried at 30 to 130 ° C., rolled, and then imidized with the polyimide precursor resin.
According to the production method of the present invention, the negative electrode for a lithium ion secondary battery of the present invention can be efficiently produced.

The negative electrode mixture slurry to be used preferably contains the conductive auxiliary material in addition to the negative electrode active material containing Si and the polyimide precursor resin (3).
As a method for preparing the negative electrode mixture slurry, a method of adding and mixing the negative electrode active material to the polyimide precursor (3), and then adding and mixing a conductive auxiliary material; production of the polyimide precursor resin (3) A method of adding and mixing a negative electrode active material and a conductive auxiliary agent at the time of polymerization; and the like, and the former method is preferred because the operation is simple.

The mass mixing ratio of the polyimide precursor resin (3), the negative electrode active material, and the conductive auxiliary material is polyimide precursor resin (3): negative electrode active material: conductive auxiliary material = 1-30: 50-99: 1-20. It is preferably 1-20: 60-95: 1-20, more preferably 1-15: 70-95: 1-15, and even more preferably 1-10: 80-95: 1. Is particularly preferred.
In addition, as the polyimide precursor resin (3), the negative electrode active material, and the conductive auxiliary material to be used, the same ones as exemplified in the above 1) can be mentioned.
As described above, the polyimide precursor resin (3) can be used as the reaction mixture solution without removing the solvent after completion of the reaction.

  When mixing the polyimide precursor resin (3), the negative electrode active material, and the conductive auxiliary material, a conventionally known planetary mixer, defoaming kneader, ball mill, paint shaker, vibration mill, reika machine, agitator mill, etc. A general mixing device may be used.

  The viscosity of the negative electrode mixture slurry may be a viscosity that can be easily applied onto the current collector in the next step, and the viscosity can be adjusted as necessary by increasing or decreasing the solvent used during the production of the polyimide precursor resin. Specifically, it is preferable to select a value of 1000 to 9000 mPa · s as measured by a rotary (B-type) viscometer at 25 ° C.

Examples of a method of applying the obtained negative electrode mixture slurry onto the surface of the negative electrode current collector include a method of applying using a conventionally known apparatus such as a doctor blade or a bar coater.
The thickness of the active material mixture layer to be formed is the thickness before drying and is usually about 10 to 500 μm.

  After application, preliminary drying is performed. Pre-drying means drying to such an extent that the solvent used evaporates to some extent, the slurry does not sag on the current collector, and does not whiten due to moisture in the air. By performing the preliminary drying, the adhesion between the negative electrode active material and the current collector is improved.

The predrying temperature is in the range of 30 to 130 ° C. without causing thermal imidization. If the preliminary drying temperature is lower than 30 ° C., the drying becomes insufficient, and if it is higher than 130 ° C., thermal imidization proceeds and the intended linear expansion coefficient may not be obtained.
The drying time is usually 1 to 60 minutes. When the drying time is shorter than 1 minute, the drying becomes insufficient, and the residual solvent amount hardly changes even when heated for longer than 60 minutes.

  Next, rolling is performed. By rolling, the negative electrode can be formed to have a desired thickness and density. There is no restriction | limiting in particular as a method of rolling, The well-known method by a roll press and a press is mentioned.

The imidization performed next can be performed by the thermal imidization method or the chemical imidization method described above.
After imidization, the negative electrode may be further shaped to have a desired thickness and density by a known method such as a roll press or a pressure press. The obtained sheet-like negative electrode for a lithium ion secondary battery is used after being cut into dimensions according to the specifications of the lithium ion secondary battery to be produced.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the following examples.

Example 1
(1) Production of negative electrode binder precursor 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 2,2′-di (p-aminophenyl) -6,6′-bisbenzoxazole , 3-aminopropyldiethoxymethylsilane and a molar ratio (3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride: 2,2′-di (p-aminophenyl) -6,6 ′ -Bisbenzoxazole: 3-aminopropyldiethoxymethylsilane) is dissolved in 120 ml of N-methyl-2-pyrrolidone (NMP) so as to be 100: 96: 8, and stirred and polymerized at room temperature for 24 hours. A binder precursor solution α1 was obtained.

