KR20120038939A - Electrode for secondary battery, and secondary battery - Google Patents

Abstract

An electrode active material layer comprising an electrical power collector and an electrode active material layer laminated on the current collector, the active material layer comprising a segment A having a swelling degree of 100 to 300% with respect to the electrolyte and an swelling degree with respect to the electrolyte. Is 500-50,000% or comprises a graft polymer composed of segment B dissolved in an electrolyte solution.

Description

Electrode for secondary battery and secondary battery {ELECTRODE FOR SECONDARY BATTERY, AND SECONDARY BATTERY}

TECHNICAL FIELD The present invention relates to a secondary battery electrode and a binder which is a constituent thereof, and more particularly, to an electrode from which a battery having high output characteristics and cycle characteristics used in a lithium ion secondary battery or the like is obtained. Moreover, this invention relates to the secondary battery which has such an electrode.

Lithium ion secondary batteries show the highest energy density among practical batteries, and are particularly used for small electronics. In addition, development for automobile applications is also expected. Among them, further improvement of reliability, such as high output of a lithium ion secondary battery and cycling characteristics, is desired.

Lithium-ion secondary battery, generally, lithium-containing metal oxide, such as, LiCoO _2, LiMn ₂ O ₄ and LiFePO ₄ is used as the positive electrode active material or the like, combined by a binder, such as polyvinylidene fluoride is a positive electrode formed It is. On the other hand, in the negative electrode, a negative electrode is formed by bonding a carbonaceous (amorphous) carbon material, a metal oxide, a metal sulfide, or the like, used as a negative electrode active material, with a binder such as a styrene-butadiene copolymer.

In order to solve the problem of the cycling characteristics of a lithium ion secondary battery, for example, patent document 1 discloses adding graft polymer as a dispersing agent in addition to binders, such as polyvinylidene fluoride, in a positive electrode. As a result of using a graft polymer made of vinylpyrrolidone and styrene as the dispersant, the dispersibility of the conductive agent is improved. As a result, nonuniformity of the conductive agent in the electrode is suppressed, and a battery having excellent cycle characteristics is obtained.

In addition, Patent Literature 2 discloses the use of a graft polymer composed of olefin and acrylonitrile in a positive electrode electrode, and maintains binding property with an active material by suppressing swelling of an electrolyte solution, thereby obtaining a battery having excellent cycle characteristics. ought.

Japanese Unexamined Patent Publication No. 2003-272634 Japanese Unexamined Patent Publication No. 2004-227974

However, the following things were understood by examination of the present inventors. That is, in the method of patent document 1, in order to maintain both the dispersibility of a electrically conductive agent and binding property with an active material, in addition to a graft polymer, binders, such as polyvinylidene fluoride, are used further, As the resistance component increases, the energy density and output characteristics of the secondary battery obtained decrease. Moreover, in the method of patent document 2, it does not have sufficient dispersibility of a electrically conductive agent, is inferior with time stability of a slurry, and the electronic resistance increase by the nonuniformity of a electrically conductive agent arises. In particular, the output characteristics are low at high outputs such as HEV (hybrid electric vehicle) applications. Moreover, in patent documents 1 and 2, reaction on the active material active surface cannot be suppressed, and swelling at the time of high temperature operation | movement by gas generation is seen.

Accordingly, an object of the present invention is to provide an electrode for a lithium ion secondary battery in which a secondary battery obtained has high output characteristics and gas generation is suppressed.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to solve the said subject, as a result, the output characteristic improves by containing in the electrode containing the said electrode active material the graft polymer which consists of a component with low swelling property with respect to electrolyte solution, and a high component as a binder. It turned out that gas generation is suppressed. That is, the inventors of the present invention can achieve the improvement of cycle characteristics by maintaining the binding properties and improving the dispersibility of the conductive agent in the methods described in Patent Documents 1 and 2, but the graft polymer is composed of only components having low swelling properties of the electrolyte solution. Therefore, it was thought that suppression of output characteristics and gas generation could not be achieved. When the graft polymer contains a component having a low swelling property to the electrolyte and a high component, the low swelling component is adsorbed to the active material and the conductive agent in the slurry, and the high swelling component is dispersed in the solvent to show high slurry stability and dispersibility. okay. Further, it is found that the output characteristics are increased by increasing the smoothness of the obtained electrode and the retention of the electrolyte solution, and that the graft polymer is adsorbed on the surface of the active material inside the battery, thereby reducing the active material active surface and significantly reducing the amount of gas generated. It came to complete this invention.

MEANS TO SOLVE THE PROBLEM This invention which solves the said subject includes the following matter as a summary.

(1) An electrode active material layer containing an electrical power collector and an active material and a binder laminated on the current collector, wherein as the binder, a segment A having a swelling degree of 100 to 300% with respect to an electrolyte solution, and an electrolyte solution A secondary battery electrode comprising a graft polymer comprising a segment B having a swelling degree of 500 to 50,000% or dissolved in an electrolyte solution.

(2) The electrode for secondary batteries as described in said (1) whose ratio of the said segment A and the said segment B in the said graft polymer is 20: 80-80: 20 (mass ratio).

(3) The electrode for secondary batteries in any one of said (1)-(2) whose weight average molecular weights of the said graft polymer are in the range of 1,000-500,000.

(4) The electrode for secondary batteries in any one of said (1)-(3) whose said segment B is a segment of the soft polymer of 15 degrees C or less of glass transition temperature.

(5) A binder for secondary batteries, comprising a graft polymer comprising a segment A having a swelling degree of 100 to 300% with respect to the electrolyte and a segment B having a swelling degree of 500 to 50,000% with respect to the electrolyte or dissolved in the electrolyte.

(6) The binder for secondary batteries as described in said (5) whose ratio of the said segment A and the said segment B in the said graft polymer is 20: 80-80: 20 (mass ratio).

(7) The binder for secondary batteries in any one of said (5)-(6) whose said segment B is a segment of the soft polymer of 15 degrees C or less of glass transition temperature.

(8) A slurry containing a graft polymer, an active material, and a solvent comprising a segment A having a swelling degree of 100 to 300% with respect to the electrolyte and a segment B having a swelling degree of 500 to 50,000% with respect to the electrolyte or dissolved in the electrolyte. The manufacturing method of the electrode for secondary batteries as described in said (1) containing the process of apply | coating on top and drying.

(9) A lithium ion secondary battery having a positive electrode, an electrolyte solution and a negative electrode, wherein at least one of the positive electrode and the negative electrode is an electrode for secondary batteries according to any one of (1) to (4).

According to the present invention, in the case of the problem of output characteristics and gas generation, by containing a predetermined graft polymer, the graft polymer suppresses gas generation on the surface of the electrode active material, and further has a high conductive agent dispersibility, thereby providing a high output. The electrode for secondary batteries which can exhibit a characteristic can be obtained.

The present invention is described in detail below.

The electrode for secondary batteries (henceforth a "electrode" hereafter) of this invention consists of the electrode active material layer which consists of an active material and a binder laminated | stacked on an electrical power collector. That is, the electrode of this invention contains an electrical power collector and the electrode active material layer containing an active material and a binder laminated | stacked on the said electrical power collector. The electrode of this invention contains the graft polymer which consists of segment A whose swelling degree with respect to electrolyte solution is 100-300%, and segment B which is 500-50,000% with respect to electrolyte solution, or melt | dissolves in electrolyte solution as said binder.

(Electrode active material)

The electrode active material used for the electrode for secondary batteries of this invention is generally selected according to the secondary battery in which an electrode is used. As said secondary battery, a lithium ion secondary battery and a nickel-hydrogen secondary battery are mentioned.

When the electrode for secondary batteries of this invention is used for a lithium ion secondary battery positive electrode, the electrode active material (positive electrode active material) for lithium ion secondary battery positive electrodes is largely divided into what consists of an inorganic compound, and consists of an organic compound.

As a positive electrode active material which consists of inorganic compounds, a transition metal oxide, the composite oxide of lithium and a transition metal, a transition metal sulfide, etc. are mentioned. Fe, Co, Ni, Mn, etc. are used as said transition metal. Specific examples of the inorganic compound used for the positive electrode active _{material, LiCoO 2, LiNiO 2, LiMnO} 2, lithium-containing composite metal oxides such as _{LiMn 2 O 4, LiFePO 4,} LiFeVO 4; Transition metal sulfides such as TiS ₂ , TiS ₃ , and amorphous MoS ₂ ; Transition, such as Cu ₂ V ₂ O _3, amorphous _{V 2 OP 2 O 5, MoO} 3, V 2 O 5, V 6 O 13 may be a metal oxide. These compounds may be element substituted partially. As a positive electrode active material which consists of organic compounds, you may use conductive polymers, such as polyacetylene and poly-p-phenylene, for example. The iron oxide lacking in electrical conductivity may be used as an electrode active material covered with a carbon material by allowing a carbon source material to be present during reduction firing. In addition, these compounds may be partially substituted with elements.

 The mixture of the said inorganic compound and an organic compound may be sufficient as the positive electrode active material for lithium ion secondary batteries. Although the particle diameter of a positive electrode active material is suitably selected from the balance with the other structural requirements of a battery, from a viewpoint of the improvement of battery characteristics, such as a load characteristic and a cycling characteristic, a 50% volume cumulative diameter is normally 0.1-50 micrometers, Preferably it is 1 20 μm. If the 50% volume cumulative diameter is within this range, a secondary battery having a large charge / discharge capacity can be obtained, and handling in the production of an electrode slurry and an electrode is easy. The 50% volume cumulative mirror can be obtained by measuring the particle size distribution by laser diffraction.

When the electrode for secondary batteries of this invention is used for a lithium ion secondary battery negative electrode, As an electrode active material (negative electrode active material) for lithium ion secondary battery negative electrodes, For example, amorphous carbon, graphite, natural graphite, mesocarbon microbeads, Carbonaceous materials, such as pitch type carbon fiber, Conductive polymers, such as polyacene, etc. are mentioned. As the negative electrode active material, metals such as silicon, tin, zinc, manganese, iron, nickel, alloys thereof, oxides or sulfates of the metals or alloys are used. Moreover, lithium alloys, such as metallic lithium, Li-Al, Li-Bi-Cd, Li-Sn-Cd, lithium transition metal nitride, silicon, etc. can be used. The electrode active material can also use the thing which made the electrically conductive provision material adhere to the surface by a mechanical modification method. Although the particle size of a negative electrode active material is suitably selected from the balance with the other component requirements of a battery, 50% volume cumulative diameter is 1-50 micrometers normally from a viewpoint of the improvement of battery characteristics, such as initial efficiency, a load characteristic, and cycling characteristics. Preferably it is 15-30 micrometers.

When the electrode for secondary batteries of this invention is used for the nickel-hydrogen secondary battery positive electrode, nickel hydroxide particle | grains are mentioned as an electrode active material (positive electrode active material) for nickel-hydrogen secondary battery positive electrodes. The nickel hydroxide particles may be dissolved in cobalt, zinc, cadmium, or the like, or may be coated with a cobalt compound whose surface is subjected to alkali heat treatment. In addition to the yttrium oxide, nickel hydroxide particles may contain additives such as cobalt compounds such as cobalt oxide, metal cobalt, and cobalt hydroxide, zinc compounds such as metal zinc, zinc oxide, and zinc hydroxide, and rare earth compounds such as erbium oxide. do.

