TW201531499A - Hydrophilic polymer, manufacturing method of the same, and application of hydrophilic polymer - Google Patents

Abstract

The invention provides a hydrophilic polymer, a manufacturing method, an electrode including the hydrophilic polymer, and a negative electrode for lithium ion secondary battery. The hydrophilic polymer has excellent hydrophilicity, and is soft and exhibits excellent adhesiveness to metal. The hydrophilic polymer is represented by the following General Formula (1).

Description

Hydrophilic polymer, method for producing the same, and using hydrophilic polymer Adhesive and electrode

The present invention relates to a hydrophilic polymer which is not only excellent in hydrophilicity but also soft and exhibits excellent adhesion to metals, has low viscosity of an organic solvent solution, and improves workability, and further relates to an inclusion A binder for a hydrophilic polymer and a negative electrode for a lithium ion secondary battery.

In recent years, a secondary battery represented by a lithium ion secondary battery can be used as a rechargeable high-capacity battery to perform high-function operation and long-term operation of an electronic device. Furthermore, it is considered to be the most promising battery for hybrid vehicles and electric vehicles. In order to further increase the energy density of the lithium ion battery, it is studied to use ruthenium, osmium or tin having a high theoretical capacity of charge and discharge as the negative electrode active material (see Patent Document 1).

In order to maintain the charge and discharge characteristics as a lithium ion secondary battery, it is necessary to keep the active material and the current collector close to a stable state, and to obtain a binder having good adhesion to the current collector. In contrast, as a conventional general-purpose binder, non-aqueous polyvinylidene fluoride (PVDF) or water system Styrene butadiene rubber (SBR) with good bulk properties is the mainstream.

However, in the lithium ion secondary battery using the negative electrode active material, the expansion and contraction of the negative electrode active material occurs due to charge and discharge, and the flexibility and adhesion of the binder resin are insufficient. Therefore, there are the following problems: It may be destroyed or may be peeled off at the interface between the negative electrode active material and the negative electrode current collector and the binder resin, and the charge/discharge cycle characteristics may be deteriorated.

Therefore, a technique is known in which a negative electrode active material containing ruthenium is bonded to a specific polyimide resin or a polyimide yttrium imide resin to obtain a negative electrode, thereby improving the cycle characteristics (see Patent Document 2) Patent Document 3) and the like.

In Patent Document 2, a non-aqueous polyimide resin having high resin strength is used, and peeling at the interface between the negative electrode current collector and the binder is suppressed, and cycle characteristics are improved. However, heat treatment at a high temperature is required in the dehydration condensation derived from the binder precursor, and there is concern about the influence on the current collector. Further, since it is a polyimide monomer, it has a hard physical property and is insufficient in elasticity and flexibility, and the adhesion is questioned.

In Patent Document 3, a urethane resin containing a soft sulfonimide group and a soft segment capable of forming a homopolymer having a glass transition point of 30 ° C or less is used as a non-aqueous binder. A negative electrode having good adhesion without peeling off from the copper foil at a relatively low temperature.

However, the coating solution is an organic solvent-based N-methyl-2-pyrrolidone (NMP), which forms a film on the surface of the active material.

In general, a flexible polyimide resin or a polyimide elastomer (see Non-Patent Document 1 and Patent Document 4) is known, but it is not particularly hydrophilic. Therefore, water dispersibility is not obtained when used. The hydrophilicity is not satisfactory. Among these, in particular, a polyimide-based resin having a hydroxyl group, a carboxyl group or a sulfonic acid group in which fine particles having a small environmental load and excellent solution stability are uniformly dispersed in water has been attracting attention (see Patent Document 5).

However, these polymers are not satisfactory in terms of flexibility and adhesion to a current collector.

In addition, when an electrode coating film is formed by using polyglycine as a precursor of a binder in the production of an electrode for a lithium secondary battery, it is pointed out that the electrode is bent due to shrinkage due to a dehydration reaction at a high temperature. A composition comprising a polyimine precursor compound and a highly flexible polymer has been proposed (see Patent Document 6). However, flexibility is not considered, and it is not satisfactory in terms of hydrophilicity. It has been noted that poly-proline which is a polyimide precursor is required to be heat-treated at a high temperature of 200 ° C to 350 ° C, and the strength of the current collector during electrode production is lowered (see Non-Patent Document 2). According to the above, in the future, a water-based system that does not coat the active material is developed, and a material having the same or equivalent adhesive properties as the conventional polyimide resin is obtained even in a heat treatment at a low temperature of 150 ° C or lower. In the meantime, the practical use of the Si-based negative electrode is expected to advance rapidly.

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-199761

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2008-34352

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2000-200608

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2013-129770

[Patent Document 5] Japanese Patent Laid-Open Publication No. 2011-137063

[Patent Document 6] Japanese Patent Laid-Open Publication No. 2008-135384

[Non-patent literature]

[Non-Patent Document 1] Hand Qian Yingzhi, Shi Ye Ye Lang, Furukawa Yuki, "Synthesis and Physical Properties of Polyamidourethane Ester Elastomers", Elastomer Seminar, 1999, pp. 72-75 page

[Non-Patent Document 2] Nakamura Masahiro, "Next Generation Battery [Latest] Material Technology and Performance Evaluation", Technical Information Association Co., Ltd., 2013, pp. 166-167

The present invention has been made in view of the above problems, and it is an object of the invention to provide an adhesive property which is not only extremely excellent in hydrophilicity but also excellent in adhesion to metals, and further has low viscosity and improved workability of an organic solvent solution. Hydrophilic polymer. Further, an object of the invention is to provide a negative electrode for a lithium ion secondary battery having a small heat deterioration of a negative electrode of a Si or Si alloy (hereinafter referred to as "Si compound"), which has a large discharge capacity and excellent cycle life characteristics.

In order to achieve the object, the inventors conducted research and found that Regarding the polymer having a specific composition, a hydrophilic polymer which is not only extremely excellent in hydrophilicity but also soft and exhibits excellent adhesion to metals and is suitable as a binder is obtained. Further, it has been found that a negative electrode for a lithium ion secondary battery exhibiting a high discharge capacity and excellent cycle characteristics, which is a negative electrode active material for a lithium ion secondary battery, containing Si or Si, is obtained in a negative electrode containing the following components. An alloy (hereinafter collectively referred to as "Si compound"), a carbonaceous material or a carbonaceous material, and graphite; a binder comprising a hydrophilic polymer that bonds the negative electrode active material to the collector or the negative electrode active material; and conductive The carbon compound is added in order to secure the conductivity of the negative electrode active material; thus, the present invention has been completed.

Hereinafter, the present invention will be described in detail.

The hydrophilic polymer of the present invention has a structure represented by the following formula (1).

(wherein R ₁ represents a divalent organic group having 4 to 30 carbon atoms, and R ₂ represents a linear or branched polyvalent alkylene group having a carbon number of 2 to 5 having an average molecular weight of 100 to 10,000. The organic group, R ₃ represents a trivalent or higher organic group having one to two aromatic rings having 4 to 30 carbon atoms, R ₄ represents a tetravalent organic group having 4 to 30 carbon atoms, and X represents a carboxyl group or a sulfonic acid group. x represents an integer from 1 to 800, y represents an integer from 1 to 800, z represents an integer from 1 to 100, and a represents an integer from 1 to 4; wherein, in the case where X is a carboxyl group, the number of aromatic rings of R ₃ is 1. a is 1; further, in the structure of the formula (1), the structure represented by the following formula (2) is 10% by weight to 99% by weight)

(wherein R ₃ represents a trivalent or higher organic group having one to two aromatic rings having 4 to 30 carbon atoms, R ₄ represents a tetravalent organic group having 4 to 30 carbon atoms, and X represents a carboxyl group or a sulfonic acid group. , y represents an integer from 1 to 800, and a represents an integer from 1 to 4; wherein, in the case where X is a carboxyl group, the number of aromatic rings of R ₃ is 1, and a is 1)

(wherein R ₁ represents a divalent organic group having 4 to 30 carbon atoms, and R ₂ represents a linear or branched polyvalent alkylene group having a carbon number of 2 to 5 having an average molecular weight of 100 to 10,000. Organic base, x means an integer from 1 to 800)

The general formula (1) is characterized in that a quinone imine unit having at least one carboxyl group or a sulfonic acid group in a repeating unit and a urethane unit are linked via a urea bond.

R _{1 of the} hydrophilic polymer is preferably a divalent organic group containing an aromatic ring or an aliphatic ring having 4 to 15 carbon atoms. The average molecular weight of R ₂ is preferably from 100 to 5,000, more preferably from 100 to 2,000. R _{3 is} preferably a trivalent or higher organic group containing one to two aromatic rings having 6 to 20 carbon atoms. x is preferably an integer representing from 1 to 600. y is preferably an integer representing from 2 to 600. In the present invention, a polymer which exhibits extremely excellent adhesion and hydrophilicity is formed by combining an aromatic ring with a carboxyl group or a sulfonic acid group.

Furthermore, the structure in which the terminal of the polymer represented by the formula (1) is sealed with the dicarboxylic acid anhydride represented by the formula (4) provides not only excellent adhesion and hydrophilicity but also excellent Further, the organic solvent solution is preferred because it has a low viscosity and an improved workability.

(wherein Z represents a divalent organic group selected from the group consisting of the following general formula (5))

The hydrophilic polymer of the present invention is suitably used for a binder, but is not particularly limited. Here, the binder refers to a combination of a current collector metal and an active material, and particularly a binder for a secondary battery.

The hydrophilic polymer of the present invention has a rigid polyimine structural unit and a soft polyalkylene structure in the structure.

In detail, the hydrophilic polymer of the present invention has a polyamidene structural unit in the structure of the hydrophilic polymer as a hard segment which is more rigid than the polyamidimide prepolymer, and further aggregates The imine structural unit has a carboxyl group or a sulfonic acid group. By having such a substituent, it is soft and exhibits excellent adhesion to metals. In particular, an electrochemically stable hydrophilic polymer can be obtained under the assumption that it is used in a secondary battery. In particular, the following situation has not been known yet: in lithium ion II Within the range of the potential usable in the secondary battery, no oxidation or reduction reaction was observed by cyclic voltammetry, and it became a stable hydrophilic polymer.

Further, in detail, the hydrophilic polymer of the present invention introduces a polyoxyalkylene group structure by a urea bond formed by a reaction of an isocyanate group and an amine group in the structure of a hydrophilic polymer, The polyoxyalkylene structure is introduced as a soft segment from the urethane prepolymer simultaneously with the polyamidylene structural unit, and imparts durability to a polyimine structure which lacks flexibility and has poor bending resistance. And softness, a hydrophilic polymer which is soft and excellent in adhesion to metals can be obtained.

The hydrophilic polymer of the present invention contains 10% by weight to 99% by weight or 10% by weight to 98% by weight of the structure of the formula (2) in terms of the balance between hydrophilicity and adhesion. In terms of good hydrophilicity, it is 40% by weight to 98% by weight or 50% by weight to 95% by weight, and the most excellent balance between hydrophilicity and adhesion is 60% by weight to 98% by weight. When it is less than 10% by weight, the hydrophilicity is inferior, and if it exceeds 99% by weight, the flexibility is insufficient.

The hydrophilic polymer of the present invention is expressed by the formula (2) with respect to the molar number A of the urethane unit structure represented by the formula (3) in terms of the balance between hydrophilicity and adhesion. The molar number B of the quinone imine unit structure is B/A=1 or more, 30 or less, or more than 1 and 30 or less, and is more than 1 and 10 or less in terms of hydrophilicity, and further hydrophilicity. In terms of improvement, it is more than 1 and 5 or less, and the balance of hydrophilicity and adhesive force is most excellently more than 1 and 2 or less. In the case of less than 1, although the cause is unknown, it will be highly viscous in the reaction and cannot be obtained. Hydrophilic polymer. It is presumed that the reason is that the end of the hydrophilic polymer chain becomes more stable than the polyaminoformate structure having a heteroisocyanic group having high reactivity with a hydroxyl group or an amine group. . If it exceeds 30, hydrophilicity and adhesive force will fall.

