JP2003100298A - Secondary battery and binder composition for electrode thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a binder composition with which an electrode of large bondability between a current collector and an active material is obtained, and a secondary battery having a large battery capacity and a superior charging/discharging rate characteristics is obtained using the electrode. SOLUTION: A liquid medium dispersed solution (1) contains a polymer in which the size of the most frequent particles in primary particles is more than 0.01 μm and less than 0.25 μm. A liquid medium dispersed solution (2) contains a polymer in which the size of the most frequent particles in primary particles is more than 0.25 μm and less than 3 μm. The dispersed solutions (1) and (2) are mixed in the ratio of 70 to 99% and 1 to 30% in terms of respective polymer weights to form the binder composition for the electrode of the secondary battery (Mixing both dispersed solutions (1), (2) results in a dispersed solution with a polymer weight ratio of 100%.).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a binder composition used for a secondary battery electrode, a slurry for electrodes, a secondary battery electrode and a secondary battery.

[0002]

2. Description of the Related Art In recent years, notebook computers, mobile phones, P
DA (Personal Digital Assist)
The popularity of mobile terminals such as tan t) is remarkable. As a secondary battery used as a power source for these portable terminals, a nickel hydrogen secondary battery, a lithium ion secondary battery, and the like are frequently used. As portable terminals are required to be more comfortable to carry, they are rapidly becoming smaller, thinner, lighter and more sophisticated, and as a result, portable terminals are used in various places. Further, with respect to the battery, similarly to the mobile terminal, there is a demand for downsizing, thinning, weight reduction, and high performance.

To improve the performance of batteries, electrodes, electrolytes,
Improvements in other battery members are being studied. For electrodes, in addition to studying the electrode active material (hereinafter sometimes simply referred to as "active material") and the current collector itself, the active material is used as the current collector. A polymer that serves as a binder for binding to is also studied. The electrode is usually a slurry obtained by mixing a binder composition in which a polymer serving as a binder is dispersed or dissolved in a liquid medium such as water or an organic liquid with an active material and optionally a conductivity-imparting agent such as conductive carbon to form a slurry. Then, the slurry is applied to a current collector and dried to produce the product.

With respect to high performance of batteries, demands for extension of operating time of mobile terminals and reduction of charging time have recently been increasing, and it is an urgent task to increase the capacity of batteries and improve charging speed (rate characteristics). There is. Battery capacity is governed by the amount of active material, and rate characteristics are affected by the ease of electron transfer. In order to increase the active material in the limited space of the battery, it is effective to suppress the amount of binder (polymer) that tends to hinder the movement of electrons due to its non-conductivity. If the amount is reduced, the binding of the active material is impaired, so the amount of the binder is limited. Further, if a large amount of a conductivity-imparting agent is added in order to improve electron mobility, the amount of active material used is relatively suppressed due to the restriction of battery volume, so it is difficult to expect improvement in battery capacity. in this way,
Up to now, it has been difficult to achieve both high capacity and improved rate characteristics of the battery.

[0005]

Under the above circumstances, the object of the present invention is to provide a small amount of binder,
A binder composition for a secondary battery electrode, a slurry for a secondary battery electrode, and a secondary battery electrode that realize a secondary battery having a high battery capacity and excellent rate characteristics.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that, as a binder of an electrode active material, a heavy-weight compound having a small particle size having a most frequent particle size in a specific particle size range. It was found that the above object can be achieved by using a binder composition in which coalesced particles and large-sized polymer particles are mixed in a specific ratio, and the present invention has been completed based on this finding. Thus, according to the invention,
(1) The most frequent particle size of the primary particles is 0.01 μm or more, 0.2
70 to 99 parts by weight of the polymer liquid medium dispersion liquid (I) having a particle size of less than 5 μm in terms of polymer, and the polymer liquid dispersion liquid having a mode of primary particles having a mode particle size of 0.25 μm or more and less than 3 μm ( II) 1 to 30 parts by weight in terms of polymer is mixed with the binder composition for a secondary battery electrode (however, the polymer after mixing the dispersion liquid (I) and the dispersion liquid (II) is Is 100 parts by weight.),

(2) A binder composition for a secondary battery electrode, comprising a polymer dispersed in a liquid medium in the form of particles, wherein the polymer primary particles have a particle size of 0.01 μm or more and a particle size of 0.
70-99% by volume in the particle size range of less than 25 μm, and
A binder composition for a secondary battery electrode, which is present in an amount of 0.25 μm or more and less than 3 μm in an amount of 1 to 30% by volume, (3)
The binder composition for a secondary battery electrode according to (1) or (2), wherein the liquid medium has a standard boiling point of 80 to 350 ° C., and (4) (1) to (3). Secondary battery electrode binder composition, and a secondary battery electrode slurry containing an electrode active material,

(5) The adsorption amount of the polymer on the electrode active material is
1 to 50 mg per 1 g of the electrode active material, the slurry for a secondary battery electrode according to (4), (6) a current collector and a mixed layer containing a polymer and an electrode active material bound together. A secondary battery electrode, wherein the polymer primary particles are 0.01 μm or more,
70 to 99% by volume in the particle size section of less than 0.25 μm, and 1 to 3 in the particle size section of 0.25 μm or more and less than 3 μm.
Secondary battery electrode, characterized in that 0% by volume is present,
(7) A secondary battery having the secondary battery electrode according to (6) is provided.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The binder composition for a secondary battery electrode of the present invention (hereinafter sometimes simply referred to as "binder composition") is for binding an electrode active material or the like to a current collector. The polymer serving as a binder is dispersed in the liquid medium in the form of particles.

The polymer which can be used in the binder composition is not particularly limited, and examples thereof include (meth) acrylic acid ester (co) polymers, styrene- (meth) acrylic acid ester copolymers and styrene-butadiene copolymers. , Acrylonitrile-butadiene copolymer, polybutadiene and the like.

