KR20150035515A - Negative electrode for secondary cell, and secondary cell - Google Patents

Abstract

[PROBLEMS] To provide a negative electrode for a secondary battery which can obtain a secondary battery having excellent cycle characteristics and output characteristics.
[MEANS FOR SOLVING PROBLEMS] The negative electrode for a secondary battery of the present invention comprises a current collector and a negative electrode active material layer laminated on the current collector, wherein the negative electrode active material layer contains a negative electrode active material (A), a particulate binder (B) (D) containing 0.5 to 20% by mass of a water-soluble polymer (C) and a fluorine-containing (meth) acrylic acid ester monomer unit, wherein the particulate binder (B) has a glass transition temperature of -30 to 20 캜 , An aromatic vinyl-conjugated diene copolymer (b1) containing an unsaturated carboxylic acid monomer unit and an aromatic vinyl-conjugated diene copolymer having a glass transition temperature of 30 to 80 DEG C and containing an unsaturated carboxylic acid monomer unit (b2).

Description

TECHNICAL FIELD [0001] The present invention relates to a negative electrode and a secondary battery for a secondary battery,

The present invention relates to a negative electrode used in a secondary battery such as a lithium ion secondary battery.

2. Description of the Related Art In recent years, portable terminals such as a notebook computer, a mobile phone, and a PDA (Personal Digital Assistant) have become popular. [0003] 2. Description of the Related Art [0004] A secondary battery used for the power supply of these portable terminals includes a nickel hydrogen secondary battery, a lithium ion secondary battery, and the like. Background of the Invention Portable terminals are demanded to be more comfortable to carry, and miniaturization, thinning, light weight, and high performance are rapidly proceeding. As a result, portable terminals are being used in various places. In addition, miniaturization, thinness, weight reduction, and high performance of batteries are required as in the case of portable terminals.

In the conventional lithium ion secondary battery, a carbon-based active material such as graphite is used as a negative electrode active material. For example, Patent Document 1 describes a negative electrode for a lithium ion secondary battery, which contains a carbon-based active material and a binder composed of two kinds of carboxy modified styrene-butadiene copolymers having different glass transition temperatures.

In addition, for the purpose of increasing the capacity of a lithium ion secondary battery, a negative electrode for a lithium ion secondary battery using an alloy-based active material containing Si or the like has been developed (for example, Patent Document 2).

Japanese Laid-Open Patent Publication No. 2011-108373 Japanese Patent No. 4025995

As a result of the investigation by the present inventors, it has been found that it is difficult to obtain a secondary battery having excellent cycle characteristics and output characteristics because the negative electrode described in Patent Document 1 has insufficient dispersibility and lithium ion conductivity of the negative electrode active material.

When an alloy active material is used as the negative electrode active material, the negative electrode active material has a large volume expansion / contraction when lithium ions are doped and dedoped, resulting in expansion of the electrode plate and desorption of the negative electrode active material from the electrode , Which may cause deterioration of battery characteristics such as cycle characteristics and output characteristics.

It is an object of the present invention to provide a negative electrode for a secondary battery which can be obtained in consideration of the above circumstances and which can obtain a secondary battery having excellent cycle characteristics and output characteristics.

As a result of intensive studies to solve the above problems, the present inventors have found that the use of a particulate binder and a specific water-soluble polymer improves the dispersibility and lithium ion conductivity of the negative electrode active material in the negative electrode, And an excellent secondary battery can be obtained. Thus, the present invention has been accomplished.

That is, the gist of the present invention for solving such a problem is as follows.

(1) A battery comprising a current collector and a negative electrode active material layer laminated on the current collector,

(D) containing 0.5 to 20% by mass of the negative electrode active material (A), the particulate binder (B), the hydroxyl group-containing water-soluble polymer (C) and the fluorine-containing (meth) ≪ / RTI >

Wherein the particulate binder (B) has a glass transition temperature of -30 to 20 占 폚 and contains an unsaturated carboxylic acid monomer unit and an aromatic vinyl-conjugated diene copolymer (b1) having a glass transition temperature of 30 to 80 占 폚, An aromatic vinyl-conjugated diene copolymer (b2) comprising an unsaturated carboxylic acid monomer unit.

(2) The negative electrode for a secondary battery according to (1), wherein the negative electrode active material (A) contains a carbonaceous active material (a1) and an alloyed active material (a2).

(3) The negative electrode for a secondary battery according to (2), wherein the alloy-based active material (a2) is contained in an amount of 1 to 50 parts by mass based on 100 parts by mass of the carbonaceous active material (a1).

(4) The negative electrode for a secondary battery according to (2) or (3), wherein the alloy active material (a2) is Si, SiO _x (x is 0.01 or more and less than 2) or SiOC.

(5), wherein the content ratio of the aromatic vinyl-conjugated diene copolymer (b1) to the aromatic vinyl-conjugated diene copolymer (b2) The negative electrode for a secondary battery according to any one of (1) to (4), wherein the copolymer (b2) is 80/20 to 30/70.

(6) The positive resist composition as described in any one of (1) to (5) above, wherein the tetrahydrofuran-insoluble matter content of each of the aromatic vinyl-conjugated diene copolymer (b1) and the aromatic vinyl-conjugated diene copolymer (b2) Negative electrode for secondary battery.

(7) A secondary battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator,

The negative electrode is the negative electrode for a secondary battery according to any one of (1) to (6).

Since the negative electrode for a secondary battery of the present invention contains a particulate binder and a specific water-soluble polymer, the negative electrode active material has excellent dispersibility and lithium ion conductivity. As a result, a secondary battery having excellent cycle characteristics (especially high temperature cycle characteristics) and output characteristics (particularly low temperature output characteristics) can be obtained.

Further, according to the present invention, even when an alloy active material having large volume expansion and contraction at the time of doping and dedoping lithium ions is used as the negative electrode active material, it is possible to prevent the electrode plate from expanding and separating the negative electrode active material from the electrode Generation can be suppressed. As a result, the cycle characteristics and the output characteristics of the secondary battery can be improved.

[Negative electrode for secondary battery]

The negative electrode for a secondary battery of the present invention (hereinafter simply referred to as " negative electrode ") comprises a current collector and a negative electrode active material layer laminated on the current collector. The negative electrode active material layer contains the following components (A) to (D) and may contain other component (E) added as needed. The negative electrode for a secondary battery of the present invention can be used for a lithium ion secondary battery, a nickel hydrogen secondary battery, or the like. Among these, lithium ion secondary batteries are preferable for applications because they are most required to improve long-term cycle characteristics and output characteristics. Hereinafter, each component will be described in detail for use in a lithium ion secondary battery.

(A) Negative electrode active material

The negative electrode active material is a material that receives electrons (lithium ions) in the negative electrode. As the negative electrode active material, a carbon-based active material (a1) or an alloy-based active material (a2) described later can be used, but the negative electrode active material preferably contains a carbon-based active material and an alloy-based active material. By using the carbon-based active material and the alloy-based active material as the negative electrode active material, it is possible to obtain a battery having a capacity larger than that of the negative electrode obtained by using only the conventional carbon-based active material and also to solve problems such as a decrease in adhesion strength of the negative electrode, .

(a1) a carbon-based active material

The carbon-based active material used in the present invention refers to an active material having carbon as a main skeleton capable of intercalating lithium, specifically, a carbonaceous material and a graphite material. The carbonaceous material generally has a low graphitization (carbonization) in which the carbon precursor is heat-treated (carbonized) at 2000 占 폚 or lower (the lower limit of the treatment temperature is not particularly limited, but may be 500 占 폚 or higher, for example) ) Graphite material and the graphite material is a graphite material having a high crystallinity close to graphite obtained by heat-treating graphitizable carbon at 2000 占 폚 or higher (the upper limit of the treatment temperature is not particularly limited, but can be, for example, 5000 占 폚 or lower) ≪ / RTI >

Examples of the carbonaceous material include graphite carbon which easily changes the structure of carbon by a heat treatment temperature or non-graphitic carbon which has a structure close to an amorphous structure typified by glassy carbon.

As the graphitizing carbon, there can be mentioned a carbon material made of tar pitch obtained from petroleum or coal as a raw material, and examples thereof include coke, mesocarbon microbeads (MCMB), mesophase pitch carbon fibers, pyrolysis- . The MCMB is a carbon fine particle obtained by extracting and extracting mesophase spherules produced in the course of heating the pitch at about 400 ° C. The mesophase pitch-based carbon fiber is a carbon fiber whose mesophase pitch is obtained by the growth and coalescence of the mesophase spherules as a raw material. The pyrolytic vapor-phase grown carbon fiber refers to (1) a method of pyrolyzing an acrylic polymer fiber or the like, (2) a method of radiating a pitch by radiating it, (3) a method of catalytic vapor phase decomposition of hydrocarbon using nanoparticles such as iron Carbon fiber obtained by the growth (catalytic CVD) method.

Examples of the non-graphitizable carbon include phenol resin fired bodies, polyacrylonitrile carbon fibers, quasi-isotropic carbon, furfuryl alcohol resin fired bodies (PFA), and the like.

Examples of the graphite material include natural graphite and artificial graphite. Artificial graphite includes artificial graphite heat-treated at 2800 ° C or higher, graphitized MCMB heat-treated at MCMB at 2000 ° C or higher, graphitized mesophase pitch carbon fibers heat-treated at a temperature of 2000 ° C or above, mesophase pitch- .

Of the carbon-based active materials, graphite materials are preferred. By using a graphite material, it becomes easy to increase the density of the negative electrode active material layer, and the density of the negative electrode active material layer is 1.6 g / cm 3 or more (the upper limit of the density is not particularly limited but 2.2 g / cm 3 or less) Can be easily manufactured. The effect of the present invention is remarkable if the negative electrode has a negative electrode active material layer having a density in the above range.

The volume average particle diameter of the carbon-based active material is preferably 0.1 to 100 占 퐉, more preferably 0.5 to 50 占 퐉, and particularly preferably 1 to 30 占 퐉. When the volume average particle diameter of the carbon-based active material is within this range, it is easy to prepare the slurry composition used for producing the negative electrode. The volume average particle diameter in the present invention can be obtained by measuring the particle size distribution by laser diffraction.

The specific surface area of the carbonaceous active material is preferably 3.0 to 20.0 m 2 / g, more preferably 3.5 to 15.0 m 2 / g, and particularly preferably 4.0 to 10.0 m 2 / g. When the specific surface area of the carbon-based active material is in the above range, the active points of the surface of the carbon-based active material are increased, so that the output characteristics of the lithium ion secondary battery are excellent.

(a2) alloy-based active material

The alloy-based active material used in the present invention includes an element capable of inserting lithium in its structure, and has a theoretical capacity per unit weight of 500 mAh / g or more when lithium is incorporated (the upper limit of the theoretical capacity is specifically limited But may be, for example, 5000 mAh / g or less), and specifically refers to a lithium metal, a single metal and an alloy thereof forming a lithium alloy, and oxides, sulfides, nitrides, silicides, carbides , Phosphates and the like are used.

Examples of the metal and the alloy that form the lithium alloy include a metal such as Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn, . ≪ / RTI > Among them, a single metal such as silicon (Si), tin (Sn) or lead (Pb), an alloy containing these atoms, or a metal compound thereof is used. Among them, a single metal of Si capable of inserting and removing lithium at low electric power is preferable.

The alloy-based active material used in the present invention may further contain at least one non-metallic element. Specifically, SiC, SiO _x C _y (hereinafter referred to as SiOC) (0 <x? 3, 0 <y? 5), Si ₃ N ₄ , Si ₂ N ₂ O, SiO _x x = less than _{0.01 2), SnO x (0} <x ≤ 2), LiSiO, there may be mentioned LiSnO, etc., capable of lithium insertion desorption over the low potential among the SiOC, SiO _x, and SiC is preferred, and SiOC, SiO _x is more preferable. For example, SiOC can be obtained by firing a polymer material containing silicon. Among SiOC, a range of 0.8? X? 3 and 2? Y? 4 is preferably used from the balance of capacity and cycle characteristics.

As oxides, sulfides, nitrides, silicides, carbides and phosphides thereof, oxides, sulfides, nitrides, silicides, carbides and phosphides of elements capable of inserting lithium are exemplified. Of these, oxides are particularly preferable. Specifically, a lithium-containing metal complex oxide containing a metal element selected from the group consisting of tin oxide, manganese oxide, titanium oxide, niobium oxide, vanadium oxide, Si, Sn, Pb and Ti atoms is used.