(2) Preparation of negative electrode mixture slurry Si powder (purity 99.9%) having a particle size of 10 μm or less as a negative electrode active material, graphite powder having an average particle size of 3 μm as a conductive auxiliary material, and the above prepared negative electrode binder precursor solution α1 was mixed so that the weight ratio (Si powder: graphite powder: negative electrode binder precursor solution α1) was 80:10:10 to obtain a negative electrode mixture slurry.

(3) Preparation of negative electrode The negative electrode mixture slurry prepared in (2) was applied to one side of a rolled copper foil (thickness 30 μm), which is a current collector, and pre-dried at 130 ° C. for 10 minutes to remove the solvent. And this was rolled. The obtained product was heated at 350 ° C. for 60 minutes in a nitrogen atmosphere, and the one obtained by completing the thermal imidization was used as the negative electrode. At this time, the obtained negative electrode was not curled and the active material layer was not peeled off.
In order to confirm that the polyimide compound was produced from the binder precursor solution α1 by the heat treatment of the negative electrode, the following test 1 was performed.

(Test 1)
The binder precursor solution α1 was pre-dried at 130 ° C. for 10 minutes to remove the solvent, heated at 350 ° C. for 60 minutes in a nitrogen atmosphere, and an infrared absorption spectrum was measured. As a result, a peak derived from an imide bond was detected in the vicinity of 1780 cm ⁻¹ . Thereby, it was confirmed by the heat treatment of the binder precursor solution α1 that the imidization reaction progressed and a polyimide compound was generated.

  Moreover, the following test 2 was performed in order to measure the linear expansion coefficient which the polyimide resin produced | generated by the heat processing of the said negative electrode had.

(Test 2)
The binder precursor solution α1 was pre-dried at 130 ° C. for 10 minutes to remove the solvent, and heated at 350 ° C. for 60 minutes in a nitrogen atmosphere to obtain a polyimide film. The film was measured for linear expansion coefficient using a thermomechanical analyzer (TMA). As a result, it showed 5 ppm / ° C. and had a linear expansion coefficient comparable to that of the negative electrode active material (Si). It was.

<Evaluation of adhesion and binding strength>
In order to evaluate the adhesive force between the binder in the negative electrode produced in Example 1 and Cu as the current collector, or the binding force between Si powder as the negative electrode active material, the following tests were performed.

  The negative electrode produced in Example 1 was cut into a 10 mm square, an aluminum pin with an epoxy adhesive (diameter 2.7 mm) on the upper surface (negative electrode composite layer side), and a ceramic plate with an epoxy adhesive on the lower surface (copper foil side) (11 mm square) was installed, and three were clamped and fixed with aluminum clips. This was heated at 150 ° C. for 60 minutes in a nitrogen atmosphere to bond the aluminum pin, the negative electrode with the active material mixture layer, and the ceramic plate. Using an adhesion force tester (product name: Romulus thin film adhesion strength measuring device, manufactured by Quad Group), the adhesion force (adhesion force between the active material and the current collector through the binder) or binding force (binder The adhesion between the active materials was determined according to the following criteria. The larger this value, the stronger the adhesive force or binding force.

A: 20 MPa or more B: 15 MPa or more and less than 20 MPa C: 10 MPa or more and less than 15 MPa D: 5 MPa or more and less than 10 MPa E: Less than 5 MPa As a result of the test, the evaluation was A.

<Cycle characteristic evaluation>
Using the negative electrode obtained in Example 1, a lithium ion secondary battery was produced as follows, and the cycle characteristics were evaluated.
(I) Production of positive electrode LiCoO ₂ (product name: cell seed C-10N, manufactured by Nippon Chemical Industry Co., Ltd.) 100 parts, polyvinylidene difluoride (PVDF) 2 parts (corresponding to solid content) and acetylene black 2 parts as a conductive agent Then, N-methylpyrrolidone was further mixed to a solid content of 80% and mixed with a planetary mixer to prepare a positive electrode slurry. This positive electrode slurry was applied on a 20 μm thick aluminum foil with a comma coater so that the film thickness after drying was about 120 μm, dried at 60 ° C. for 20 minutes, and then heat treated at 150 ° C. for 2 hours to form an electrode. I got the original fabric. This electrode original fabric was rolled by a roll press to produce a positive electrode in which the density was 3.7 g / cm ³ and the total thickness of the copper foil and the positive electrode active material layer was controlled to 100 μm.