The glass transition temperature (hereinafter sometimes referred to as "Tg") of the polymer used in the binder composition of the present invention is usually -80 to + 50 ° C, preferably -75.
It is desirable that it is a rubbery polymer having a temperature of ˜ + 30 ° C., more preferably −70 to + 10 ° C. If a polymer having a too low Tg is used, the battery capacity may be lowered, and if a polymer having a too high Tg is used, the binding force may be decreased, or the change in battery characteristics with temperature may be large. is there.

The amount of the polymer used as the binder of the present invention is usually 1 to 50 per 1 g of the electrode active material.
mg, preferably 2-45 mg. When the amount of the binder adsorbed on the active material is less than 1 mg, a free polymer may be generated to suppress the amount of the active material used even if the binder required for binding the active material is used. On the contrary, if the amount of the binder adsorbed to the active material is larger than 50 mg, a large amount of the binder is required, and the amount of the active material may be limited by the battery volume, which may reduce the battery capacity.

The amount of the binder polymer adsorbed on the electrode active material can be determined by the following method. About 1
0 g of the electrode active material and about 2 g of the binder composition in terms of solid content were weighed and charged into a beaker, and the liquid medium used in the binder composition (hereinafter sometimes referred to as “dispersion medium”) was used. Add so that the total is about 100 g. At this time, the concentration C ₀ of the polymer with respect to the total weight of the polymer and the dispersion medium (initial concentration, the unit is mg / g) and the concentration m of the active material with respect to the total weight of the polymer and the dispersion medium.
(Unit is g / g) is calculated. Shake with a shaker to sufficiently adsorb the polymer on the electrode active material, then centrifuge to separate the solid content (active material with adsorbed polymer) and the separation liquid (free polymer particles dispersed in the dispersion medium). Dispersion). Then, the weight of the free polymer in the separated liquid is measured, and this is divided by the total weight of the initial polymer and the dispersion medium to obtain the free binder concentration C _e (equilibrium concentration, unit: mg / g). The amount W of polymer adsorbed on the electrode active material (unit: mg / g) is calculated by the following formula. W = (C ₀ -C _e ) / m The binder used in the present invention has a high packing density when adsorbed on the surface of the active material by mixing the above-mentioned polymer dispersion liquid, and is effective even when used in a small amount. Since the surface of the substance is covered with the binder, it is strongly bound to the current collector. The glass transition temperature of the polymer in the dispersion liquid can be determined by measuring the glass transition temperature with a differential scanning calorimeter using a cast film obtained by coating the dispersion liquid and drying it.

The liquid medium (dispersion medium) that can be used in the binder composition of the present invention is preferably water or a non-aqueous medium having a boiling point of 80 to 350 ° C. at atmospheric pressure.
Examples of such a non-aqueous medium include amides such as N-methylpyrrolidone, dimethylformamide and dimethylacetamide; hydrocarbons such as toluene, xylene, n-dodecane and tetralin; 2-ethyl-1-hexanol, 1 -Alcohols such as nonanol and lauryl alcohol; ketones such as methyl ethyl ketone, cyclohexanone, phorone, acetophenone and isophorone; esters such as benzyl acetate, isopentyl butyrate, methyl lactate, ethyl lactate and butyl lactate; o-toluidine, m-toluidine , Amines such as p-toluidine;
Examples thereof include amides such as N, N-dimethylacetamide and dimethylformamide; lactones such as γ-butyrolactone and δ-butyrolactone; sulfoxides and sulfones such as dimethyl sulfoxide and sulfolane. Of these, water and N-methylpyrrolidone are preferable.

In the binder composition of the present invention, the liquid medium dispersion liquid (I) of a polymer having a primary particle mode particle size of 0.01 μm or more and less than 0.25 μm is 70 to 9 in terms of polymer.
9 parts by weight and the mode particle size of primary particles is 0.25 μm or more, 3
A binder composition for a secondary battery electrode, which is obtained by mixing 1 to 30 parts by weight of a polymer liquid medium dispersion liquid (II) having a particle size of less than μm in terms of polymer (provided that the dispersion liquid (I) and the dispersion liquid ( I
The total amount of the polymer after mixing with I) is 100 parts by weight. ).

The most frequent particle size of the primary particles is 0.01 μm or more,
Liquid medium dispersion liquid (I) of polymer having a size of less than 0.25 μm
Is less than 70 parts by weight (the same as the amount of the polymer dispersion in which the mode particle diameter of primary particles is 0.25 μm or more and less than 3 μm is more than 30 parts by weight based on the polymer).
If so, the binding force may be reduced and the rate characteristics may be deteriorated. On the other hand, if the binding force is increased, a large amount of binder may be required and a high battery capacity may not be obtained.

The primary particles of the polymer preferably satisfy the following requirements [1] and [2]. [1] Primary particles of the polymer are usually present in an amount of from 70 to 99% by volume, preferably from 75 to 97% by volume, more preferably from 80 to 97% by volume in a particle size section of 0.01 μm or more and less than 0.25 μm. . [2] The primary particles of the polymer are contained in a particle size range of 0.25 μm or more and less than 3 μm, usually 1 to 30% by volume, preferably 3 to
25% by volume, more preferably 3-20% by volume.

If the abundance ratio of the primary particles of the polymer in the above requirement [1] is too small, the binding force becomes small,
There is a possibility that the rate characteristic may be deteriorated. On the contrary, if it is excessively large, a large amount of binder may be required and a high battery capacity may not be obtained. If the abundance ratio of the polymer primary particles in the above requirement [2] is too small, the battery capacity may decrease, and conversely, if it is too large, the binding force may decrease.