In the case where the terminal of the polymer is sealed with a dicarboxylic acid anhydride represented by the formula (4), the hydrophilic polymer of the present invention is passed through 100 parts by weight of the polymer represented by the formula (1). The ratio of the structure in which the dicarboxylic anhydride represented by the formula (4) is sealed is not particularly limited, but the dicarboxylic anhydride represented by the formula (4) is 100 parts by weight based on 100 parts by weight of the polymer represented by the formula (1). The structure to be sealed is preferably from 0.02 part by weight to 100 parts by weight, more preferably from 0.02 part by weight to 50 parts by weight in terms of balance between hydrophilicity and low viscosity, and the balance between hydrophilicity and adhesion is most excellent. In other words, it is preferably from 1 part by weight to 50 parts by weight.

In particular, in order to further improve the binding force between the active material of the secondary battery, particularly the lithium ion secondary battery, and the electrode, the hydrophilic polymer of the present invention preferably exhibits excellent adhesion to metals, particularly copper. In the manner of the T-stripping test (stretching speed of 300 mm/min), the initial adhesion to copper was 0.05 N/mm or more. More preferably, it is 1.0 N/mm or more. In addition to this, aluminum, iron, stainless steel, or the like can be used for the metal.

In particular, in order to further improve the binding force between the active material of the secondary battery, particularly the lithium ion secondary battery, and the electrode, the hydrophilic polymer of the present invention preferably exhibits excellent adhesion to metals, particularly copper. In addition to this, aluminum, iron, stainless steel, or the like can be used for the metal.

The hydrophilic polymer of the present invention can be obtained by using a urethane prepolymer represented by the following formula (6) and a polyazide having an amine group at both terminals represented by the following formula (7). Obtained by reacting an amine prepolymer obtained by reacting a diisocyanate with a polyol, and the polyamidene prepolymer is a tetracarboxylic dianhydride and two The amine is polycondensed in a solvent and passed through polyamic acid to obtain a ruthenium cyclization.

(wherein R ₁ represents a divalent organic group having 4 to 30 carbon atoms, and R ₂ represents a linear or branched polyvalent alkylene group having a carbon number of 2 to 5 having an average molecular weight of 100 to 10,000. Organic base, x means an integer from 1 to 800)

(wherein R ₃ represents a trivalent or higher organic group having one to two aromatic rings having 4 to 30 carbon atoms, R ₄ represents a tetravalent organic group having 4 to 30 carbon atoms, and X represents a carboxyl group or a sulfonic acid group. , y represents an integer from 1 to 800, and a represents an integer from 1 to 4; wherein, in the case where X is a carboxyl group, the number of aromatic rings of R ₃ is 1, and a is 1)

In the case where the terminal of the polymer is to be sealed with a dicarboxylic acid anhydride represented by the formula (4), it can be obtained by using the urethane prepolymer represented by the formula (6) The polymer represented by the formula (1) is obtained by reacting with a polyimine prepolymer having an amine group at both terminals represented by the formula (7), wherein the urethane prepolymer is Obtained by the reaction of a diisocyanate with a polyhydric alcohol, and the polydiimide dianhydride is subjected to polycondensation of a tetracarboxylic dianhydride and a diamine in a solvent to carry out a ruthenium imine. It is obtained by cyclization. Further, the dicarboxylic acid anhydride represented by the following formula (4) is further reacted with the polymer represented by the obtained formula (1).

The urethane prepolymer represented by the formula (6) used for producing the hydrophilic polymer of the present invention can be obtained by the diisocyanate represented by the following formula (8) and the following formula (9) In the reaction of the polyol described, the molar ratio (isocyanate group/hydroxy group) of the isocyanate group to the hydroxyl group in the polyol is in the range of 1 to 2.

OCN-R ₁ -NCO (8)

(wherein R ₁ represents a divalent organic group having 4 to 30 carbon atoms)

HO-R ₂ -OH (9)

(wherein R ₂ represents a linear or branched divalent organic group having a polyoxyalkylene group having a carbon number of 2 to 5 having an average molecular weight of 100 to 10,000)

Examples of the diisocyanate represented by the formula (8) include 4,4'-diphenylmethane diisocyanate (MDI) and 2,4-methylphenylene diisocyanate (2, 4-tolylene diisocyanate, TDI), 2,6-tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), polymeric MDI, dianisidine diisocyanate , diphenyl ether diisocyanate, methyl phenyl diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, diisocyanate methyl ester, m-diphenyl diisocyanate, 2,2,4-trimethyl Hexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, isopropylidene bis(4-cyclohexyl isocyanate), cyclohexylmethane diisocyanate, methylcyclohexane diisocyanate Methylcyclohexane diisocyanate 2 polymer or the like may be used alone or in combination of two or more.

Examples of the polyhydric alcohol represented by the formula (9) include polyether polyols such as polyoxytetramethylene glycol, polypropylene glycol, and polyethylene glycol. These compounds may be used alone or in combination of two or more. use. Further, a polybutadiene polyol, an acrylic polyol, or the like may be used in combination as needed.

The urethane prepolymer can be, for example, an inert gas such as argon or nitrogen. The diisocyanate is obtained by mixing a diisocyanate and a polyol in a predetermined ratio. The closer the ratio of the isocyanate group in the diisocyanate to the hydroxyl group in the polyol, that is, the ratio of the isocyanate group/hydroxy group (the molar ratio) is closer to 1, the polymerization degree of the urethane prepolymer becomes larger, and the molecular weight is higher. increase. In the present invention, the isocyanate group/hydroxy group is added in a ratio (molar ratio) of 1 to 2, or more than 1 and 2 or less, and in consideration of reactivity with the polyimide intermediate prepolymer, it is preferably 1.01. 2. When the ratio of addition of the isocyanate group/hydroxy group (mol ratio) is less than 1, the urethane prepolymer having an isocyanate group at both terminals is not formed, which is not preferable.

In the preparation of the urethane prepolymer, the reaction is carried out at room temperature to 140 ° C in the absence or presence of a catalyst depending on the reactivity of the commonly used diisocyanate. Examples of the catalyst include an organotin compound, an amine compound, and the like. Examples of the organotin compound include dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin bisacetate, tin octylate, and the like. Examples of the amine compound include 1,4-diazabicyclo[2,2,2]octane and the like. The reaction can also be carried out arbitrarily in the presence or absence of a solvent. Examples of the solvent include acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, dimethoxyethane, methoxypropyl acetate, dimethylformamide, dimethylacetamide, and N,N'. - dimethyl-2,5-diazapentanone, N-methylpyrrolidone, and the like. The reaction time is preferably from 1 hour to 24 hours.

The polyimine prepolymer represented by the formula (7) for producing the hydrophilic polymer of the present invention can be represented by a diamine represented by the following formula (10) and a formula (11) below In the reaction of the tetracarboxylic dianhydride, the molar ratio of the diamine to the tetracarboxylic dianhydride (diamine/tetracarboxylic dianhydride) is more than 1 and 2 or less, and then the reaction is carried out. Obtained by dehydration and imidization.

(wherein R ₃ represents a trivalent or higher organic group having one to two aromatic rings having 4 to 30 carbon atoms, X represents a carboxyl group or a sulfonic acid group, and a represents an integer of 1 to 4; wherein, X is In the case of a carboxyl group, the number of aromatic rings of R ₃ is 1, and a is 1)

(wherein R ₄ represents a tetravalent organic group having 4 to 30 carbon atoms)

Examples of the diamine represented by the formula (10) include 3,5-diaminobenzoic acid, 3,4-diaminobenzoic acid, 2,4-diaminobenzoic acid, and 3,5-diamine. Base-trimethylbenzenesulfonic acid, 2,2'-disulfonic acid benzidine, 1,4-diaminobenzene-3-sulfonic acid, 1,3-diaminobenzene-4-sulfonic acid, 4, 4'-Diamino-5,5'-dimethyl-(1,1'-biphenyl)-2,2'-disulfonic acid benzidine. These diamines may be used in combination of two or more kinds as needed. Further, if necessary, p-phenylenediamine, m-phenylenediamine, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylanthracene, 4,4'-diaminodiphenyl Bismuth, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, bis(3-amino-4-hydroxyphenyl)hexafluoropropane, double (3 -Amino-4-hydroxyphenyl)indole, bis(3-amino-4-hydroxyphenyl)propane, bis(3-amino-4-hydroxyphenyl)methylene, bis(4-amine A mixture of -3-hydroxyphenyl)methylene groups is used.

Examples of the tetracarboxylic dianhydride represented by the formula (11) include 4,4'-oxydiphthalic dianhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride. , pyromellitic dianhydride, 3,4,9,10-decanetetracarboxylic dianhydride, 3,3',4,4'-diphenylphosphonium tetracarboxylic dianhydride, 3,3',4, 4'-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 3,3',4,4'-terphenyl tricarboxylic acid dianhydride, 3,3 ', 4, 4'-inter-linked triphenyltetracarboxylic dianhydride. These compounds may be used in combination of two or more kinds as needed. In the present invention, one to four hydrogen atoms of the compounds may be optionally substituted by a carboxyl group, a sulfonic acid group or a hydroxyl group.

The polyimine prepolymer can be cyclized with ruthenium imide by mixing diamine and tetracarboxylic dianhydride in a predetermined ratio under an inert gas atmosphere such as argon or nitrogen. Obtained by reaction. The polycondensation in the synthesis of the polyimine prepolymer is the same as the usual polycondensation reaction, and the closer the ratio of the diamine/tetracarboxylic dianhydride (mol ratio) is to 1, the degree of polymerization of the produced polyamine The larger the size, the more the molecular weight increases. In the present invention, the addition ratio (molar ratio) of the diamine/tetracarboxylic dianhydride is more than 1 and 2 or less, and when it is considered to be reactive with the polyimide intermediate prepolymer, it is preferably 1.01 to 2. When the addition ratio (molar ratio) of the diamine/tetracarboxylic dianhydride is 1 or less, it is not formed in the polyimine prepolymer having both terminal amino groups, which is not preferable.

As the organic solvent used in the synthesis of the polyimine prepolymer, as long as it is The tetracarboxylic dianhydride and the diamine are inert, and the produced polylysine is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone (NMP) and N, N'. - dimethyl acetamide, N,N-dimethylformamide, N-methylformamide, N,N-dimethylacetamide, dimethyl hydrazine, N-methyl hexane Indoleamine, γ-butyrolactone, dimethylimidazoline, cyclobutyl hydrazine, methyl isobutyl ketone, acetonitrile, benzonitrile, phenol, m-cresol, chlorophenol, 4-methylphenol, nitrophenol One type or two or more types can be used as the organic solvent. The amount of the organic solvent to be used is not particularly limited as long as the reaction between the tetracarboxylic dianhydride and the diamine can be carried out efficiently. It is preferred that the concentration of the tetracarboxylic dianhydride and the diamine be 1% by weight. ~50% by weight, more preferably 5% by weight to 40% by weight. Further, toluene, acetone, tetrahydrofuran, xylene or the like may be added in any ratio which does not inhibit the reaction.

Usually, a polyamic acid as a polyimide precursor is obtained by reacting a tetracarboxylic dianhydride with a diamine at a temperature of 100 ° C or lower in the organic solvent. Then, the ruthenium imidization is preferably carried out at a reaction temperature of from 100 ° C to 300 ° C to obtain a polyamidimide prepolymer. In the case of imidization, a base such as triethylamine, isoquinoline, pyridine or methylmorpholine may be added as a catalyst. Further, the water produced by the by-product is azeotroped with a non-polar solvent such as toluene and removed to the outside of the system, and the reaction can be carried out. If necessary, a reaction liquid may be added to a solvent in which a polyimine imide such as water, methanol or ethanol is insoluble, and the polymer may be precipitated and dried to take out the polyimine prepolymer. Further, the reaction solution of the polyamidene prepolymer may be used for the reaction with the urethane prepolymer without separating the polyimine prepolymer.