(Ii) Production of Battery The negative electrode obtained in Example 1 was punched into a circle of 14 mm, the positive electrode produced in (i) was punched into a circle of 13 mm, a diameter of 16 mm, and a single layer of 25 μm thickness produced by a dry method. In a stainless steel outer container (diameter 20 mm, height 1.8 mm, stainless steel thickness) in which a polypropylene separator (porosity 55%) is interposed and the active material layers face each other and a polypropylene packing is arranged. 0.2 mm). In the container, an electrolytic solution (manufactured by Kishida Chemical Co., Ltd.) in which LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate / diethyl carbonate = 1/2 (volume ratio) at a concentration of 1 mol / L was used so that no air remained. Inject and cover with a stainless steel cap with a thickness of 0.2 mm, and fix the outer container and cap through polypropylene packing so that the copper foil is in contact with the cap and the aluminum foil is in contact with the lower surface of the container. The contents were sealed to manufacture a coin-type battery β1 having a diameter of 20 mm and a thickness of 2.0 mm.

(Iii) Evaluation of cycle characteristics Using the obtained lithium ion secondary battery, charging was performed at 20 ° C. with a constant current of 0.1 C up to 4.2 V and discharged with a constant current of 0.1 C up to 3.0 V. A discharge cycle was performed. The charge / discharge cycle was performed up to 100 cycles, and the ratio of the discharge capacity at the 100th cycle to the initial discharge capacity was defined as the capacity retention rate, and the following criteria were used. Larger values indicate less capacity loss due to repeated charge and discharge.

A: 80% or more B: 75% or more and less than 80% C: 70% or more and less than 75% D: 50% or more and less than 70% E: less than 50% The evaluation result was A.

(Example 2)
During the preparation of the negative electrode binder precursor, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2′-di (p-aminophenyl) -6,6′-bisbenzoxazole, 3 -Aminopropyldiethoxymethylsilane with a molar ratio of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride: 2,2'-di (p-aminophenyl) -6,6'-bis Benzoxazole: 3-aminopropyldiethoxymethylsilane = negative electrode binder precursor in the same manner as in Example 1 except that it was dissolved in 150 ml of NMP and stirred and polymerized at room temperature for 24 hours so as to be 100: 96: 8. Solution α2 was prepared, and a negative electrode was produced in the same manner as in Example 1. The produced negative electrode did not cause wrinkles or curls, and the evaluation of adhesive strength and binding strength was A.

A polyimide film was obtained in the same manner as in Test 1 of Example 1 using the obtained negative electrode binder precursor solution α2. As a result of measuring the infrared absorption spectrum of the obtained polyimide film, a peak derived from an imide bond was detected in the vicinity of 1780 cm ⁻¹ , and it was confirmed that a polyimide compound was produced. Moreover, it carried out similarly to the test 2 of Example 1, and measured the linear expansion coefficient of the obtained polyimide film. The measurement results are shown in Table 1.
Furthermore, when a coin-type battery β2 was produced in the same manner as in Example 1, the cycle characteristic evaluation was B.

(Example 3)
At the time of preparing the negative electrode binder precursor, pyromellitic anhydride, 4,4′-diaminodiphenyl ether, and 3-aminopropylethoxydimethylsilane are in a molar ratio of pyromellitic anhydride: 4,4′-diaminodiphenyl ether: A negative electrode binder precursor solution α3 was prepared in the same manner as in Example 1 except that it was dissolved in 115 ml of NMP so that 3-aminopropylethoxydimethylsilane = 100: 92: 10, and stirred and polymerized at room temperature for 24 hours. In the same manner as in Example 1, a negative electrode was produced. The produced negative electrode did not cause wrinkles or curls, and the evaluation of adhesive strength and binding strength was A.