The method of measuring the most frequent particle size and the particle size distribution of the polymer particles is not particularly limited, and examples thereof include a Coulter counter, a Microtrac, and a transmission electron microscope.

The method for producing the binder polymer is as follows:
It is not particularly limited, and examples thereof include emulsion polymerization, seed emulsion polymerization, suspension polymerization, seed suspension polymerization, and solution precipitation polymerization. A dissolution / dispersion method in which the polymer is dissolved or swollen in a solvent, the mixture is stirred and mixed in a medium incompatible with the solvent, and then the solvent is removed is also possible. Further, the polymer particles obtained by these may be subjected to physical modification such as chemical modification or electron beam irradiation.

The binder composition satisfying the above requirements [1] and [2] is obtained by separately obtaining a small particle size polymer particle component and a large particle size polymer particle component by the above-mentioned polymerization method, and preparing them. Although it may be obtained in two steps by mixing, it can also be obtained in one step by newly adding a dispersion stabilizer to the polymerization system during the reaction such as emulsion polymerization and suspension polymerization among the above-mentioned polymerization methods. .

The polymerizable unsaturated monomer for obtaining the polymer that is the binder is not particularly limited as long as it is a monomer that can give polymer particles satisfying the above particle size distribution requirements. . Examples of such monomers include ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, ethoxyethyl acrylate, methyl methacrylate, 2-ethylhexyl methacrylate, n-decyl methacrylate. , 2-hydroxyethyl methacrylate, isoamyl crotonic acid, n-hexyl crotonic acid, dimethylaminoethyl methacrylate, monomethyl maleate and other ethylenically unsaturated carboxylic acid esters; 1,3-butadiene, 1,3-
Pentadiene, 2,3-pentadiene, isoprene,
1,3-hexadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-
Conjugated diene compounds such as heptadiene; ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride; styrene, α-methylstyrene, 2,4-dimethylstyrene,
Aromatic vinyl compounds such as ethylstyrene and vinylnaphthalene; cyano group-containing vinyl compounds such as acrylonitrile and methacrylonitrile; vinyl ester compounds such as vinyl acetate and vinyl propionate; ethyl vinyl ether,
Examples thereof include vinyl ether compounds such as cetyl vinyl ether and hydroxybutyl vinyl ether. These may be used alone or in combination of two or more.

In order to impart a cross-linking structure to a polymer serving as a binder by polymerizing the above-mentioned monomer as a main component and adding a small amount of the cross-linking monomer thereto, the polymer may be a dispersion medium or a dispersion medium. It is preferable because it becomes difficult to dissolve in the electrolytic solution. Examples of such crosslinkable monomers include divinyl compounds such as divinylbenzene; polyfunctional dimethacrylates such as diethylene glycol dimethacrylate and ethylene glycol dimethacrylate; polyfunctional trimethacrylates such as trimethylolpropane trimethacrylate; Examples thereof include polyfunctional diacrylic acid esters such as polyethylene glycol diacrylate and 1,3-butylene glycol diacrylate; and polyfunctional triacrylic acid esters such as trimethylolpropane triacrylate. The crosslinkable monomer is usually used in a proportion of 0.1 to 20% by weight, preferably 0.5 to 15% by weight, based on the whole polymerizable monomer.

Further, an aqueous dispersion of the polymer obtained by the above-mentioned emulsion polymerization or suspension polymerization contains ammonia,
The pH can be adjusted by adding an aqueous solution of an alkali metal (lithium, sodium, potassium, rubidium, cesium, etc.) hydroxide, an inorganic ammonium compound (ammonium chloride, etc.), an organic amine compound (ethanolamine, diethylamine, etc.). Above all, using ammonia or alkali metal hydroxide, pH 5 to 13,
It is preferable to adjust the amount to be in the range of 6 to 12 because the binding property between the current collector and the active material is improved.

The method for preparing the binder composition of the present invention is not particularly limited. An aqueous dispersion of a polymer obtained by emulsion polymerization or the like can be used as it is as a binder composition, but the composition is obtained by substituting the non-aqueous liquid medium with water as a dispersion medium and dispersing the polymer in the non-aqueous liquid medium. It can also be a thing. When the polymer as a binder is powder particles, the powder may be dispersed in a dispersion medium to prepare the binder composition of the present invention. When the dispersion medium is replaced, the non-aqueous liquid medium is added to the aqueous dispersion, and then the water in the dispersion medium is removed by distillation, ultrafiltration or the like. When used as a dispersion medium after removing the residual water until the residual water content is 5% by weight or less, preferably 0.5% by weight or less, excellent initial battery capacity can be obtained. The concentration of all polymer components in the binder composition, that is, the solid content concentration is usually 0.5 to 80% by weight, preferably 1 to 70% by weight, and more preferably 1 to 60% by weight.

A thickener may be added to the binder composition of the present invention in order to improve coatability. Examples of the thickener include celluloses such as carboxymethyl cellulose, methyl cellulose and hydroxypropyl cellulose, and ammonium salts or alkali metal salts thereof; polycarboxylic acids such as poly (meth) acrylic acid and modified poly (meth) acrylic acid. , And alkali metal salts thereof; polyvinyl alcohol-based (co) polymers such as polyvinyl alcohol, modified polyvinyl alcohol, ethylene-vinyl alcohol copolymer; and unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid and fumaric acid. And a water-soluble polymer such as a saponified product of a vinyl ester copolymer.

Particularly preferable examples are alkali metal salts of carboxymethyl cellulose and alkali metal salts of poly (meth) acrylic acid. When the binder composition of the present invention contains a thickener, the proportion of the thickener used is usually 5 to 95 relative to the total polymer weight (total solid content weight).
%, Preferably 10 to 80% by weight, more preferably 20 to 75% by weight.