The reaction of the urethane prepolymer with the polyimine prepolymer can be optionally It is carried out in the presence of an organic solvent in the absence of a solvent. In the case of carrying out in the presence of an organic solvent, it is preferred to add the urethane prepolymer and the polyimine prepolymer to the organic solvent in a predetermined ratio and mix them in argon, nitrogen, etc. The reaction is carried out under an inert gas atmosphere to obtain a reaction liquid containing a hydrophilic polymer. In order to apply the reaction liquid and the active material as a binder, it is preferred to form a homogeneous reaction liquid in which an insoluble gel component is not present.

The reaction liquid containing the hydrophilic polymer obtained by reacting the urethane prepolymer with the polyimine prepolymer exhibits a low temperature due to the presence of a soft phase due to the urethane moiety. Glass transition temperature below 25 ° C).

The composition at the time of obtaining the reaction of the hydrophilic polymer of the present invention: polyimine fraction = (addition amount of polyimine prepolymer) / (addition amount of polyamidene prepolymer + uric acid) The amount of the ester prepolymer added is from 100% by weight to 99% by weight, preferably from 10% by weight to 98% by weight, more preferably from 40% by weight to 98% by weight, most preferably from 60% by weight to 98% by weight. %, particularly preferably in the range of 80% by weight to 98% by weight. When it is less than 10% by weight, the hydrophilicity is inferior, and if it exceeds 99% by weight, the flexibility is insufficient. Further, the hydrophilic polymer of the present invention is a urethane prepolymer represented by the formula (6), and the polyamidene prepolymer represented by the formula (7) is more than 1 and 30. Hereinafter, the reaction is preferably carried out under conditions of 1 or more and 2 or less, more preferably 1 or more and 2 or less. In the case of less than 1, the hydrophilicity is remarkably lowered, or it is solidified (gelled) in the reaction. In the case of more than 30, the hydrophilicity also decreases. The molecular weight of the urethane prepolymer represented by the formula (6) can be determined by calculation based on the degree of polymerization determined by the addition of the diisocyanate compound and the polyol. Alternatively, it can be obtained by a known molecular weight measurement method such as Gel Permeation Chromatography (GPC). The molecular weight of the polyamidene prepolymer represented by the formula (7) can be determined by calculation based on the degree of polymerization determined by the addition of a diamine and an acid anhydride, or can be determined by a known molecular weight such as GPC. Determined by the method. Details of the polyimide fraction are shown below.

<Polyimine fraction>

Polyimine fraction (% by weight) = [W _PI / (W _PU + W _PI )]

W _PU : urethane prepolymer addition amount

W _PI : polyamidimide prepolymer addition amount

The molecular weight used for the molar ratio of the reaction between the urethane prepolymer and the polyimine prepolymer can be calculated or a value obtained by a known molecular weight measurement method such as GPC can be used.

The organic solvent which can be used for the reaction of the urethane prepolymer and the polyimine prepolymer is not particularly limited as long as it can be used for synthesizing a polyimine prepolymer and is inert to an isocyanate group. For example, N-methyl-2-pyrrolidone (NMP), N,N'-dimethylacetamide, N,N-dimethylformamide, γ-butyrolactone, etc. are mentioned. Usually, the reaction is carried out at a temperature of from 0 ° C to 150 ° C, preferably from 10 ° C to 100 ° C. The reaction time is, for example, 1 hour to 72 hours, and preferably 1 hour to 42 hours. When the reaction is carried out under no solvent conditions, it may be carried out in an extruder equipped with a heating mechanism having an exhaust system in addition to a usual stirred tank type reactor.

The reaction between the hydrophilic polymer represented by the formula (1) and the dicarboxylic anhydride represented by the formula (4) can be carried out arbitrarily in the presence of an organic solvent or in the absence of a solvent. When it is carried out in the presence of an organic solvent, the hydrophilic polymer represented by the formula (1) and the dicarboxylic anhydride represented by the formula (4) can be added to the organic solvent at a predetermined ratio and mixed. The reaction is carried out under an inert gas atmosphere such as argon or nitrogen to obtain a reaction liquid containing a hydrophilic polymer. In addition, an organic solvent may be added to the reaction liquid or mixture obtained by reacting the urethane prepolymer with the polyimine prepolymer, and the dicarboxylic anhydride represented by the formula (4) may be added. The reaction is carried out under an inert gas atmosphere such as nitrogen to obtain a reaction liquid containing a hydrophilic polymer.

The dicarboxylic acid anhydride represented by the formula (4) is one in which the dicarboxylic acid is subjected to intramolecular dehydration condensation, and examples thereof include phthalic anhydride, 2,3-naphthalene dicarboxylic anhydride, malonic anhydride, and phenyl group. Ethylene phthalic anhydride, 1,8-naphthalene dicarboxylic anhydride, and the like.

The amount of the dicarboxylic acid anhydride represented by the formula (4) used in the production is not particularly limited, and is preferably 0.02 to 100 parts by weight based on 100 parts by weight of the polymer represented by the formula (1). In terms of the balance between the hydrophilicity and the low viscosity, it is more preferably from 0.02 part by weight to 50 parts by weight, and further preferably from 1 part by weight to 50 parts by weight in terms of improving the viscosity.

In order to apply the reaction liquid and the active material as a binder, it is preferred to form a uniform reaction liquid in which an insoluble gel component is not present.

A dicarboxylic acid anhydride other than the dicarboxylic acid anhydride represented by the formula (4) can also be used as needed. For example, 4-cyclohexene-1,2-dicarboxylic anhydride, cyclohexane-1,2-dicarboxylate Anhydride, 4-methylcyclohexane-1,2-dicarboxylic anhydride, 3-methylphthalic anhydride, 4-methylphthalic anhydride, 4-tert-butylphthalic anhydride, 3-fluorophthalic anhydride, 4-fluorophthalic anhydride, tetrafluorophthalic anhydride, succinic anhydride, butyl succinic anhydride, n-octyl succinic anhydride, dodecyl succinic anhydride , tetrapropenyl succinic anhydride, tetradecyl succinic anhydride, octadecyl succinic anhydride, allyl succinic anhydride, 2-buten-1-yl succinic anhydride, 2-dodecene-1 - butyl succinic anhydride, 2,3-dimethyl maleic anhydride, glutaric anhydride, citraconic anhydride, allyl nadic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, p- Trimethoxydecyl)phenylsuccinic anhydride, m-(trimethoxydecyl)phenylsuccinic anhydride, trimethoxydecylpropyl succinic anhydride, triethoxydecyl propyl succinic anhydride Nadick Anhydride, citraconic anhydride, 1,2-naphthalene dicarboxylic anhydride, 2,3-naphthalene dicarboxylic anhydride, 2,3-biphenyldicarboxylic anhydride, 3,4-biphenyldicarboxylic anhydride, 1,2, 3,6-tetrahydrophthalic anhydride, 1,2-cyclohexanedicarboxylic anhydride, methyl-5-norbornene-2,3-dicarboxylate Anhydride.

The dicarboxylic acid anhydride may be used alone or in combination of two or more.

The reaction between the hydrophilic polymer represented by the formula (1) and the tetracarboxylic dianhydride is not particularly limited, and the reaction can be carried out at a temperature of 100 ° C or lower in an organic solvent or without a solvent, and more preferably, The reaction is carried out at a temperature of from 100 ° C to 300 ° C to obtain a hydrophilic polymer in which the terminal of the polymer represented by the formula (1) is sealed with a dicarboxylic acid anhydride represented by the formula (4). When the reaction is carried out at a temperature of from 100 ° C to 300 ° C, a base such as triethylamine, isoquinoline, pyridine or methylmorpholine may be added as a catalyst. Further, the water generated by the secondary reaction may be azeotropically removed from the nonpolar solvent such as toluene to be removed from the system to carry out the reaction. If necessary, the reaction solution may be added to a solvent in which the polyamidimide prepolymer such as water, methanol or ethanol is insoluble to precipitate the polymer. The hydrophilic polymer was taken out.

The solution for a binder of the present invention can be directly used as a reaction liquid of an organic solvent solution of the hydrophilic polymer of the present invention. In addition, the organic solvent which can be used other than this is not particularly limited as long as it can dissolve the hydrophilic polymer, and examples thereof include N-methyl-2-pyrrolidone (NMP) and N,N'-dimethylacetamidine. Amine, N,N-dimethylformamide, monomethylformamide, γ-butyrolactone, monomethylformamide, p-chlorophenol, 4-methylphenol, o-dichlorobenzene, phenol, Chlorobenzene, etc. Other usage patterns are as follows.

In general, an aqueous solution of an aqueous polymer or an aqueous organic solvent solution is synthesized by a special polymerization method using water as a medium by emulsion polymerization or suspension polymerization. For the hydrophilic polymer of the present invention, an alkali metal hydroxide or an alkali metal is used. A carbonate, a tertiary amine compound, a quaternary amine compound or ammonia is reacted with the hydrophilic polymer of the present invention to obtain a salt of a hydrophilic polymer, thereby obtaining a salt comprising water and an organic solvent or an aqueous organic solvent. The solution for the binder (aqueous solution or aqueous organic solvent solution). The method is not particularly limited, and 5 parts by weight to 1000 parts by weight of an alkali metal hydroxide, an alkali metal carbonate, a tertiary amine compound, a quaternary amine compound or may be added to 100 parts by weight of the hydrophilic polymer. Ammonia, after forming a salt with a hydrophilic polymer, adding water, performing aqueous solution or solution of an aqueous organic solvent, and preparing a solution for a binder. Further, drying under reduced pressure or an organic solvent in which a reactant of a urethane prepolymer and a polyamidiminated prepolymer is added to a poor solvent such as water or a hydrophilic solvent such as methanol or hexane After the solution is precipitated and dried, it is dispersed or dissolved in 5 parts by weight to 1000 parts by weight of an alkali metal hydroxide, an alkali metal carbonate, and the like, with respect to 100 parts by weight of the hydrophilic polymer. In the aqueous solution of the amine compound, the quaternary amine compound or ammonia, the aqueous solution or the aqueous organic solvent is dissolved to prepare a solution for the binder. The method of forming a salt can use any of the presence or absence of an organic solvent. The organic solvent is not particularly limited as long as it can dissolve the hydrophilic polymer, and examples thereof include N-methyl-2-pyrrolidone (NMP), N,N'-dimethylacetamide, and monomethyl B. Indoleamine, N,N-dimethylformamide, and the like. Further, the hydrophilic polymer is added to an aqueous solution in which a predetermined amount of an alkali metal hydroxide, an alkali metal carbonate, a tertiary amine compound, a quaternary amine compound or ammonia is dissolved, and stirred to obtain a hydrophilicity. An aqueous solution of a polymer or an aqueous organic solvent solution. In order to promote the solution of the aqueous solution or the aqueous organic solvent, the temperature may be increased at a temperature of 30 ° C to 150 ° C, or ultrasonic treatment may be performed. After the dissolution, water may be further added or concentrated.

The hydrophilic polymer of the present invention can be used as a reaction liquid (solution for a binder) containing the organic solvent, or as a desired form (solution for a binder) of an aqueous solution or an aqueous organic solvent solution. Since it has excellent adhesion to metals, it is suitable for a binder that bonds an active material of a secondary battery to an electrode. Examples of the active material include carbon, ruthenium, tin, aluminum, titanium, ruthenium or iron. For example, graphite, hard carbon, niobium, tantalum oxide, niobium carbide, tin compound, alloy of niobium and aluminum, alloy of niobium and tin, alloy of niobium and titanium, alloy of aluminum and tin, alloy of tin and titanium, etc. .