As the lithium-containing metal composite oxide, a lithium-titanium composite oxide represented by Li _x Ti _y M _z O ₄ (0.7 ≤ x ≤ 1.5, 1.5 ≤ y ≤ 2.3, 0 ≤ z ≤ 1.6, and M is Na, K, Co, Al Li ₄ Ti ₃ O ₄ , Li ₁ Ti ₂ O ₄ , Li _4/5 Ti _11/5, O ₄ is used.

Among them, preferred are materials containing silicon and, among them is a SiO _x C _y, SiO _x, and SiC, such as SiOC more preferred. In this compound, it is presumed that Li intercalation desorption occurs to Si (silicon) at a high electric potential and C (carbon) at a low electric potential at a high electric potential, so that expansion and contraction are suppressed more than other alloy active materials. Therefore, easy.

The volume average particle diameter of the alloy-based active material is preferably 0.1 to 50 占 퐉, more preferably 0.5 to 20 占 퐉, and particularly preferably 1 to 10 占 퐉. When the volume average particle diameter of the alloy-based active material is within this range, it becomes easy to prepare the slurry composition used for producing the negative electrode.

The specific surface area of the alloy-based active material is preferably 3.0 to 20.0 m 2 / g, more preferably 3.5 to 15.0 m 2 / g, and particularly preferably 4.0 to 10.0 m 2 / g. When the specific surface area of the alloy-based active material is in the above range, the active points of the surface of the alloy-based active material are increased, so that the output characteristics of the lithium ion secondary battery are excellent.

The mixing method of the alloy-based active material and the carbon-based active material is not particularly limited, and conventionally known dry mixing or wet mixing may be mentioned.

The negative electrode active material (A) of the present invention preferably contains 1 to 50 parts by mass of the alloy-based active material (a2) based on 100 parts by mass of the carbon-based active material (a1). By mixing the alloy-based active material and the carbon-based active material in the above-described range, it is possible to obtain a battery having a capacity larger than that of the negative electrode obtained by using only the conventional carbon-based active material.

(B) particulate binder

The particulate binder has a property of being dispersed in a dispersion medium to be described later. By using a particulate binder, binding strength between the current collector and the negative electrode active material layer to be described later can be enhanced to improve the negative electrode strength, and the deterioration due to repetition of charging and discharging of the obtained negative electrode can be suppressed.

The particulate binder may be present in a state in which the particle shape is maintained in the negative electrode active material layer. In the present invention, &quot; a state in which a particle state is maintained &quot; is not necessarily a state in which the particle shape is completely maintained, but the particle shape can be maintained to some extent.

The particulate binder includes, for example, a state in which particles of a binder are dispersed in water, such as latex, and a powdery one obtained by drying such a dispersion.

In the present invention, the particulate binder is water-insoluble. That is, it is preferable that they are dispersed in the form of particles without dissolving in an aqueous solvent. Specifically, the term "water-insoluble" means that the insoluble content is 90% by mass or more when 0.5 g of the binder is dissolved in 100 g of water at 25 ° C.

The particulate binder (B) in the present invention is an aromatic vinyl-conjugated diene copolymer (b1) having a glass transition temperature of -30 to 20 ° C and containing an unsaturated carboxylic acid monomer unit (hereinafter simply referred to as "aromatic vinyl- Conjugated diene copolymer (b2) (hereinafter sometimes referred to as "conjugated diene copolymer (b1)") having a glass transition temperature of 30 to 80 ° C. and containing an unsaturated carboxylic acid monomer unit Quot; aromatic vinyl-conjugated diene copolymer (b2) &quot; in some cases).

(b1) an aromatic vinyl-conjugated diene copolymer

The aromatic vinyl-conjugated diene copolymer (b1) used in the present invention is a copolymer of a structural unit obtained by polymerizing an aromatic vinyl monomer (hereinafter may be referred to as an "aromatic vinyl monomer unit"), a structural unit obtained by polymerizing a conjugated diene (Hereinafter sometimes referred to as &quot; conjugated diene monomer unit &quot;), and a copolymer containing an unsaturated carboxylic acid monomer unit. The aromatic vinyl-conjugated diene copolymer (b1) may contain other monomer units copolymerizable therewith, if necessary.

The proportion of the monomer units constituting the aromatic vinyl-conjugated diene copolymer (b1) corresponds to the injection ratio of the monomers at the time of polymerization. Hereinafter, unless otherwise stated, the proportion of the monomer units constituting the polymer corresponds to the injection ratio of the monomers at the time of polymerization.

&Lt; Aromatic vinyl monomer unit &gt;

The aromatic vinyl monomer unit is a structural unit obtained by polymerizing an aromatic vinyl monomer.

Examples of the aromatic vinyl monomer include styrene,? -Methylstyrene, vinyltoluene, and divinylbenzene. Among them, styrene is preferable. These aromatic vinyl monomers may be used alone or in combination of two or more. The content of the aromatic vinyl monomer unit in the aromatic vinyl-conjugated diene copolymer (b1) is preferably 40% by mass or more, and more preferably 50 to 65% by mass.

&Lt; Conjugated diene monomer unit &gt;

The conjugated diene monomer unit is a structural unit obtained by polymerizing a conjugated diene monomer.

Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene and 2-chloro- . These conjugated diene monomers may be used alone or in combination of two or more.

The content of the conjugated diene monomer unit in the aromatic vinyl-conjugated diene copolymer (b1) is preferably 25% by mass or more, and more preferably 31 to 46% by mass.

The total ratio of the aromatic vinyl monomer unit and the conjugated diene monomer unit in the aromatic vinyl-conjugated diene copolymer (b1) is preferably 65% by mass or more, and more preferably 80 to 96% by mass.

Hereinafter, the unsaturated carboxylic acid monomer unit and other monomer units will be described in detail.

<Unsaturated Carboxylic Acid Monomer Unit>

The unsaturated carboxylic acid monomer unit is a structural unit obtained by polymerizing an unsaturated carboxylic acid monomer. Examples of the unsaturated carboxylic acid monomer include an unsaturated monocarboxylic acid and a derivative thereof, an unsaturated dicarboxylic acid and an acid anhydride thereof, and derivatives thereof. Examples of the unsaturated monocarboxylic acid include acrylic acid, methacrylic acid, and crotonic acid. Examples of the unsaturated monocarboxylic acid derivatives include 2-ethyl acrylic acid, isocrotonic acid,? -Acetoxy acrylic acid,? -Trans-aryloxy acrylic acid,? -Chloro-? -E-methoxy acrylic acid, Acrylic acid. Examples of unsaturated dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of the acid anhydrides of unsaturated dicarboxylic acids include maleic anhydride, acrylic acid anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. Examples of the derivative of the unsaturated dicarboxylic acid include methyl allyl maleate such as methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloromaleic acid, dichloromaleic acid, and fluoromaleic acid; And maleic acid esters such as maleic acid diphenyl, maleic anonil, maleic decyl, maleic acid dodecyl, maleic acid octadecyl, and maleic acid fluoroalkyl.

Among them, unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid and unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid are preferable, and acrylic acid, methacrylic acid and itaconic acid are more preferable, and itaconic acid is particularly preferable desirable. The dispersibility of the obtained aromatic vinyl-conjugated diene copolymer (b1) to a dispersion medium such as water can be further increased, and the binding properties of the current collector and the negative electrode active material layer can be improved to obtain a secondary battery having excellent cycle characteristics It is because. By using the above-mentioned unsaturated carboxylic acid monomer, an acidic functional group can be introduced into the aromatic vinyl-conjugated diene copolymer (bl).

The content of the unsaturated carboxylic acid monomer unit in the aromatic vinyl-conjugated diene copolymer (b1) is preferably 0.1 to 6% by mass, more preferably 0.5 to 5% by mass. By setting the content ratio of the unsaturated carboxylic acid monomer unit within the above range, the binding strength between the current collector and the negative electrode active material layer can be enhanced and the negative electrode strength can be improved. As a result, a negative electrode for a secondary battery having excellent cycle characteristics can be obtained.

<Other monomer units>

The other monomer unit is a structural unit obtained by polymerizing another monomer copolymerizable with the above-mentioned monomer.

Other monomers constituting the other monomer unit include hydrocarbons such as ethylene, propylene and isobutylene; ?,? - unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; Halogen-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; Vinylpyrrolidone, vinylpyridine, vinylimidazole, and other heterocyclic-containing vinyl compounds.

The proportion of other monomer units in the aromatic vinyl-conjugated diene copolymer (b1) is preferably from 1 to 35 mass%, more preferably from 4 to 20 mass%.

The glass transition temperature (Tg) of the aromatic vinyl-conjugated diene copolymer (bl) is -30 to 20 占 폚, preferably -20 to 20 占 폚, and more preferably -10 to 15 占 폚. When the glass transition temperature of the aromatic vinyl-conjugated diene copolymer (b1) is too low, it is difficult to suppress the expansion and contraction of the negative electrode active material, and the cycle characteristics of the secondary battery are lowered. If the glass transition temperature of the aromatic vinyl-conjugated diene copolymer (b1) is too high, the binding property with the current collector becomes insufficient and the cycle characteristics of the secondary battery are lowered.

Further, when the aromatic vinyl monomer unit constituting the aromatic vinyl-conjugated diene copolymer (b1) is increased, the glass transition temperature tends to be increased, and when the conjugated diene monomer unit is increased, the glass transition temperature tends to be lowered. The ratio of each monomer unit is adjusted on the basis of the ratio of the unsaturated carboxylic acid monomer unit and other monomer units in the polymer so that the glass transition temperature is within the above range.

The number average particle diameter of the aromatic vinyl-conjugated diene copolymer (bl) is not particularly limited, but is usually 80 to 250 nm, preferably 100 to 200 nm, and more preferably 120 to 180 nm. When the number average particle diameter of the aromatic vinyl-conjugated diene copolymer (b1) is within this range, an excellent binding force can be imparted to the negative electrode active material layer even when a small amount is used. The number average particle diameter in the present invention is the number average particle diameter calculated as the arithmetic mean value by measuring the diameter of 100 randomly selected polymer particles in a transmission electron microscope photograph. The shape of the particles may be spherical, deformed, or any shape. These aromatic vinyl-conjugated diene copolymers (b1) may be used alone or in combination of two or more.

(b2) an aromatic vinyl-conjugated diene copolymer

The aromatic vinyl-conjugated diene copolymer (b2) used in the present invention is an aromatic vinyl-conjugated diene copolymer obtained by copolymerizing an aromatic vinyl monomer unit, a conjugated diene monomer unit and an unsaturated carboxylic acid monomer unit in the same manner as the aromatic vinyl- It is united. The aromatic vinyl-conjugated diene copolymer (b2) may contain other monomer units copolymerizable therewith, if necessary. The aromatic vinyl monomer, the conjugated diene monomer, the unsaturated carboxylic acid monomer and other monomers copolymerizable therewith are as exemplified in the aromatic vinyl-conjugated diene copolymer (b1).

The proportion of the aromatic vinyl monomer units in the aromatic vinyl-conjugated diene copolymer (b2) is preferably 55% by mass or more, and more preferably 68 to 80% by mass.

The proportion of the conjugated diene monomer unit in the aromatic vinyl-conjugated diene copolymer (b2) is preferably 10% by mass or more, and more preferably 16 to 28% by mass.

The total ratio of the aromatic vinyl monomer unit to the conjugated diene monomer unit in the aromatic vinyl-conjugated diene copolymer (b2) is preferably 65% by mass or more, and more preferably 84 to 98% by mass.

The proportion of the unsaturated carboxylic acid monomer units in the aromatic vinyl-conjugated diene copolymer (b2) is preferably 0.1 to 6% by mass, and more preferably 0.5 to 5% by mass. By setting the content ratio of the unsaturated carboxylic acid monomer within the above range, the binding strength between the current collector and the negative electrode active material layer can be enhanced and the negative electrode strength can be improved. As a result, a negative electrode for a secondary battery having excellent cycle characteristics can be obtained.

The proportion of other monomer units in the aromatic vinyl-conjugated diene copolymer (b2) is preferably 1 to 35 mass%, more preferably 2 to 16 mass%.

The glass transition temperature (Tg) of the aromatic vinyl-conjugated diene copolymer (b2) is 30 to 80 캜, preferably 30 to 70 캜, more preferably 35 to 60 캜. When the glass transition temperature of the aromatic vinyl-conjugated diene copolymer (b2) is too low, it is difficult to suppress the expansion and contraction of the negative electrode active material, and the cycle characteristics of the secondary battery are deteriorated. If the glass transition temperature of the aromatic vinyl-conjugated diene copolymer (b2) is too high, the flexibility of the aromatic vinyl-conjugated diene copolymer (b2) lowers and it becomes difficult to suppress the expansion and contraction of the negative electrode active material. Is broken.