The secondary battery electrode slurry of the present invention (hereinafter, referred to as
Sometimes referred to simply as "slurry". ) Is obtained by mixing and dispersing an electrode active material and, if necessary, an additive such as a conductivity-imparting agent in the binder composition of the present invention described above, and is applied to a current collector to form a secondary battery electrode. It is for manufacturing.

The electrode active material varies depending on the type of secondary battery. In the case of a lithium-ion secondary battery, both the negative electrode active material and the positive electrode active material can be used as long as they are used in the production of ordinary lithium-ion secondary battery electrodes. That is, as the negative electrode active material, amorphous carbon, graphite, natural graphite, mesocarbon microbeads (MCMB), carbonaceous material such as pitch-based carbon fiber, conductive polymer such as polyacene, A _X B _Y
O _Z (where A is an alkali metal or a transition metal, B is at least one selected from transition metals such as cobalt, nickel, aluminum, tin and manganese, O is an oxygen atom, and X, Y and Z are each 1 10>X>
0.05, 4.00>Y> 0.85, 5.00>Z>
It is a number in the range of 1.5. Examples thereof include complex metal oxides represented by) and other metal oxides.

As the positive electrode active material of the lithium ion secondary battery, TiS ₂ , TiS ₃ , amorphous MoS ₃ and C are used.
u ₂ V ₂ O _3, amorphous _{V 2 O-P 2 O 5} ,
Transition metal oxides such as MoO ₂ , V ₂ O ₅ , and V ₆ O ₁₃ , LiCoO ₂ , LiNiO ₂ , and LiMn.
Examples thereof include lithium-containing composite metal oxides such as O ₂ and LiMn ₂ O ₄ . In addition, polyacetylene,
It is also possible to use an organic compound such as a conductive polymer such as poly-p-phenylene.

In the case of a nickel-hydrogen secondary battery, the active material is
Any of those used in ordinary nickel-hydrogen secondary batteries can be used, and as the negative electrode active material,
A hydrogen storage alloy can be used. Further, as the positive electrode active material, nickel oxyhydroxide, nickel hydroxide or the like can be used.

The amount of the polymer used as the binder in the present invention is usually 0.2 to 2 parts by weight, preferably 0.5 to 1.2 parts by weight, for the positive electrode, per 100 parts by weight of the active material. In the negative electrode, it is generally 0.3 to 3 parts by weight, preferably 0.5 to 1.8 parts by weight. Since the predetermined binding force can be obtained even when the amount of the binder used in the present invention is about half to 1/10 of the conventional binder, the secondary battery using the secondary battery electrode of the present invention has a high capacity. The charging speed is obtained.

Carbon, such as graphite and activated carbon, is used in the lithium ion secondary battery as the conductivity-imparting agent that is optionally added to the secondary battery electrode slurry of the present invention. Examples of the nickel-hydrogen secondary battery include cobalt oxide for the positive electrode, nickel powder, cobalt oxide, titanium oxide, and carbon for the negative electrode. In both of the above batteries, examples of carbon include acetylene black, furnace black, graphite, carbon fiber, and fullerenes. Of these, acetylene black and furnace black are preferable. The conductivity-imparting agent is usually used in an amount of 1 to 20 parts by weight, preferably 2 to 10 parts by weight, per 100 parts by weight of the active material.

For mixing and stirring for preparing the slurry, it is necessary to select a mixer that does not leave an aggregate of the electrode active material in the slurry and a necessary and sufficient dispersion condition. Although the degree of dispersion can be measured by a particle gauge, it should be mixed and dispersed so that aggregates at least larger than 100 μm are eliminated. As a mixer, a ball mill,
A sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, a Hobart mixer and the like are exemplified.

The secondary battery electrode of the present invention is obtained by applying the secondary battery electrode slurry of the present invention to a current collector such as a metal foil,
By drying, a binder and an active material are further bound to a mixed layer containing a thickener, a conductivity-imparting agent, and the like, which are added if necessary. The secondary battery electrode of the present invention can be used as either a positive electrode or a negative electrode as shown below. The current collector is not particularly limited as long as it is made of a conductive material. The lithium-ion secondary battery is made of a metal such as iron, copper, aluminum, nickel, and stainless. However, when aluminum is used for the positive electrode and copper is used for the negative electrode, the effect of the binder composition of the present invention is most effective. It often appears. Examples of the nickel-hydrogen secondary battery include punching metal, expanded metal, wire mesh, foam metal, reticulated metal fiber sintered body, and metal-plated resin plate. The shape of the current collector is not particularly limited, but is usually a sheet having a thickness of about 0.001 to 0.5 mm.

The method for applying the slurry to the current collector is not particularly limited. For example, doctor blade method, dip method,
Reverse roll method, direct roll method, gravure method,
Examples of the method include an extrusion method, a dipping method, and a brush coating method. The amount of the slurry to be applied is not particularly limited, but the thickness of the mixed layer formed of the active material, the binder, etc., which is formed after the liquid medium is dried and removed, is usually
The amount is generally 0.005 to 5 mm, preferably 0.01 to 2 mm. The drying method is not particularly limited, and examples thereof include drying with warm air, hot air, and low humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams. The drying speed is usually adjusted so that the liquid medium can be removed as soon as possible within a speed range in which the active material layer is not cracked due to stress concentration and the active material layer is not separated from the current collector. Further, the density of the electrode active material may be increased by pressing the dried current collector. Examples of the pressing method include a die pressing method and a roll pressing method.

The secondary battery of the present invention contains the above-mentioned secondary battery electrode and electrolytic solution and is manufactured by a conventional method using parts such as a separator. As a specific manufacturing method, for example, a negative electrode and a positive electrode are stacked via a separator, which is wound or folded according to the shape of the battery, put into a battery container by folding, etc., and the electrolytic solution is injected into the battery container for sealing. To do. The shape of the battery may be any of coin type, button type, sheet type, cylindrical type, prismatic type, flat type and the like.