Since the hydrophilic polymer of the present invention is soft and exhibits excellent adhesion to metals, it is particularly suitable for a binder in which a secondary battery, particularly an active material of a lithium ion secondary battery, is bonded to an electrode.

When the solution for a binder of the present invention is produced, a buffer, a thickener, a condensed phosphate, a dispersant may be added for the purpose of stabilizing or reducing the amount of the aqueous organic solvent solution and the organic solvent solution. , adhesion-imparting agent, pH adjuster, antifoaming agent, preservative, film-forming auxiliary, surfactant, and anti-freezing agent. When the hydrophilic polymer of the present invention is coated and dried with a metal, it is not particularly required to be subjected to high-temperature treatment like polyacrylic acid, and coating drying can be carried out according to a usual method, so that deformation of the metal foil does not occur.

The lithium negative electrode active material used in the present invention is preferably a composite material having an average particle diameter of 1 μm to 40 μm, and contains Si or a Si alloy having an average particle diameter of 0.01 μm to 5 μm, carbonaceous matter, carbonaceous material, and graphite.

Hereinafter, the negative electrode active material for a lithium ion secondary battery used in the present invention will be described in detail.

The Si in the present invention is a general-grade metal ruthenium having a purity of about 98%, a metal ruthenium of a chemical grade of 2N to 4N in purity, and a high-purity polycrystalline ruthenium higher than 4N obtained by chlorination and distillation purification. Ultra-high-purity single crystal germanium obtained by a precipitation step by a single crystal growth method, fines such as polishing or cutting of a wafer generated in a semiconductor manufacturing process, and a defective wafer which is defective in the manufacturing process The purity above the metal ruthenium is not particularly limited.

The Si alloy in the present invention is an alloy containing Si as a main component. In the Si alloy, the element contained in addition to Si is preferably one or more elements of Groups 2 to 15 of the periodic table, and it is preferable that the melting point of the phase contained in the alloy is 900 ° C or higher. The choice and / or amount of addition.

In the negative electrode active material for a lithium ion secondary battery of the present invention, the Si compound has an average particle diameter (D50) of from 0.01 μm to 5 μm, more preferably from 0.05 μm to 0.5 μm. When the thickness is less than 0.01 μm, the decrease in capacity or initial efficiency due to surface oxidation is rapid. When the thickness is more than 5 μm, cracks are rapidly generated due to expansion due to lithium insertion, and the cycle is likely to rapidly deteriorate. Further, the average particle diameter (D50) is a volume average particle diameter measured by a laser particle size distribution meter.

The composite material containing the Si compound and the carbonaceous material or the carbonaceous material and graphite of the present invention has an average particle diameter of 1 μm to 40 μm. When the average particle diameter of the composite particles is less than 1 μm, it becomes bulky and it is difficult to produce a high-density electrode, and since it is a fine powder having a small particle diameter, there is a problem in handling. When the particle diameter exceeds 40 μm, the sheet cannot be produced without increasing the coating thickness of the negative electrode. Therefore, the electrode sheet resistance is increased, and the discharge capacity or cycle characteristics are lowered.

The carbonaceous material in the present invention is an amorphous or microcrystalline carbon material, and is easily graphitized carbon (soft carbon) graphitized by heat treatment at over 2000 ° C, and hardly graphitizable carbon (hard carbon) which is difficult to graphitize. ).

The graphite in the present invention is a crystal in which a graphene layer is parallel to the c-axis, and includes natural graphite obtained by purifying ore, artificial graphite obtained by graphitizing petroleum or stone carbon pitch, and the shape of the raw material. It is scaly, elliptical or spherical, cylindrical or fibrous. Further, after the graphite is subjected to an acid treatment or an oxidation treatment, it is expanded by heat treatment, and a part of the graphite layer is peeled off to become an object of the accordion-like expanded graphite or expanded graphite, or the interlayer is made by ultrasonic waves or the like. Exfoliated graphene or the like can also be used.

In the negative electrode active material for a lithium ion secondary battery of the present invention, the amount of the Si compound present in the composite is preferably 10% by weight or more and 80% by weight or less, more preferably 15% by weight to 50% by weight. When the content of the Si compound is less than 10% by weight, a sufficiently large capacity compared to the conventional graphite cannot be obtained, and when it is more than 80% by weight, the cycle is liable to be rapidly deteriorated.

In the negative electrode active material for a lithium ion secondary battery of the present invention, the amount of the carbide added to the composite compound is preferably 0.5% by weight or more and 99.5 parts by weight based on the total amount of the composite compound and the added carbide. % or less, more preferably 10% by weight to 90% by weight, particularly preferably 20% by weight to 80% by weight.

In the negative electrode active material for a lithium ion secondary battery of the present invention, the particle diameter of the added carbide is preferably from 0.1 μm to 40 μm. When the particle diameter is less than 0.1 μm, since it is very fine particles, it is difficult to uniformly mix with the composite particles. When the particle diameter exceeds 40 μm, the sheet cannot be produced without increasing the coating thickness of the negative electrode. Therefore, the electrode sheet resistance is increased, and the discharge capacity or cycle characteristics are lowered.

In the negative electrode active material for a lithium ion secondary battery of the present invention, it is preferable that the Si compound and the carbonaceous material are sandwiched between a thin layer of graphite having a thickness of 0.5 μm or less, and it is preferable that the structure is expanded to The active material particles are formed by laminating and/or meshing, and the graphite thin layer is bent in the vicinity of the surface of the active material particles to cover the composite particles, and graphite or a carbonaceous material is disposed around the composite particles. When the thickness of the graphite thin layer exceeds 0.5 μm, there is a possibility that the electron conductivity of the graphite thin layer is lowered.

Then, the negative electrode active material for a lithium ion secondary battery of the present invention is produced. The method of making is explained.

The method for producing a negative electrode active material for a lithium ion secondary battery of the present invention comprises the steps of mixing a Si compound, a carbon precursor, and optionally graphite; and performing granulation. a step of compacting; a step of pulverizing the mixture to form composite particles; a step of calcining the composite particles in an inert gas atmosphere; and a step of mixing the composite with the carbide.

As the Si compound as a raw material, a powder having an average particle diameter (D50) of 0.01 μm to 5 μm is used. In order to obtain a Si compound having a predetermined particle diameter, a raw material (ingot, wafer, powder, or the like) of the Si compound is pulverized by a pulverizer, and a classifier is used as the case may be. In the case of a block such as an ingot or a wafer, first, it can be powdered using a coarse pulverizer such as a jaw crusher. Then, the micro-pulverization can be performed using, for example, a ball mill or a medium agitating mill to move the pulverizing medium such as a ball or a bead, and the object to be crushed by the impact force or the frictional force or the compressive force caused by the kinetic energy. Smashing; or a roll mill that pulverizes by a compressive force caused by a roller; and a jet mill that causes the scraped object to collide with the inner lining material at a high speed or cause the particles to collide with each other, and pulverizes by the impact force caused by the impact. a hammer mill, a pin mill, a disc mill, which is crushed by an impact force caused by rotation of a roller to which a hammer, a blade, a needle, or the like is fixed; or a colloid mill or a high pressure using a shear force; Wet-type contra-type collision disperser "Ultimaizer" and the like.

For pulverization, both wet and dry can be used. Further, when finely pulverizing, for example, a very fine particle can be obtained by gradually reducing the diameter of the bead or the like by using a wet bead mill. In addition, in order to adjust the particle size distribution after pulverization, dry can be used. Graded or wet graded or sieved graded. Dry classification mainly uses air flow, dispersion or separation (separation of fine particles and coarse particles), collection (separation of solid and gas), and discharge process, in order not to interfere with particles, shape of particles, The classification efficiency is lowered by the disturbance of the air flow, the velocity distribution, the electrostatic influence, etc., and the pretreatment (adjustment of moisture, dispersibility, humidity, etc.) or the adjustment of the moisture or oxygen concentration of the gas stream used is performed before the classification. In the type in which the dry classifier is integrated, it can be pulverized and classified at one time to have a desired particle size distribution.

Other methods for obtaining a Si compound having a predetermined particle diameter include a method of heating a Si compound by plasma or laser to evaporate it, and solidifying it in an inert gas; using a gas raw material by chemical vapor deposition (Chemical Vapor Deposition, CVD) or plasma CVD, etc., which are suitable for obtaining ultrafine particles of 0.1 μm or less.

The carbon precursor of the raw material is not particularly limited as long as it is a carbon-based compound mainly composed of carbon and is carbonaceous by heat treatment in an inert gas atmosphere, and may be used: petroleum-based pitch, stone-carbon-based pitch, and synthetic asphalt. , tar, cellulose, sucrose, polyvinyl chloride, polyvinyl alcohol, phenolic resin, furan resin, decyl alcohol, polystyrene, epoxy resin, polyacrylonitrile, melamine resin, acrylic resin, polyamidoximine resin , polyamide resin, polyimide resin, and the like.

As the raw material, graphite may be made of natural graphite or artificial graphite obtained by graphitizing petroleum or stone carbon pitch, and a scaly, elliptical or spherical shape, a cylindrical shape, or a fibrous shape may be used. Further, after the graphite is subjected to an acid treatment or an oxidation treatment, it is expanded by heat treatment, and a part of the graphite layer is peeled off to become an accordion. A pulverized product of expanded graphite or expanded graphite, or graphene obtained by separating layers by ultrasonic waves or the like may be used. The graphite of the raw material is adjusted to a usable size in advance in the mixing step, and the particle size before mixing is 1 μm to 100 μm in the case of natural graphite or artificial graphite, and is a pulverized product or graphene of expanded graphite or expanded graphite. It is about 5μm~5mm.

In the case where the carbon precursor is softened or liquefied by heating, the Si compound, the carbon precursor, and optionally the graphite may be mixed by heating the Si compound and the carbon precursor. Furthermore, it is carried out by kneading the graphite as needed. Further, in the case where the carbon precursor is soluble in the solvent, the Si compound can be dispersed and mixed in the solution in which the carbon precursor is dissolved by introducing a Si compound, a carbon precursor, and optionally graphite into the solvent. The carbon precursor, and optionally the graphite, is then removed by removing the solvent. The solvent to be used is not particularly limited as long as it is a carbon-soluble precursor. For example, when asphalt or tar is used as the carbon precursor, quinoline, pyridine, toluene, benzene, tetrahydrofuran, creosote oil, or the like can be used, and in the case of using polyvinyl chloride, tetrahydrofuran or cyclohexane can be used. For the ketone, nitrobenzene or the like, in the case of using a phenol resin or a furan resin, ethanol, methanol or the like can be used.

As a mixing method, a kneading machine (kneader) can be used in the case of heating and softening the carbon precursor. In the case of using a solvent, in addition to the kneading machine, a Nauta mixer, a Loedige mixer, a Henschel mixer, a high-speed mixer can be used. (high-speed mixer), homomixer (homomixer), etc. In addition, using these devices for jacketing After heating, the solvent is removed by a vibration dryer, a paddle dryer, or the like.

By using the devices, the carbon precursor is continuously subjected to a certain degree of solidification or agitation during the solvent removal, thereby granulating the Si compound, the carbon precursor, and optionally the mixture with the graphite. Compaction. Further, a mixture such as a roller compactor is used to compress the carbon precursor or the mixture after the solvent is removed, and the mixture is coarsely pulverized by a pulverizer to granulate. Compaction. The granulation is in terms of the ease of operation in the subsequent pulverization step. The size of the compacted material is preferably from 0.1 mm to 5 mm.