When the electrode for secondary batteries of this invention is used for the nickel-hydrogen secondary battery negative electrode, as an electrode active material (negative electrode active material) for a nickel-hydrogen secondary battery negative electrode, a hydrogen storage alloy particle is electrochemically in alkaline electrolyte at the time of charge of a battery. What is necessary is just to be able to occlude | generate the generated hydrogen, and to be able to discharge | release easily the occlusion hydrogen at the time of discharge, and although it does not specifically limit, The particle | grains which consist of AB5 type | system | group type | system | group, TiNi type | system | group, and a TiFe type | system | group hydrogen storage alloy are preferable. . Specifically, for example, LaNi5, MmNi5 (Mm is micrometal), LmNi5 (Lm is at least one selected from rare earth elements including La), and a part of Ni of these alloys is Al, Mn, Co, Ti , Elemental hydrogen-scavenging alloy particles substituted with at least one element selected from among Cu, Zn, Zr, Cr, B and the like can be used. In particular, hydrogen storage alloy particles having a composition represented by the general formula: LmNiwCoxMnyAlz (the sum of atomic ratios w, x, y, z are 4.80 ≦ w + x + y + z ≦ 5.40) are involved in the progress of the charge / discharge cycle. It is preferable because the differentiation which becomes is suppressed and a charge / discharge cycle characteristic improves.

The content rate of the electrode active material used for this invention in an electrode active material layer becomes like this. Preferably it is 90-99.9 mass%, More preferably, it is 95-99 mass%. By making content of the electrode active material in an electrode into the said range, flexibility and binding property can be exhibited, showing a high capacity | capacitance.

(Binder)

The electrode for secondary batteries of this invention contains the graft polymer which consists of a segment A whose swelling degree with respect to electrolyte solution is 100-300%, and the segment B which has a swelling degree with respect to electrolyte solution 500-50,000% or melt | dissolves in electrolyte solution as a binder. .

(Graft polymer)

The graft polymer used for this invention has two segments (segment A, segment B), one segment has a main chain, and the other has a branched structure which comprises a graft part (side chain). The graft polymer may further comprise one or more optional segments in addition to having a first segment and a second segment. In addition, each of the 1st segment and the 2nd segment may be a segment based on only one type of polymer unit, and the segment based on two or more types of polymer units may be sufficient as it.

The two segments are made of segment A having a swelling degree of 100 to 300% in the electrolyte solution and the electrolyte solution so as to increase the retention of the electrolyte solution to improve the output characteristics and further increase the adsorption property to the active material to suppress the generation of gas. Swelling degree is 500-50,000% or consists of segment B which melt | dissolves in electrolyte solution. The graft polymer forms a branching structure in the segment A and the segment B, so that in the electrode including the graft polymer, a structure is formed even by two segments, whereby the graft polymer exhibits an adequate swelling property to the electrolyte solution while It is possible to exhibit high lithium conductivity by maintaining the binding state with the electrode and maintaining the electrolyte without causing peeling of the electrode in the electrolyte. Further, when the graft polymer includes segment A having a swelling degree of 100 to 300% with respect to the electrolyte solution and segment B having a swelling degree with respect to the electrolyte solution having 500 to 50,000% or dissolved in the electrolyte solution, segment A which is a low swelling component in the slurry is It was found that, by being adsorbed by the active material and the conductive agent, segment B, which is a high swelling component, spreads in a solvent, exhibiting high slurry stability and dispersibility. And the smoothness of the obtained electrode and the retention of electrolyte solution become high, an output characteristic becomes high, and the graft polymer adsorb | sucks to the surface of an active material in a battery inside, and an active material active surface is reduced and the amount of gas generation is reduced significantly.

As for the graft polymer used for this invention, any of two segments may comprise a principal chain, and may comprise a graft part (side chain). Among them, the high-swelling segment B spreads in the slurry solvent in the slurry, and the low-swelling segment A is adsorbed by the active material and the conductive agent, thereby exhibiting a high conductive agent dispersibility and an active material protection effect, so that the side chain is particularly composed of the low-swelling segment A. The structure is preferred. Therefore, the graft polymer in which segment A comprises a graft part (side chain) and segment B comprises a main chain is preferable.

(Swelling degree)

In the present invention, the swelling degree of each segment is measured by the following method.

The polymer composed of the constituents of the segment A and the polymer composed of the constituents of the segment B are each molded into a film having a thickness of about 0.1 mm, and cut into about 2 centimeters in width and length to measure the weight (weight before immersion). Then, it is immersed for 72 hours in electrolyte solution of the temperature of 60 degreeC. The immersed film is pulled up, the weight immediately after wiping off the electrolytic solution (weight after immersion) is measured, and the value of (after immersion weight) / (weight before immersion) x 100 (%) is defined as the swelling degree.

As the electrolyte solution, a mixed solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) in EC: DEC = 1: 2 (volume ratio, where EC is a volume at 40 ° C. and DEC is a volume at 20 ° C.). In the solution, a solution of LiPF ₆ dissolved at a concentration of 1 mol / liter is used.

Swelling degree with respect to the electrolyte solution of the segment A and the segment B can be controlled with composition, molecular weight, and a crosslinking degree. The swelling degree with respect to the electrolyte solution of the segment A is 100%-300%, Since the adsorption property with respect to an active material and a conductive agent becomes high, and the suppression effect of gas generation becomes high, it is preferable that it is 100%-200%. On the other hand, since the swelling degree with respect to the electrolyte solution of segment B is 500% -50,000% or melt | dissolution, and it can maintain high binding property while maintaining electrolyte solution retention, Preferably it is 500%-10,000%, More preferably, 500%-5,000% to be.

(Segment A)

In order to control swelling degree with respect to the electrolyte solution of segment A according to a composition, and to make swelling degree with respect to electrolyte solution 100-300%, it is preferable to comprise by the monomer component whose solubility parameter is less than 8.0 or 11 or more, or the monomer component which has a hydrophobic part. Do. In addition, when controlling swelling degree by weight average molecular weight, it is preferable to make the weight average molecular weight of segment A into 4,000 or more and 10,000 or less. By making a weight average molecular weight into this range, the dispersibility and slurry stability with respect to a electrically conductive agent and an active material can be improved. In this invention, a weight average molecular weight says the polystyrene conversion weight average molecular weight measured by gel permeation chromatography (GPC).

As a monomer component whose solubility parameter is less than 8.0 or 11 or more, (alpha), (beta)-unsaturated nitrile compounds, such as an acrylonitrile and methacrylonitrile; Fluorine-containing acrylic esters such as fluoroalkyl acrylate, 2- (fluoroalkyl) methyl acrylate, and 2- (fluoroalkyl) ethyl acrylate; Fluorine-containing acrylic acid esters such as fluoroalkyl methacrylate, 2- (fluoroalkyl) methyl methacrylate and 2- (fluoroalkyl) ethyl methacrylate.

The solubility parameter of a monomer can be calculated | required according to the "molecular attraction constant method" proposed by Small. This method is characterized by the characteristic value of the functional group (atomic group) constituting the compound molecule, that is, the statistical value of the molecular attraction constant (G) and the molecular value, according to the following equation. The SP value (δ) (cal / cm 3) ¹ How to get ^{/ 2} .

δ = ΣG / V = dΣG / M

ΣG: Total of molecular attraction constant G

V: cost

M: molecular weight

d: specific gravity

As a monomer component which has a hydrophobic part, Styrene-type monomers, such as styrene, (alpha)-styrene, chloro styrene, vinyltoluene, methyl t-butylstyrene vinyl benzoate, vinyl naphthalene, chloromethyl styrene, (alpha) -methylstyrene, and divinylbenzene, are mentioned. Can be.

In the present invention, the segment A having a swelling degree of 100 to 300% exhibits no swelling property to the electrolyte solution, and therefore, an α, β-unsaturated nitrile compound and a styrene monomer are preferable. Furthermore, a styrene monomer is the most preferable at the point that the dispersibility of a electrically conductive agent is high.

Content of the monomer component which has a hydrophobic part in segment A becomes like this. Preferably it is 10 mass% or more and 100 mass% or less with respect to 100 mass% of monomer whole amounts, More preferably, it is 20 mass% or more and 100 mass% or less. Content of the monomer component which has a hydrophobic part in segment A can be controlled by the monomer injection ratio at the time of graft polymer manufacture. By making content of the monomer component which has a hydrophobic part in segment A into the said range, higher electrolyte resistance and high temperature characteristic are shown.

Segment A may use these monomers individually or in combination of 2 or more types.

(Segment B)

In order to control the swelling degree with respect to the electrolyte solution of segment B according to a composition, and to make swelling degree with respect to electrolyte solution 500-50,000%, it is preferable to comprise by the monomer component whose solubility parameter is 8.0 or more and less than 11, or the monomer component which has a hydrophilic group. . In addition, when controlling swelling degree by weight average molecular weight, it is preferable to make the weight average molecular weight of segment B into 10,000 or more and 500,000 or less. By making a weight average molecular weight into this range, it has high binding property and does not produce peeling of an electrode active material layer, etc.

As a monomer whose said solubility parameter is 8.0 or more and less than 11, Alkenes, such as ethylene and propylene; Methacrylic acid alkyl esters such as butyl methacrylate, hexyl methacrylate, lauryl methacrylate and stearyl methacrylate; Acrylic acid alkyl esters such as butyl acrylate, hexyl acrylate, lauryl acrylate and stearyl acrylate; Diene monomers such as butadiene and isoprene; And vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl benzoate. Among these, an alkyl acrylate or a methacrylic acid alkyl ester is more preferable at the point that swelling property with respect to electrolyte solution is high, and stability of oxidation reduction is high.

As alkyl acrylate or alkyl methacrylate, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, 2-methoxy acrylate Alkyl acrylates such as ethyl, -2-ethoxyethyl acrylate, and benzyl acrylate; Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate Alkyl methacrylates such as tridecyl methacrylate, stearyl methacrylate, and benzyl methacrylate; .

Content of the monomer component whose solubility parameter (SP) in component B is 8.0 or more and less than 11 becomes like this. Preferably it is 30 mass% or more, More preferably, it is the range of 50-90 mass% with respect to 100 mass% of monomer total amounts. Content of the monomer component whose solubility parameter (SP) in a 2nd segment is 8.0 or more and less than 11 can be controlled by the monomer injection ratio at the time of graft polymer manufacture. When content of the monomer component whose solubility parameter (SP) is 8.0 or more and less than 11 exists in an appropriate range, it does not melt | dissolve even showing swelling property with respect to electrolyte solution, and does not cause elution inside a battery, and shows high high temperature characteristic.

Examples of the monomer component having a hydrophilic group include a monomer having a -COOH group (carboxylic acid group), a monomer having a -OH group (hydroxyl group), a monomer having a -SO ₃ H group (sulfonic acid group), and a monomer having a -PO ₃ H ₂ group. , A monomer having a -PO (OH) (OR) group (R represents a hydrocarbon group), and a monomer having a lower polyoxyalkylene group.

As a monomer which has a carboxylic acid group, monocarboxylic acid, its derivative (s), dicarboxylic acid, its acid anhydride, these derivatives, etc. are mentioned. As monocarboxylic acid, acrylic acid, methacrylic acid, crotonic acid, etc. are mentioned. As monocarboxylic acid derivative, 2-ethylacrylic acid, 2-ethylacrylic acid, isocrotonic acid, (alpha)-acetoxyacrylic acid, (beta) -trans-allyloxyacrylic acid, (alpha)-chloro- (beta) -E-methoxyacrylic acid, (beta)- Diamino acrylic acid etc. are mentioned. Examples of the dicarboxylic acid include maleic acid, fumaric acid and itaconic acid. Examples of the acid anhydride of the dicarboxylic acid include maleic anhydride, acrylic acid anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. Examples of the dicarboxylic acid derivatives include methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloro maleic acid, dichloromaleic acid, and fluoromaleic acid, such as methyl allyl maleate, diphenyl maleic acid, nonyl maleate, and maleic acid maleic acid; Maleic acid esters such as dodecyl maleate, octadecyl maleate and fluoroalkyl maleate; .