A polyimide film was obtained in the same manner as in Test 1 of Example 1 using the obtained negative electrode binder precursor solution α3. As a result of measuring the infrared absorption spectrum of the obtained polyimide film, a peak derived from an imide bond was detected in the vicinity of 1780 cm ⁻¹ , and it was confirmed that a polyimide compound was produced. Moreover, it carried out similarly to the test 2 of Example 1, and measured the linear expansion coefficient of the obtained polyimide film. The measurement results are shown in Table 1.
Furthermore, when a coin-type battery β3 was produced in the same manner as in Example 1, the cycle characteristic evaluation was B.

Example 4
At the time of preparing the negative electrode binder precursor, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, p-phenylenediamine, and 3-aminopropyltriethoxysilane were mixed at a molar ratio of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride: p-phenylenediamine: 3-aminopropyltriethoxysilane = 100: 98: 6, dissolved in 125 ml of NMP, stirred and polymerized at room temperature for 24 hours Prepared a negative electrode binder precursor solution α4 in the same manner as in Example 1, and produced a negative electrode in the same manner as in Example 1. The produced negative electrode did not cause wrinkles or curls, and the adhesive strength / binding strength evaluation was B.

A polyimide film was obtained in the same manner as in Test 1 of Example 1 using the obtained negative electrode binder precursor solution α4. As a result of measuring the infrared absorption spectrum of the obtained polyimide film, a peak derived from an imide bond was detected in the vicinity of 1780 cm ⁻¹ , and it was confirmed that a polyimide compound was produced. Moreover, it carried out similarly to the test 2 of Example 1, and measured the linear expansion coefficient of the obtained polyimide film. The measurement results are shown in Table 1.
Furthermore, when a coin-type battery β4 was produced in the same manner as in Example 1, the cycle characteristic evaluation was B.

(Example 5)
During the preparation of the negative electrode binder precursor, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2′-dimethylbiphenyl-4,4′-diamine, and 3-aminopropyldiethoxymethylsilane And a molar ratio of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride: 2,2′-dimethylbiphenyl-4,4′-diamine: 3-aminopropyldiethoxymethylsilane = 100: A negative electrode binder precursor solution α5 was prepared in the same manner as in Example 1 except that it was dissolved in 155 ml of NMP so as to be 95: 7 and stirred and polymerized at room temperature for 24 hours. Was made. The produced negative electrode did not cause wrinkles or curls, and the adhesive strength / binding strength evaluation was C.

Using the obtained negative electrode binder precursor solution α5, a polyimide film was obtained in the same manner as in Test 1 of Example 1. As a result of measuring the infrared absorption spectrum of the obtained polyimide film, a peak derived from an imide bond was detected in the vicinity of 1780 cm ⁻¹ , and it was confirmed that a polyimide compound was produced. Moreover, it carried out similarly to the test 2 of Example 1, and measured the linear expansion coefficient of the obtained polyimide film. The measurement results are shown in Table 1.
Furthermore, when a coin-type battery β5 was produced in the same manner as in Example 1, the cycle characteristic evaluation was B.

(Example 6)
At the time of preparing the negative electrode binder precursor, pyromellitic anhydride, N- (4-aminophenyl) -4-aminobenzamide, and 3-aminopropyldiethoxymethylsilane have a molar ratio of pyromellitic anhydride: N Example except that-(4-aminophenyl) -4-aminobenzamide: 3-aminopropyldiethoxymethylsilane = 100: 85: 6 was dissolved in 120 ml of NMP and stirred and polymerized at room temperature for 24 hours. In the same manner as in Example 1, a negative electrode binder precursor solution α6 was prepared, and in the same manner as in Example 1, a negative electrode was produced. The produced negative electrode did not cause wrinkles or curls, and the adhesive strength / binding strength evaluation was B.