In order to bring the glass transition temperature of the aromatic vinyl-conjugated diene copolymer (b2) to the above-mentioned range, it can be carried out in the same manner as in the case of the aromatic vinyl-conjugated diene copolymer (b1).

The number average particle diameter of the aromatic vinyl-conjugated diene copolymer (b2) is not particularly limited, but is usually 80 to 250 nm, preferably 100 to 200 nm, and more preferably 120 to 180 nm. When the number average particle diameter of the aromatic vinyl-conjugated diene copolymer (b2) is within this range, an excellent binding force can be imparted to the negative electrode active material layer even when a small amount is used. These aromatic vinyl-conjugated diene copolymers (b2) may be used alone or in combination of two or more.

The content ratio (mass ratio) of the aromatic vinyl-conjugated diene copolymer (b1) to the aromatic vinyl-conjugated diene copolymer (b2) in the negative electrode for a secondary battery according to the present invention is such that the content of the aromatic vinyl-conjugated diene copolymer Conjugated diene copolymer (b2) = 80/20 to 30/70, and more preferably 70/30 to 40/60. By setting the content ratio of the aromatic vinyl-conjugated diene copolymer (b1) and the aromatic vinyl-conjugated diene copolymer (b2) within the above range, the expansion / contraction of the negative electrode active material is suppressed to improve the tackiness of the current collector and the negative electrode active material layer, The negative electrode strength can be improved.

The difference between the glass transition temperature of the aromatic vinyl-conjugated diene copolymer (bl) and the glass transition temperature of the aromatic vinyl-conjugated diene copolymer (b2) is preferably 10 to 90 캜, more preferably 20 to 70 캜. If the difference in glass transition temperature is excessively large, the strength of the electrode may be weakened and the cycle characteristics may be lowered. In addition, if the difference in glass transition temperature is too small, the electrode plate may be easily expanded.

The amount of tetrahydrofuran insoluble matter in each of the aromatic vinyl-conjugated diene copolymer (b1) and the aromatic vinyl-conjugated diene copolymer (b2) is preferably 70 to 98%, more preferably 90 to 93%. By setting the tetrahydrofuran insoluble content of the aromatic vinyl-conjugated diene copolymer (b1) and the aromatic vinyl-conjugated diene copolymer (b2) within the above range, the binding force between the negative electrode active materials is increased, and the cycle characteristics of the secondary battery are improved. Here, the tetrahydrofuran-insoluble matter is a value representing the mass ratio of the components that are not soluble in tetrahydrofuran in each of the aromatic vinyl-conjugated diene copolymer (b1) and the aromatic vinyl-conjugated diene copolymer (b2). The tetrahydrofuran-insoluble matter can be measured by the method described in the following Examples.

The blending amount of the particulate binder (B) is preferably 0.7 to 2 parts by mass based on 100 parts by mass of the total amount of the negative electrode active material. By setting the amount of the particulate binder (B) in the above range, expansion and contraction of the negative electrode active material can be suppressed and the internal resistance of the electrode can be reduced, so that a secondary battery having excellent cycle characteristics and output characteristics can be obtained.

[Production of particulate binder (B)] [

The method for producing the particulate binder (B) is not particularly limited, but the monomer mixture containing the monomers constituting each copolymer is subjected to emulsion polymerization to obtain the aromatic vinyl-conjugated diene copolymers (b1) and (b2) , And mixing them. The emulsion polymerization method is not particularly limited, and conventionally known emulsion polymerization methods may be employed. The mixing method is not particularly limited, and examples thereof include a method using a mixing device such as a stirring type, shaking type, and rotary type. A method using a dispersion kneading apparatus such as a homogenizer, a ball mill, a sand mill, a roll mill, a planetary mixer and a planetary kneader may be used.

Examples of the polymerization initiator used in the emulsion polymerization include inorganic peroxides such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, and hydrogen peroxide; butyl peroxide, t-butyl peroxide, cumene hydroperoxide, p-menthol hydroperoxide, di-t-butyl peroxide, t-butyl cumyl peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, , Organic peroxides such as 3,5,5-trimethylhexanoyl peroxide and t-butyl peroxyisobutyrate; Azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, and methyl azobisisobutyrate.

Of these, inorganic peroxides can be preferably used. These polymerization initiators may be used alone or in combination of two or more. The peroxide initiator may be used as a redox polymerization initiator in combination with a reducing agent such as sodium bisulfite.

The amount of the polymerization initiator to be used is preferably 0.05 to 5 parts by mass, more preferably 0.1 to 2 parts by mass based on 100 parts by mass of the total amount of the monomer mixture used in the polymerization.

In order to control the amount of tetrahydrofuran insolubles in the resulting copolymer, it is preferable to use a chain transfer agent in emulsion polymerization. By increasing the amount of the chain transfer agent to be used, the tetrahydrofuran insolubles are reduced and the amount of the chain transfer agent to be used is decreased, so that the tetrahydrofuran insolubles content tends to increase. Thus, by controlling the amount of the chain transfer agent, The amount can be controlled within a range. Examples of the chain transfer agent include an alkylmercury such as n-hexylmercaptan, n-octylmercaptan, t-octylmercaptan, n-dodecylmercaptan, t-dodecylmercaptan and n-stearylmercaptan &Lt; / RTI &gt; Xanthene compounds such as dimethylxanthogen disulfide and diisopropylxanthogen disulfide; A thiuram-based compound such as terpinolene, tetramethylthiouram disulfide, tetraethylthiouram disulfide, and tetramethylthiouram monosulfide; 2,6-di-t-butyl-4-methylphenol, and styrenated phenol; Allyl compounds such as allyl alcohol; Halogenated hydrocarbon compounds such as dichloromethane, dibromomethane and carbon tetrabromide; Thioglycolic acid, thiomalic acid, 2-ethylhexyl thioglycolate, diphenylethylene and? -Methylstyrene dimer.

Of these, alkyl mercaptans are preferable, and t-dodecyl mercaptan can be more preferably used. These chain transfer agents may be used alone or in combination of two or more.

The amount of the chain transfer agent to be used is preferably 0.05 to 2 parts by mass, more preferably 0.1 to 1 part by mass based on 100 parts by mass of the monomer mixture.

A surfactant may be used in emulsion polymerization. The surfactant is different from the reactive surfactant preferably contained in the water-soluble polymer (D) to be described later, and is non-reactive, and any of anionic surfactants, nonionic surfactants, cationic surfactants and amphoteric surfactants It is acceptable. Specific examples of the anionic surfactant include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecyl sulfate, ammonium dodecyl sulfate, sodium octyl sulfate, sodium decyl sulfate, sodium tetradecyl sulfate, sodium hexadecyl sulfate, Sulfuric acid ester salts of higher alcohols such as phthalate, sodium octadecylsulfate; Alkyl benzene sulfonic acid salts such as sodium dodecylbenzenesulfonate, sodium laurylbenzenesulfonate and sodium hexadecylbenzenesulfonate; Aliphatic sulfonic acid salts such as sodium laurylsulfonate, sodium dodecylsulfonate and sodium tetradecylsulfonate, and the like.

Only the reactive surfactant may be used in that the reactive surfactant described below also has the same emulsifying action, or a reactive surfactant and a non-reactive surfactant may be used in combination. In the case where a reactive surfactant is not used, emulsion polymerization is stabilized by using the non-reactive surfactant. The amount of the surfactant (including the reactive surfactant) is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass based on 100 parts by mass of the monomer mixture.

In emulsion polymerization, pH adjusting agents such as sodium hydroxide and ammonia; Various additives such as a dispersant, a chelating agent, an oxygen scavenger, a builder, and a seed latex for controlling the particle diameter can be suitably used. The seed latex refers to a dispersion of fine particles which becomes the nucleus of the reaction during emulsion polymerization. The fine particles often have a particle diameter of 100 nm or less. The fine particles are not particularly limited, and general purpose polymers such as diene polymers are used. According to the seed polymerization method, copolymer particles having relatively uniform particle diameters can be obtained.

The polymerization temperature at the time of carrying out the polymerization reaction is not particularly limited, but is usually 0 to 100 占 폚, preferably 40 to 80 占 폚. The polymerization reaction is terminated by emulsion polymerization in such a temperature range, adding a polymerization terminator at a predetermined polymerization conversion rate, or cooling the polymerization system. The polymerization conversion rate for stopping the polymerization reaction is preferably 93% by mass or more, and more preferably 95% by mass or more.

Conjugated diene copolymers (b1) and (b2) with a form (latex) in which the particulate copolymer is dispersed in the dispersion medium by adjusting the pH and the solid content concentration after removing the unreacted monomers as desired, ) Is obtained. Thereafter, the dispersion medium may be replaced as necessary, or the dispersion medium may be evaporated to obtain a particulate copolymer in powder form.

A known dispersant, thickener, antioxidant, antifoaming agent, preservative, antimicrobial agent, blister inhibitor, pH adjuster and the like may be added to the latex of the particulate copolymer to be obtained, if necessary.

(C) a water-soluble polymer containing a hydroxyl group

The water-soluble polymer containing a hydroxyl group is a polymer containing a hydroxyl group and having water-solubility. The hydroxyl group-containing water-soluble polymer is a water-soluble polymer containing a polymer different from the water-soluble polymer (D) described later, i.e., a hydroxyl group, and containing no fluorine-containing (meth) acrylic acid ester monomer unit.

The water-soluble polymer (C) (hereinafter, simply referred to as &quot; water-soluble polymer (C) &quot;) may be used after being dissolved in a slurry composition for producing a negative electrode for a secondary battery and the negative electrode active material And has a function of dispersing uniformly in the composition. Therefore, by using the water-soluble polymer (C), a uniform negative electrode for a secondary battery can be obtained.

Examples of the hydroxyl group-containing water-soluble polymer (C) include cellulose-based polymers such as carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose and the like, and their ammonium salts and alkali metal salts; (Modified) poly (meth) acrylic acid and their ammonium salts and alkali metal salts; (Modified) polyvinyl alcohols, copolymers of acrylic acid or acrylic acid salts with vinyl alcohol, polyvinyl alcohols such as maleic anhydride or maleic acid, or copolymers of fumaric acid and vinyl alcohol; Polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, modified polyacrylic acid, oxidized starch, starch phosphate, casein, various modified starches, chitin, chitosan derivatives and the like. Among these, a cellulose-based polymer is preferable, and carboxymethyl cellulose is particularly preferable.

In the case of using the water-soluble polymer (C), the viscosity of the 1% aqueous solution is preferably 100 to 3000 mPa · s, more preferably 500 to 2500 mPa · s, particularly preferably 1000 to 2000 mPa · s . When the viscosity of the 1% aqueous solution of the water-soluble polymer (C) falls within the above range, the viscosity of the slurry composition used for producing the negative electrode can be adjusted to a suitable viscosity for application and the drying time of the slurry composition can be shortened, Excellent productivity. In addition, a negative electrode having good binding property can be obtained. The viscosity of the aqueous solution can be adjusted by the average degree of polymerization of the water-soluble polymer (C). When the average degree of polymerization is high, the viscosity of the aqueous solution tends to be high. The average degree of polymerization of the water-soluble polymer (C) is preferably 100 to 1500, more preferably 300 to 1200, and particularly preferably 500 to 1000. When the average degree of polymerization of the water-soluble polymer (C) is within the above-mentioned range, the viscosity of the aqueous solution of 1% can be set within the above-mentioned range, and the above-mentioned effect is exerted thereby.

The 1% aqueous solution viscosity was measured according to JIS Z8803; 1991, which is a value measured by a single cylindrical rotational viscometer (25 ° C, rotation number = 60 rpm, spindle shape: 1).

In the present invention, the degree of etherification of the cellulose polymer preferably used as the water-soluble polymer (C) is preferably 0.6 to 1.5, more preferably 0.7 to 1.2, and particularly preferably 0.8 to 1.0. Since the degree of etherification of the cellulose-based polymer is in the above range, the affinity with the negative electrode active material is lowered to prevent the water-soluble polymer (C) from being unevenly distributed on the surface of the negative electrode active material, and the negative electrode active material layer The binding property of the negative electrode can be remarkably improved. Here, the degree of etherification refers to the degree of substitution of a carboxymethyl group with respect to hydroxyl groups (three) per cellulose anhydroglucose unit in cellulose. Theoretically, values of 0 to 3 can be taken. As the degree of etherification increases, the proportion of hydroxyl groups in cellulose decreases, the proportion of substituents increases, and as the degree of etherification decreases, hydroxyl groups in cellulose increase and substituents decrease. The degree of etherification (degree of substitution) is determined by the following method and formula.