The electrolytic solution is used in ordinary secondary batteries.
If so, it may be liquid or gel, and the negative electrode active material
It also functions as a battery depending on the type of polar active material.
You can select. Lithium ion as the electrolyte
In the secondary battery, any conventionally known lithium salt is used.
Can be used, LiClO_Four, LiBF₆, LiP
F₆, LiCF_Three CO_Two, LiAsF₆, LiS
bF₆, LiB₁₀Cl₁₀, LiAlCl_Four, L
iCl, LiBr, LiB (C_TwoH₅)_Four, Li
CF_ThreeSO_Three, LiCH_ThreeSO_Three, LiC_Four
F₉S_Three3, Li (CF_ThreeSO_Two)_TwoN, low
Lithium fatty acid carboxylate and the like can be mentioned. Also,
In a nickel-hydrogen secondary battery, for example, the conventionally known concentration is
Use an aqueous solution of potassium hydroxide of 5 mol / liter or more
You can

The solvent that dissolves this electrolyte is not particularly limited. Specific examples include propylene carbonate, ethylene carbonate, butylene carbonate,
Carbonates such as dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate; lactones such as γ-butyl lactone; trimethoxymethane, 1,
Examples thereof include ethers such as 2-dimethoxyethane, diethyl ether, 2-ethoxyethane, tetrahydrofuran, and 2-methyltetrahydrofuran; sulfoxides such as dimethyl sulfoxide, and these may be used alone or as a mixed solvent of two or more kinds. it can.

[0040]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto. The parts and% in the examples are based on weight unless otherwise specified. The properties of the binder compositions in Examples and Comparative Examples and the production and evaluation of electrodes and batteries were performed by the following methods.

[Characteristics of Binder Composition] (1) Particle Size Distribution The particle size distribution of the polymer is measured using a particle size distribution analyzer Coulter LS230 and LS-100 (both manufactured by Coulter Co.) by light diffraction using laser light. However, the data was calculated on a volume basis. (2) Glass transition temperature (Tg) The Tg of the polymer serving as the binder was measured by a differential scanning calorimeter (DSC) at a heating rate of 10 ° C / min. Unit: ° C. (3) Adsorption to active material In case of negative electrode, specific surface area 5 m ² / g, average particle diameter 25 μm
Of artificial graphite (manufactured by Nippon Graphite Co., Ltd.), and in the case of a positive electrode, lithium cobalt oxide having a specific surface area of 1.5 m ² / g and an average particle diameter of 10 μm is used as an active material,
The amount W of the polymer adsorbed on the electrode active material was calculated. Unit m
g / g-active material.

[Production and Evaluation of Electrode and Battery] (4) Production of Lithium Ion Secondary Battery Electrode A positive electrode and a negative electrode were produced by the following method. That is, the positive electrode slurry was uniformly applied to an aluminum foil (thickness 20 μm) and the negative electrode slurry was applied to a copper foil (thickness 18 μm) on one side of each by a doctor blade method and dried at 120 ° C. for 15 minutes. After that, it was further dried in a vacuum dryer at 5 mmHg and 120 ° C. under reduced pressure for 2 hours, and then the active material density was positive electrode 3.4 g / c by a biaxial roll press.
m ³ and the negative electrode were compressed to 1.4 g / cm ³ ,
In each case, an electrode having a mixed layer thickness of 100 μm was obtained.

(5) Production of Lithium Ion Secondary Battery The positive electrode and the negative electrode were cut into a circular shape having a diameter of 15 mm, and the active materials face each other with a separator made of a circular polypropylene porous film having a diameter of 18 mm and a thickness of 25 μm interposed. , Placed so that the positive electrode aluminum foil or metallic lithium comes into contact with the bottom of the outer container, and further put the expanded metal on the negative electrode copper foil or metallic lithium, and install the polypropylene packing into the stainless steel coin type outer container ( Diameter 20 mm, height 1.8 mm, stainless steel thickness 0.25 mm). The following electrolytic solution was poured into this container so that air would not remain, and a 0.2 mm-thick stainless steel cap was put on the outer container via a polypropylene packing to fix it, and the battery can was sealed. A coin-type battery having a diameter of 20 mm and a thickness of about 2 mm was manufactured. The electrolytic solution is L in ethylene carbonate / ethyl methyl carbonate = 33/67 (volume ratio at 20 ° C.)
A solution in which 1 mol / l of iPF ₆ was dissolved was used.

(6) Bonding force test From the secondary battery electrode, length 100 mm in the coating direction, width 25
A rectangle of mm is cut out and used as a test piece. After sticking the cellophane tape on the entire surface of the mixed layer of the test piece, the stress when the cellophane tape end at one end of the test piece and the current collector foil end are pulled up and down at a pulling speed of 50 mm / min and peeled off is measured. It is judged that the greater the stress, the greater the binding force of the mixed layer to the current collector. Unit: g / cm.

(7) Measurement of battery capacity The battery capacity was measured at a negative electrode at 25 ° C. with a charge / discharge rate of 0.1 C and a constant current method (current density: 0.5 mA / g-
The active material) is charged to 1.2 V and discharged to 0 V, charging and discharging are repeated 5 times, and the battery capacity is measured each time. The average value of the battery capacity measured repeatedly is used as the evaluation result. In the positive electrode, the charge / discharge rate was set to 0.1 C at 25 ° C., the charge / discharge was performed to 1.2 V by the constant current method (current density: 0.5 mA / g-active material), and discharge to 3 V was measured 5 times each. Then, it is obtained in the same manner as the negative electrode. The unit is (mAh / g).