As a monomer which has a hydroxyl group, Ethylenic unsaturated alcohols, such as (meth) allyl alcohol, 3-butene-1-ol, and 5-hexene-1-ol; 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, maleic acid-di-2-hydroxyethyl, maleic acid- Alkanol esters of ethylenically unsaturated carboxylic acids such as 4-hydroxybutyl and di-2-hydroxypropyl itaconic acid; Polyalkylene glycol represented by general formula CH ₂ = CR ¹ -COO- (CnH ₂ nO) mH (m is an integer of 2 to 9, n is an integer of 2 to 4, R1 represents hydrogen or a methyl group) and (meth ) Esters of acrylic acid; Mono of dihydroxy esters of dicarboxylic acids such as 2-hydroxyethyl-2 '-(meth) acryloyloxyphthalate and 2-hydroxyethyl-2'-(meth) acryloyloxysuccinate Meth) acrylic acid esters; Vinyl ethers such as 2-hydroxyethyl vinyl ether and 2-hydroxypropyl vinyl ether; (Meth) allyl-2-hydroxyethyl ether, (meth) allyl-2-hydroxypropyl ether, (meth) allyl-3-hydroxypropyl ether, (meth) allyl-2-hydroxybutyl ether, (meth Mono (meth) allyl ethers of alkylene glycols such as allyl-3-hydroxybutyl ether, (meth) allyl-4-hydroxybutyl ether, and (meth) allyl-6-hydroxyhexyl ether; Polyoxyalkylene glycol (meth) monoallyl ethers such as diethylene glycol mono (meth) allyl ether and dipropylene glycol mono (meth) allyl ether; Halogen of (poly) alkylene glycols such as glycerin mono (meth) allyl ether, (meth) allyl-2-chloro-3-hydroxypropyl ether, (meth) allyl-2-hydroxy-3-chloropropyl ether And mono (meth) allyl ethers of hydroxy substituents; Mono (meth) allyl ethers of polyhydric phenols such as eugenol and isoeugenol and halogen substituents thereof; (Meth) allylthio ethers of alkylene glycols such as (meth) allyl-2-hydroxyethylthioether and (meth) allyl-2-hydroxypropylthioether; And the like.

Examples of the monomer having a sulfonic acid group include vinylsulfonic acid, methylvinylsulfonic acid, (meth) allylsulfonic acid, styrenesulfonic acid, ethyl (meth) acrylic acid-2-sulfonic acid, 2-acrylamide-2-methylpropanesulfonic acid, and 3-allyloxy-2. -Hydroxypropanesulfonic acid, etc. are mentioned.

-PO ₃ H ₂ group and / or -PO (OH) (OR) group of the monomer having the (R represents a hydrocarbon group) is phosphate-2- (meth) acryloyloxyethyl phosphate, methyl-2- ( (Meth) acryloyloxyethyl, ethyl phosphate ((meth) acryloyloxyethyl, etc. are mentioned.

As a monomer containing a lower polyoxyalkylene group, poly (alkylene oxide), such as poly (ethylene oxide), etc. are mentioned.

As segment B, when comprised by having the monomer component which has the said hydrophilic group, among the monomers which have these hydrophilic groups, the monomer which has a carboxylic acid group is preferable from a viewpoint of further improving the dispersibility of an active material.

Content of the monomer component which has a hydrophilic group in segment B is 0.5-40 mass% with respect to 100 mass% of monomer total amounts as monomer amount which has a hydrophilic group at the time of superposition | polymerization, More preferably, it is the range of 3-20 mass% to be. Content of the monomer which has a hydrophilic group in segment B can be controlled by the monomer injection ratio at the time of graft polymer manufacture. By making content of the monomer which has a hydrophilic group in the segment B into a predetermined range, it shows swelling property with respect to appropriate electrolyte solution, and neither dissolution inside a battery arises.

You may use segment B for these monomers individually or in combination of 2 or more types. In particular, a copolymer of an alkyl acrylate ester or a methacrylic acid alkyl ester and a monomer having a carboxylic acid group is preferable because of high swelling property to the electrolyte and high stability to redox.

Moreover, it is preferable that segment A, segment B, or both glass transition temperatures are 15 degrees C or less, since the electrode with high flexibility is obtained. Particularly, since the segment A is adsorbed on the surface of the active material inside the electrode and the segment B is on the outside (the surface on the side farther from the active material of the layer of the binder attached to the surface of the particles of the active material), the flexibility is further improved. It is preferable that the glass transition temperature of B is 15 degrees C or less, More preferably, it is -5 degrees C or less, Especially preferably, it is -40 degrees C or less. When Tg of segment B exists in the said range, since the mobility of the segment B site | part becomes high in the state which the segment A site | part in the graft polymer adsorb | sucked to the surface of an active material, Li ion water solubility at low temperature improves. The lower limit of the glass transition temperature of the segment A, the segment B, or both thereof (in particular, the glass transition temperature of the segment when the glass transition temperature of the segment is 15 ° C. or lower) is not particularly limited, but is -100 ° C. or higher. can do.

In addition, the glass transition temperature of a segment can be adjusted by further combining the combination of the monomer illustrated and the copolymerizable monomer mentioned later.

Although the ratio of segment A and segment B in the graft polymer has high rate characteristics while controlling the swelling degree with respect to the electrolyte within a predetermined range, the graft polymer differs from the segment A in terms of its composition, crosslinking degree, and the like. When there is no copolymerization component other than segment B, the ratio of segment A: segment B is 20: 80-80: 20 by mass ratio, More preferably, it is 30: 70-70: 30.

The swelling degree with respect to the electrolyte solution of the segment A and the segment B in a graft polymer can be adjusted by controlling also molecular weight and a crosslinking degree in addition to the ratio of the segment A and the segment B mentioned above.

The swelling degree with respect to electrolyte solution tends to become large, so that molecular weight is small, and it becomes small, so that molecular weight is large. Therefore, although the range of the weight average molecular weight of a graft polymer for making it into a preferable swelling degree changes with the structure, the crosslinking degree, etc., it is measured by the gel permeation chromatography using tetrahydrofuran (THF) as a developing solvent, for example. In one standard polystyrene conversion value, it is 1,000-500,000, More preferably, it is 2,000-100,000. By making the weight average molecular weight of a graft polymer into the said range, segment A and segment B show predetermined swelling property, and show high rate characteristic and gas generation suppression effect.

In the case where the degree of swelling of the electrolytes of the segment A and the segment B in the graft polymer is controlled by the degree of crosslinking of the graft polymer, the range of the preferred degree of crosslinking varies depending on the structure, molecular weight and the like, for example, such as tetrahydrofuran and the like. When immersed in a polar solvent for 24 hours, it is preferable to set it as the degree of crosslinking of the grade which melt | dissolves or swells at 400% or more. By making crosslinking degree into the said range, segment A and segment B show predetermined swelling property, and show high rate characteristic and cycling characteristic.

As a crosslinking method of a graft polymer, the method of crosslinking by heating or energy-beam irradiation is mentioned. By crosslinking and using the graft polymer which can be bridge | crosslinked by heating or energy-beam irradiation, crosslinking degree can be adjusted by heating conditions or irradiation conditions (strength etc.) of energy-beam irradiation. In addition, since the degree of swelling tends to decrease as the degree of crosslinking is higher, the degree of swelling can be adjusted by changing the degree of crosslinking.

As a method of making the graft polymer which can be bridge | crosslinked by heating or energy-beam irradiation, the method of introduce | transducing a crosslinkable group in a graft polymer, or the method of using a crosslinking agent together is mentioned.

As a method of introducing a crosslinkable group in the said graft polymer, the method of introducing a photocrosslinkable crosslinkable group in a graft polymer, and the method of introducing a heat crosslinkable crosslinkable group are mentioned. Among these, the method of introducing a heat crosslinkable crosslinkable group into the graft polymer is capable of crosslinking the binder by suppressing dissolution in the electrolyte solution by performing heat treatment on the electrode plate after electrode plate application, and is robust and flexible. It is preferable because an electrode plate is obtained. In the case of introducing a heat crosslinkable crosslinkable group into the graft polymer, at least one member selected from the group consisting of an epoxy group, an N-methylolamide group, an oxetanyl group, and an oxazoline group is preferable as the heat crosslinkable crosslinkable group. And an epoxy group is more preferable at the point which crosslinking and control of a crosslinking density are easy.

As a monomer containing an epoxy group, the monomer containing a carbon-carbon double bond and an epoxy group, and the monomer containing a halogen atom and an epoxy group are mentioned.

As a monomer containing a carbon-carbon double bond and an epoxy group, unsaturated glycidyl, such as vinylglycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, o-allylphenyl glycidyl ether, is mentioned, for example. Ether; Dienes such as butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5,9-cyclododecadiene or Monoepoxide of polyene; Alkenylepoxides such as 3,4-epoxy-1-butene, 1,2-epoxy-5-hexene and 1,2-epoxy-9-decene; Glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl-4-methyl- Glycidyl esters of unsaturated carboxylic acids such as glycidyl ester of 3-pentenoate, 3-cyclohexene carboxylic acid and glycidyl ester of 4-methyl-3-cyclohexene carboxylic acid; .

As a monomer which has a halogen atom and an epoxy group, For example, epihalohydrin, such as epichlorohydrin, epibromohydrin, epiiodhydrin, epifluorohydrin, (beta) -methyl epichlorohydrin; p-chloro styrene oxide; Dibromophenyl glycidyl ether; .

As a monomer containing an N-methylolamide group, (meth) acrylamide which has methylol groups, such as N-methylol (meth) acrylamide, is mentioned.

As a monomer containing an oxetanyl group, 3-((meth) acryloyloxymethyl) oxetane, 3-((meth) acryloyloxymethyl) -2-trifluoromethyloxetane, 3- ( (Meth) acryloyloxymethyl) -2-phenyloxetane, 2-((meth) acryloyloxymethyl) oxetane, 2-((meth) acryloyloxymethyl) -4-trifluoromethyl Oxetane etc. are mentioned.

Examples of the monomer containing an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, and 2-isopropenyl- 2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, etc. Can be mentioned.

The content rate of the heat crosslinkable crosslinkable group in the graft polymer is a monomer amount containing a heat crosslinkable crosslinkable group at the time of polymerization, and is preferably 0.1 to 10% by mass, more preferably relative to 100% by mass of the total monomer. It is the range of 0.1-5 mass%. The content rate of the heat crosslinkable crosslinkable group in a graft polymer can be controlled by the monomer injection ratio at the time of manufacturing a graft polymer. By the content rate of the heat crosslinkable crosslinking group in a graft polymer being in the said range, segment A and segment B show predetermined swelling property, and can exhibit high rate characteristic and gas generation suppression effect.

The thermally crosslinkable crosslinkable group can be introduced into the graft polymer by copolymerizing a monomer containing a thermally crosslinkable crosslinkable group in addition to the monomers described above and / or other monomers copolymerizable with the monomers described above. .

In the present invention, the swelling degree of the graft polymer with respect to the electrolyte solution is preferably in the range of 100% or more and 300% or less, and more preferably in the range of 100% or more and 200% or less. By the swelling degree with respect to the electrolyte solution of the graft polymer being the said range, it shows the swelling property with respect to electrolyte solution, showing the binding property in a positive electrode layer at the time of battery manufacture, and can express a rate characteristic, without falling off of an active material. The swelling degree of the graft polymer with respect to the electrolyte solution can be adjusted by controlling the composition, molecular weight and crosslinking degree in the same manner as the swelling with respect to the electrolyte solutions of the above-mentioned segments A and Segment B.