Granulation. The pulverization method of the compacted material is preferably a dry pulverization method such as a ball mill or a medium agitating mill, which pulverizes the crushed material by a compressive force; the roll mill pulverizes by a compressive force caused by the roller; and a jet mill, Causing the object to collide with the inner lining material at a high speed or colliding the particles with each other, and pulverizing by the impact force caused by the impact; the hammer mill, the pin mill, the disc grinder, the hammer, the blade, The impact force caused by the rotation of the roller of the needle or the like is pulverized by the debris. Further, in order to adjust the particle size distribution after the pulverization, dry classification such as wind classification or sieving is used. In the type in which the pulverizer and the classifier are integrated, pulverization and classification can be performed at one time to set a desired particle size distribution.

The composite particles obtained by the pulverization are calcined in an inert gas atmosphere such as an argon gas or a nitrogen gas stream.

The negative electrode for a lithium ion secondary battery of the present invention preferably has a content of the negative electrode active material of 60% by weight or more and 99% by weight or less, and a hydrophilic polymer. The (the binder) content is 1% by weight or more and 40% by weight or less, and contains 0.01% by weight or more and 20% by weight or less of the conductive carbon compound. When the amount of the negative electrode active material is less than 60% by weight, the discharge capacity as the negative electrode cannot be ensured, and if it is more than 99% by weight, the adhesion or conductivity cannot be ensured, and the cycle characteristics may be lowered. In addition, when the content of the hydrophilic polymer (adhesive) exceeds 40% by weight and/or the conductive carbon compound exceeds 20% by weight, the content of the negative electrode active material cannot be ensured, and the initial discharge capacity may be lowered.

When the content of the hydrophilic polymer (adhesive) is less than 1% by weight and/or the conductive carbon compound is less than 0.01% by weight, the adhesion or conductivity cannot be ensured, and the cycle characteristics may be lowered.

Next, a method of producing the negative electrode for a lithium ion secondary battery of the present invention will be described.

The negative electrode active material for a lithium ion secondary battery described above, the hydrophilic polymer (adhesive) having high flexibility and high adhesion, and a conductive carbon compound are mixed and dispersed in water. An organic solvent or an aqueous organic solvent is used to form a slurry, and then the slurry is applied onto a collecting electrode to be coated, and then the active material, the binder, the conductive carbon compound, and the collector constituting the electrode are formed by press molding. Integration, drying and removing water and organic solvent contained in the electrode. Further, in addition to the application of the slurry to the collector, there is a method of kneading the active material, the binder, the conductive carbon compound, and the solvent to form a shape such as a sheet or a pellet.

Further, a negative electrode can also be produced by using a solution in which a hydrophilic polymer (adhesive) is dissolved in water, an organic solvent or an aqueous organic solvent.

Further, the electrode drying temperature after press molding is sufficient at 150 ° C or lower. Since the purpose of this drying is to remove the water and the organic solvent remaining in the electrode, it may be carried out under vacuum, air, or an inert gas such as nitrogen at a temperature of about 100 °C. Usually, in order to carry out polyimidization, a relatively high heat treatment temperature of about 200 ° C to 400 ° C is required, but the hydrophilic polymer (adhesive) of the present invention has become a low molecular weight sulfimine at the time of electrode fabrication. The adhesion can be exhibited by drying at a low temperature.

The type of the conductive agent of the present invention is not particularly limited, and any of the batteries to be formed may be any material that does not cause decomposition or deterioration of electron conductivity. Specifically, Al, Ti, Fe, Ni, and Cu may be used. Metal powder or metal fiber such as Zn, Ag, Sn, Si, or natural graphite, artificial graphite, various coke powders, mesophase carbon, vapor-grown carbon fiber, pitch-based carbon fiber, polyacrylonitrile (PAN) It is a graphite such as carbon fiber or various resin calcined bodies. The amount of the conductive agent added is 0% by weight to 20% by weight, and more preferably 1% by weight to 10% by weight based on the entire negative electrode material. When the amount of the conductive agent is small, there is a case where the conductivity of the negative electrode material is lacking, and the initial resistance tends to be high. On the other hand, there is a concern that an increase in the amount of the conductive material causes a decrease in the battery capacity.

The solvent is not particularly limited, and examples thereof include N-methyl-2-pyrrolidone, dimethylformamide, isopropyl alcohol, and pure water, and the amount thereof is not particularly limited.

As the current collector, for example, a foil such as nickel or copper, a mesh or the like can be used.

For example, it can be integrated by a forming method such as a roll or a press.

The negative electrode obtained in the manner described is connected to the positive electrode via a separator In the opposite arrangement, the electrolyte solution is injected, whereby a lithium secondary battery having excellent characteristics such as excellent cycle characteristics, high capacity, and high initial efficiency can be produced as compared with a lithium secondary battery using conventional niobium for a negative electrode material.

As the material used in the positive electrode, for example, LiNiO ₂ , LiCoO ₂ , LiMn ₂ O ₄ , LiNi _x Mn _y Co _1-xy O ₂ , LiFePO ₄ , Li _0.5 Ni _0.5 Mn _1.5 O ₄ , Li ₂ MnO ₃ -LiMO may be used. ₂ (M=Co, Ni, Mn), etc., used alone or in combination.

As the electrolytic solution, a so-called organic electrolytic solution in which a lithium salt such as LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiBF ₄ or LiSO ₃ CF _{3 is} dissolved in, for example, ethyl carbonate, diethyl carbonate or dimethyl carbonate can be used. It is a non-aqueous solvent such as oxyethane, dimethyl carbonate, tetrahydrofuran or propyl carbonate. Further, an ionic liquid using imidazolium, ammonium, and pyridinium type cations can be used. The counter anion is not particularly limited, and examples thereof include BF ₄ ^- , PF ₆ ^- , (CF ₃ SO ₂ ) ₂ N ^- and the like. An ionic liquid can be used in combination with the organic electrolyte solvent. A solid electrolyte interface layer (SEI) forming agent such as vinylene carbonate or ethyl fluorocarbonate may be added to the electrolytic solution.

Further, the salt may be mixed with polyethylene oxide, polyphosphazene, polyaziridine, polyvinyl sulfide or the like, or a derivative, a mixture thereof, a composite or the like. Solid electrolyte. In this case, the solid electrolyte may also serve as a separator, and the separator may not be required. For the separator, for example, a nonwoven fabric, a cloth, a microporous film containing a polyolefin such as polyethylene or polypropylene as a main component, or a combination thereof may be used. By.

Then, a charge and discharge device was used to evaluate battery performance. Battery evaluation conditions There are no particular restrictions, and examples thereof include a constant current method, a constant current constant voltage method, a constant capacity method, a constant power method, and a pulse method. In particular, the constant current method and the constant current constant voltage method are often used as battery characteristics evaluations in which the Depth of Discharge (DOD) is close to 100%. The constant capacity method or the constant power method can also be used for shallower charge and discharge depth (DOD). Battery evaluation in the area.

The hydrophilic polymer of the present invention is excellent in adhesion to metal, has low environmental load, and is electrochemically stable when used in a secondary battery, and thus can be applied to bonding of an active material of a secondary battery to an electrode. Even if the negative electrode active material containing a composite of a ruthenium compound and a carbonaceous material is heat-treated at a relatively low drying temperature, it is homogeneously dispersed with a binder exhibiting high adhesion, thereby suppressing repeated charge and discharge. The micronization of the active material gives a negative electrode having a high capacity and exhibiting excellent cycle characteristics. Further, it can also be applied to a sizing agent such as a circuit board, an insulating film of a semiconductor device, or a composite material.

11‧‧‧ Graphite or carbide layer in the reflected electron image of the composite profile (gray)

12‧‧‧Micro-Si particles in the electron image of the composite profile (white)

13‧‧‧Composite particles

14‧‧‧Adhesive

Fig. 1 is a graph showing the results of Cyclic Voltammetry (CV) measurement of a hydrophilic polymer.

2 is a view showing an initial charge and discharge curve of a battery produced using a hydrophilic polymer.

Fig. 3 is a view showing an initial charge and discharge curve of a battery produced using a hydrophilic polymer.

4 is a view showing an initial charge and discharge curve of a battery produced using a hydrophilic polymer.

Fig. 5 is a view showing an initial charge and discharge curve of a battery produced using a hydrophilic polymer.

Fig. 6 is a cross section (reflected electron image) of the composite particles (low magnification).

Fig. 7 is a cross section (reflected electron image) of the composite particles (high magnification).

Fig. 8 is a scanning electron microscope (SEM) photograph of the electrode surface after the negative electrode sheet obtained in Example 72 was produced.

Fig. 9 is a SEM photograph of the surface of the electrode after the preparation of the negative electrode sheet obtained in Example 73.

Fig. 10 is a SEM photograph of the surface of the electrode after the preparation of the negative electrode sheet obtained in Comparative Example 13.

Fig. 11 is a SEM photograph of the surface of the electrode after the preparation of the negative electrode sheet obtained in Comparative Example 15.

[Examples]

Hereinafter, the present invention will be further described in detail by way of examples, but the invention is not limited thereto.

In addition, the values used in the following examples and the like are obtained by measurement using the following measurement methods.

<molecular weight>

The molecular weight of the urethane prepolymer is based on esterification by diisocyanate The degree of polymerization determined by the addition of the compound and the polyol was calculated.

r ₁ = addition of a molar amount of a diisocyanate compound to a mole number of a polyol

Degree of polymerization of urethane prepolymer (N _A )=(r ₁ +1)÷(r ₁ -1)

The molecular weight of the urethane prepolymer = (N _A ÷ 0.5 × molecular weight of the diisocyanate compound) + (N _A ÷ 0.5 × molecular weight of the polyol)

The molecular weight of the polyimine prepolymer is calculated based on the degree of polymerization determined by the addition of the diamine compound and the acid anhydride.

r ₂ = addition of a molar amount of a diamine compound to a molar amount of tetracarboxylic dianhydride

Degree of polymerization of polyimine prepolymer (N _B )=(r ₂ +1)÷(r ₂ -1)

Molecular weight of polyimine prepolymer = (N _B ÷ 0.5 × molecular weight of diamine compound) + (molecular weight of N _B ÷ 0.5 × tetracarboxylic dianhydride) - degree of polymerization × 18

<Infrared Absorption Spectroscopy>

The infrared absorption spectrum was measured using a system 2000 Fourier Transform-Infrared Spectroscopy (FT-IR) manufactured by PERKIN ELMER.

<Hydrophilic evaluation>

80 g of a 1% by weight solution of N-methylpyrrolidone was prepared, and 100 parts by weight of sodium hydroxide was added to 100 parts by weight of the hydrophilic polymer, and 320 g of water was added thereto for 1 hour. The hydrophilicity of the polymer was evaluated.

(1) Formation of aqueous organic solvent solution: ◎

(2) Generation of a little condensate: ○

(3) Generation of a large amount of aggregates: △

(4) Formation of a block in hydrogenation: ×

<Evaluation of adhesion>

A 10% by weight solution of N-methylpyrrolidone having a hydrophilic polymer was prepared and applied to a strip of 2×10 cm long copper foil by a doctor blade, followed by drying (hot air drying at 120 ° C for 2 hours). The coating film obtained was used for the adhesion test at 120 ° C for 2 hours under reduced pressure.

Copper foil: C122OR (100mm × 100mm × thickness 0.05mm) manufactured by Japan Test Panel Co., Ltd.

<Bending test 1>

The metal foil coated with the hydrophilic polymer and dried was bent to 180°, and the peeling of the polymer in the bent portion was visually evaluated. The visual criteria are as follows.

(1) No peeling off (excellent adhesion): ◎

(2) It is seen that the coated surface is slightly peeled off (good adhesion): ○

(3) peeling off and slightly exposing the metal foil: △

(4) peeling off and completely exposing the metal foil: ×

<Bending test 2>

The metal foil obtained by applying the hydrophilic polymer and dried was repeatedly bent from a horizontal state to a tube having a diameter of 1 cm so that the coating surface was outside, and the number of times until the coating film was peeled off was measured.