First, 0.5 to 0.7 g of a sample is precisely weighed, and the mixture is stirred in a porcelain crucible. After cooling, the thus-obtained retentate is transferred to a 500 ml beaker, and about 250 ml of water and 35 ml of N / 10 sulfuric acid are further pipetted into the beaker and mercury is added for 30 minutes. This is cooled, the phenolphthalein indicator is added and the excess acid is reversed with N / 10 potassium hydroxide to yield the degree of substitution from the following formulas (I) and (II).

[Equation 1]

A = (a x f - b x f ¹ ) / sample (g) - alkalinity (or + acidity) (I)

&Quot; (2) &quot;

Substitution degree = M x A / (10000 - 80A) ... (II)

In the above formulas (I) and (II), A is the amount (ml) of N / 10 sulfuric acid consumed in the bonded alkali metal ion in 1 g of the sample. and a is the amount (ml) of N / 10 sulfuric acid. f is the activity coefficient of N / 10 sulfuric acid. b is an appropriate amount (ml) of N / 10 potassium hydroxide. f ¹ is the potency coefficient of N / 10 potassium hydroxide. M is the weight average molecular weight of the sample.

The blending amount of the water-soluble polymer (C) is preferably 1 to 3 parts by mass based on 100 parts by mass of the total amount of the negative electrode active material. When the blending amount of the water-soluble polymer (C) is within the above range, the coating property is improved, so that the internal resistance of the secondary battery is prevented from rising and the binding property with the current collector is excellent. In addition, since expansion and contraction of the negative electrode active material can be suppressed, the cycle characteristics of the secondary battery are improved.

(D) a water-soluble polymer containing 0.5 to 20% by mass of a fluorine-containing (meth) acrylic acid ester monomer unit

The water-soluble polymer (D) containing 0.5 to 20 mass% of the fluorine-containing (meth) acrylic acid ester monomer unit used in the present invention (hereinafter sometimes simply referred to as "water-soluble polymer (D)") ) Acrylic acid ester monomer unit in an amount of 0.5 to 20% by mass, preferably 2 to 15% by mass, and more preferably 3 to 12% by mass. The copolymer may further contain an unsaturated carboxylic acid monomer unit, a (meth) acrylic acid ester monomer unit or a crosslinkable monomer unit, and may further contain a structural unit obtained by polymerizing a monomer having a functional group such as a reactive surfactant monomer , And a structural unit obtained by polymerizing other copolymerizable monomers.

Also, in the present specification, (meth) acryl includes both acryl and methacryl.

By using such a water-soluble polymer (D), the binding strength between the current collector and the negative electrode active material layer can be enhanced and the negative electrode strength can be improved. Further, the water-soluble polymer (D) covers the surface of the negative electrode active material to suppress the decomposition of the electrolytic solution by the negative electrode active material in the secondary battery, thereby improving the durability (cycle characteristics) of the secondary battery. Further, by coating the negative electrode active material with the water-soluble polymer (D), the affinity between the negative electrode active material and the electrolytic solution is increased, and the ion conductivity is improved, thereby reducing the internal resistance of the secondary battery.

&Lt; Fluorine-containing (meth) acrylic acid ester monomer unit &gt;

The fluorine-containing (meth) acrylic acid ester monomer unit is a structural unit formed by polymerization of a fluorine-containing (meth) acrylic acid ester monomer.

Examples of the fluorine-containing (meth) acrylic ester monomers include monomers represented by the following formula (I).

[Chemical Formula 1]

In the above formula (I), R ¹ represents a hydrogen atom or a methyl group. In the above formula (I), R ² represents a hydrocarbon group containing a fluorine atom. The carbon number of the hydrocarbon group is usually 1 or more, and usually 18 or less. The number of fluorine atoms contained in R ² may be one or two or more.

Examples of the fluorine-containing (meth) acrylic acid ester monomer represented by the formula (I) include alkyl (meth) acrylate, aryl fluoride (meth) acrylate and aralkyl fluoride (meth) acrylate. Among them, alkyl (meth) acrylate is preferred. Specific examples of such monomers include (meth) acrylic acid-2,2,2-trifluoroethyl, (meth) acrylic acid- beta - (perfluorooctyl) ethyl, (meth) 3-tetrafluoropropyl, (meth) acrylic acid-2,2,3,4,4,4-hexafluorobutyl, (meth) acrylic acid-1H, 1H, 9H-perfluoro- ) Perfluorooctyl (meth) acrylate, perfluorooctyl (meth) acrylate, and (meth) acrylic acid -3- [4- [1-trifluoromethyl-2,2- (Trifluoromethyl) fluoromethyl] ethynyloxy] benzooxy] -2-hydroxypropyl, and the like.

The fluorine-containing (meth) acrylic acid ester monomers may be used alone or in combination of two or more at any ratio. Therefore, the water-soluble polymer (D) may contain only one fluorine-containing (meth) acrylic acid ester monomer unit, or may contain two or more kinds of fluorine-containing (meth) acrylic acid ester monomer units in any combination.

The content of the fluorine-containing (meth) acrylic acid ester monomer unit in the water-soluble polymer (D) is in the range of 0.5 to 20 mass%, preferably 2 to 15 mass%, and more preferably 3 to 12 mass%. If the ratio of the fluorine-containing (meth) acrylic acid ester monomer units is too low, the water-soluble polymer (D) can not impart a repulsive force to the electrolytic solution and the swelling property can not be set in an appropriate range. If the ratio of the fluorine-containing (meth) acrylic acid ester monomer units is too high, wettability to the electrolytic solution can not be imparted to the water-soluble polymer (D), and low-temperature cycle characteristics are deteriorated.

When the water-soluble polymer (D) contains a fluorine-containing (meth) acrylic acid ester monomer unit, alkali resistance is imparted to the negative electrode active material layer. An alkaline substance may be contained in the slurry composition for forming the negative electrode, and an alkaline substance may be generated due to oxidation and reduction by the operation of the device. Such an alkaline substance corrodes the current collector to deteriorate the lifetime of the device, but the negative active material layer has alkali resistance, so that corrosion of the current collector by the alkaline substance is suppressed.

<Unsaturated Carboxylic Acid Monomer Unit>

The unsaturated carboxylic acid monomer unit is a structural unit formed by polymerizing an unsaturated carboxylic acid monomer. The unsaturated carboxylic acid monomer is the same as the unsaturated carboxylic acid monomer described in detail in the particulate binder (B).

Of the unsaturated carboxylic acid monomers, unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid and unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid are preferable, and unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid are more preferable Do. The dispersibility of the resulting water-soluble polymer (D) in water can be further increased.

The content of the unsaturated carboxylic acid monomer unit in the water-soluble polymer (D) is preferably from 1 to 40% by mass, and more preferably from 5 to 30% by mass. By setting the content ratio of the unsaturated carboxylic acid monomer within the above range, the binding property between the current collector and the negative electrode active material layer can be enhanced and the negative electrode strength can be improved. In addition, since the dispersibility of the water-soluble polymer (D) can be improved, a uniform negative electrode slurry composition can be obtained. As a result, a secondary battery having excellent cycle characteristics can be obtained.

<(Meth) acrylic acid ester monomer unit>

The (meth) acrylic acid ester monomer unit is a structural unit obtained by polymerizing a (meth) acrylic acid ester monomer. Among the (meth) acrylic acid ester monomers, those containing fluorine are distinguished from the (meth) acrylic acid ester monomers as the above-mentioned fluorine-containing (meth) acrylic acid ester monomers.

Examples of the (meth) acrylic acid ester monomers include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, Alkyl acrylate esters such as octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate and stearyl acrylate; And examples of the monomer include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, Methacrylic acid such as methacrylic acid, methacrylic acid such as methacrylic acid, methacrylic acid, methacrylic acid, etc., such as acrylate, methacrylate, Alkyl esters.

The (meth) acrylic acid ester monomers may be used singly or in a combination of two or more. Therefore, the water-soluble polymer (D) may contain only one type of (meth) acrylic acid ester monomer unit, or may include two or more kinds in combination at an arbitrary ratio.

In the water-soluble polymer (D), the content of the (meth) acrylic acid ester monomer unit is preferably 30 mass% or more, more preferably 35 mass% or more, particularly preferably 40 mass% or more, Is not more than 75 mass%, more preferably not more than 70 mass%, particularly preferably not more than 65 mass%. By making the content ratio of the (meth) acrylic acid ester monomer unit be not less than the lower limit value in the above range, the binding property of the negative electrode active material layer to the current collector can be increased, and if it is not more than the upper limit value, the flexibility of the negative electrode active material layer can be increased .

<Crosslinkable monomer unit>

The water-soluble polymer (D) may further comprise a crosslinkable monomer unit in addition to the respective structural units. The crosslinkable monomer unit is a structural unit capable of forming a crosslinked structure during or after polymerization by heating or energy irradiation. Examples of the cross-linkable monomer include monomers having thermal crosslinkability. More specifically, a monofunctional monomer having a thermally crosslinkable crosslinkable group and one olefinic double bond per molecule, and a polyfunctional monomer having at least two olefinic double bonds per molecule can be mentioned.

Examples of the thermally crosslinkable crosslinkable group contained in the monofunctional monomer include an epoxy group, an N-methylolamide group, an oxetanyl group, an oxazoline group, and a combination thereof. Of these, the epoxy group is more preferable because the crosslinking and the crosslinking density can be easily controlled.

Examples of the crosslinkable monomer having an epoxy group as the thermally crosslinkable crosslinkable group and having an olefinic double bond include vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, o-allylphenylglycidyl Unsaturated glycidyl ethers such as diesters; Butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene and 1,2-epoxy-5,9-cyclododecadien Monoepoxide of diene or polyene; Alkenyl epoxide such as 3,4-epoxy-1-butene, 1,2-epoxy-5-hexene and 1,2-epoxy-9-decene; And glycidyl methacrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl-4-methyl Glycidyl esters of unsaturated carboxylic acids such as glycidyl esters of 3-cyclohexenecarboxylic acid and glycidyl esters of 4-methyl-3-cyclohexenecarboxylic acid, .

Examples of the crosslinkable monomer having an N-methylolamide group as the thermally crosslinkable crosslinkable group and having an olefinic double bond include (meth) acrylamides having a methylol group such as N-methylol (meth) acrylamide .

Examples of the crosslinkable monomer having an oxetanyl group as the thermally crosslinkable crosslinkable group and having an olefinic double bond include 3 - ((meth) acryloyloxymethyl) oxetane, 3 - ((meth) acryloyl (Meth) acryloyloxymethyl) oxetane, 2- ((meth) acryloyloxymethyl) oxetane, 2- ((Meth) acryloyloxymethyl) -4-trifluoromethyl oxetane.

Examples of the crosslinkable monomer having an oxazoline group as the thermally crosslinkable crosslinkable group and having an olefinic double bond include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, Methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl- , And 2-isopropenyl-5-ethyl-2-oxazoline.

Examples of the multifunctional monomer having two or more olefinic double bonds include allyl (meth) acrylate, ethylenedi (meth) acrylate, diethyleneglycol di (meth) acrylate, triethyleneglycol di (meth) (Meth) acrylate, dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diaryl ether, tetraallyloxy (meth) acrylate, tetraethylene glycol di Ethane, trimethylolpropane-diallyl ether, allyl or vinyl ethers of polyfunctional alcohols other than the above, triallylamine, methylenebisacrylamide, and divinylbenzene.

As the crosslinkable monomer, ethylene dimethacrylate, allyl glycidyl ether, and glycidyl methacrylate can be preferably used.

When the water-soluble polymer (D) contains a crosslinkable monomer unit, its content is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, particularly preferably 0.5% by mass or more, By mass or less, more preferably 4% by mass or less, and particularly preferably 2% by mass or less. By setting the content ratio of the crosslinkable monomer unit to the lower limit value or more in the above range, the weight average molecular weight of the water-soluble polymer (D) can be increased to prevent the swelling degree from being excessively increased. On the other hand, when the ratio of the crosslinkable monomer units is not more than the upper limit of the above range, the water-soluble polymer (D) can be made highly soluble in water and the dispersibility can be improved. Therefore, both the degree of swelling and the degree of dispersion can be improved by making the content of the crosslinkable monomer unit fall within the above range.

&Lt; Reactive surfactant monomer unit &gt;

The water-soluble polymer (D) may contain, in addition to each monomer unit, a structural unit obtained by polymerizing a monomer having a functional group such as a reactive surfactant monomer.

The reactive surfactant monomer is a monomer having a polymerizable group capable of copolymerizing with another monomer to be described later and also having a surfactant group (a hydrophilic group and a hydrophobic group). The monomer unit obtained by polymerizing the reactive surfactant monomer constitutes a part of the molecule of the water-soluble polymer (D) and is a structural unit capable of functioning as a surfactant.