The graft polymer used for this invention may contain the monomer copolymerizable with these other than the monomer component mentioned above. As a monomer copolymerizable with these, Carboxylic acid ester which has 2 or more carbon-carbon double bonds, such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and trimethylol propane triacrylate; Halogen atom-containing monomers such as vinyl chloride and vinylidene chloride; Vinyl esters such as vinyl acetate, vinyl propionate and vinyl butyrate; Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and butyl vinyl ether; Vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, and isopropenyl vinyl ketone; Heterocyclic ring-containing vinyl compounds such as N-vinylpyrrolidone, vinylpyridine and vinylimidazole; Amide system monomers, such as acrylamide and N-methylol acrylamide; . The graft polymer of the said structure is obtained by graft copolymerizing these monomers by a suitable method.

In the present invention, the glass transition temperature of the graft polymer is preferably from the viewpoint of providing flexibility to the electrode plate at room temperature and suppressing cracks during roll winding and winding of the electrode plate, defects in the electrode plate layer, and the like. Is 20 degrees C or less, More preferably, it is 0 degrees C or less. The lower limit of the glass transition temperature of the graft polymer is not particularly limited, but may be -100 ° C or higher. The glass transition temperature of a graft polymer can be prepared by changing the use ratio etc. of the monomer which comprises.

The graft polymer used for this invention is synthesize | combined by the method of 1) copolymerizing so that a branched structure may be comprised, or 2) the method of modifying the obtained polymer and producing a branched structure. Especially, since the target structure can be obtained in one process, the method of said 1) is preferable.

As a method of copolymerizing so that the said 1) branch structure may be comprised, a graft polymer can be obtained by a chain transfer reaction, for example by polymerizing a graft monomer by a well-known polymerization method in presence of a stem polymer. The graft polymer can also be obtained by introducing a functional group capable of generating radicals or ions into the stem polymer and initiating the polymerization reaction of the graft monomer from the functional group. In addition, the branch polymer obtained by superposing | polymerizing the graft monomer which can form a branched structure at the time of superposition | polymerization by a well-known polymerization method may be added to a stem polymer by radical addition reaction etc. Specifically, the graft polymer can be manufactured by the method described in JP-A-6-51767.

Among these, the method of adding the branch polymer obtained by superposing | polymerizing the graft monomer which can form a branched structure at the time of superposition | polymerization by a well-known polymerization method to a stem polymer by radical addition reaction etc. is the most easy to control a structure later, Since it is easy to stabilize the slurry for secondary battery electrodes, it is preferable. Specifically, the method of copolymerizing using a macromonomer as a branch polymer is mentioned.

As said macromonomer, for example, single-end methacryloylated polystyrene oligomer which has acryloyl group or a methacryloyl group at the one end of a polymer (Toa Synthetic Chemical Co., Ltd. make, "AS-6", Mn = 6000) , Single terminal methacryloylated polymethyl methacrylate oligomer (manufactured by Toa Synthetic Chemical Co., Ltd., "AA-6", Mn = 6000), single terminal methacryloylated polyacrylate butyl oligomer (manufactured by Toa Synthetic Chemical Co., Ltd., "AB -6 ", Mn = 6000), single-end methacryloylated polystyrene-acrylonitrile oligomer (The Toa Synthetic Chemical Co., Ltd. make," AN-6S "), etc. are mentioned.

Moreover, isocyanate ethyl methacrylate, acrylic acid, or methacrylic acid (it may abbreviate as "(meth) acrylic acid" hereafter) to the polymer which has functional groups, such as a hydroxyl group, on one end like polyoxyethylene monomethyl ether, ( Various macromonomer can also be obtained by making ethylenic unsaturated monomer which has functional groups, such as a meth) acrylic acid chloride and glycidyl (meth) acrylate, react. The graft polymer can be obtained by copolymerizing these macromonomers with other ethylenically unsaturated monomers.

The polymerization method of the graft polymer is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method or an emulsion polymerization method can be used. As the polymerization method, any method such as ionic polymerization, radical polymerization or living radical polymerization can be used. As a polymerization initiator used for superposition | polymerization, a lauroyl peroxide, diisopropyl peroxy dicarbonate, di-2-ethylhexyl peroxy dicarbonate, t-butylperoxy pivalate, 3,3,5-trimethyl hexa, for example Organic peroxides, such as a noyl peroxide, Azo compounds, such as (alpha), (alpha) '-azobisisobutyronitrile, ammonium persulfate, potassium persulfate, etc. are mentioned.

It is preferable that the graft polymer used for this invention is obtained through the particulate metal removal process which removes the particulate metal contained in a polymer solution or a polymer dispersion liquid in the manufacturing process of a graft polymer. By content of the particulate metal component contained in a graft polymer composition being 0 ppm or more and 10 ppm or less, metal ion bridge | crosslinking with the passage of time between polymers in the slurry for secondary battery electrodes mentioned later can be prevented, and a viscosity rise can be prevented. . Moreover, there is little possibility of the increase of the self discharge by the internal short circuit of a secondary battery or melt | dissolution and precipitation at the time of charge, and the cycling characteristics and safety of a battery improve.

The method of removing a particulate metal component from the polymer solution or polymer dispersion liquid in the said particulate metal removal process is not specifically limited, For example, the method of removing by filtration by a filtration filter, the method of removing by a vibrating sieve, and centrifugation The removal by separation, the removal by magnetic force, etc. are mentioned. Especially, since the removal object is a metal component, the method of removing by magnetic force is preferable. The method of removing by magnetic force is not particularly limited as long as it is a method capable of removing a metal component. However, in view of productivity and removal efficiency, the magnetic filter is preferably disposed in a graft polymer production line.

The content rate of the graft polymer in a binder makes 100 mass% of all binder amounts, Preferably it is 30 mass% or more and 100 mass% or less, More preferably, it is 45 mass% or more and 100 mass% or less, Most preferably, 60 It is mass% or more and 100 mass% or less. When the content ratio of the graft polymer in the binder is in the above range, it is possible to suppress the increase in resistance by inhibiting the movement of lithium while maintaining the binding property of the active material particles and the binding property to the electrode or the separator. have.

The binder may further contain other binder components in addition to the graft polymer (that is, the binder of the present invention may include components that can function as a binder other than the graft polymer). Moreover, the electrode for secondary batteries of this invention may contain the component which can function as a binder other than the said graft polymer in addition to the said graft polymer as a binder). As another binder component, various resin components can be used together. For example, polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid, polyacrylonitrile, polyacrylate, Polymethacrylate and the like can be used. In addition, a copolymer containing 50% or more of the resin component (that is, in the unit constituting the copolymer as the copolymer, the same unit as the unit constituting the resin occupies 50% or more and 100% or less (weight ratio)). Polyacrylonitrile, such as polyacrylic acid derivatives such as acrylic acid-styrene copolymers and acrylic acid-acrylate copolymers, acrylonitrile-styrene copolymers and acrylonitrile-acrylate copolymers. Derivatives can also be used.

Moreover, the soft polymer illustrated below can also be used as a binder.

Polybutyl acrylate, polybutyl methacrylate, polyhydroxyethyl methacrylate, polyacrylamide, polyacrylonitrile, butyl acrylate styrene copolymer, butyl acrylate acrylonitrile copolymer, butyl acrylate? Acrylic soft polymer which is a homopolymer of acrylic acid or methacrylic acid derivatives, such as an acrylonitrile glycidyl methacrylate copolymer, or a copolymer of the monomer copolymerizable with it; Isobutylene soft polymers such as polyisobutylene, isobutylene isoprene rubber and isobutylene styrene copolymer; Polybutadiene, polyisoprene, butadiene styrene random copolymer, isoprene styrene random copolymer, acrylonitrile butadiene copolymer, acrylonitrile butadiene styrene copolymer, butadiene styrene block copolymer, styrene butadiene? Diene soft polymers such as styrene block copolymers, isoprene styrene block copolymers, and styrene isoprene styrene block copolymers; Silicon-containing soft polymers such as dimethylpolysiloxane, diphenylpolysiloxane, and dihydroxypolysiloxane; Olefins such as liquid polyethylene, polypropylene, poly-1-butene, ethylene-α-olefin copolymers, propylene-α-olefin copolymers, ethylene-propylene-diene copolymers (EPDM) and ethylene-propylene-styrene copolymers Soft polymer; Vinyl-based soft polymers such as polyvinyl alcohol, polyvinyl acetate, polyvinyl stearate, and vinyl acetate-styrene copolymers; Epoxy soft polymers such as polyethylene oxide, polypropylene oxide and epichlorohydrin rubber; Fluorine-containing soft polymers such as vinylidene fluoride rubber and tetrafluoroethylene-propylene rubber; And other soft polymers such as natural rubber, polypeptides, proteins, polyester-based thermoplastic elastomers, vinyl chloride-based thermoplastic elastomers, and polyamide-based thermoplastic elastomers. These soft polymers may have a crosslinked structure, or may introduce a functional group by modification. These may be used independently and may be used in combination of 2 or more type.

Especially, since a polyacrylonitrile derivative improves the dispersibility of an active material, it is preferable. The content ratio of the other binder is 100% by mass of the total binder, preferably 5% by mass or more and 80% by mass or less, more preferably 10% by mass or more and 70% by mass or less, most preferably 20% by mass. It is more than 60 mass%. When the other binder is in the above range, the resistance inside the battery does not increase, and high life characteristics can be exhibited.

Content of the whole binder in a secondary battery electrode is 0.1-10 mass parts with respect to 100 mass parts of active materials, More preferably, it is 0.5-5 mass parts. When content of the binder in a secondary battery electrode exists in the said range, it is excellent in binding property with respect to active materials and an electrical power collector, maintains flexibility, and does not increase resistance without inhibiting Li movement.

(Current collector)

In the electrode for secondary batteries of this invention, the electrode active material layer containing an active material and a binder is laminated | stacked on an electrical power collector.

The current collector is not particularly limited as long as it is an electrically conductive and electrochemically durable material, but from the viewpoint of heat resistance, for example, iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum Metal materials, such as these, are preferable. Especially, aluminum is especially preferable for the positive electrode of a lithium ion secondary battery, and copper is especially preferable for the negative electrode of a lithium ion secondary battery. Although the shape of an electrical power collector is not specifically limited, It is preferable that it is a sheet form with a thickness of about 0.001-0.5 mm. In order that a collector may raise the adhesive strength of an electrode, it is preferable to use it, roughening previously. Examples of the roughening method include mechanical roughening, electrolytic roughening, and chemical roughening. In the mechanical polishing method, a wire brush provided with abrasive cloth, a grindstone, an emery buff, a steel wire or the like to which abrasive particles are fixed are used. Moreover, you may form an intermediate | middle layer in the electrical power collector surface for the purpose of improving the adhesive strength and electroconductivity of an electrode.

The electrode for secondary batteries of this invention may contain arbitrary components other than the said component further. As said arbitrary component, the electrolyte solution additive which has functions, such as electroconductivity imparting material, a reinforcing material, a dispersing agent, a leveling agent, antioxidant, a thickener, and electrolyte solution decomposition suppression, is mentioned. These are not particularly limited as long as they do not affect the battery reaction.

As the conductive imparting material, conductive carbon such as acetylene black, Ketjen black, carbon black, graphite, vapor grown carbon fiber, and carbon nanotube can be used. Carbon powder, such as graphite, fiber of various metals, foil, etc. are mentioned. By using an electroconductivity imparting material, the electrical contact of electrode active materials can be improved, and discharge load characteristics can be improved especially when using for a lithium ion secondary battery. As the reinforcing material, various inorganic and organic spherical, plate-like, rod-like or fibrous fillers can be used. By using the reinforcing material, a strong and flexible electrode can be obtained, and excellent long-term cycle characteristics can be exhibited. The usage-amount of electroconductivity imparting material and a reinforcing agent is 0.01-20 mass parts normally with respect to 100 mass parts of electrode active materials, Preferably it is 1-10 mass parts. By being included in the above range, it is possible to exhibit high capacity and high load characteristics.