<Polyimide fraction (ratio of the structure of the general formula (2) in the polymer)>

Polyimine fraction (% by weight) = [W _PI / (W _PU + W _PI )]

W _PU : urethane prepolymer addition amount

W _PU : polyamidimide prepolymer addition amount

<Measurement of glass transition temperature>

The measurement of the glass transition temperature was carried out by using a differential scanning calorimeter DSC200F3 manufactured by Netzsch Co., Ltd. in a temperature range of -100 ° C to 250 ° C under a nitrogen atmosphere at a temperature rising condition of 10 ° C / min.

<Evaluation of Initial Adhesive Force by T-Peel Test with Copper Foil>

Evaluation of initial adhesion by T-stripping test with copper foil This is done as follows.

1. The reaction solution of the hydrophilic polymer was cast on a glass plate, dried at 120 ° C for 2 hours, and further dried under reduced pressure at 120 ° C to prepare a film having a thickness of 100 μm.

2. The obtained film was cut into a width of 35 mm × a length of 70 mm, and a copper foil: C122OR (100 mm × 100 mm × thickness 0.05 mm) manufactured by Nippon Test Panel Co., Ltd. and a hot press device were used at 180 ° C for 1 minute. fit. The bonded sample was punched into a strip shape having a width of 15 mm as a measurement sample for adhesion.

3. Regarding the adhesion, the peel strength (n=3) was measured by a T-stripping test (tensile speed: 300 mm/min) as the adhesion.

<Circular voltammetry (CV) measurement>

A 12% by weight solution of N-methylpyrrolidone having a hydrophilic polymer was prepared and coated on a C122OR (100 mm × 100 mm × thickness 0.05 mm) copper foil manufactured by Nippon Test Panel Co., Ltd. using a 150 μm doctor blade. Thereafter, the mixture was dried (120 ° C × 2 hours hot air drying, and further dried at 120 ° C for 2 hours under reduced pressure), and the obtained coating film was used as an electrode, and CV measurement was performed under the following conditions.

○CV measurement conditions

. Relative electrode = Li (16.6cm ² )

. Relative electrode = Li / Li ⁺

. Test pole area = 0.5cm ²

. Measurement temperature = room temperature (25 ° C)

. Scanning speed = 0.5mV/sec

. Electrolyte=1M-LiPF ₆ /ethyl carbonate / dimethyl carbonate mixture (1.2v.v%)

. Measuring device = electrochemical interface (ELECTROCHEMICAL INTERFACE) SI-1287 (SOLARTRON)

First, after scanning at 2 V → 0 V → 2 V, defoaming was performed twice in the range of 2 V to 0 V (vsLi/Li ⁺ ) and scanning, and the current flowing was recorded to carry out CV measurement.

<Preparation of Electrode>

A predetermined amount of the active material, the binder, the conductive auxiliary agent, and N-methylpyrrolidone (NMP) were mixed, and the mixture was stirred and mixed by a spin-rotation mixer to prepare a coating liquid for an electrode.

The obtained electrode coating liquid was applied onto a copper foil having a thickness of 18 μm at a coating speed of 1 cm/min. using a coater having a gap of 0.4 cm/min, and subjected to vacuum drying at 120 ° C for 30 minutes to prepare a coating. A copper foil coated with an active material.

The obtained copper foil was punched into a diameter of 16 mm as an electrode.

<Evaluation of Electrode>

The electrodes were evaluated using the following conditions.

Relative electrode: Li

Electrolyte: 1M LiPF ₆ ethyl carbonate: ethyl dimethyl carbonate (1:2 vol%)

Current: 0.2CA

Temperature: 25 ° C

Synthesis Example 1a

Add to a 500ml four-neck separable flask under nitrogen 20.0 g of 4,4'-diphenylmethane diisocyanate (MDI) of diisocyanate and 76.1 g of polyoxytetramethylene glycol (molecular weight 1000, PTMG1000 manufactured by Mitsubishi Chemical Corporation) as a polyol (diisocyanate / The polyol (mol ratio = 1.05) was reacted at 80 ° C for 2 hours to obtain a urethane prepolymer 1a.

Synthesis Example 2a to Synthesis Example 11a were synthesized in the same manner as in Synthesis Example 1a. The results are shown in Table 1.

Synthesis Example 1b

To a 200 ml four-necked flask equipped with a moisture metering tube and a reflux condenser, 6.25 g of 3,5-diaminobenzoic acid (DAB) as a diamine and N-substrate were placed under a nitrogen atmosphere. After dissolving 122.9 g of methylpyrrolidone (NMP), 12.5 g of 4,4'-oxydiphthalic dianhydride as tetracarboxylic dianhydride was added, and the mixture was heated to 50 ° C for 1 hour (diamine). /tetracarboxylic dianhydride (mol ratio = 1.02)). Then, a solution obtained by dissolving 0.04 g of isoquinoline in 10.5 g of toluene was added, and the mixture was stirred at 180 ° C for 3 hours, and water obtained by azeotroping with toluene was removed to obtain an organic phase of the polyimine prepolymer 1b. Solvent solution.

Synthesis Example 2b to Synthesis Example 13b were synthesized in the same manner as in Synthesis Example 1b. The results are shown in Table 2.

Example 1

To a 500 ml four-neck separable flask, 4.4 g of a urethane prepolymer 1a and 3.1 g of NMP were added under a nitrogen atmosphere, and the mixture was stirred and dissolved. Then, 77.4 g (equivalent to 8.9 g based on the polymer) of the organic solvent solution of the polyimine prepolymer 1b was added, and the reaction was carried out at room temperature for 24 hours to obtain a uniform hydrophilic polymer in which no insoluble component was present. Organic solvent solution. The polyamidene fraction was 66.9 wt%, and according to the infrared absorption spectrum, the 2270 cm ^-1 absorption derived from the isocyanate group disappeared, and the absorption derived from the quinone imine structure was present at 1780 cm ^-1 and 1360 cm ^-1 at 3290 cm ^{-1 .} There was an absorption derived from the urethane structure at 1540 cm ^-1 , and thus the progress of the reaction was confirmed. The glass transition temperature of the obtained polymer showed -58 °C. The quinone imine unit/urethane unit (Mohr ratio) was 2.4.

N-methylpyrrolidone was added to the obtained organic solvent solution of the hydrophilic polymer, and 80 g of a 1% by weight organic solvent solution of the hydrophilic polymer was prepared in a 500 ml four-neck separable flask. 0.11 g of sodium hydroxide was added, and 320 g of water was added thereto for 1 hour, and the mixture was filtered through a 200-mesh nylon filter to obtain an aqueous organic solvent solution (solution for a binder) of a salt of a hydrophilic polymer (hydrophilic ◎). .

The organic solvent solution of the hydrophilic polymer obtained by the reaction was applied onto a copper foil using a 0.15 μm doctor blade to evaluate the adhesion. It was an extremely excellent result (evaluation ◎) in the bending test 1. In the bending test 2, even if the bending was repeated 100 times or more, there was no peeling of the coating film.

In addition, the initial adhesion to the copper foil was 1.20 N/mm.

According to the CV measurement results, it was found that the current derived from the oxidation reaction and the reduction reaction was not measured, and it was suitable for the use of a binder.

With respect to Example 2 to Example 31, the synthesis was carried out in the same manner as in Example 1. The results are shown in Table 3.

Fig. 1 shows the results of CV measurement of the hydrophilic polymer of Example 3.

Example 32

In terms of the solid content in the reaction liquid obtained in Example 1, 22 parts by weight of phenylethynyl phthalic anhydride was added to 100 parts by weight of the polymer, and 5% by weight of the NMP solution was used. 40 g of toluene was added to 40 g of toluene, and the reaction was carried out at 50 ° C for 1 hour, and then the water obtained by azeotroping with toluene at 160 ° C for 2 hours was removed to carry out a reaction. The reaction solution was concentrated to obtain a modified hydrophilic polymer solution having a solid content of 15%. According to the infrared absorption spectrum, the absorption of 3466 cm ^-1 derived from NH ₂ as a terminal amine group disappeared, and it was confirmed that the terminal of the polymer was sealed with phenylethynyl phthalic anhydride (dicarboxylic anhydride). The solution viscosity is 130mPa. s.

According to the results, it is understood that the tip is sealed to have a low viscosity and is excellent in workability, and is suitable for use as a binder or as a binder.

With respect to Example 33 to Example 66, the synthesis was carried out in the same manner as in Example 32. The results are shown in Table 4.

Comparative example 1

N-methylpyrrolidone was added to the urethane prepolymer 1a in a 500 ml four-neck separable flask to prepare 80 g of a 1 wt% organic solvent solution. When 0.06 g of sodium hydroxide was added and 320 g of water was added thereto for 1 hour, a large amount of aggregates were formed, and an aqueous organic solvent solution (solution for a binder) (hydrophilicity x) of the salt of the polymer could not be obtained, relative to the implementation. For example, it is poor.

Further, an organic solvent solution of the urethane prepolymer was applied onto the copper foil using a 0.15 μm doctor blade to evaluate the adhesion. It was an extremely excellent result (evaluation ◎) in the bending test 1. In the bending test 2, even if the bending was repeated 100 times or more, there was no peeling of the coating film.

Further, the initial adhesion to the copper foil was 0.1 N/mm, which was inferior to the examples.

As a result of CV measurement of the organic solvent solution of the urethane prepolymer, the current derived from the oxidation reaction and the reduction reaction was not measured. The results are shown in Table 5.

Comparative example 2

N-methylpyrrolidone was added to the polyimine prepolymer 1b in a 500 ml four-neck separable flask to prepare 80 g of a 1 wt% organic solvent solution. When 0.06 g of sodium hydroxide was added and 320 g of water was added thereto for 1 hour, a uniform aqueous solution (hydrophilicity ○) of a salt of a hydrophilic polymer was obtained.

Further, an organic solvent solution of the obtained polyimide intermediate was applied onto a copper foil with a 0.15 μm doctor blade to evaluate the adhesion. In the bending test 1, the polymer was peeled off from the metal foil (evaluation ×), with respect to the examples. difference. In the bending test 2, 53 times, the polymer was completely peeled off from the copper foil, which was inferior to the examples.

Further, the initial adhesion to the copper foil was 0.00 N/mm, which was low relative to the examples.

As a result of CV measurement of the polyimine prepolymer, the current derived from the oxidation reaction and the reduction reaction was not measured. The results are shown in Table 5.

Comparative Example 3 to Comparative Example 11

The hydrophilic polymer was attempted to be synthesized in the same manner as in Example 1 under the conditions described in Table 5. However, any of the hydrophilic polymers is a result of poor properties relative to the examples. Further, in Comparative Example 10, the viscosity was increased during the reaction and the stirring was impossible, and the hydrophilic polymer could not be obtained. The results are shown in Table 5.

Comparative Example 12

The same evaluation as in the examples was carried out using a commercially available PVDF (KF #1120, manufactured by Kureha Co., Ltd.) as a polymer. The results are shown in Table 5. Regarding the evaluation of hydrophilicity, no NaOH was added. However, compared with the examples, the hydrophilicity, the initial adhesion, the bending test 1, and the bending test 2 were poor (the adhesive durability was low), which was inferior to the examples. In addition, a current derived from the reaction was observed in the CV measurement.

Example 67

SiO (manufactured by Osaka Titanium) is used as an active material, and the composition is made of an active material/hydrophilic polymer (Example 18) / conductive auxiliary agent (acetylene black) = 70/20/10 (parts by weight). The coating liquid was used to prepare an electrode for a lithium ion secondary battery. Using this electrode, Li was used as a counter electrode to perform a charge and discharge test. The charge and discharge curves are shown in Fig. 2. From the results of Fig. 2, it is understood that the electrode using a hydrophilic polymer as a binder can be charged and discharged.