(8) Charging / discharging cycle characteristics Using a coin-type battery in an atmosphere of 25 ° C., a negative electrode test was carried out from 0 V to 1.2 V with metallic lithium as the positive electrode, and a positive electrode test was carried out from 3 V with metallic lithium as the negative electrode. 4.2V
Up to the discharge capacity at the 5th cycle [unit = mAh / g: per active material (hereinafter, the same applies to the electric capacity)] and discharge capacity at the 50th cycle (unit = mAh / This is a value obtained by measuring g) and calculating the ratio of the discharge capacity at the 50th cycle to the discharge capacity at the 5th cycle as a percentage. The larger this value is, the smaller the decrease in discharge capacity is, which is a good result.

Synthesis Example 1 of Polymer Dispersion Liquid 1 in the reactor
00 parts, 42 parts of butadiene, 30 parts of styrene, 8 parts of acrylonitrile, 18 parts of methyl methacrylate and 2 parts of itaconic acid, 100 parts of a monomer, 1 part of t-dodecyl mercaptan as a chain transfer agent, and a surfactant. And 1.5 parts of sodium alkyl diphenyl ether disulfonate as an initiator and 0.4 parts of potassium persulfate as an initiator,
Charge with 0.3 parts of sodium carbonate and stir 70
Polymerization was performed at 8 ° C. for 8 hours, and the reaction was completed at a polymerization conversion rate of 96%. Subsequently, 10 parts of water and 14 parts of butadiene were added to the reactor.
Parts, monomers consisting of 15 parts of styrene and 6 parts of methyl methacrylate, 0.1 part of sodium alkyldiphenyl ether disulfonate as a surfactant, 0.2 part of potassium persulfate as an initiator, and 0 sodium carbonate. ．
1 part was added and the polymerization reaction was continued at 80 ° C. for 8 hours, and then the reaction was terminated. Polymerization conversion rate at this time is 98%
Met. After removing unreacted monomers from the polymer dispersion and concentrating, 10% sodium hydroxide aqueous solution and water were added to adjust the solid content concentration and pH of the polymer dispersion, and the solid content concentration was 41%. A polymer dispersion (A) having a pH of 7.2 was obtained. The most frequent particle size (mode diameter) of polymer particles is 0.15 μm
Met.

[Synthesis Example 2 of Polymer Dispersion] Water 1 was added to the reactor.
00 parts, 100 parts of butadiene and t as a chain transfer agent
-Prepare 0.5 parts of dodecyl mercapun, 2.5 parts of potassium rosinate as a surfactant, 0.2 parts of potassium persulfate and 0.5 parts of sodium carbonate as an initiator, and polymerize at a temperature of 60 ° C for 50 hours. After continuing the reaction, the reaction was terminated. The polymerization conversion rate at this time was 97%. After removing unreacted monomers from the polymer dispersion liquid, water was added to adjust the solid content concentration of the polymer dispersion liquid to obtain a polymer dispersion liquid (B) having a solid content concentration of 50%. . The most frequent particle size of the polymer particles was 0.35 μm.

[Synthesis Example 3 of Polymer Dispersion] Water 2 was added to the reactor.
00 parts, 100 parts of a monomer consisting of 70 parts of butadiene and 30 parts of styrene, 0.2 part of t-dodecyl mercaptan as a chain transfer agent, 4.5 parts of potassium rosinate and an alkylnaphthalenesulfonic acid as a surfactant. 0.2 part of sodium, 0.07 part of paramenthane hydroperoxide as an initiator system, 0.01 part of sodium hydrosulfite, 0.025 part of ethylenediamine tetraacetic acid tetrasodium salt, and 0 of sodium formaldehyde sulfoxylate. 0.06 part of iron sulfate, 0.04 part of iron sulfate and 0.2 part of sodium carbonate were charged, the polymerization reaction was started at a temperature of 5 ° C., sampling was continued, and the polymerization was performed at a polymerization conversion rate of 62%. The reaction was completed. After removing the unreacted monomer from the polymer dispersion and concentrating it, water is added to adjust the solid content concentration of the polymer dispersion to obtain a polymer dispersion (C) having a solid content concentration of 32%. Obtained. The most frequent particle size of the polymer particles was 0.10 μm.

Synthesis Example 4 of Polymer Dispersion Liquid A reactor was charged with 6 parts of the polymer dispersion liquid (C) and 2 parts of butadiene,
The mixture was stirred and mixed at 60 ° C. for 2 hours. Butadiene was recovered from the polymer dispersion, concentrated, and then water was added to adjust the polymer dispersion to obtain a polymer dispersion (D) having a solid content concentration of 45%. The most frequent particle size of the polymer particles was 0.31 μm.

Synthesis Example 5 of Polymer Dispersion Liquid 2 in the reactor
40 parts, 85 parts of 2-ethylhexyl acrylate, 11 parts of acrylonitrile, 2 parts of methoxy polyethylene glycol methacrylate, 2 parts of triethylene glycol dimethacrylate, 100 parts of monomers, and 1.5 parts of potassium persulfate as a polymerization initiator. Was charged, and the mixture was heated to 80 ° C. with stirring to start the polymerization reaction, sampling was continued, and the reaction was terminated by cooling when the polymerization conversion rate reached 98%. After removing unreacted monomers from the polymer dispersion and concentrating, 10% sodium hydroxide aqueous solution and water are added to adjust the solid content concentration and pH of the polymer dispersion to a solid content concentration of 40%. A polymer dispersion (E) having a pH of 7.3 was obtained. The most frequent particle size of the polymer particles was 0.15 μm.