Examples of the dispersant include anionic compounds, cationic compounds, nonionic compounds, and high molecular compounds. The dispersant is selected according to the electrode active material and the conductive agent to be used. The content rate of the dispersing agent in an electrode becomes like this. Preferably it is 0.01-10 mass parts. When the amount of the dispersant is within the above range, the slurry is excellent in stability, a smooth electrode can be obtained, and high battery capacity can be exhibited.

Examples of the leveling agent include surfactants such as alkyl surfactants, silicone surfactants, fluorine surfactants, and metal surfactants. By mixing the said surfactant, the cratering which arises at the time of coating can be prevented, or the smoothness of an electrode can be improved. The content rate of the leveling agent in an electrode becomes like this. Preferably it is 0.01-10 mass parts. When the leveling agent is in the above range, the productivity, smoothness and battery characteristics at the time of electrode production are excellent.

As antioxidant, a phenol compound, a hydroquinone compound, an organic phosphorus compound, a sulfur compound, a phenylenediamine compound, a polymeric phenol compound, etc. are mentioned. The polymer type phenol compound is a polymer having a phenol structure in a molecule, and a polymer type phenol compound having a weight average molecular weight of 200 to 1000, preferably 600 to 700 is preferably used. The content rate of antioxidant in an electrode becomes like this. Preferably it is 0.01-10 mass parts, More preferably, it is 0.05-5 mass parts. When the antioxidant is in the above range, the slurry stability, battery capacity and cycle characteristics are excellent.

As a thickener, Cellulose polymers, such as carboxymethylcellulose, methylcellulose, and hydroxypropyl cellulose, these ammonium salts, and alkali metal salts; (Modified) poly (meth) acrylic acid and ammonium salts and alkali metal salts thereof; (Modified) polyvinyl alcohols such as a copolymer of polyvinyl alcohol, acrylic acid or acrylate and vinyl alcohol, a copolymer of maleic anhydride or maleic acid, or fumaric acid and vinyl alcohol; Polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, modified polyacrylic acid, starch oxide, starch phosphate, casein, various modified starches, acrylonitrile-butadiene copolymer hydride and the like. If the usage-amount of a thickener is this range, coatability and adhesiveness with an electrode or an organic separator are favorable. In the present invention, "(modified) poly" means "unmodified poly" or "modified poly", and "(meth) acryl" means "acryl" or "methacryl". The content rate of the thickener in an electrode becomes like this. Preferably it is 0.01-10 mass parts. When the thickener is in the above range, excellent dispersibility of active materials and the like in the slurry can be obtained, and a smooth electrode can be obtained, and excellent load characteristics and cycle characteristics are shown.

As an electrolyte solution additive, the vinylene carbonate etc. which are used in the electrode slurry mentioned later and in electrolyte solution can be used. The content rate of the electrolyte solution additive in an electrode becomes like this. Preferably it is 0.01-10 mass parts. When electrolyte solution additive is the said range, it is excellent in cycling characteristics and high temperature characteristics. In addition, nano fine particles, such as fumed silica and fumed alumina: Surfactant, such as alkyl type surfactant, silicone type surfactant, fluorine type surfactant, and metal type surfactant. By mixing the said nanoparticles, the thixotropy of the slurry for electrode formation can be controlled, and the leveling property of the electrode obtained by it can be improved. The nano fine particles and the content ratio in the electrode are preferably 0.01 to 10 parts by mass. When nanoparticles are in the said range, it is excellent in slurry stability and productivity, and shows high battery characteristics. By mixing the said surfactant, dispersibility, such as an active material in the slurry for electrode formation, can be improved, and also the smoothness of the electrode obtained by it can be improved. The content rate of surfactant in an electrode becomes like this. Preferably it is 0.01-10 mass parts. When surfactant is in the said range, it is excellent in slurry stability and electrode smoothness, and shows high productivity.

The manufacturing method of the electrode for secondary batteries of this invention should just be a method of binding an electrode in layer form at least one side, preferably both surfaces of the said electrical power collector. For example, the slurry for secondary battery electrodes mentioned later is apply | coated to an electrical power collector, it is dried, and then heat-processed at 120 degreeC or more for 1 hour or more, and forms an electrode. Although the upper limit of heat processing temperature is not specifically limited, It can be 200 degrees C or less. Although the upper limit of heat processing time is not specifically limited, It can be 24 hours or less.

(Slurry for Secondary Battery Electrode)

The slurry for secondary battery electrodes used for this invention contains the binder containing an graft polymer, an active material, and a solvent. Examples of the binder and the active material containing the graft polymer include those similar to those described for the electrode for secondary batteries.

(menstruum)

The solvent is not particularly limited as long as it can uniformly dissolve or disperse the binder of the present invention.

As a solvent used for the slurry for secondary battery electrodes, any of water and an organic solvent can be used. As an organic solvent, Cycloaliphatic hydrocarbons, such as cyclopentane and cyclohexane; Aromatic hydrocarbons such as toluene, xylene and ethylbenzene; Ketones such as acetone, ethyl methyl ketone, diisopropyl ketone, cyclohexanone, methylcyclohexane and ethylcyclohexane; Chlorine aliphatic hydrocarbons such as methylene chloride, chloroform and carbon tetrachloride; Esters such as ethyl acetate, butyl acetate, γ-butyrolactone and ε-caprolactone; Acyl nitriles such as acetonitrile and propionitrile; Ethers such as tetrahydrofuran and ethylene glycol diethyl ether: alcohols such as methanol, ethanol, isopropanol, ethylene glycol and ethylene glycol monomethyl ether; Amides, such as N-methylpyrrolidone and N, N- dimethylformamide, are mentioned.

These solvents may be used alone, or two or more thereof may be mixed and used as a mixed solvent. Among these, especially the solvent which is excellent in the solubility of the polymer of this invention, excellent in the dispersibility of an electrode active material and a electrically conductive agent, and having a low boiling point and high volatility can be removed in a short time and at low temperature. Acetone, toluene, cyclohexanone, cyclopentane, tetrahydrofuran, cyclohexane, xylene, water, or N-methylpyrrolidone, or a mixed solvent thereof is preferable.

Solid content concentration of the slurry for secondary battery electrodes used for this invention is a grade which can apply | coat and immerse the slurry, and is not specifically limited as long as it becomes a viscosity which has fluidity, but is generally about 10-80 mass% to be.

Components other than solid content are components volatilized by a drying process, and are added to the said solvent, for example, also the medium which melt | dissolved or disperse | distributed these at the time of preparation and addition of a graft polymer.

Since the slurry for secondary battery electrodes of this invention is for forming the electrode for secondary batteries of this invention, the content rate of an electrode active material and a graft polymer in solid content whole quantity of the slurry for secondary battery electrodes is, of course, the secondary of this invention. The electrode active material layer of the battery electrode is as described above.

Further, the slurry for secondary battery electrodes includes, in addition to the binder, the active material, and the solvent containing a graft polymer, an optional component such as an electrolyte solution additive having a function such as a dispersing agent or electrolyte solution decomposition suppression used in the above secondary battery electrode. May be included. These are not particularly limited as long as they do not affect the battery reaction.

(Slurry Production Method for Secondary Battery Electrodes)

In this invention, the manufacturing method of the slurry for secondary battery electrodes is not specifically limited, It is obtained by mixing the binder containing a graft polymer, an active material, and the solvent and another component added as needed.

In the present invention, by using the above components, a slurry for electrodes in which the electrode active material and the conductive agent are highly dispersed can be obtained regardless of the mixing method and the mixing order. The mixing device is not particularly limited as long as it is a device capable of uniformly mixing the above components, and may be a bead mill, a ball mill, a roll mill, a sand mill, a pigment disperser, a brain trajectory, an ultrasonic disperser, a homogenizer, a planetary mixer, a peel mix, or the like. Among them, from the viewpoint of high dispersion, it is particularly preferable to use a ball mill, roll mill, pigment disperser, brain trajectory, planetary mixer.

The viscosity of the slurry for secondary battery electrodes is 10 mPa * s-100,000 mPa * s, More preferably, it is 100-50,000 mPa * s from a viewpoint of uniform coating property and slurry aging stability. The said viscosity is a value when it measures by 25 degreeC and rotation amount 60rpm using a Brookfield viscometer.

The method of apply | coating the slurry for secondary battery electrodes to an electrical power collector is not specifically limited. For example, methods, such as a doctor blade method, the jeep method, the reverse roll method, the direct roll method, the gravure method, the extrusion method, the brush coating method, are mentioned. As a drying method, the drying method by irradiation with warm air, hot air, low humidity wind, vacuum drying, (far) infrared rays, an electron beam, etc. are mentioned, for example.

Subsequently, it is preferable to make the porosity of an electrode low by a pressurization process using a metal mold | die press, a roll press, etc. The range with a porosity is 5%-15%, More preferably, it is 7%-13%. If the porosity is too high, the charging efficiency and the discharge efficiency deteriorate. When the porosity is too low, problems such as high volume capacity are difficult to be obtained or the electrode is easily peeled off and easily causes defects. In addition, when using a curable polymer, it is preferable to harden.

The thickness of the electrode for secondary batteries of this invention is 5-300 micrometers normally, Preferably it is 10-250 micrometers. By the electrode thickness being in the above range, both the load characteristics and the energy density exhibit high characteristics.

(Secondary battery)

The secondary battery of this invention contains a positive electrode, a negative electrode, a separator, and electrolyte solution, and at least any one of the said positive electrode and a negative electrode is the said secondary battery electrode. Among them, the conductive agent and the active material are often used in combination, and the rate characteristic due to the poor dispersibility of the conductive agent is often seen, and the reaction of the electrolyte solution on the surface of the active material due to the high potential is likely to occur. Since a lot of gas generation is seen, when used for a positive electrode, a big effect can be acquired.

Examples of the secondary battery include a lithium ion secondary battery, a nickel hydrogen secondary battery, and the like. A lithium ion secondary battery is preferable for the use because performance improvement such as suppression of gas generation and improvement of output characteristics is most demanded. Hereinafter, the case where it uses for a lithium ion secondary battery is demonstrated.

(Electrolyte for lithium ion secondary battery)

As an electrolyte solution for lithium ion secondary batteries, the organic electrolyte solution which melt | dissolved the supporting electrolyte in the organic solvent is used. Lithium salt is used as a supporting electrolyte. The lithium salt is not particularly limited, but LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO ) ₂ NLi, (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi, and the like. Among them, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li that are easily dissolved in a solvent and exhibit high dissociation degree are preferable. These may use 2 or more types together. Since the higher the degree of dissociation of the supporting electrolyte, the higher the lithium ion conductivity, the lithium ion conductivity can be adjusted according to the type of the supporting electrolyte.

The organic solvent used in the electrolyte solution for lithium ion secondary batteries is not particularly limited as long as the supporting electrolyte can be dissolved therein, but is not limited to dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), and propylene carbonate (PC). Carbonates such as butylene carbonate (BC) and methyl ethyl carbonate (MEC); esters such as γ-butyrolactone and methyl formate; Ethers such as 1,2-dimethoxyethane and tetrahydrofuran; Sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; Is preferably used. Moreover, you may use the liquid mixture of these solvent. Among them, carbonates are preferable because the dielectric constant is high and the stable potential region is wide. Since the lower the viscosity of the solvent used, the higher the lithium ion conductivity is, so that the lithium ion conductivity can be adjusted according to the type of the solvent.

Moreover, it is also possible to contain and use an additive in the said electrolyte solution. As an additive, carbonate type compounds, such as vinylene carbonate (VC) used in the slurry for secondary battery electrodes mentioned above, are mentioned.

The density | concentration of the supporting electrolyte in the electrolyte solution for lithium ion secondary batteries is 1-30 mass% normally, Preferably it is 5 mass%-20 mass%. In addition, depending on the type of the supporting electrolyte, it is usually used at a concentration of 0.5 to 2.5 mol / l. Even if the concentration of the supporting electrolyte is too low or too high, the ion conductivity tends to be lowered.