Usually, the reactive surfactant monomer has a polymerizable unsaturated group, and this group also acts as a hydrophobic group after polymerization. Examples of the polymerizable unsaturated group contained in the reactive surfactant monomer include a vinyl group, an allyl group, a vinylidene group, a propenyl group, an isopropenyl group, and an isobutylidene group. These polymerizable unsaturated groups may be of one kind or two or more kinds.

In addition, the reactive surfactant monomer has a hydrophilic group and usually has a hydrophilic group. The reactive surfactant monomers are classified into anionic, cationic, and nonionic surfactants depending on the kind of the hydrophilic group.

Examples of anionic hydrophilic groups include -SO ₃ M, -COOM, and -PO (OH) ₂ . Wherein M represents a hydrogen atom or a cation. Examples of cations include alkali metal ions such as lithium, sodium, and potassium; Alkaline earth metal ions such as calcium and magnesium; Ammonium ion; Ammonium ions of alkylamines such as monomethylamine, dimethylamine, monoethylamine and triethylamine; And ammonium ions of alkanolamines such as monoethanolamine, diethanolamine and triethanolamine.

Examples of hydrophilic groups in the cationic system include -Cl, -Br, -I, and -SO ₃ ORX. Wherein RX represents an alkyl group. Examples of RX include a methyl group, an ethyl group, a propyl group, and an isopropyl group.

An example of a nonionic system hydrophilic group is -OH.

Examples of preferred reactive surfactant monomers include compounds represented by the following formula (II).

(2)

In formula (II), R represents a divalent linking group. Examples of R include -Si-O- group, methylene group and phenylene group. In the formula (II), R ³ represents a hydrophilic group. An example of R ³ is -SO ₃ NH ₄ . In the formula (II), n is an integer of 1 or more and 100 or less. The reactive surfactant monomers may be used singly or in combination of two or more at any desired ratio.

When the water-soluble polymer (D) contains a reactive surfactant monomer unit, the ratio is preferably in the range of 0.1 to 15 mass%, more preferably 0.5 to 10 mass%, and particularly preferably 1 to 5 mass% . The dispersibility of the negative electrode active material (A) and the particulate binder (B) can be improved by setting the ratio of the reactive surfactant monomer units to the lower limit of the above range. On the other hand, by setting the ratio of the reactive surfactant monomer units to the upper limit of the above range, the durability of the negative electrode active material layer can be improved.

<Other monomer units>

Further examples of the optional units that the water-soluble polymer (D) may have include structural units obtained by polymerizing the following monomers. That is, styrene-based monomers such as styrene, chlorostyrene, vinyltoluene, t-butylstyrene, vinylbenzoic acid, vinylbenzoate, vinylnaphthalene, chloromethylstyrene, hydroxymethylstyrene,? -Methylstyrene and divinylbenzene; Amide-based monomers such as acrylamide and acrylamide-2-methylpropanesulfonic acid; Alpha, beta -unsaturated nitrile compound monomers such as acrylonitrile and methacrylonitrile; Olefin monomers such as ethylene and propylene; Halogen-containing monomers such as vinyl chloride and vinylidene chloride; Vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl benzoate; Vinyl ether monomers such as methyl vinyl ether, ethyl vinyl ether and butyl vinyl ether; Vinyl ketone monomers such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, and isopropenyl vinyl ketone; , And structural units obtained by polymerizing at least one of the heterocyclic-containing vinyl compound monomers such as N-vinylpyrrolidone, vinylpyridine and vinylimidazole. The proportion of these structural units in the water-soluble polymer (D) is preferably 0 to 10% by mass, and more preferably 0 to 5% by mass.

The water-soluble polymer in the present specification means a polymer having a viscosity of 1% aqueous solution of 0.1 to 100,000 mPa.s at pH 8.

The solution viscosity of the water-soluble polymer (D) when adjusted to 1% aqueous solution at pH 8 is preferably 0.1 to 20,000 mPa · s, more preferably 1 to 10,000 mPa · s, particularly preferably 10 To 5000 mPa · s. If the solution viscosity is too high, the binding property of the negative electrode active material layer to the current collector may be deteriorated. If the viscosity is too low, the flexibility of the negative electrode active material layer may be deteriorated.

The weight average molecular weight of the water-soluble polymer (D) is usually smaller than the polymer (aromatic vinyl-conjugated diene copolymers (b1) and (b2)) to be a binder, preferably 100 or more, more preferably 500 or more, Is preferably 1000 or more, preferably 500000 or less, more preferably 2500000 or less, particularly preferably 100000 or less. The weight average molecular weight of the water-soluble polymer (D) is a value obtained by dissolving 0.85 g / ml sodium nitrate in a 10% by volume aqueous solution of dimethylformamide by gel permeation chromatography (GPC) as a developing solvent in terms of polystyrene .

The glass transition temperature of the water-soluble polymer (D) is usually 0 ° C or higher, preferably 5 ° C or higher, and usually 100 ° C or lower, preferably 50 ° C or lower. The glass transition temperature of the water-soluble polymer (D) can be adjusted by combining various monomers.

The blending amount of the water-soluble polymer (D) is preferably determined according to the blending amount of the water-soluble polymer (C), and the total amount of the water-soluble polymers (C) and (D) relative to 100 parts by mass of the total amount of the negative- Mass part, and more preferably 0.7 to 3 mass parts. By setting the total amount of the water-soluble polymers (C) and (D) within the above range, the binding property between the current collector and the negative electrode active material layer can be enhanced and the cycle characteristics of the secondary battery can be improved. In addition, since the internal resistance of the secondary battery can be reduced, the output characteristics (particularly the low temperature output characteristics) can be improved.

The weight ratio of the water-soluble polymer (D) and the water-soluble polymer (C) is "water-soluble polymer (C) / water-soluble polymer (D)", preferably 99/1 to 70/30, 15, particularly preferably 99/1 to 90/10. By setting the weight ratio of the water-soluble polymer (D) and the water-soluble polymer (C) to the above range, the lithium ion conductivity on the surface of the negative electrode active material is increased, and thereby the output of the secondary battery can be improved.

[Preparation of water-soluble polymer (D)] [

As a method of producing the water-soluble polymer (D), a method of polymerizing a monomer mixture containing a monomer constituting the water-soluble polymer (D) in a dispersion medium to obtain a water-dispersible polymer and alkalizing the mixture at pH 7 to 13. The polymerization method is the same as that described above for the particulate binder.

Examples of the method of alkalinizing with a pH of 7 to 13 include, but not particularly limited to, an aqueous solution of an alkali metal such as aqueous solution of lithium hydroxide, aqueous solution of sodium hydroxide and aqueous solution of potassium hydroxide, aqueous solution of calcium hydroxide, aqueous solution of magnesium hydroxide and alkali solution of alkaline earth metal such as aqueous ammonia, And then adding an aqueous solution.

The dispersion medium used in the production of the particulate binder (B) or the water-soluble polymer (D) is not particularly limited as long as it can uniformly disperse the above components and can stably maintain the dispersed state. Can be used. From the viewpoint of streamlining the production process, it is preferable to directly prepare the particulate binder (B) or the water-soluble polymer (D) after the above emulsion polymerization without carrying out operations such as solvent substitution and the like. Is preferably used. In emulsion polymerization, water is often used as a reaction solvent, and it is particularly preferable to use water as a dispersion medium from the viewpoint of working environment.

(E) Other components

The negative electrode active material layer may contain other components such as a conductive agent, a reinforcing agent, a leveling agent, an antioxidant, and an electrolyte additive having a function of inhibiting decomposition of an electrolyte, in addition to the above components. They are not particularly limited as long as they do not affect the cell reaction.

As the conductive agent, conductive carbon such as acetylene black, ketjen black, carbon black, graphite, vapor grown carbon fiber, and carbon nanotube can be used. By containing a conductive agent, electrical contact between the negative electrode active materials can be improved, and the discharge rate characteristic can be improved when used in a lithium ion secondary battery. The content of the conductive agent is preferably 1 to 20 parts by mass, more preferably 1 to 10 parts by mass based on 100 parts by mass of the total amount of the negative electrode active material.

As the reinforcing material, various inorganic and organic spherical, plate-like, rod-like or fibrous fillers can be used. By using the reinforcing material, it is possible to obtain a strong and flexible negative electrode, and to exhibit excellent long-term cycle characteristics. The content of the reinforcing material in the negative electrode active material layer is usually 0.01 to 20 parts by mass, preferably 1 to 10 parts by mass based on 100 parts by mass of the total amount of the negative electrode active material. When the content of the reinforcing material is within the above range, a secondary battery exhibiting high capacity and high load characteristics can be obtained.

Examples of the leveling agent include surfactants such as alkyl surfactants, silicone surfactants, fluorochemical surfactants, and metal surfactants. By mixing the leveling agent, it is possible to prevent the occurrence of cratering at the time of coating or to improve the smoothness of the negative electrode. The content of the leveling agent in the negative electrode active material layer is preferably 0.01 to 10 parts by mass based on 100 parts by mass of the total amount of the negative electrode active material. When the content of the leveling agent is in the above range, the productivity, smoothness and cell characteristics at the time of producing the negative electrode are excellent.

Examples of the antioxidant include a phenol compound, a hydroquinone compound, an organic phosphorus compound, a sulfur compound, a phenylenediamine compound, and a polymer type phenol compound. The polymer type phenol compound is a polymer having a phenol structure in the 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 of the antioxidant in the negative electrode active material layer is preferably 0.01 to 10% by mass, more preferably 0.05 to 5% by mass. Since the content of the antioxidant is in the above range, the stability of the slurry composition used for producing the negative electrode and the battery capacity and cycle characteristics of the resulting secondary battery are excellent.

As the electrolyte additive, vinylene carbonate or the like used in an electrolytic solution may be used. The content of the electrolyte additive in the negative electrode active material layer is preferably 0.01 to 10 parts by mass based on 100 parts by mass of the total amount of the negative electrode active material. The content of the electrolyte additive in the above range is excellent in high-temperature cycle characteristics and high-temperature characteristics. Other examples include nanoparticles such as fumed silica and fumed alumina. By mixing nanoparticles, the thixotropy of the slurry composition can be controlled and the leveling property of the negative electrode obtained thereby can be improved. The content of the nano-particles in the negative electrode active material layer is preferably 0.01 to 10 parts by mass based on 100 parts by mass of the total amount of the negative electrode active material. The content of the nano-particles is in the above-mentioned range, so that the slurry stability and productivity are excellent and high battery characteristics are exhibited.

In addition to the above, an isothiazoline compound or a chelate compound may be added as an additive.

Whole house

The current collector used in the present invention is not particularly limited as long as it is an electrically conductive and electrochemically durable material. However, it is preferably a metallic material because it has heat resistance, and examples thereof include iron, copper, aluminum, nickel, stainless steel, Titanium, tantalum, gold, platinum, and the like. Among them, copper is particularly preferable as the collector used for the secondary battery negative electrode. The shape of the current collector is not particularly limited, but it is preferable that the current collector is in the form of a sheet having a thickness of about 0.001 to 0.5 mm. The collector may be subjected to a surface roughening treatment beforehand in order to increase the bonding strength with the negative electrode active material layer. Examples of roughening methods include mechanical polishing, electrolytic polishing, and chemical polishing. In the mechanical polishing, a wire brush having polishing abrasive particles fixed to abrasive particles, a grinding wheel, an emery buff, a steel wire, or the like is used. An intermediate layer may be formed on the surface of the current collector in order to improve the bonding strength and conductivity between the negative electrode active material layer and the current collector. Among them, it is preferable to form a conductive adhesive layer.

[Manufacturing method of negative electrode for secondary battery]

As a method of producing the negative electrode for a secondary battery of the present invention, a method of binding the negative electrode active material layer on at least one surface of the current collector may be used. For example, a negative electrode slurry composition for a secondary battery (hereinafter sometimes referred to as &quot; negative electrode slurry composition &quot;) described below is applied to a current collector, dried, and then heat- . The method of applying the negative electrode slurry composition to the current collector is not particularly limited. For example, methods such as a doctor blade method, an agglomeration method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush application method can be mentioned. Examples of the drying method include hot air, hot air, low-humidity air drying, vacuum drying, and drying by irradiation with (circle) infrared rays or electron beams. The drying time is usually 5 to 50 minutes, and the drying temperature is usually 40 to 180 ° C.

In the production of the negative electrode for a secondary battery of the present invention, a step of forming a negative electrode active material layer composed of the negative electrode slurry composition on the current collector and then lowering the porosity of the negative electrode active material layer by pressure treatment using a die press or roll press . The porosity of the negative electrode active material layer is preferably 5 to 30%, more preferably 7 to 20%. If the porosity is excessively high, the charging efficiency and the discharge efficiency may deteriorate. When the porosity is too low, it is difficult to obtain a high volume capacity, and the negative electrode active material layer may easily peel off from the current collector, thus causing a problem that defects tend to occur. When a curable polymer is used for the particulate binder (B), curing is preferred.