[Synthesis Example 6 of Polymer Dispersion] Water 2 was added to the reactor.
Monomer 1 consisting of 50 parts, butyl acrylate 45 parts, methyl methacrylate 54 parts and methacrylic acid 1 part
70 parts and polyvinyl alcohol 5 parts were charged, and 70 parts
Suspension polymerization was carried out at 0 ° C., sampling was continued, and the reaction was terminated when the conversion of polymerization reached 95%. After removing unreacted monomers from the polymer dispersion and concentrating, 10% aqueous sodium hydroxide solution and water are added to adjust the solid content concentration and pH of the polymer dispersion to a solid content concentration of 38%. ,
A polymer dispersion (F) having a pH of 7.2 was obtained. The most frequent particle size of the polymer particles was 1.7 μm.

Synthesis Example 7 of Polymer Dispersion Liquid 2 in a reactor
00 parts, 100 parts of butadiene and t as a chain transfer agent
-Prepare 0.5 parts of dodecyl mercaptan, 2 parts of potassium rosinate as a surfactant, 0.3 parts of potassium persulfate and 0.3 parts of sodium carbonate as an initiator, start polymerization at a temperature of 60 ° C, and sample. Continuously,
When the polymerization conversion rate reached 50% and 80%, 1 part of potassium rosinate was added, and the reaction was terminated when the polymerization conversion rate reached 95%. After removing unreacted monomer from the polymer dispersion and concentrating it, water is added to adjust the solid content concentration of the polymer dispersion to obtain a polymer dispersion (G) having a solid content concentration of 32%. It was The most frequent particle size of the polymer particles was 0.08 μm.

Example 1 The polymer dispersion liquid (A) and the polymer dispersion liquid (B) were mixed at a solid content weight ratio of 90:10 to obtain a binder composition having a solid content concentration of 42%. . When the particle size distribution of this binder composition was measured, particles having a particle size of 0.01 μm or more and less than 0.25 μm were 88.8.
Particles having a volume percentage of 0.25 μm or more and less than 3 μm are 11.
It was 2% by volume. The glass transition temperature is -15 ° C,
The amount of the polymer adsorbed on 1 g of the electrode active material was 18 mg. An automatic mortar (Ishikawa formula) was used together with 4.8 parts of this composition, 100 parts of the same graphite used for measuring the amount of adsorption, 75 parts of 2% aqueous solution of carboxymethyl cellulose [Serogen WSC, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.] and 100 parts of water. It was mixed for 20 minutes with a crusher, manufactured by Ishikawa Factory. 25 parts of water was added and further mixed for 2 minutes to obtain a negative electrode slurry having a solid content concentration of 34%. The viscosity of the negative electrode slurry was 3500 mPa · s with a Brookfield viscometer [BM type, rotor # 4, 60 rpm, manufactured by Tokimec]. This negative electrode slurry was dried on a 18 μm thick copper foil with a doctor blade to a thickness of 1
After coating to a thickness of about 20 μm and drying on a hot plate at 120 ° C, the density is 1.4 g using a roll press machine.
/ Cm ³ was subjected to a consolidation treatment to obtain a negative electrode (1). Table 1 shows the binder binding force of the negative electrode (1), and the battery capacity and rate characteristics of the secondary battery incorporating the negative electrode (1) and the positive electrode metallic lithium.

Example 2 In Example 1, the polymer dispersion liquid (A) was changed to the polymer dispersion liquid (C), and the polymer dispersion liquid (B) was changed to the polymer dispersion liquid (D). 3. A binder composition having a solid content concentration of 33% was obtained, and the amount of the composition was 4.
A negative electrode (2) was obtained in the same manner as in Example 1 except that 8 parts was changed to 6.1 parts. The particle size distribution of the binder composition is
9 particles with a particle size of 0.01 μm or more and less than 0.25 μm
2.7% by volume, and particles having a size of 0.25 μm or more and less than 3 μm were 7.3% by volume. At this time, the negative electrode slurry had a solid content concentration of 34% and a viscosity of 3100 mPa · s. The characteristics of the binder composition used for the production of the negative electrode (2), the binder binding force of the negative electrode (2), and the battery capacity and rate characteristics of the secondary battery incorporating the negative electrode (2) and metallic lithium as the positive electrode are shown. Note 1.

Example 3 The polymer dispersion (E) and the polymer dispersion (F) were mixed at a solid content weight ratio of 90:10 to obtain a binder composition having a solid content concentration of 40%. . The particle size distribution of the binder composition is 0.01 μm or more,
90.2% by volume of particles less than 0.25 μm, 0.25 μm
Particles of m or more and less than 3 μm were 9.8% by volume. The properties of the binder composition are shown in Table 1. After mixing 3 parts of the binder composition, 16 parts of 5% aqueous solution of carboxymethyl cellulose (Daiichi Kogyo Seiyaku Co., serogen 7A), 2 parts of acetylene black, 3 parts of graphite powder and 11 parts of water in an automatic mortar for 20 minutes, the adsorbed amount 100 parts of the same LiCoO ₂ used for the measurement was added and mixed for 10 minutes,
A positive electrode slurry having a solid content concentration of 79% and a viscosity of 2800 mPa · s was obtained. This positive electrode slurry was applied to a 21 μm thick aluminum foil with a doctor blade to a dry thickness of about 120 μm, dried on a hot plate at 120 ° C., and then compacted to a density of 3.4 g / cm ³ with a roll press machine. Thus, a positive electrode (3) was obtained. Table 1 shows the binder binding force of the positive electrode (3), and the battery capacity and rate characteristics of the secondary battery incorporating the positive electrode (3) and the metal lithium as the negative electrode.