Examples of the electrolytic solution other than the above include polymer electrolytes such as polyethylene oxide and polyacrylonitrile, gel polymer electrolytes in which the polymer electrolyte is impregnated with an electrolyte solution, and inorganic solid electrolytes such as LiI and Li ₃ N.

(Separator for lithium ion secondary battery)

As a separator, Microporous film or nonwoven fabric made of polyolefin, such as polyethylene and a polypropylene; Porous resin coat containing inorganic ceramic powder; And the like can be used. As a separator for lithium ion secondary batteries, Microporous film or nonwoven fabric containing polyolefin resin, such as polyethylene and a polypropylene, and aromatic polyamide resin; Porous resin coat containing inorganic ceramic powder; And the like can be used. For example, a microporous membrane made of resin such as polyolefin-based (polyethylene, polypropylene, polybutene, polyvinyl chloride), and mixtures or copolymers thereof, polyethylene terephthalate, polycycloolefin, polyether sulfone, polyamide, poly Woven microporous membranes or polyolefin fibers made of resins such as meads, polyimideamides, polyaramids, polycycloolefins, nylons, and polytetrafluoroethylene, or aggregates of nonwoven fabrics and insulating material particles thereof. Among these, the microporous membrane which consists of polyolefin resin is preferable, since the film thickness of the whole separator can be made thin and the ratio of the active material in a battery can be raised and a capacity per volume can be raised.

The thickness of the separator is usually 0.5 to 40 µm, preferably 1 to 30 µm, and more preferably 1 to 10 µm. If it is this range, resistance by the separator in a battery will become small and it is excellent in the workability at the time of battery manufacture.

As a specific manufacturing method of a lithium ion secondary battery, the method of laminating | stacking a positive electrode and a negative electrode through a separator, winding this according to a battery shape, folding it, etc. into a battery container, inject | pouring electrolyte solution into a battery container, and sealing it is mentioned. have. If necessary, an expanded metal, an overcurrent prevention element such as a fuse, a PTC element, a lead plate, or the like may be put therein to prevent pressure increase and overcharge / discharge inside the battery. The shape of the battery may be any of a coin type, a button type, a sheet type, a cylindrical shape, a square shape, and a flat type.

Example

Although an Example is given to the following and this invention is demonstrated, this invention is not limited to this. In addition, the part and% in a present Example are a mass reference | standard unless there is particular notice.

In Examples and Comparative Examples, various physical properties were evaluated as follows.

<Polymer Properties: Swelling Degree>

A film of polymer of about 0.1 mm thickness is cut out to about 2 centimeters in width and width and the weight (weight before dipping) is measured. Then, it is immersed for 72 hours in electrolyte solution of the temperature of 60 degreeC. The immersed film is pulled up, the electrolyte is wiped off and the weight (weight after immersion) is measured immediately, and the value of (weight after immersion) / (weight before immersion) x 100 (%) is determined as swelling and determined by the following criteria. do. In addition, as electrolyte solution, ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed by EC: DEC = 1: 2 (volume ratio, EC is the volume at 40 degreeC, DEC is the volume at 20 degreeC). A solution in which LiPF ₆ was dissolved in a solvent at a concentration of 1 mol / liter is used. The smaller the swelling degree, the higher the electrolyte resistance of the polymer.

A: more than 100% and less than 200%

B: 200% or more and 300% or less

C: greater than 300% and less than 500%

D: 500% or more, 700% or less

E: over 700% and less than 1500%

F: more than 1500% less than 50,000%

G: exceeds 50,000% or dissolves

<Slurry Properties: Dispersibility>

A slurry is put in a test tube of 1 cm in diameter up to 5 cm in height (depth) to obtain a test sample. Five test samples are prepared regarding the measurement of one sample. The test sample is installed vertically on a desk. The state of the installed slurry is observed for 10 days, and it determines by the following reference | standard. Of the five samples, the earliest settling day is the day on which the settling was seen. The less sedimentation is seen, the better the dispersibility.

A: No sedimentation is seen after 10 days.

B: Sedimentation is seen after 6-10 days.

C: Sedimentation is seen after 2-5 days.

D: Sedimentation is seen in more than 10 hours and less than 24 hours.

E: Sedimentation is seen in more than 3 hours and less than 10 hours.

F: Sedimentation is seen in less than 3 hours.

Battery characteristics: output characteristics

A half-cell coin-type lithium ion secondary battery is charged to 4.3 V by a 0.1 C constant current method, then discharged from 0.1 C to 3.0 V, and 0.1 C discharge capacity is obtained. Thereafter, the battery was charged from 0.1 C to 4.3 V and then discharged from 20 C to 3.0 V to obtain a 20 C discharge capacity. These measurements are performed about 10 cells of a half cell coin-type lithium ion secondary battery. The average value of the 0.1 C discharge capacity of the 10 cells and the average value of the 20 C discharge capacity of the 10 cells are determined to be a and b, respectively. The capacity retention rate expressed by the ratio ((b / a) × 100 (unit:%)) of the electric capacity of the 20 C discharge capacity b and the 0.1 C discharge capacity a was obtained, and this was made into the evaluation criteria of the rate characteristic, It judges by. The higher this value, the better the output characteristic (rate characteristic).

A: 50% or more

B: 40% or more but less than 50%

C: 20% or more but less than 40%

D: 1% or more and 20% or less

E: less than 1%

<Battery characteristics: gas generation amount>

The laminate cell type lithium secondary ion battery was charged to 4.3 V by a 0.1 C constant current method and then stored at 80 ° C. for 50 hours. A laminated cell type lithium secondary ion battery is sandwiched between cells with a glass plate, and the thickness of the cell is measured with a micro gauge. A, the thickness of the cell after 80 degreeC 50 hours storage is set to b as thickness of the cell before 80 degreeC storage, the ratio (b / a) of the thickness before and after 80 degreeC storage is calculated | required, and it determines with the following references | standards.

A: more than 1.00 times 1.05 times

B: 1.05 times or more, 1.10 times or less

C: 1.10 times or more, 1.15 times or less

D: 1.15 times or more, 1.20 times or less

E: 1.20 times or more

<Lithium low temperature storage characteristics>

Each of the obtained laminate cell-type batteries is charged at a constant current at 25 ° C. with a constant current until the charge and discharge rate is 0.1 C, and becomes 4.2 V by the constant current constant voltage charging method. Discharge to 3 V after charging. This cycle of constant current constant voltage charging and discharging was repeated once more, and constant current constant voltage charging was performed at 0.1 C in the thermostat set to 0 degreeC after that. The battery capacity obtained at the time of constant current in this constant current constant voltage charging was made into the index of lithium water solubility, and was determined on the following reference | standard. The larger this value is, the better the lithium water solubility is, and the battery performance does not decrease even at low temperatures.

A: 200 mAh / g or more

B: 180 mAh / g or more and less than 200 mAh / g

C: 160 mAh / g or more but less than 180 mAh / g

D: 140 mAh / g or more and less than 160 mAh / g

E: less than 140 mAh / g

(Example 1)

<Production of Graft Polymer>

To the autoclave with a stirrer, as a monomer which comprises 230 parts of toluene, 40 parts of styrene macromonomers (one terminal methacryloylated polystyrene oligomer, Toa Synthetic Chemical Co., Ltd., "AS-6") as segment A, and a segment B 60 parts of butyl acrylates and 1 part of t-butylperoxy-2-ethylhexanate are respectively added as a polymerization initiator, and after fully stirring, it is heated at 90 degreeC and superposed | polymerized, and is a polymer (henceforth "graft polymer 1"). A solution of was obtained. The polymerization conversion ratio determined from the solid content concentration was almost 98%. In addition, the weight average molecular weight of this graft polymer 1 was about 50,000. The weight average molecular weight was measured by gel permeation chromatography (GPC), and the weight average molecular weight of standard polystyrene conversion was calculated | required. GPC was performed using HLC-8220 (manufactured by Tosoh Corporation). In the obtained graft polymer, the main chain was composed of butyl acrylate (component that exhibits swellability to the electrolyte) and the side chain of styrene (component that does not exhibit swelling of the electrolyte). The toluene solution of the obtained graft polymer 1 was dried in 120 degreeC 10 hours nitrogen atmosphere, the polymer film was produced, and the swelling degree and glass transition temperature were measured. The results are shown in Table 1.

<Production of Polymer Film Composed of Segment A>

The toluene solution of styrene macromonomer (one-terminal methacryloylated polystyrene oligomer, manufactured by Toa Synthetic Chemical Co., Ltd., "AS-6") was dried in a nitrogen atmosphere at 120 ° C. for 10 hours to prepare a polymer film of segment A, and the degree of swelling, The glass transition temperature was measured. The results are shown in Table 1.

<Production of Polymer Film Composed of Segment B>

230 parts of toluene, 100 parts of butyl acrylate, and 1 part of t-butylperoxy-2-ethylhexanate as a polymerization initiator were put into the autoclave with a stirrer, and after fully stirring, it heated at 90 degreeC and superposed | polymerized, The solution of the polymer which consists of segment B was obtained. The obtained polymer solution was dried in nitrogen atmosphere at 120 degreeC for 10 hours, the polymer film of segment B was produced, and swelling degree and the glass transition temperature were measured. The results are shown in Table 1.

 <Production of Graft Polymer Solution>

The toluene solution of the obtained graft polymer 1 was phase-phased with the N-methyl- 2-pyrrolidone (henceforth NMP) solution, and the NMP solution of the graft polymer 1 of 17.8% of solid content concentration was obtained.

<Production of Electrode Slurry for Positive Electrode>

100 parts of lithium manganate as a positive electrode active material were put into the planetary mixer with a disper, and 5 parts of acetyl black were added and mixed with this as a conductive agent. 3.4 parts (1.2 parts as graft polymer 1) of the said NMP solution (solid content concentration 17.8%) of the said graft polymer 1 were added to the obtained mixture, and it mixed for 60 minutes. Furthermore, after adjusting to 84% of solid content concentration by NMP, it mixed for 10 minutes. This was defoamed to obtain an electrode slurry for positive electrodes having good lubricity and fluidity. The settling property of the obtained slurry was evaluated. The results are shown in Table 2.

<Manufacture of positive electrode>

The electrode slurry for positive electrodes was applied to an aluminum foil having a thickness of 18 μm, dried at 120 ° C. for 3 hours, and then roll-pressed to obtain a positive electrode having a positive electrode mixture layer having a thickness of 50 μm.

<Production of a negative electrode slurry and a negative electrode>

98 parts of graphite having a particle diameter of 20 µm and a specific surface area of 4.2 m 2 / g as a negative electrode active material, and 5 parts of PVDF (polyvinylidene fluoride) as a solid content as a binder are mixed, and N-methylpyrrolidone is further added to the planner. It mixed with the battery mixer and prepared the electrode slurry for negative electrodes. This electrode slurry for negative electrodes was apply | coated to the single side | surface of the copper foil of thickness 10micrometer, and it dried at 110 degreeC for 3 hours, and then roll-pressed and obtained the negative electrode which has a negative electrode active material layer of thickness 60micrometer.

<Production of Laminate Cell Battery>

The battery container was manufactured using the laminated | multilayer film coated with resin which consists of polypropylene on both surfaces of an aluminum sheet. Subsequently, the active material layer was removed from each end of the positive electrode and the negative electrode obtained above, and the tab was welded to the exposed foil. As the tab, the positive electrode used Ni tab, and the negative electrode used Cu tab. The separator which consists of the obtained positive electrode with a tab, a negative electrode, and the polyethylene microporous film was overlapped so that the active material layer surface of a positive electrode might oppose and a separator would be located therebetween. The obtained laminate was wound up and stored in the battery container. Subsequently, LiPF ₆ was dissolved in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 2 at 25 ° C so as to have a concentration of 1 mol / liter to prepare an electrolyte solution. This electrolyte solution was injected into a battery container. Subsequently, the laminate film was sealed and the laminate cell which is the lithium ion secondary battery of this invention was manufactured. The gas generation amount of the obtained laminate cell was measured. Table 2 shows the results of the evaluation.