Using the obtained negative electrode binder precursor solution α6, a polyimide film was obtained in the same manner as in Test 1 of Example 1. As a result of measuring the infrared absorption spectrum of the obtained polyimide film, a peak derived from an imide bond was detected in the vicinity of 1780 cm ⁻¹ , and it was confirmed that a polyimide compound was produced. Moreover, it carried out similarly to the test 2 of Example 1, and measured the linear expansion coefficient of the obtained polyimide film. The measurement results are shown in Table 1.
Furthermore, when a coin-type battery β6 was produced in the same manner as in Example 1, the cycle characteristic evaluation was A.

(Example 7)
In preparing the negative electrode binder precursor, pyromellitic anhydride, 4-aminophenyl-4-aminobenzoate, and 3-aminopropyldiethoxymethylsilane were mixed in a molar ratio of pyromellitic anhydride: 4-aminophenyl- 4-aminobenzoate: 3-aminopropyldiethoxymethylsilane = Negative binder as in Example 1 except that it was dissolved in 140 ml of NMP and stirred and polymerized at room temperature for 24 hours so as to be 100: 90: 7. A precursor solution α7 was prepared, and a negative electrode was produced in the same manner as in Example 1. The produced negative electrode did not cause wrinkles or curls, and the evaluation of adhesive strength and binding strength was A.

Using the resulting negative electrode binder precursor solution α7, a polyimide film was obtained in the same manner as in Test 1 of Example 1. As a result of measuring the infrared absorption spectrum of the obtained polyimide film, a peak derived from an imide bond was detected in the vicinity of 1780 cm ⁻¹ , and it was confirmed that a polyimide compound was produced. Moreover, it carried out similarly to the test 2 of Example 1, and measured the linear expansion coefficient of the obtained polyimide film. The measurement results are shown in Table 1.
Furthermore, when a coin-type battery β7 was produced in the same manner as in Example 1, the cycle characteristic evaluation was B.

(Comparative Example 1)
A negative electrode binder precursor solution γ1 was prepared in the same manner as in Example 1 except that 3-aminopropyldiethoxymethylsilane was not used at the time of preparing the negative electrode binder precursor. Produced. The produced negative electrode did not cause wrinkles or curls, but the evaluation of adhesive strength and binding strength was E.

Using the resulting negative electrode binder precursor solution γ1, a polyimide film was obtained in the same manner as in Test 1 of Example 1. As a result of measuring the infrared absorption spectrum of the obtained polyimide film, a peak derived from an imide bond was detected in the vicinity of 1780 cm ⁻¹ , and it was confirmed that a polyimide compound was produced. Moreover, it carried out similarly to the test 2 of Example 1, and measured the linear expansion coefficient of the obtained polyimide film. The measurement results are shown in Table 1.
Further, a coin-type battery δ1 was produced in the same manner as in Example 1, but the cycle characteristic evaluation was E.

(Comparative Example 2)
A negative electrode binder precursor solution γ2 was prepared in the same manner as in Example 2 except that 3-aminopropyldiethoxymethylsilane was not used at the time of preparing the negative electrode binder precursor. Produced. The produced negative electrode did not cause wrinkles or curls, but the evaluation of adhesive strength and binding strength was E.

A polyimide film was obtained in the same manner as in Test 1 of Example 1 using the obtained negative electrode binder precursor solution γ2. As a result of measuring the infrared absorption spectrum of the obtained polyimide film, a peak derived from an imide bond was detected in the vicinity of 1780 cm ⁻¹ , and it was confirmed that a polyimide compound was produced. Moreover, it carried out similarly to the test 2 of Example 1, and measured the linear expansion coefficient of the obtained polyimide film. The measurement results are shown in Table 1.
Further, a coin-type battery δ2 was produced in the same manner as in Example 1, but the cycle characteristic evaluation was E.

(Comparative Example 3)
At the time of preparing the negative electrode binder precursor, pyromellitic anhydride and p-phenylenediamine were dissolved in 125 ml of NMP so that the molar ratio was pyromellitic anhydride: p-phenylenediamine = 100: 96, and at room temperature. A negative electrode binder precursor solution γ3 was prepared in the same manner as in Example 1 except that the mixture was stirred and polymerized for 24 hours, and a negative electrode was prepared in the same manner as in Example 1. The produced negative electrode did not cause wrinkles or curls, but the evaluation of adhesive strength and binding strength was E.