Example 68

An electrode for a lithium ion secondary battery was fabricated in the same manner as in Example 67 except that Example 22 was used as the hydrophilic polymer. Using this electrode, Li was used as a counter electrode to perform a charge and discharge test. The charge and discharge curves are shown in Fig. 3. According to the results of FIG. 3, it is understood that the electrode using a hydrophilic polymer as a binder can be charged and discharged.

Example 69

Graphite (CGB-10 manufactured by Nippon Graphite) was used for the active material, and a coating liquid for an electrode was prepared by using a composition of an active material/hydrophilic polymer (Example 18) = 100/5 (parts by weight). An electrode for a lithium ion secondary battery. Using this electrode, Li was used as a counter electrode to perform a charge and discharge test. The charge and discharge curves are shown in Fig. 4. From the results of Fig. 4, it is understood that the electrode using a hydrophilic polymer as a binder can be charged and discharged.

Example 70

In addition to using Example 19 as a hydrophilic polymer, In the same manner as in Example 67, an electrode for a lithium ion secondary battery was produced. Using this electrode, Li was used as a counter electrode to perform a charge and discharge test. The charge and discharge curves are shown in Fig. 5. From the results of Fig. 5, it is understood that the electrode using a hydrophilic polymer as a binder can be charged and discharged.

Example 71

The reaction liquid (organic solvent (NMP) solution) obtained in Example 18 was filtered through a 200-mesh SUS metal mesh, and the formation of insoluble matter could not be confirmed by visual observation.

As a result of measuring the solubility, the hydrophilic polymer was dissolved in 13% by weight.

Further, the reaction liquid obtained in Example 18 was vacuum dried at 110 ° C until a constant amount was obtained. In an aqueous solution obtained by dissolving 3.8 g of sodium hydroxide in 180 g of water, 16.2 g of the obtained hydrophilic polymer was dissolved, and the mixture was stirred at room temperature for 4 hours. The aqueous solution was filtered through a 400-mesh SUS metal mesh, and the obtained aqueous solution was dried by a hot air dryer at 120 ° C until a constant amount was obtained. As a result of measuring the solubility of the solid component, the hydrophilic polymer was dissolved by 9.5% by weight.

Example 72

A chemical grade metal Si (purity: 3N) having an average particle diameter (D50) of 7 μm was mixed with 20% by weight in ethanol, and a micropulverized wet bead mill using a zirconia bead having a diameter of 0.3 mm was used for 6 hours. An ultrafine particle Si slurry having an average particle diameter (D50) of 0.3 μm and a BET surface area at the time of drying of 100 m ² /g was obtained.

A flat shape having a particle diameter of about 0.5 mm and a thickness of about 0.02 mm Natural graphite was immersed in a liquid containing 1% by weight of sodium nitrate and 7% by weight of potassium permanganate in concentrated sulfuric acid for 24 hours, and then washed with water and dried to obtain acid-treated graphite. The acid-treated graphite was passed through a mullite tube having a length of 1 m and an inner diameter of 11 mm, and the mullite tube was flowed with nitrogen at a flow rate of 14 L/min at a supply rate of 5 g/min. The heater is heated to 1150 °C. By the heat treatment, sulfuric acid in the acid-treated graphite is decomposed into a gas such as sulfurous acid and discharged, whereby the acid-treated graphite is expanded and collected in a stainless steel container. The expansion ratio calculated from the ratio of the light bulk density before and after the heat treatment was 350%. It was confirmed by SEM observation that the graphite layer was peeled and expanded in the thickness direction, and was a powder having an accordion-like shape.

86 g of the ultrafine particle Si slurry, 20.6 g of the expanded graphite, a resole type phenol resin (manufactured by ASBERY Co., Ltd., grade 3772), 12.9 g, and 3.2 L of ethanol were placed in a stirred vessel. The mixture was stirred at 8000 rpm for 1 hour using a homomixer. Then, the mixed liquid was transferred to a rotary evaporator, heated to 60 ° C in a warm bath while rotating, and evacuated by a suction machine to remove the solvent. Then, it was expanded into a batt in a draft, dried for 2 hours while being exhausted, and passed through a net having a pore diameter of 2 mm, followed by drying for 12 hours to obtain a mixed dried product of about 50 g (light bulk density 80 g/L). ).

The mixed dried product was passed through a three-roll mill 2 times to granulate. The compaction was about 2 mm in particle size and 480 g/L in light bulk density.

Then, the granulation will be carried out. The compacted compound is added to a new power mill (New Power Mill), which is typically water cooled while performing a 15 minute powder at 21,000 rpm. The powder was simultaneously spheronized to obtain a spheroidized powder having a light bulk density of 640 g/L. The obtained powder was placed in an alumina boat, and calcined at a maximum temperature of 900 ° C for 1 hour while flowing nitrogen gas in a tubular furnace. Then, a composite having an average particle diameter (D50) of 18.6 μm and a light bulk density of 753 g/L was obtained through a mesh having a pore diameter of 45 μm.

FIG. 6 and FIG. 7 show a reflected electron image obtained by FE-SEM of a cross section obtained by ion beam cutting of the obtained composite material particles. Inside the composite particles, a structure in which fine particles of Si having a length of 0.05 μm to 1.0 μm and carbonaceous materials are sandwiched in a thin layer of graphite having a thickness of 0.02 μm to 0.5 μm is expanded into a network and laminated.

"Production of a negative electrode for lithium ion secondary batteries"

The composite compound obtained by weighing was used as a negative electrode active material in an amount of 83.7 wt% (content in the total solid content; the same applies hereinafter) to 1.0 wt% of acetylene black as a conductive auxiliary agent, and examples. The hydrophilic polymer described in 18: a binder (NMP solution having a solid concentration of 14.8% by weight) was mixed with 0.66 g of NMP in 15.3 wt%, and a rotation was used for 40 wt% of the slurry. A revolution mixer (manufactured by Thinky, defoaming Ryotaro) was used, and the negative electrode active material was dispersed and mixed to prepare a slurry containing a negative electrode mixture.

The obtained slurry was applied onto a copper foil having a thickness of 18 μm so that the coating amount of the solid component was 3 mg/cm ² , and dried at 110 ° C for 0.5 hour in a stationary operation dryer. A SEM photograph of the surface shape of the sheet electrode at this time is shown in Fig. 8 . It was observed that the binder cemented the particles homogeneously.

After drying, it was punched into a circular shape of 13.8 mmφ, uniaxially pressed under the conditions of a pressure of 0.6 t/cm ² , and further heat-treated under vacuum at 110 ° C for 2 hours to obtain lithium having a negative electrode mixture layer having a thickness of 25 μm. A negative electrode for an ion secondary battery.

"Production of evaluation unit"

The evaluation unit was produced by immersing the negative electrode, a 24 mm Φ polypropylene separator, a 21 mm Φ glass filter, a metal foil of 18 mm Φ and a thickness of 0.2 mm, and a stainless steel foil of the substrate thereof in an electrolytic solution. , in the set of work box, layered on the screw unit, and finally screw the cover. The electrolyte solution was obtained by dissolving ethyl carbonate and diethyl carbonate in a mixed solvent having a volume ratio of 1 to 1, and dissolving LiPF ₆ so as to have a concentration of 1.2 mol/L, and adding 2% by volume thereto. The fluorocarbonate is derived from ethyl ester. The evaluation unit was placed in a sealed glass container to which a silicone resin was further added, and the electrode of the lid of the silicone rubber was attached to a charge and discharge device (manufactured by Hokuto Denko, SD-8).

"Evaluation conditions"

The evaluation unit was subjected to a cycle test in a constant temperature room at 25 °C. For charging, after charging to 0.01 V at a constant current of 3 mA, the battery was charged at a constant voltage of 0.01 V until the current value became 0.2 mA. In addition, regarding discharge, it was discharged at a constant current of 2 mA to a voltage value of 1.5V. The initial discharge capacity and the initial charge and discharge efficiency were the results of the initial charge and discharge test.

In addition, the discharge capacity after the 50-time charge and discharge test was performed under the above-described charge and discharge conditions was compared with the initial discharge capacity, and the cycle characteristics were evaluated as the cycle capacity retention rate.

Example 73

In addition to using 64.5 g of the ultrafine particle Si slurry, 25.8 g of the expanded graphite, and 10.8 g of a novolac type phenol resin (manufactured by ASBERY Co., Ltd., grade 3772), a composite compound was produced, and In the same manner as in Example 72, a negative electrode active material, a negative electrode, and an evaluation unit were sequentially produced, and unit evaluation was performed.

"Production of a negative electrode for lithium ion secondary batteries"

The composite compound obtained by weighing was used as a negative electrode active material in an amount of 84.0% by weight based on the negative electrode active material (content in the total solid content; the same applies hereinafter), 1.1% by weight of acetylene black as a conductive auxiliary agent, and Example 18 The described hydrophilic polymer (NMP solution having a solid concentration of 14.8% by weight) was mixed with 0.66 g of NMP in 14.9% by weight, and 35 wt% of the slurry was mixed with water, and then rotated. A revolution mixer (manufactured by Thinky, defoaming Ryotaro) was used, and the negative electrode active material was dispersed and mixed to prepare a slurry containing a negative electrode mixture.

The obtained slurry was applied onto a copper foil having a thickness of 18 μm so that the coating amount of the solid component was 3 mg/cm ² , and dried at 110 ° C for 0.5 hour in a stationary operation dryer. A SEM photograph of the surface shape of the sheet electrode at this time is shown in Fig. 9 . It was observed that the binder succinctly and homogeneously bonded between the particles.

Comparative Example 13

The same procedure as in Example 72 was carried out, except that a commercially available ruthenium (manufactured by Sakae Kogyo Co., Ltd.) having an average particle diameter of 7 μm and a negative electrode active material of 30:70 (% by weight) of the natural graphite were used. A negative electrode active material, a negative electrode, and an evaluation unit were produced, and unit evaluation was performed.

Comparative Example 14

The composite compound used in Example 72 was weighed as a negative electrode active material, and was used as a negative electrode active material in an amount of 79.4% by weight (the content in the total solid content; the same applies hereinafter) to 5.0% by weight of acetylene black as a conductive auxiliary agent. Polyimide binder (trade name Dreambond (manufactured by IST)) (NMP solution having a solid concentration of 46.7 wt%) was mixed with 0.438 g of NMP in 15.6 wt%, and rotation was used for 25 wt% of the slurry. A revolution mixer (manufactured by Thinky, defoaming Ryotaro) was used, and the negative electrode active material was dispersed and mixed to prepare a slurry containing a negative electrode mixture.

The obtained slurry was applied onto a copper foil having a thickness of 18 μm so that the coating amount of the solid component was 3 mg/cm ² , and dried at 110 ° C for 0.5 hour in a stationary operation dryer. A SEM photograph of the surface shape of the sheet electrode at this time is shown in FIG. It was observed that the commercially available polyimine binder contained fine particles, and the binder was coated so as to cover the surface of the active material.

After drying, it was punched into a circular shape of 13.8 mmφ, uniaxially pressed under the conditions of a pressure of 0.6 t/cm ² , and further heat-treated under vacuum at 110 ° C for 2 hours to obtain a negative electrode mixture layer having a thickness of 14 μm. A negative electrode for a lithium ion secondary battery.

Comparative Example 15

A negative electrode active material, a negative electrode, and an evaluation unit were sequentially produced in the same manner as in Example 73 except that a commercially available polyimide resin (trade name: Dreambond (manufactured by IST)) was used as the binder to be used. Unit evaluation.

Comparative Example 16

A commercially available ruthenium (manufactured by Sakae Industrial Co., Ltd.) having an average particle diameter of 7 μm and a negative electrode active material of 30:70 (% by weight) of the natural graphite were weighed, and 95.5% by weight based on the negative electrode active material ( The content of the total solid content; the same below), 0.5% by weight of acetylene black as a conductive auxiliary agent, 1.5% by weight of carboxymethyl cellulose (CMC) as a binder, and styrene butadiene rubber ( After the SBR) was added in an amount of 2.5% by weight and water was mixed, a negative electrode mixture was prepared by dispersing and mixing the negative electrode active material using a rotation/revolution mixer (manufactured by Thinky, defoaming Ryotaro).