<Production of Half Coin Cell Battery>

The positive electrode obtained above was cut out circularly [diameter 13mm]. As a negative electrode, the metallic lithium metal foil was cut out circularly [diameter 14mm]. The polypropylene separator (porosity 55%) of the monolayer manufactured by the dry method of thickness 25micrometer was cut out circularly [diameter 18mm]. The circular positive electrode, the metallic lithium metal foil, and the separator were disposed in a stainless steel coin-type outer container (20 mm in diameter, 1.8 mm in height, 0.25 mm in thickness of stainless steel) provided with polypropylene packing. With this arrangement, the surface on the positive electrode mixture layer side of the positive electrode and the metal lithium metal foil of the negative electrode faced through the separator, and the aluminum foil of the positive electrode was in contact with the bottom of the outer container. Furthermore, an expanded metal was placed on the metallic lithium of the negative electrode and stored in an outer container. An electrolyte (EC / DEC = 1/2, 1 M LiPF ₆ ) is injected into the outer container so that no air remains, and the outer container is fixed with a 0.2 mm thick stainless steel cap through a polypropylene packing to fix the battery. The can was sealed and a lithium ion secondary battery having a diameter of 20 mm and a thickness of about 3.2 mm was manufactured (coin cell CR2032). The rate characteristic was measured about the obtained battery. The results are shown in Table 2.

(Example 2)

40 parts of styrene-acrylonitrile macromonomers (one-terminal methacryloylated polystyrene-acrylonitrile oligomer, manufactured by Toa Synthetic Chemical Industry Co., Ltd.) as 230 parts of toluene and segment A in an autoclave with a stirrer. 60 parts of butyl acrylate as a monomer constituting segment B and 1 part of t-butylperoxy-2-ethylhexanate as a polymerization initiator were added, and after stirring sufficiently, the mixture was heated to 90 ° C to polymerize (hereinafter referred to as "graft A polymer 2 "was obtained. The polymerization conversion ratio determined from the solid content concentration was almost 98%. The weight average molecular weight of the obtained graft polymer 2 was about 50,000. The obtained graft polymer 2 consisted of butyl acrylate (component which shows swelling property with respect to electrolyte solution), and the side chain was acrylonitrile and styrene (component which does not show swelling property with respect to electrolyte solution).

Except having used the styrene-acrylonitrile macromonomer instead of the styrene macromonomer, the polymer film of the segment A and the segment B was produced like Example 1, and the swelling degree and the glass transition temperature were measured. The results are shown in Table 1.

The polymer film, the slurry for positive electrode, and the battery were produced like Example 1 except having used graft polymer 2 instead of the graft polymer 1 as a binder which comprises a positive electrode. And the swelling degree of a polymer film, the glass transition temperature, the settling property in the slurry for positive electrode electrodes, the rate characteristic of a battery, and the gas generation amount were evaluated. The results are shown in Tables 1 and 2.

(Example 3)

To the autoclave with a stirrer, 230 parts of toluene, 57 parts of ethyl acrylate as a monomer constituting segment B, 3 parts of glycidyl methacrylate, and 1 part of t-butylperoxy-2-ethylhexanate as a polymerization initiator After stirring and stirring sufficiently, it heated at 80 degreeC and superposed | polymerized and obtained the polymer solution. Subsequently, after adding 40 parts of polyacrylonitrile whose terminal was modified by the carboxyl group as a component which comprises segment A, it heats at 120 degreeC and denatures, and the solution of a heat-modified polymer (henceforth "graft polymer 3") is added. Got it. The polymerization conversion ratio determined from the solid content concentration was almost 98%. In addition, the weight average molecular weight of this graft polymer 3 was about 70,000. The obtained graft polymer was comprised with ethyl acrylate (component which shows swelling property with respect to electrolyte solution), and the side chain was acrylonitrile (component which does not show swellability with respect to electrolyte solution).

230 parts of toluene, 100 parts of acrylonitrile, 1 part of t-butylperoxy-2-ethylhexanate as a polymerization initiator were put into the autoclave with a stirrer, and after fully stirring, it heated at 90 degreeC and superposed | polymerized, The solution of the polymer which consists of segment A was obtained. The obtained polymer solution was dried in nitrogen atmosphere at 120 degreeC for 10 hours, the polymer film of segment A was produced, and swelling degree and the glass transition temperature were measured. The results are shown in Table 1.

To the autoclave with a stirrer, 230 parts of toluene, 95 parts of ethyl acrylate, 5 parts of glycidyl methacrylate, and 1 part of t-butylperoxy-2-ethylhexanate as polymerization initiators were added, followed by stirring sufficiently. And the mixture was heated to 90 ° C to polymerize to obtain a solution of a polymer composed of segment B. The obtained polymer solution was dried in nitrogen atmosphere at 120 degreeC for 10 hours, the polymer film of segment B was produced, and swelling degree and the glass transition temperature were measured. The results are shown in Table 1.

The polymer film, the slurry for positive electrode, and the battery were produced like Example 1 except having used graft polymer 3 instead of the graft polymer 1 as a binder which comprises a positive electrode. And the swelling degree of a polymer film, the glass transition temperature, the settling property in the slurry for positive electrode electrodes, the rate characteristic of a battery, and the gas generation amount were evaluated. The results are shown in Tables 1 and 2.

(Example 4)

40 parts of styrene-acrylonitrile macromonomers (one-terminal methacryloylated polystyrene-acrylonitrile oligomer, manufactured by Toa Synthetic Chemical Industry Co., Ltd.) as 230 parts of toluene and segment A in an autoclave with a stirrer. 60 parts of n-ethyl acrylate as a monomer constituting segment B, 1 part of t-butylperoxy-2-ethylhexanate as a polymerization initiator, and 0.05 parts of n-dodecyl mercaptan as a molecular weight modifier were sufficiently stirred, and , And heated to 90 ° C to polymerize to obtain a solution of a polymer (hereinafter referred to as "graft polymer 4"). The polymerization conversion ratio determined from the solid content concentration was almost 98%. In addition, the weight average molecular weight of this graft polymer 4 was about 30,000. The obtained graft polymer was comprised with n-ethyl acrylate (component which shows swelling property with respect to electrolyte solution), and a side chain with styrene acrylonitrile (component which does not show swelling property with respect to electrolyte solution).

The polymer film of segment A was produced like Example 1 except having used the styrene-acrylonitrile macromonomer instead of the styrene macromonomer, and swelling degree and the glass transition temperature were measured. The results are shown in Table 1.

To the autoclave with a stirrer, 230 parts of toluene, 100 parts of n-ethyl acrylate, 1 part of t-butylperoxy-2-ethylhexanate as a polymerization initiator, 0.05 part of n-dodecyl mercaptan as a molecular weight modifier, After stirring sufficiently, it heated at 90 degreeC and superposed | polymerized, and obtained the solution of the polymer which consists of segments B. The obtained polymer solution was dried in nitrogen atmosphere at 120 degreeC for 10 hours, the polymer film of segment B was produced, and swelling degree and the glass transition temperature were measured. The results are shown in Table 1.

A polymer film, a slurry for positive electrode, and a battery were prepared in the same manner as in Example 1 except that the graft polymer 4 was used instead of the graft polymer 1 as the binder constituting the positive electrode. And the swelling degree of a polymer film, the glass transition temperature, the settling property in the slurry for positive electrode electrodes, the rate characteristic of a battery, and gas generation were evaluated. The results are shown in Tables 1 and 2.

(Example 5)

<Production of Graft Polymer>

To the autoclave with a stirrer, as a monomer which comprises 230 parts of toluene, 40 parts of styrene macromonomers (one terminal methacryloylated polystyrene oligomer, Toa Synthetic Chemical Co., Ltd., "AS-6") as segment A, and a segment B 58 parts of butyl acrylate, 2 parts of glycidyl methacrylate, and 1 part of t-butylperoxy-2-ethylhexanate are added as a polymerization initiator, and after fully stirring, it is heated to 90 degreeC and superposed | polymerized, and a polymer (hereinafter, A solution of "grafted polymer 5" was obtained. The polymerization conversion ratio determined from the solid content concentration was almost 98%. In addition, the weight average molecular weight of this graft polymer 5 was about 50,000. The obtained graft polymer was comprised from the copolymer of a butyl acrylate and glycidyl methacrylate (component which shows swelling property with respect to electrolyte solution), and a side chain with styrene (component which does not show swellability with respect to electrolyte solution). The toluene solution of the obtained graft polymer 5 was dried in nitrogen atmosphere at 120 degreeC for 10 hours, the polymer film was produced, and the swelling degree was measured. The results are shown in Table 1.

<Production of Polymer Film Composed of Segment A>

The toluene solution of styrene macromonomer (one-terminal methacryloylated polystyrene oligomer, manufactured by Toa Synthetic Chemical Co., Ltd., "AS-6") was dried in a nitrogen atmosphere at 120 ° C. for 10 hours to prepare a polymer film of segment A, and the degree of swelling, The glass transition temperature was measured. The results are shown in Table 1.

<Production of Polymer Film Composed of Segment B>

230 parts of toluene, 96.3 parts of butyl acrylate, 3.3 parts of glycidyl methacrylate, 1 part of t-butylperoxy-2-ethylhexanate as a polymerization initiator were put into the autoclave with a stirrer, and after fully stirring, It heated and heated at 90 degreeC and superposed | polymerized, and obtained the solution of the polymer which consists of segments B. The toluene solution of the polymer which consists of obtained segment B was dried in nitrogen atmosphere at 120 degreeC for 10 hours, the polymer film of the segment B was produced, and swelling degree and the glass transition temperature were measured. The results are shown in Table 3.

<Production of Graft Polymer Solution>

The toluene solution of the obtained graft polymer 5 was phase-phased by the NMP solution, and the NMP solution of the graft polymer 5 of 17.8% of solid content concentration was obtained.

<Production of Electrode Slurry for Positive Electrode>

100 parts of lithium manganate as a positive electrode active material were put into the planetary mixer with a disper, and 5 parts of acetyl black were added and mixed with this as a conductive agent. PVDF (polyvinylidene fluoride) was added 5 parts by solid content correspondence as a binder, and it mixed for 60 minutes. Furthermore, after adjusting to 84% of solid content concentration by NMP, it mixed for 10 minutes. This was degassed and the electrode slurry for positive electrodes was obtained.

<Manufacture of positive electrode>

The electrode slurry for positive electrodes was applied to an aluminum foil having a thickness of 18 μm, dried at 120 ° C. for 3 hours, and then roll-pressed to obtain a positive electrode having a positive electrode mixture layer having a thickness of 50 μm.

<Production of a negative electrode slurry and a negative electrode>

98 parts of graphite having a particle diameter of 20 µm and a specific surface area of 4.2 m 2 / g as a negative electrode active material, and 1.6 parts of graft polymer 5 as solids are mixed as a binder, and N-methylpyrrolidone is further added and mixed with a planetary mixer. To prepare an electrode slurry for the negative electrode. This electrode slurry for negative electrodes was apply | coated to the single side | surface of the copper foil of thickness 10micrometer, and it dried at 110 degreeC for 3 hours, and then roll-pressed and obtained the negative electrode which has a negative electrode active material layer of thickness 60micrometer.