In the present invention, the density of the negative electrode active material layer in the negative electrode for a secondary battery is preferably 1.6 to 2.2 g / cm 3, more preferably 1.65 to 1.85 g / cm 3. Since the density of the negative electrode active material layer is in the above range, a high capacity secondary battery can be obtained.

The thickness of the negative electrode active material layer in the lithium ion secondary battery negative electrode of the present invention is usually 5 to 300 占 퐉, preferably 30 to 250 占 퐉. When the thickness of the negative electrode active material layer is in the above range, it is possible to obtain a secondary battery exhibiting both high load characteristics and high cycle characteristics.

In the present invention, the content ratio of the negative electrode active material in the negative electrode active material layer is preferably 85 to 99 mass%, more preferably 88 to 97 mass%. When the content ratio of the negative electrode active material in the negative electrode active material layer is in the above range, it is possible to obtain a secondary battery exhibiting flexibility and tackiness while exhibiting high capacity.

(Negative electrode slurry composition for secondary battery)

The negative electrode slurry composition for a secondary battery contains the components (A) to (D), other components (E) to be added as required, and a dispersion medium.

The dispersion medium is not particularly limited as long as it can uniformly disperse or dissolve the above components. In the present invention, a dispersion medium exemplified as a dispersion medium used for producing the particulate binder (B) or the water-soluble polymer (D) can be used.

The solid content concentration of the negative electrode slurry composition is not particularly limited as long as it is capable of being coated and immersed and has a viscosity having fluidity, but is generally about 10 to 80 mass%.

[Preparation of negative electrode slurry composition for secondary battery]

The negative electrode slurry composition for a secondary battery is obtained by mixing the components (A) to (D), the other component (E) to be added as required and the dispersion medium. The amount of the dispersion medium used when preparing the negative electrode slurry composition is such that the solid concentration of the negative electrode slurry composition is usually in the range of 40 to 80 mass%, preferably 60 to 80 mass%, and more preferably 72 to 80 mass% . When the solid concentration of the negative electrode slurry composition is in this range, each of the above components can be uniformly dispersed. In addition, since the change in the thickness of the negative electrode slurry composition before and after drying can be reduced, the residual stress remaining in the negative electrode can be reduced. Thereby, it is possible to improve the suppression of cracking and adhesion in the negative electrode.

In the present invention, by using the above-described components, a negative electrode slurry composition in which the above components are highly dispersed can be obtained regardless of the mixing method or mixing order. The mixing apparatus is not particularly limited as long as it is an apparatus capable of uniformly mixing the components, and examples thereof include a bead mill, a ball mill, a roll mill, a sand mill, a pigment dispersing apparatus, a brain trajectory, an ultrasonic dispersing apparatus, a homogenizer, a planetary mixer, Among them, it is particularly preferable to use a ball mill, a roll mill, a pigment disperser, a cerebellum, and a planetary mixer in order to disperse at a high concentration.

The viscosity of the negative electrode slurry composition is preferably from 10 to 100,000 mPa,, more preferably from 100 to 50,000 mPa s, from the viewpoints of uniform coating property and slurry time-course stability. The viscosity was measured using a B-type viscometer at 25 DEG C and a rotation speed of 60 rpm.

[Secondary Battery]

The secondary battery of the present invention is a secondary battery having a positive electrode, a negative electrode, an electrolyte, and a separator, and the negative electrode is the above-described negative electrode for a secondary battery.

(Positive electrode)

The positive electrode is formed by laminating a positive electrode active material layer including a positive electrode active material and a positive electrode binder on a current collector.

Positive active material

The positive electrode active material is largely classified into an inorganic compound and an organic compound, in which an active material capable of doping and dedoping lithium ions is used.

Examples of the positive electrode active material composed of an inorganic compound include transition metal oxides, transition metal sulfides, and lithium-containing composite metal oxides of lithium and a transition metal. Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo are used as the transition metal.

Examples of transition metal oxides include MnO, MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , Cu ₂ V ₂ O ₃ , amorphous V ₂ OP ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O ₁₃ Among them, MnO, V ₂ O ₅ , V ₆ O ₁₃ and TiO ₂ are preferable from the cycle characteristics and the capacity. Transition metal sulfides include TiS ₂ , TiS ₃ , amorphous MoS ₂ , and FeS. Examples of the lithium-containing composite metal oxide include a lithium-containing composite metal oxide having a layered structure, a lithium-containing composite metal oxide having a spinel structure, and a lithium-containing composite metal oxide having an olivine structure.

The lithium-containing composite metal oxide having a layered structure includes lithium-containing cobalt oxide (LiCoO ₂ ), lithium-containing nickel oxide (LiNiO ₂ ), lithium composite oxide of Co-Ni-Mn, lithium composite oxide of Ni- And a lithium complex oxide of -Co-Al. Examples of the lithium-containing composite metal oxide having a spinel structure include lithium manganese oxide (LiMn ₂ O ₄ ) and Li [Mn _3/2 M _1/2 ] O ₄ in which a part of Mn is substituted with another transition metal (M is Cr, Fe, Co, Ni, Cu, etc.). As the lithium-containing composite metal oxide having an olivine structure, Li _X MPO ₄ (wherein M is at least one element selected from the group consisting of Mn, Fe, Co, Ni, Cu, Mg, Zn, V, Ca, Sr, Ba, Ti, B and Mo, and 0 &lt; = X &lt; = 2).

As the organic compound, for example, a conductive polymer such as polyacetylene or poly-p-phenylene may be used. The iron-based oxide lacking electric conductivity may be used as an electrode active material covered with a carbon material by causing a carbon source material to exist at the time of reduction calcination. These compounds may be partially substituted with an element. The positive electrode active material for a lithium ion secondary battery may be a mixture of the inorganic compound and the organic compound.

The average particle diameter of the positive electrode active material is usually 1 to 50 占 퐉, preferably 2 to 30 占 퐉. When the average particle diameter of the positive electrode active material is within the above range, the amount of the positive electrode binder in the positive electrode active material layer can be reduced, thereby suppressing the capacity drop of the battery. In order to form the positive electrode active material layer, a slurry (hereinafter sometimes referred to as &quot; positive electrode slurry composition &quot;) including a positive electrode active material and a binder for positive electrode is prepared, and a viscosity suitable for applying the positive electrode slurry composition Can be easily prepared, and a uniform positive electrode can be obtained.

The content of the positive electrode active material in the positive electrode active material layer is preferably 90 to 99.9 mass%, more preferably 95 to 99 mass%. By setting the content of the positive electrode active material in the positive electrode active material layer within the above range, flexibility and adhesion can be exhibited while exhibiting high capacity.

Binder for positive electrode

The positive electrode binder is not particularly limited and any known binder may be used. For example, the number of polyolefins such as polyethylenes, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid derivatives, polyacrylonitrile derivatives A soft polymer such as an acrylic soft polymer, a diene soft polymer, an olefin soft polymer, and a vinyl soft polymer can be used. These may be used alone, or two or more of them may be used in combination.

In addition to the above components, the positive electrode may further contain other components such as an electrolyte additive having a function of suppressing decomposition of the electrolyte solution as described above. They are not particularly limited as long as they do not affect the cell reaction.

The collector may be a current collector used for the negative electrode for the secondary battery described above, and is not particularly limited as long as it is an electrically conductive and electrochemically durable material. However, aluminum is particularly preferable for the positive electrode of the secondary battery.

The thickness of the positive electrode active material layer is usually 5 to 300 占 퐉, preferably 10 to 250 占 퐉. When the thickness of the positive electrode active material layer is in the above range, both the load characteristics and the energy density exhibit high characteristics.

The positive electrode can be manufactured in the same manner as the above-described negative electrode for a secondary battery.

(Separator)

(B) a porous separator having a polymer coating layer formed on one surface or both surfaces thereof, or (c) an inorganic ceramic powder; and (c) an inorganic ceramic powder. The separator includes a porous separator, And a porous separator in which a porous resin-coated layer is formed. Nonlimiting examples of these include polypropylene-based, polyethylene-based, polyolefin-based or aramid-based porous separators, polyvinylidene fluoride, polyethylene oxide, polyacrylonitrile or polyvinylidene fluoride hexafluoropropylene copolymer A polymer film for a solid polymer electrolyte or a gel polymer electrolyte, a separator coated with a gelated polymer coat layer, or a separator coated with a porous film layer comprising an inorganic filler and a dispersant for an inorganic filler.

(Electrolytic solution)

The electrolyte used in the present invention is not particularly limited, and for example, a lithium salt dissolved in a non-aqueous solvent as a supporting electrolyte may be used. The lithium salt is, for example, _{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₎ can be cited lithium salts such as _{2 NLi, (C 2 F 5} SO 2) NLi. LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li, which are particularly easy to dissolve in a solvent and exhibit a high degree of dissociation, are preferably used. These may be used alone or in combination of two or more. The amount of the supporting electrolyte is usually 1% by mass or more, preferably 5% by mass or more, and usually 30% by mass or less, and preferably 20% by mass or less, based on the electrolytic solution. If the amount of the supporting electrolyte is excessively large or excessively large, the ionic conductivity decreases and the charging and discharging characteristics of the battery deteriorate.

The solvent used for the electrolytic solution is not particularly limited as long as it dissolves the supporting electrolyte. The solvent is usually selected from the group consisting of dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate ), And methyl ethyl carbonate (MEC); ethers such as tetrahydrofuran and 1,2-dimethoxyethane; Sulfolane, and dimethyl sulfoxide are used. Particularly, dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and methyl ethyl carbonate are preferable because it is easy to obtain high ionic conductivity and has a wide use temperature range. These may be used alone or in combination of two or more. It is also possible to add an additive to the electrolytic solution. The additive is preferably a carbonate compound such as vinylene carbonate (VC).

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

[Manufacturing Method of Secondary Battery]

The method for producing the secondary battery of the present invention is not particularly limited. For example, the negative electrode and the positive electrode described above are superimposed with a separator interposed therebetween, and they are wound or bent according to the shape of the battery, and the electrolyte is injected into the battery container and the inlet is sealed. If necessary, it is also possible to prevent the rise of the internal pressure of the battery and the overcharge discharge by inserting an over-current prevention element such as X-fund metal, fuse, PTC element, or a lead plate. The shape of the battery may be any of a laminate cell type, a coin type, a button type, a sheet type, a cylindrical type, a square type, and a flat type.

Example

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited thereto. In the present embodiment, parts and% are based on mass unless otherwise specified. In Examples and Comparative Examples, various physical properties were evaluated as follows.

<Glass transition temperature>

The glass transition temperature (Tg) of the aromatic vinyl-conjugated diene copolymer (b1) and the aromatic vinyl-conjugated diene copolymer (b2) was measured using a differential scanning calorimetry analyzer (DSC6220SII, manufactured by Nanotechnology Co., Ltd.) and measured according to JIS K 7121; 1987. &lt; / RTI &gt; In the measurement using a differential scanning calorimeter, when two or more peaks were observed, the peak on the high temperature side was defined as Tg.

<Tetrahydrofuran insoluble matter>

The aqueous dispersion was placed in an aluminum dish and dried for 48 hours under a 50% humidity environment at 23 to 25 ° C to form a film with a thickness of 3 ± 0.3 mm. The film thus formed was cut into 1 mm x 1 mm, and 1 g was precisely weighed. The mass of the film obtained by this cutting is referred to as W0. The film piece was immersed in 100 g of tetrahydrofuran (THF) at 25 DEG C for 24 hours. Thereafter, the film piece lifted from THF was vacuum-dried at 105 DEG C for 3 hours to measure the mass W1 of the insoluble matter. Then, the ratio (%) of tetrahydrofuran insoluble matter was calculated according to the following formula.

Tetrahydrofuran insoluble matter (%) = W1 / W0 100

<High temperature cycle characteristics>

The lithium ion secondary batteries of the laminate type cells prepared in the examples and comparative examples were kept still at 25 캜 for 24 hours and then charged at 4.2 V and 0.1 C in an environment of 25 캜 and discharged at 3.0 V and 0.1 C Discharge operation was performed to measure the initial capacity C ₀ . Charging and discharging were repeated under an environment of 45 캜, and the capacity C ₂ after 100 cycles was measured.

The high-temperature cycle characteristics were evaluated by calculating the capacity change rate? _{C C} expressed by? _{C C} = C ₂ / C ₀ × 100 (%). The higher the value of the capacity change rate? _{C C,} the better the high-temperature cycle characteristics.