Using the obtained negative electrode binder precursor solution γ3, an attempt was made to obtain a polyimide film in the same manner as in Test 1 of Example 1. However, since it was a very hard and brittle film, self-supportability could not be obtained and linear expansion was observed. The rate could not be measured.
Further, a coin-type battery δ3 was produced in the same manner as in Example 1, but the cycle characteristic evaluation was E.

(Comparative Example 4)
At the time of preparing the negative electrode binder precursor, the molar ratio of 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether is 3,3 ′, 4,4′-benzophenone. Tetracarboxylic acid dianhydride: 4,4′-diaminodiphenyl ether = 100: 94 In the same manner as in Example 1 except that it was dissolved in 130 ml of NMP and stirred and polymerized at room temperature for 24 hours. A body solution γ4 was prepared, and a negative electrode was produced in the same manner as in Example 1. The produced negative electrode was wrinkled and curled, and the evaluation of adhesive strength and binding strength was E.

A polyimide film was obtained in the same manner as in Test 1 of Example 1 using the obtained negative electrode binder precursor solution γ4. As a result of measuring the infrared absorption spectrum of the obtained polyimide film, a peak derived from an imide bond was detected in the vicinity of 1780 cm ⁻¹ , and it was confirmed that a polyimide compound was generated. Moreover, it carried out similarly to the test 2 of Example 1, and measured the linear expansion coefficient of the obtained polyimide film. The measurement results are shown in Table 1.
Further, a coin-type battery δ4 was produced in the same manner as in Example 1, but the cycle characteristic evaluation was E.

  From Table 1, the negative electrode for a lithium ion secondary battery using a polyimide resin having a silicon-containing group at the end and having a linear expansion coefficient of 2 to 30 ppm / ° C. has no occurrence of wrinkles or curls during the production of the negative electrode. It can be said that it is excellent in terms of adhesive strength / binding strength or cycle characteristics.

Claims (4)

A negative electrode for a lithium ion secondary battery in which an active material mixture layer containing a negative electrode active material containing silicon and a binder is disposed on the surface of a negative electrode current collector,
The negative electrode for a lithium ion secondary battery, wherein the binder comprises a silicon-containing polyimide resin represented by the following formula (1).

[Wherein, X represents a tetravalent organic group, Y represents a divalent organic group, and n represents an integer of 1 to 10,000. T is the formula (2)

(In the formula, R _{1 to} R ₃ each independently represent a hydrocarbon group having 1 to 8 carbon atoms or an oxygen-containing hydrocarbon group having 1 to 8 carbon atoms, and m represents an integer of 1 to 8). Represents a silicon-containing group represented by ]   2. The negative electrode for a lithium ion secondary battery according to claim 1, wherein the silicon-containing polyimide resin has a linear expansion coefficient of 2 to 30 ppm / ° C. 3. The lithium ion secondary battery according to claim 1 or 2, wherein the silicon-containing polyimide resin is obtained by imidizing a silicon-containing polyimide precursor resin represented by the following formula (3). Negative electrode.

(In the formula, T, X, Y and n represent the same meaning as described above. R represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms.) After apply | coating the negative mix slurry containing the negative electrode active material containing silicon, and the silicon containing polyimide precursor resin represented by following formula (3) on the surface of a negative electrode electrical power collector, it pre-drys at 30-130 degreeC. 3. The method for producing a negative electrode for a lithium ion secondary battery according to claim 1, further comprising: imidizing the silicon-containing polyimide precursor resin after performing and rolling.

[Wherein, X represents a tetravalent organic group, Y represents a divalent organic group, and n represents an integer of 1 to 10,000. T is the formula (2)

(In the formula, R _{1 to} R ₃ each independently represent a hydrocarbon group having 1 to 8 carbon atoms or an oxygen-containing hydrocarbon group having 1 to 8 carbon atoms, and m represents an integer of 1 to 8). And R represents a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms. ]