<Production of Laminate Cell Battery>

The battery container was manufactured using the laminated | multilayer film coated with resin which consists of polypropylene on both surfaces of an aluminum sheet. Subsequently, the active material layer was removed from each end of the positive electrode and the negative electrode obtained above, and the tab was welded to the exposed foil. As the tab, the positive electrode used Ni tab, and the negative electrode used Cu tab. The separator which consists of the obtained positive electrode with a tab, a negative electrode, and the polyethylene microporous film was overlapped so that the active material layer surface of a positive electrode might oppose and a separator would be located therebetween. The obtained laminate was wound up and stored in the battery container. Subsequently, LiPF ₆ was dissolved in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 2 at 25 ° C so as to have a concentration of 1 mol / liter to prepare an electrolyte solution. This electrolyte solution was injected into a battery container. Subsequently, the laminate film was sealed and the laminate cell which is the lithium ion secondary battery of this invention was manufactured. The low-temperature lithium characteristics of the obtained laminate cell were evaluated. Table 3 shows the results of the evaluation.

(Example 6)

To the autoclave with a stirrer, as a monomer which comprises 230 parts of toluene, 40 parts of styrene macromonomers (one terminal methacryloylated polystyrene oligomer, Toa Synthetic Chemical Co., Ltd., "AS-6") as segment A, and a segment B 50 parts of n-ethyl acrylate, 10 parts of acrylonitrile, and 1 part of t-butylperoxy-2-ethylhexanate as a polymerization initiator are added, and after stirring sufficiently, it is heated to 90 degreeC and superposed | polymerized, and a polymer ("graft" Polymer 6 "). The polymerization conversion ratio determined from the solid content concentration was almost 98%. In addition, the weight average molecular weight of this graft polymer 6 was about 50,000. The obtained graft polymer was comprised from the copolymer (component which shows swelling property with respect to electrolyte solution) of n-ethyl acrylate and acrylonitrile, and styrene (component which does not show swellability with respect to electrolyte solution) of the main chain.

A polymer film of segments A and B was prepared in the same manner as in Example 5, except that 83.3 parts of n-ethyl acrylate and 16.7 parts of acrylonitrile were used instead of 96.7 parts of butyl acrylate, 3.3 parts of glycidyl methacrylate, Swelling degree and glass transition temperature were measured. The results are shown in Table 1.

A polymer film, a slurry for negative electrode, and a battery were prepared in the same manner as in Example 5 except that the graft polymer 6 was used instead of the graft polymer 5 as the binder constituting the positive electrode. And the swelling degree of a polymer film and lithium low temperature accommodating characteristic were evaluated. The results are shown in Tables 1 and 3.

(Comparative Example 1)

40 parts of butyroacrylate macromonomer (one-terminal methacryloylated polystyrene oligomer, manufactured by Toa Synthetic Chemical Co., Ltd., "AB-6") synthesized as 230 parts of toluene and segment A in an autoclave with a stirrer. 60 parts of vinylpyrrolidone as a monomer which comprises and 1 part of t-butylperoxy-2-ethylhexanate as a polymerization initiator were added, and after stirring sufficiently, the mixture was heated to 90 DEG C to polymerize (hereinafter, "grafted polymer 7 "). The polymerization conversion ratio determined from the solid content concentration was almost 98%. In addition, the weight average molecular weight of this graft polymer 7 was about 50,000.

Polymer films of segments A and B were prepared in the same manner as in Example 1, except that vinylpyrrolidone was used instead of butyl acrylate and butyroacrylate macromonomer was used instead of styrene macromonomer. The transition temperature was measured. The results are shown in Table 1.

A polymer film, a slurry for a positive electrode, and a battery were prepared in the same manner as in Example 1 except that the graft polymer 7 was used instead of the graft polymer 1 as the binder constituting the positive electrode. And the swelling degree of a polymer film, the glass transition temperature, the settling property in the slurry for positive electrode electrodes, the rate characteristic of a battery, and gas generation were evaluated. The results are shown in Tables 1 and 2.

(Comparative Example 2)

40 parts of styrene-acrylonitrile macromonomers (one-terminal methacryloylated polystyrene-acrylonitrile oligomer, manufactured by Toa Synthetic Chemical Industry Co., Ltd.) as 230 parts of toluene and segment A in an autoclave with a stirrer. 30 parts of butyl acrylate, 30 parts of styrene, and 1 part of t-butylperoxy-2-ethylhexanate as a polymerization initiator were added as a monomer which comprises segment B, and after stirring sufficiently, it warms up at 90 degreeC and superposes | polymerizes, and a polymer The solution of (hereinafter referred to as "graft polymer 8") was obtained. The polymerization conversion ratio determined from the solid content concentration was almost 98%. In addition, the weight average molecular weight of this graft polymer 8 was about 50,000.

Polymer films of segments A and B were the same as in Example 1 except that 500 parts of butyl acrylate and 50 parts of styrene were used instead of 100 parts of butyl acrylate, and styrene-acrylonitrile macromonomer was used instead of styrene macromonomer. Was prepared and the swelling degree and glass transition temperature were measured. The results are shown in Table 1.

A polymer film, a slurry for a positive electrode, and a battery were prepared in the same manner as in Example 1 except that the graft polymer 8 was used instead of the graft polymer 1 as the binder constituting the positive electrode. And the swelling degree of a polymer film, the glass transition temperature, the settling property in the slurry for positive electrode electrodes, the rate characteristic of a battery, and gas generation were evaluated. The results are shown in Tables 1 and 2.

(Comparative Example 3)

To autoclave with a stirrer, 230 parts of toluene, 40 parts of butyl acrylate macromonomer (one-terminal methacryloylated polybutyl acrylate oligomer, Toa Synthetic Chemical Co., Ltd. make, "AB-6"), segment B 60 parts of butyl acrylates as a monomer constituting a monomer, 1 part of t-butylperoxy-2-ethylhexanate as a polymerization initiator, and 0.5 parts of n-dodecyl mercaptan as a molecular weight modifier were added, and after stirring sufficiently, it heated at 90 degreeC. It superposed | polymerized and obtained the solution of the polymer (henceforth "graft polymer 9"). The polymerization conversion ratio determined from the solid content concentration was almost 98%. In addition, the weight average molecular weight of this graft polymer 9 was about 10,000.

Segment A and Segment B were the same as in Example 1 except that 100 parts of butyl acrylate and 0.5 part of n-dodecyl mercaptan were used instead of 100 parts of butyl acrylate, and butyl acrylate macromonomer was used instead of styrene macromonomer. A polymer film was prepared and the swelling degree and glass transition temperature were measured. The results are shown in Table 1.

A polymer film, a slurry for a positive electrode, and a battery were prepared in the same manner as in Example 1 except that the graft polymer 9 was used instead of the graft polymer 1 as the binder constituting the positive electrode. And the swelling degree of a polymer film, the glass transition temperature, the settling property in the slurry for positive electrode electrodes, the rate characteristic of a battery, and gas generation were evaluated. The results are shown in Tables 1 and 2.

(Comparative Example 4)

To the autoclave with a stirrer, as a monomer which comprises 230 parts of toluene, 40 parts of styrene macromonomers (one terminal methacryloylated polystyrene oligomer, Toa Synthetic Chemical Co., Ltd., "AS-6") as segment A, and a segment B 30 parts of butyl acrylate, 30 parts of styrene, and 1 part of t-butylperoxy-2-ethylhexanate as a polymerization initiator were added, and after sufficiently stirring, the mixture was heated to 90 deg. C to polymerize (hereinafter referred to as `` graft polymer 10 Was obtained. The polymerization conversion ratio determined from the solid content concentration was almost 98%. In addition, the weight average molecular weight of this graft polymer 10 was about 50,000.

A polymer film of segments A and S was prepared in the same manner as in Example 1 except that 50 parts of butyl acrylate and 50 parts of styrene were used instead of 100 parts of butyl acrylate, and the swelling degree and the glass transition temperature were measured. The results are shown in Table 1.

A polymer film, a slurry for a positive electrode, and a battery were prepared in the same manner as in Example 1 except that the graft polymer 10 was used instead of the graft polymer 1 as the binder constituting the positive electrode. And the swelling degree of a polymer film, the glass transition temperature, the settling property in the slurry for positive electrode electrodes, the rate characteristic of a battery, and gas generation were evaluated. The results are shown in Tables 1 and 2.

(Comparative Example 5)

To the autoclave with a stirrer, as a monomer which comprises 230 parts of toluene, 40 parts of styrene macromonomers (one terminal methacryloylated polystyrene oligomer, Toa Synthetic Chemical Co., Ltd., "AS-6") as segment A, and a segment B 20 parts of ethylene, 40 parts of ethyl acrylate, and 1 part of t-butylperoxy-2-ethylhexanate as a polymerization initiator were added, and after sufficiently stirring, the mixture was heated to 90 ° C to polymerize, and the polymer (hereinafter referred to as `` graft polymer 11 Was obtained. The polymerization conversion ratio determined from the solid content concentration was almost 98%. Moreover, the glass transition temperature of this graft polymer 11 was 10 degreeC, and the weight average molecular weight was about 50,000.

Except having used 33.3 parts of ethylene and 66.7 parts of ethyl acrylate instead of 100 parts of butyl acrylate, the polymer film of the segment A and the segment B was produced like Example 1, and the swelling degree and glass transition temperature were measured. The results are shown in Table 1.

A polymer film, a slurry for a positive electrode, and a battery were prepared in the same manner as in Example 1 except that the graft polymer 11 was used instead of the graft polymer 1 as the binder constituting the positive electrode. And the swelling degree of a polymer film, the glass transition temperature, the settling property in the slurry for positive electrode electrodes, the rate characteristic of a battery, and gas generation were evaluated. The results are shown in Tables 1 and 2.

From the results of Tables 1 and 2, by using a graft polymer obtained by grafting a component that swells with respect to an electrolyte and a component that does not swell as a binder constituting the positive electrode, the degree of swelling of the electrolyte can be controlled to suppress gas generation. It has become clear that a battery having excellent, and rate characteristics can be produced.

In addition, it is clear from Table 3 that the lithium low-temperature receiving property is improved by using this graft polymer as a binder constituting the negative electrode.

Claims (9)

An electrode active material layer containing an electrical power collector and an active material and a binder laminated on the current collector, wherein, as the binder, a segment A having a swelling degree of 100 to 300% with respect to the electrolyte and a swelling degree with respect to the electrolyte The secondary battery electrode containing the graft polymer which consists of segment B which is 500-50,000% or melt | dissolves in electrolyte solution. The method of claim 1,
The secondary battery electrode whose ratio of the said segment A and the said segment B in the said graft polymer is 20: 80-80: 20 (mass ratio). The method of claim 1,
The secondary battery electrode whose weight average molecular weight of the said graft polymer exists in the range of 1,000-500,000. The method of claim 1,
Said segment B is a segment of a soft polymer with a glass transition temperature of 15 degrees C or less, The electrode for secondary batteries. A binder for secondary batteries, comprising a graft polymer comprising a segment A having an swelling degree of 100 to 300% with respect to an electrolyte solution and a segment B having a swelling degree with respect to an electrolyte solution of 500 to 50,000% or dissolved in the electrolyte solution. The method of claim 5, wherein
The binder for secondary batteries whose ratio of the said segment A and the said segment B in the said graft polymer is 20: 80-80: 20 (mass ratio). The method according to claim 5 or 6,
The binder for secondary batteries whose said segment B is a segment of the soft polymer whose glass transition temperature is 15 degrees C or less. A slurry containing a graft polymer, an active material, and a solvent comprising a segment A having a swelling degree of 100 to 300% with respect to the electrolyte and a segment B having a swelling degree of 500 to 50,000% with respect to the electrolyte or dissolved in the electrolyte is coated on the current collector. The manufacturing method of the electrode for secondary batteries of Claim 1 containing the process to dry. A lithium ion secondary battery having a positive electrode, an electrolyte solution and a negative electrode,
At least one of the said positive electrode and a negative electrode is an electrode for secondary batteries of Claim 1, The secondary battery characterized by the above-mentioned.