A: 93% or more

B: 88% or more and less than 93%

C: 83% or more and less than 88%

D: Less than 83%

<Expansion Characteristics of Plate>

After the evaluation of the &quot; high temperature cycle characteristics &quot;, the cell of the lithium ion secondary battery was disassembled and the thickness d ₁ of the negative electrode plate was measured. (D ₁ - d ₀ ) / d ₀ of the negative electrode was calculated with the thickness of the negative electrode plate before making the cell of the lithium ion secondary battery as d ₀ , and evaluated by the following criteria. The lower this value is, the better the expansion property of the electrode plate is. In the case of using only graphite as the negative electrode active material (Example 12), evaluation was made based on the criteria in parentheses.

A: less than 30% (less than 20%)

B: 30% to less than 38% (20% to less than 29%)

C: 38% to less than 45% (29% to less than 36%)

D: 45% or more (36% or more)

<Low Temperature Output Characteristics>

The lithium ion secondary batteries of the laminate type cells prepared in the examples and the comparative examples were stopped for 24 hours under an environment of 25 캜 and then charged at a charging rate of 4.2 V and 1 C under an environment of 25 캜. Thereafter, the discharging operation was carried out at a discharge rate of 1 C under an environment of -10 캜, and a voltage V ₁₀ was measured 10 seconds after the start of discharge. The low temperature output characteristic was calculated by calculating the voltage change? V indicated by? V = 4.2 V - V ₁₀ , and evaluated by the following criteria. The smaller the value of the voltage change? V, the better the low temperature output characteristic.

A: Less than 1.1 V

B: 1.1 V or more and less than 1.3 V

C: 1.3 V or more and less than 1.6 V

D: 1.6 V or more

<Initial capacity>

A negative electrode was cut into a disk having a diameter of 15 mm and a separator made of a polypropylene-made porous film having a diameter of 18 mm and a thickness of 25 占 퐉, a metal lithium counter electrode and an extender metal were stacked in this order on the active material layer side of the negative electrode , Which was housed in a stainless steel coin-shaped outer container (diameter 20 mm, height 1.8 mm, stainless steel thickness 0.25 mm) equipped with a polypropylene packing.

A stainless steel cap having a thickness of 0.2 mm was fixed to the outer container through a polypropylene packing to fix the battery can, and the battery can was sealed to form a half-diameter portion having a diameter of 20 mm and a thickness of about 2 mm Cells were fabricated.

Further, LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at EC: EMC = 3: 7 (volume ratio at 20 캜) as the electrolytic solution at a concentration of 1 mol / Was used.

Using this coin-type battery, constant current-constant voltage charging was performed at 0.05 C, and the initial capacity was confirmed.

The case where the initial capacity was 420 mAh / g or more was evaluated as "good", and the case where the initial capacity was less than 420 mAh / g was evaluated as "poor".

(Example 1)

(1) Production of aromatic vinyl-conjugated diene copolymer (b1)

46 parts of 1,3-butadiene, 4 parts of itaconic acid, 50 parts of styrene, 0.3 part of t-dodecyl mercaptan (TDM), 4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of water, and 0.5 parts of potassium persulfate as a polymerization initiator were put in the flask and sufficiently stirred, followed by heating to 50 캜 to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (bl). The glass transition temperature of the aromatic vinyl-conjugated diene copolymer (bl) was -10 占 폚.

(2) Production of aromatic vinyl-conjugated diene copolymer (b2)

Similarly, 21 parts of 1,3-butadiene, 4 parts of itaconic acid, 75 parts of styrene, 0.25 part of t-dodecyl mercaptan (TDM), and 4 parts of sodium dodecylbenzenesulfonate as an emulsifier 150 parts of ion-exchanged water, and 0.5 parts of potassium persulfate as a polymerization initiator were put into the flask and sufficiently stirred, followed by heating to 50 DEG C to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (b2). The glass transition temperature of the aromatic vinyl-conjugated diene copolymer (b2) was 45 ° C.

(3) Production of particulate binder (B)

The aqueous dispersion containing the aqueous dispersion containing the aromatic vinyl-conjugated diene copolymer (b1) obtained in the step (1) and the aromatic vinyl-conjugated diene copolymer (b2) obtained in the step (2) (B1) of the vinyl-conjugated diene copolymer (b1) / the aromatic vinyl-conjugated diene copolymer (b2) = 50/50 to obtain an aqueous dispersion of the particulate binder (B).

(4) Preparation of water-soluble polymer (D)

30 parts of methacrylic acid (unsaturated carboxylic acid monomer), 0.8 parts of ethylene dimethacrylate (crosslinkable monomer), and 0.2 part of 2,2,2-trifluoroethyl methacrylate (fluorine (Meth) acrylic acid ester monomer), 60.5 parts of butyl acrylate ((meth) acrylic acid ester monomer), 30 parts of ammonium polyoxyalkylene alkyl ether sulfate (reactive surfactant monomer, Kao Co., ), 0.6 part of t-dodecylmercaptan, 150 parts of ion-exchanged water, and 0.5 part of potassium persulfate (polymerization initiator). After sufficiently stirring, the polymerization was started by heating at 60 占 폚. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the aqueous dispersion type polymer. 10% ammonia water was added to the mixture containing the aqueous dispersion type polymer to adjust the pH to 8 to obtain an aqueous solution containing the desired water-soluble polymer (D).

(5) Preparation of negative electrode slurry composition

Display buffer is equipped with a Plastic artificial graphite as a negative electrode active material (A) to the four planetary mixer (specific surface area: 4 ㎡ / g, volume-average particle diameter: 24.5 ㎛) 90 part, and SiO _x (x = 1.1, the volume average particle diameter: 10 mu m) and 1% aqueous solution of carboxymethylcellulose ("BSH-12" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as the hydroxyl group-containing water-soluble polymer (C) An aqueous solution containing the water-soluble polymer (D) synthesized in the above (4) was further added in an amount of 0.03 parts in terms of solid equivalent.

These mixtures were adjusted to a solid content concentration of 55% with ion-exchanged water and mixed at 25 DEG C for 60 minutes. Next, the solid content concentration was adjusted to 52% with ion-exchanged water and further mixed at 25 캜 for 15 minutes to obtain a mixed solution.

Subsequently, 1 part of the aqueous dispersion of the particulate binder (B) obtained in the above step (3) corresponding to the solid content and ion-exchanged water were added to the mixed solution, and the final solid content concentration was adjusted to 42%, followed by mixing for 10 minutes. This was degassed under reduced pressure to obtain a negative electrode slurry composition.

(6) Production of negative electrode

The negative electrode slurry composition obtained in the above step (5) was coated on a copper foil having a thickness of 20 mu m as a current collector with a comma coater so as to have a thickness of about 150 mu m after drying and dried. This drying was carried out by conveying the copper foil in an oven at 60 ° C for 2 minutes at a speed of 0.5 m / min. Thereafter, the substrate was subjected to heat treatment at 120 캜 for 2 minutes to obtain a negative electrode disc. This negative electrode disc was rolled by a roll press to obtain a negative electrode having a thickness of 80 m of the negative electrode active material layer.

(7) Preparation of positive electrode

A 40% aqueous dispersion of an acrylate polymer having a glass transition temperature Tg of -40 DEG C and a number average particle diameter of 0.20 mu m was prepared as a positive electrode binder. The acrylate polymer is a copolymer obtained by emulsion polymerization of a monomer mixture comprising 78% by mass of 2-ethylhexyl acrylate, 20% by mass of acrylonitrile, and 2% by mass of methacrylic acid.

As a positive electrode active material, 100 parts of LiFePO ₄ having a volume average particle diameter of 0.5 μm and an olivine crystal structure and 1% aqueous solution of carboxymethyl cellulose ("BSH-12" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) And 5 parts of a 40% aqueous dispersion of the acrylate polymer corresponding to the solid content as a binder were mixed and ion-exchanged water was added thereto so as to have a total solid content concentration of 40%. The mixture was mixed with a planetary mixer, A composition was prepared.

The positive electrode slurry composition was coated on aluminum having a thickness of 20 mu m as a current collector by a comma coater so as to have a thickness of about 200 mu m after drying and dried. This drying was carried out by conveying aluminum in an oven at 60 DEG C for 2 minutes at a rate of 0.5 m / min. Thereafter, it was heat-treated at 120 DEG C for 2 minutes to obtain a positive electrode.

(8) Preparation of separator

A single-layered polypropylene separator (width 65 mm, length 500 mm, thickness 25 占 퐉, manufactured by the dry method, porosity of 55%) was cut into a square of 5 cm 占 5 cm.

(9) Production of laminate cell of lithium ion secondary battery

An aluminum-coated sheath was prepared as an exterior of the battery. The positive electrode obtained in the above step (7) was cut into a square of 4 cm x 4 cm, and the surface of the current collector side was arranged so as to be in contact with the aluminum-covered sheath. The separator prepared in the above step (8) was disposed on the surface of the positive electrode active material layer of the positive electrode. Further, the negative electrode obtained in the above step (6) was cut into a square of 4.2 cm x 4.2 cm on the separator, and the surface of the negative electrode active material layer side was arranged facing the separator. Further, in order to seal the openings of the aluminum foil, a lithium ion secondary battery was prepared by subjecting the aluminum jacket to heat sealing at 150 ° C. As the electrolytic solution, LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at EC: EMC = 3: 7 (volume ratio at 20 캜) at a concentration of 1 mol / Solution.

Each of the obtained laminate type lithium ion secondary batteries was evaluated except for the initial capacity check. The results are shown in Table 1.

(10) Coin cell manufacturing of lithium ion secondary battery

The negative electrode obtained in the above step (6) is cut into a disk having a diameter of 16 mm and used as a positive electrode. The same separator as used in the above step (8) was cut into a circular disk having a diameter of 18 mm and a thickness of 25 탆, a metal lithium used as a negative electrode, and an extruded metal were laminated in this order on a positive electrode. (20 mm in diameter, 1.8 mm in height, and 0.25 mm in thickness of stainless steel) made of stainless steel. A stainless steel cap having a thickness of 0.2 mm was covered with a cap made of polypropylene through a packing made of polypropylene, and the battery can was sealed to form a lithium ion battery having a diameter of 20 mm and a thickness of about 2 mm A coin cell (half cell) was fabricated. Further, LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at EC: EMC = 3: 7 (volume ratio at 20 캜) as the electrolyte solution at a concentration of 1 mol / Was used.

The obtained coin-type lithium ion secondary battery was subjected to initial capacity confirmation. The results are shown in Table 1.

(Example 2)

Except that the following aromatic vinyl-conjugated diene copolymer (b1) and aromatic vinyl-conjugated diene copolymer (b2) were used in place of the aromatic vinyl-conjugated diene copolymer (b1). The evaluation results are shown in Table 1.

Preparation of aromatic vinyl-conjugated diene copolymer (b1)

To a pressure vessel of 5 MPa equipped with a stirrer, 47.5 parts of 1,3-butadiene, 0.3 parts of itaconic acid, 52.2 parts of styrene, 0.3 part of t-dodecyl mercaptan (TDM), 4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of water, and 0.5 parts of potassium persulfate as a polymerization initiator were put in the flask and sufficiently stirred, followed by heating to 50 캜 to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (bl). The glass transition temperature of the aromatic vinyl-conjugated diene copolymer (bl) was -10 占 폚.

Production of aromatic vinyl-conjugated diene copolymer (b2)

22.5 parts of 1,3-butadiene, 0.3 parts of itaconic acid, 77.2 parts of styrene, 0.25 parts of t-dodecyl mercaptan (TDM), 4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of water, and 0.5 parts of potassium persulfate as a polymerization initiator were put in the flask and sufficiently stirred, followed by heating to 50 캜 to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (b2). The glass transition temperature of the aromatic vinyl-conjugated diene copolymer (b2) was 45 ° C.

(Example 3)

Except that the following aromatic vinyl-conjugated diene copolymer (b1) and aromatic vinyl-conjugated diene copolymer (b2) were used in place of the aromatic vinyl-conjugated diene copolymer (b1). The evaluation results are shown in Table 1.

Preparation of aromatic vinyl-conjugated diene copolymer (b1)

44.5 parts of 1,3-butadiene, 5.5 parts of itaconic acid, 50 parts of styrene, 0.3 part of t-dodecyl mercaptan (TDM), 4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of water, and 0.5 parts of potassium persulfate as a polymerization initiator were put in the flask and sufficiently stirred, followed by heating to 50 캜 to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (bl). The glass transition temperature of the aromatic vinyl-conjugated diene copolymer (bl) was -10 占 폚.