The obtained slurry was applied onto a copper foil having a thickness of 18 μm so that the coating amount of the solid component was 3 mg/cm ² , and dried at 110 ° C for 0.5 hour in a stationary operation dryer. A SEM photograph of the surface shape of the sheet electrode at this time is shown in Fig. 6 . It was observed that the commercially available polyimine binder contained fine particles, and the binder was coated so as to cover the surface of the active material.

After drying, it was punched into a circular shape of 13.8 mmφ, uniaxially pressed under the conditions of a pressure of 0.6 t/cm ² , and further heat-treated under vacuum at 110 ° C for 2 hours to obtain a negative electrode mixture layer having a thickness of 30 μm. A negative electrode for a lithium ion secondary battery.

Comparative Example 17

The composite compound described in Example 72 was used as a negative electrode active material, and a binder containing 1.5% by weight of the carboxymethylcellulose (CMC) and 2.5% by weight of styrene butadiene rubber (SBR) was used as a binder. In the same manner as in Example 72, a negative electrode active material, a negative electrode, and an evaluation unit were sequentially produced, and unit evaluation was performed.

Comparative Example 18

The composite compound described in Example 2 was used as a negative electrode active material, and a binder containing 1.5% by weight of the carboxymethylcellulose (CMC) and 2.5% by weight of styrene butadiene rubber (SBR) was used as a binder. In the same manner as in Example 73, a negative electrode active material, a negative electrode, and an evaluation unit were sequentially produced, and unit evaluation was performed.

Comparative Example 19

The composite compound described in Comparative Example 1 was used as a negative electrode active material, and a binder containing 1.5% by weight of the carboxymethylcellulose (CMC) and 2.5% by weight of styrene butadiene rubber (SBR) was used as a binder. In the same manner as in Example 72, a negative electrode active material, a negative electrode, and an evaluation unit were sequentially produced, and unit evaluation was performed.

The negative electrode active material preparation conditions of Examples 72 to 73 and the negative electrode active material production conditions of Comparative Example 13 to Comparative Example 19 are shown in Table 6. Further, the results of Examples 72 to 73 and the results of Comparative Examples 13 to 19 are shown in Table 7.

As is clear from Table 7, it is understood that a battery fabricated by using a copolymer of a polyurethane and a polyimide copolymer after the combination of Si, carbonaceous material and graphite has a discharge capacity at a low heat treatment temperature. High and excellent cycle characteristics.

On the other hand, it is understood that Comparative Example 13 and Comparative Example 16 produced by using a negative electrode active material prepared by mixing commercially available Si particles having a size of about 7 μm and graphite and various commercially available binders other than the binder of the present invention are compared. The cycle characteristics of the lithium ion secondary battery of Example 19 were drastically lowered.

It is understood that, as compared with the embodiment of the present invention, an anode active material and a polyimide pigment binder which are composited of Si and graphite as a negative electrode active material or In Comparative Example 14, Comparative Example 15, Comparative Example 17, and Comparative Example 18 of the water-based binder such as SBR/CMC, the cycle retention rate was low. Further, in the case of using a commercially available polyimine binder, the heat treatment temperature is set to 200 ° C or higher in order to improve the cycle characteristics.

Claims (20)

A hydrophilic polymer characterized by being represented by the following general formula (1), (wherein R ₁ represents a divalent organic group having 4 to 30 carbon atoms, and R ₂ represents a linear or branched polyalkylene group having a carbon number of 2 to 5 in a number average molecular weight of 100 to 10,000; The valence organic group, R ₃ represents a trivalent or higher organic group having one to two aromatic rings having 4 to 30 carbon atoms, R ₄ represents a tetravalent organic group having 4 to 30 carbon atoms, and X represents a carboxyl group or a sulfonic acid group. x represents an integer from 1 to 800, y represents an integer from 1 to 800, z represents an integer from 1 to 100, and a represents an integer from 1 to 4; wherein, in the case where X is a carboxyl group, the number of aromatic rings of R ₃ is 1, a is 1; in the structure of the formula (1), the structure represented by the following formula (2) is 10% by weight to 99% by weight, based on the amine group represented by the formula (3). The molar number A of the acid ester unit structure, and the molar number B of the quinone imine unit structure represented by the general formula (2) is B/A = 1 to 30) (wherein R ₃ represents a trivalent or higher organic group having one to two aromatic rings having 4 to 30 carbon atoms, R ₄ represents a tetravalent organic group having 4 to 30 carbon atoms, and X represents a carboxyl group or a sulfonic acid group. , y represents an integer from 1 to 800, and a represents an integer from 1 to 4; wherein, in the case where X is a carboxyl group, the number of aromatic rings of R ₃ is 1, and a is 1) (wherein R ₁ represents a divalent organic group having 4 to 30 carbon atoms, and R ₂ represents a linear or branched polyvalent alkylene group having a carbon number of 2 to 5 having an average molecular weight of 100 to 10,000. Organic group, x represents an integer from 1 to 800). The hydrophilic polymer according to claim 1, wherein the terminal of the polymer represented by the formula (1) is sealed by a dicarboxylic acid anhydride represented by the following formula (4). (wherein Z represents a divalent organic group selected from the group consisting of the following general formula (5)) The hydrophilic polymer according to the second aspect of the invention, wherein the dicarboxylic anhydride represented by the formula (4) is 0.02 by weight based on 100 parts by weight of the polymer represented by the formula (1). Parts ~ 100 parts by weight. The hydrophilic polymer according to the first to third aspects of the invention, wherein the initial adhesion to copper by a T-stripping test (tensile speed: 300 mm/min) is 0.05 N/mm or more. A method for producing a hydrophilic polymer according to the first or fourth aspect of the invention, which is characterized in that the urethane prepolymer represented by the following formula (6) is used (A) The polyiminoimine prepolymer (B) represented by the following formula (7) is reacted to obtain the hydrophilic polymer, and the composition at the time of the reaction: the polyamidene fraction [(B) Weight] / [weight of (A) + weight of (B)] × 100 = 10% by weight to 99% by weight, and relative to the urethane prepolymer represented by the above formula (6), The polyamidene prepolymer represented by the above formula (7) has a molar ratio of 1 or more and 30 or less. (wherein R ₁ represents a divalent organic group having 4 to 30 carbon atoms, and R ₂ represents a linear or branched polyvalent alkylene group having a carbon number of 2 to 5 having an average molecular weight of 100 to 10,000. Organic base, x means an integer from 1 to 800) (wherein R ₃ represents a trivalent or higher organic group having one to two aromatic rings having 4 to 30 carbon atoms, R ₄ represents a tetravalent organic group having 4 to 30 carbon atoms, and X represents a carboxyl group or a sulfonic acid group. y represents an integer of 1 to 800, and a represents an integer of 1 to 4. wherein, when X is a carboxyl group, the number of aromatic rings of R ₃ is 1, and a is 1). A method for producing a hydrophilic polymer according to any one of claims 2 to 4, characterized in that the amine group represented by the above formula (6) is obtained. The acid ester prepolymer (A) is reacted with the polyamidimide prepolymer (B) represented by the above formula (7) to obtain the polymer represented by the above formula (1). Composition: Polyimine fraction is [(B) weight] / [(A) weight + (B) weight] × 100 = 10% by weight to 99% by weight, and the above formula (6) The urethane prepolymer has a molar ratio of 1 or more and 30 or less, and then the dicarboxylic acid anhydride represented by the above formula (4) is allowed to react. The method for producing a hydrophilic polymer according to claim 5, wherein the urethane prepolymer (A) is a diisocyanate represented by the following formula (8). When reacting with a polyhydric alcohol represented by the following general formula (9), the molar ratio (isocyanate group/hydroxyl group) of the isocyanate group to the hydroxyl group is from 1 to 2, and OCN-R ₁ -NCO (8) ( In the formula, R ₁ represents a divalent organic group having 4 to 30 carbon atoms) HO-R ₂ -OH (9) (wherein R ₂ represents a linear or branched carbon number having an average molecular weight of 100 to 10,000; ~5 polyoxyalkylene structure of divalent organic groups). The method for producing a hydrophilic polymer according to the above-mentioned item, wherein the polyimine prepolymer (B) is a diamine represented by the following formula (10). In the reaction of the tetracarboxylic dianhydride represented by the following formula (11), the molar ratio of the diamine to the tetracarboxylic dianhydride (diamine/tetracarboxylic dianhydride) is more than 1 and 2 or less. , (wherein R ₃ represents a trivalent or higher organic group having one to two aromatic rings having 4 to 30 carbon atoms, X represents a carboxyl group or a sulfonic acid group, and a represents an integer of 1 to 4; wherein, X is In the case of a carboxyl group, the number of aromatic rings of R ₃ is 1, and a is 1) (wherein R ₄ represents a tetravalent organic group having 4 to 30 carbon atoms). A salt of a hydrophilic polymer, which is characterized in that the hydrophilic polymer according to any one of claims 1 to 4, and an alkali metal hydroxide, an alkali metal carbonate, and a third The amine compound, the quaternary amine compound or ammonia is obtained by a reaction. A solution for a binder, which is characterized in that the hydrophilic polymer according to any one of claims 1 to 4 and/or the scope of the patent application The salt of the hydrophilic polymer according to item 9 is dissolved in water, an organic solvent or an aqueous organic solvent. A binder for a secondary battery, which is obtained by drying a solution for a binder as described in claim 10 of the patent application. An electrode comprising a hydrophilic polymer according to any one of claims 1 to 4, and/or a salt of a hydrophilic polymer according to claim 9 of the patent application. An electrode for a lithium ion secondary battery, comprising the electrode according to claim 12 of the patent application. A negative electrode for a lithium ion secondary battery according to the invention of claim 13, wherein the negative electrode active material contains Si or a Si alloy, carbonaceous matter or carbonaceous material, and Made of graphite. The negative electrode for a lithium ion secondary battery according to claim 14, wherein the negative electrode active material is a composite compound having an average particle diameter of 1 μm to 40 μm, and contains Si or Si having an average particle diameter of 0.01 μm to 5 μm. Alloys, carbonaceous or carbonaceous materials and graphite. The negative electrode for a lithium ion secondary battery according to claim 14, wherein the negative electrode active material is a thin layer of graphite in which Si or a Si alloy and a carbonaceous material are both held at a thickness of 0.5 μm or less. In the inter-structure, the structure is expanded into a laminate and/or a network, and the graphite thin layer is bent in the vicinity of the surface of the active material particles to cover the composite particles, and graphite or a carbonaceous material is disposed around the composite particles. Lithium ion as described in any one of claims 14 to 16 The negative electrode for a secondary battery, which contains 60% by weight or more and 99% by weight or less of the negative electrode active material, and 1% by weight or more and 40% by weight or less of the binder according to Item 11 of the patent application, and 0.01% by weight More than or equal to 20% by weight of the conductive carbon compound. The method for producing a negative electrode for a lithium ion secondary battery according to any one of claims 14 to 17, wherein the negative electrode active material is as described in claim 11 a binder or a binder solution according to claim 10, and a step of slurrying the conductive carbon compound in water, an organic solvent or an aqueous organic solvent to form a slurry; coating the slurry a step of forming an applicator on the collector; a press forming step of pressing the applicator to integrate with the collector; and a drying step of removing water and an organic solvent contained in the electrode . The method for producing a negative electrode for a lithium ion secondary battery according to claim 18, wherein the slurry is used in a binder as described in claim 11 or as claimed in claim 10 The binder solution described above is prepared by using a solution of a binder of water, an organic solvent or an aqueous organic solvent. The method for producing a negative electrode for a lithium ion secondary battery according to claim 18, wherein the drying step is carried out at 150 ° C or lower.