Production of aromatic vinyl-conjugated diene copolymer (b2)

To a pressure vessel of 5 MPa equipped with a stirrer, 21.5 parts of 1,3-butadiene, 5.5 parts of itaconic acid, 73 parts of styrene, 0.25 part of t-dodecyl mercaptan (TDM), 4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of water, and 0.5 parts of potassium persulfate as a polymerization initiator were put in the flask and sufficiently stirred, followed by heating to 50 캜 to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (b2). The glass transition temperature of the aromatic vinyl-conjugated diene copolymer (b2) was 45 ° C.

(Example 4)

Except that the following aromatic vinyl-conjugated diene copolymer (b1) and aromatic vinyl-conjugated diene copolymer (b2) were used in place of the aromatic vinyl-conjugated diene copolymer (b1). The evaluation results are shown in Table 1.

Preparation of aromatic vinyl-conjugated diene copolymer (b1)

50 parts of 1,3-butadiene, 4 parts of itaconic acid, 46 parts of styrene, 0.3 part of t-dodecyl mercaptan (TDM), 4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of water, and 0.5 parts of potassium persulfate as a polymerization initiator were put in the flask and sufficiently stirred, followed by heating to 50 캜 to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (bl). The glass transition temperature of the aromatic vinyl-conjugated diene copolymer (bl) was -18 占 폚.

Production of aromatic vinyl-conjugated diene copolymer (b2)

17 parts of butanediol, 4 parts of itaconic acid, 79 parts of styrene, 0.25 part of t-dodecyl mercaptan (TDM), 4 parts of sodium dodecylbenzenesulfonate as an emulsifier, and 10 parts of ion exchanged 150 parts of water, and 0.5 parts of potassium persulfate as a polymerization initiator were put in the flask and sufficiently stirred, followed by heating to 50 캜 to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (b2). The aromatic vinyl-conjugated diene copolymer (b2) had a glass transition temperature of 55 占 폚.

(Example 5)

Except that the following aromatic vinyl-conjugated diene copolymer (b1) and aromatic vinyl-conjugated diene copolymer (b2) were used in place of the aromatic vinyl-conjugated diene copolymer (b1). The evaluation results are shown in Table 1.

Preparation of aromatic vinyl-conjugated diene copolymer (b1)

32 parts of 1,3-butadiene, 4 parts of itaconic acid, 64 parts of styrene, 0.3 part of t-dodecyl mercaptan (TDM), 4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of water, and 0.5 parts of potassium persulfate as a polymerization initiator were put in the flask and sufficiently stirred, followed by heating to 50 캜 to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (bl). The glass transition temperature of the aromatic vinyl-conjugated diene copolymer (bl) was 18 占 폚.

Production of aromatic vinyl-conjugated diene copolymer (b2)

26 parts of 1,3-butadiene, 4 parts of itaconic acid, 70 parts of styrene, 0.25 part of t-dodecyl mercaptan (TDM), 4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of water, and 0.5 parts of potassium persulfate as a polymerization initiator were put in the flask and sufficiently stirred, followed by heating to 50 캜 to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (b2). The glass transition temperature of the aromatic vinyl-conjugated diene copolymer (b2) was 33 ° C.

(Example 6)

Except that the following aromatic vinyl-conjugated diene copolymer (b1) was used in place of the aromatic vinyl-conjugated diene copolymer (b1). The evaluation results are shown in Table 1.

Preparation of aromatic vinyl-conjugated diene copolymer (b1)

46 parts of 1,3-butadiene, 4 parts of itaconic acid, 50 parts of styrene, 0.48 parts of t-dodecyl mercaptan (TDM), 4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of water, and 0.5 parts of potassium persulfate as a polymerization initiator were put in the flask and sufficiently stirred, followed by heating to 50 캜 to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (bl). The glass transition temperature of the aromatic vinyl-conjugated diene copolymer (bl) was -10 占 폚.

(Example 7)

In the production of the particulate binder (B) in the step (3), an aqueous dispersion containing an aqueous dispersion containing an aromatic vinyl-conjugated diene copolymer (b1) and an aromatic vinyl-conjugated diene copolymer (b2) (B2) = 80/20 to obtain an aqueous dispersion of the particulate binder (B) was obtained in the same manner as in Example 1, except that an aqueous dispersion of the particulate binder (B) was obtained in an amount equivalent to that of the aromatic vinyl-conjugated diene copolymer To prepare a lithium ion secondary battery. The evaluation results are shown in Table 1.

(Example 8)

In the production of the particulate binder (B) in the step (3), an aqueous dispersion containing an aqueous dispersion containing an aromatic vinyl-conjugated diene copolymer (b1) and an aromatic vinyl-conjugated diene copolymer (b2) Except that the aqueous dispersion of the particulate binder (B) was obtained by mixing the aromatic vinyl-conjugated diene copolymer (b1) / aromatic vinyl-conjugated diene copolymer (b2) To prepare a lithium ion secondary battery. The evaluation results are shown in Table 1.

(Example 9)

A lithium ion secondary cell was produced in the same manner as in Example 1 except that the amount of the aqueous dispersion of the particulate binder (B) was 2 parts in terms of solid content in the production of the negative electrode slurry composition of the step (5). The evaluation results are shown in Table 1.

(Example 10)

The same operations as in Example 1 were carried out except that the aqueous solution containing the water-soluble polymer (D) was added in an amount such that the amount of the aqueous solution containing the water-soluble polymer (D) A battery was prepared. The evaluation results are shown in Table 1.

(Example 11)

Except that 90 parts of artificial graphite (specific surface area: 4 m 2 / g, volume average particle diameter: 24.5 μm) and 10 parts of SiOC (volume average particle diameter: 10 μm) were used as the negative electrode active material (A) The lithium ion secondary battery was manufactured. The evaluation results are shown in Table 1.

(Example 12)

A lithium ion secondary cell was produced in the same manner as in Example 1 except that 100 parts of artificial graphite (specific surface area: 4 m &lt; 2 &gt; / g, volume average particle diameter: 24.5 mu m) was used as the negative electrode active material (A) The evaluation results are shown in Table 1.

(Example 13)

In the preparation of the water-soluble polymer (D) of the step (4), the same procedure as in Example 1 was carried out except that 7.5 parts of 2,2,2-trifluoroethyl methacrylate was changed to 1.0 part and 60.5 parts of butyl acrylate was changed to 67.0 parts The lithium ion secondary battery was manufactured. The evaluation results are shown in Table 1.

(Example 14)

In the preparation of the water-soluble polymer (D) of the step (4), the same procedure as in Example 1 was carried out except that 15.0 parts of 2,2,2-trifluoroethyl methacrylate was changed to 15.0 parts and 60.5 parts of butyl acrylate was changed to 53.0 parts The lithium ion secondary battery was manufactured. The evaluation results are shown in Table 1.

(Example 15)

The same operation as in Example 1 was carried out except that 0.25 part of t-dodecyl mercaptan (TDM) was used in the production of the aromatic vinyl-conjugated diene copolymer (b2) of the step (2) . The evaluation results are shown in Table 1.

(Example 16)

The same operation as in Example 1 was carried out except that 0.25 part of t-dodecyl mercaptan (TDM) was used in the production of the aromatic vinyl-conjugated diene copolymer (b2) of the step (2) . The evaluation results are shown in Table 1.

(Comparative Example 1)

Except that the following aromatic vinyl-conjugated diene copolymer (b1) and aromatic vinyl-conjugated diene copolymer (b2) were used in place of the aromatic vinyl-conjugated diene copolymer (b1). The evaluation results are shown in Table 1.

Preparation of aromatic vinyl-conjugated diene copolymer (b1)

48 parts of 1,3-butadiene, 52 parts of styrene, 0.3 parts of t-dodecyl mercaptan (TDM), 4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion exchanged water, 0.5 part of potassium persulfate was added as a polymerization initiator, and the mixture was sufficiently stirred and then heated to 50 캜 to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (bl). The glass transition temperature of the aromatic vinyl-conjugated diene copolymer (bl) was -10 占 폚.

Production of aromatic vinyl-conjugated diene copolymer (b2)

23 parts of 1,3-butadiene, 77 parts of styrene, 0.25 parts of t-dodecyl mercaptan (TDM), 4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion exchanged water, 0.5 part of potassium persulfate was added as a polymerization initiator, and the mixture was sufficiently stirred and then heated to 50 캜 to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (b2). The glass transition temperature of the aromatic vinyl-conjugated diene copolymer (b2) was 45 ° C.

(Comparative Example 2)

Except that the particulate binder (B) was produced only from the aromatic vinyl-conjugated diene copolymer (b1) without using the aromatic vinyl-conjugated diene copolymer (b2) . The evaluation results are shown in Table 1.

(Comparative Example 3)

The procedure of Example 1 was repeated except that the particulate binder (B) was produced only from the aromatic vinyl-conjugated diene copolymer (b2) without using the aromatic vinyl-conjugated diene copolymer (b1) . The evaluation results are shown in Table 1.

(Comparative Example 4)

Except that the following aromatic vinyl-conjugated diene copolymer (b1) was used in place of the aromatic vinyl-conjugated diene copolymer (b1). The evaluation results are shown in Table 1.

Preparation of aromatic vinyl-conjugated diene copolymer (b1)

29 parts of butanediol, 4 parts of itaconic acid, 67 parts of styrene, 0.3 part of t-dodecyl mercaptan (TDM), 4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of water, and 0.5 parts of potassium persulfate as a polymerization initiator were put in the flask and sufficiently stirred, followed by heating to 50 캜 to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (bl). The glass transition temperature of the aromatic vinyl-conjugated diene copolymer (bl) was 23 占 폚.

(Comparative Example 5)

Except that the following aromatic vinyl-conjugated diene copolymer (b2) was used in place of the aromatic vinyl-conjugated diene copolymer (b2). The evaluation results are shown in Table 1.

Production of aromatic vinyl-conjugated diene copolymer (b2)

27 parts of 1,3-butadiene, 4 parts of itaconic acid, 69 parts of styrene, 0.3 part of t-dodecyl mercaptan (TDM), 4 parts of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of water, and 0.5 parts of potassium persulfate as a polymerization initiator were put in the flask and sufficiently stirred, followed by heating to 50 캜 to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the polymer. A 5% aqueous solution of sodium hydroxide was added to the mixture to adjust the pH to 8, and the unreacted monomers were removed by distillation under reduced pressure. Thereafter, the mixture was cooled to 30 DEG C or lower to obtain an aqueous dispersion containing the desired aromatic vinyl-conjugated diene copolymer (b2). The glass transition temperature of the aromatic vinyl-conjugated diene copolymer (b2) was 27 ° C.

(Comparative Example 6)

A lithium ion secondary battery was produced in the same manner as in Example 1 except that the water-soluble polymer (D) was not used. The evaluation results are shown in Table 1.

As shown in the results of Table 1, the lithium ion secondary batteries using the secondary battery electrodes of Examples 1 to 16 are superior in balance of evaluation as compared with Comparative Examples 1 to 6. [

Claims (7)

And a negative electrode active material layer laminated on the current collector,
(D) containing 0.5 to 20% by mass of the negative electrode active material (A), the particulate binder (B), the hydroxyl group-containing water-soluble polymer (C) and the fluorine-containing (meth) &Lt; / RTI &gt;
The particulate binder (B)
An aromatic vinyl-conjugated diene copolymer (b1) having a glass transition temperature of -30 to 20 DEG C and containing an unsaturated carboxylic acid monomer unit,
And an aromatic vinyl-conjugated diene copolymer (b2) having a glass transition temperature of 30 to 80 DEG C and containing an unsaturated carboxylic acid monomer unit. The method according to claim 1,
Wherein the negative electrode active material (A) contains the carbon-based active material (a1) and the alloy-based active material (a2). 3. The method of claim 2,
Wherein the alloy-based active material (a2) is contained in an amount of 1 to 50 parts by mass based on 100 parts by mass of the carbon-based active material (a1). The method according to claim 2 or 3,
Wherein the alloy-based active material (a2) is Si, SiO _x (x = 0.01 or more and less than 2), or SiOC. 5. The method according to any one of claims 1 to 4,
Wherein the content ratio of the aromatic vinyl-conjugated diene copolymer (b1) to the aromatic vinyl-conjugated diene copolymer (b2) = 80/20 to 30/70 for secondary batteries. 6. The method according to any one of claims 1 to 5,
Wherein the tetrahydrofuran-insoluble content of each of the aromatic vinyl-conjugated diene copolymer (b1) and the aromatic vinyl-conjugated diene copolymer (b2) is 70 to 98%. A secondary battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator,
The secondary battery according to any one of claims 1 to 6, wherein the negative electrode is a negative electrode for a secondary battery.