Example 4 In Example 1, the polymer dispersion liquid (A) and the polymer dispersion liquid (B) were mixed in a solid content weight ratio of 90:
Instead of using 4.8 parts of the binder composition having a solid content concentration of 42% obtained by mixing in 10 the polymer dispersion (A)
And a polymer dispersion (B) at a solid content weight ratio of 75:25 to obtain a binder composition having a solid content concentration of 43%.
A negative electrode (4) was obtained in the same manner as in Example 1 except that 7 parts were used. Regarding the particle size distribution of the binder composition, particles having a particle size of 0.01 μm or more and less than 0.25 μm are 73.9.
26% of particles having a volume percentage of 0.25 μm or more and less than 3 μm.
It was 1% by volume. At this time, the negative electrode slurry had a solid content concentration of 34% and a viscosity of 3,400 mPa · s. The characteristics of the binder composition used for the production of the negative electrode (4), the binder binding force of the negative electrode (4), and the battery capacity and rate characteristics of a secondary battery incorporating the negative electrode (4) and metallic lithium as the positive electrode are shown. Note 1.

Example 5 The polymer dispersion liquid (A) and the polymer dispersion liquid (B) were mixed at a solid content weight ratio of 96: 4 to obtain a binder composition. Three times the volume of N-methylpyrrolidone (hereinafter referred to as "NM
It may be written as "P". ) Are mixed and the water is distilled off at 80 ° C. under reduced pressure using a rotary evaporator,
NMP was further added for viscosity adjustment to obtain a binder composition having NMP as a dispersion medium and a solid content concentration of 9%. NMP
Since it is difficult to measure the characteristics of the binder composition using the dispersion medium as the dispersion medium, particularly the particle size distribution, Table 1 shows the characteristic values of the binder composition before NMP substitution. Regarding the particle size distribution of the binder composition, particles having a particle size of 0.01 μm or more and less than 0.25 μm are 96.2% by volume, 0.25 μm or more and 3 μm.
Less than 3.8% by volume of particles. Twenty-three parts of the NMP-substituted binder composition was mixed with 100 parts of the same graphite used for measuring the amount of adsorption, 20 parts of a 10% NMP solution of ethylene-vinyl alcohol copolymer (40 mol% of ethylene unit) and 140 parts of NMP in an automatic mortar for 20 minutes. 20 parts of NMP was added and further mixed for 2 minutes to obtain a negative electrode slurry having a solid content concentration of 34% and a viscosity of 2900 mPa · s. This negative electrode slurry was applied to a copper foil having a thickness of 18 μm by a doctor blade so that the dry thickness was about 100 μm, dried on a hot plate at 120 ° C., and then compacted to a density of 1.4 g / cc with a roll press machine. Thus, a negative electrode (5) was obtained. Table 1 shows the binder binding force of the negative electrode (5), and the battery capacity and rate characteristics of the secondary battery incorporating the negative electrode (5) and the positive electrode metallic lithium.

Example 6 The polymer dispersion (E) and the polymer dispersion (F) were mixed at a solid content weight ratio of 90:10 to obtain a binder composition. Regarding the particle size distribution of the binder composition, particles having a particle size of 0.01 μm or more and less than 0.25 μm were 90.1% by volume, and particles having a particle size of 0.25 μm or more and less than 3 μm were 9.9% by volume. After mixing 3 parts by volume of NMP with 100 parts of the composition and distilling off water at 80 ° C. under reduced pressure using a rotary evaporator, NMP was further added to adjust the viscosity, and NMP was added as a dispersion medium. A binder composition having a solid content concentration of 8% was obtained. For the same reason as in Example 5, Table 1 shows characteristic values of the binder composition before NMP substitution. The NMP-substituted binder composition 1
5 parts were mixed with 18 parts of a 10% ethylene-vinyl alcohol copolymer (40 mol% of ethylene unit) NMP solution, 3 parts of acetylene black and 5 parts of NMP in an automatic mortar for 20 minutes. Next, the same L used to measure the adsorption amount
Add 100 parts of iCoO _{2 and} mix for 10 minutes, then add 9 parts of NMP and mix for 10 minutes to obtain a solid content of 7
A positive electrode slurry having a viscosity of 2400 mPa · s and 8% was obtained.
This positive electrode slurry was applied to a 21 μm thick aluminum foil with a doctor blade to a dry thickness of about 120 μm, dried on a hot plate at 120 ° C., and then compacted to a density of 3.4 g / cc with a roll press machine. Thus, a positive electrode (6) was obtained. Table 1 shows the binder binding force of the positive electrode (6), and the battery capacity and rate characteristics of the secondary battery incorporating the positive electrode (6) and the negative electrode, metallic lithium.

[Comparative Example 1] In Example 1, the polymer dispersion (A) was replaced with 4.8 parts of the binder composition obtained by mixing the polymer dispersion (A) and the polymer dispersion (B). ) 4.9
A negative electrode (7) was obtained in the same manner as in Example 1 except that parts were used. The particle size distribution of the binder composition is 0.01
99.8% by volume of particles having a size of at least μm and less than 0.25 μm,
Particles having a size of 0.25 μm or more and less than 3 μm were 0.2% by volume. The negative electrode slurry has a solid content concentration of 34% and a viscosity of 36.
It was 00 mPa · s. The characteristics of the binder composition used in the production of the negative electrode (7), the binder binding force of the negative electrode (7), and the battery capacity and rate characteristics of the secondary battery incorporating the negative electrode (7) and metallic lithium as the positive electrode are shown. Note 1.

[Comparative Example 2] In Example 1, instead of 4.8 parts of the binder composition obtained by mixing the polymer dispersion (A) and the polymer dispersion (B), the polymer dispersion (B ) A negative electrode (8) was obtained in the same manner as in Example 1 except that 4 parts were used.
The particle size distribution of the binder composition is such that particles having a particle size of 0.01 μm or more and less than 0.25 μm are 1.6% by volume, 0.25
Particles having a size of μm or more and less than 3 μm were 98.4% by volume. The negative electrode slurry has a solid content concentration of 34% and a viscosity of 3200.
It was mPa · s. Characteristics of the binder composition used in the production of the negative electrode (8), the binder binding force of the negative electrode (8),
Table 1 shows the battery capacity and rate characteristics of the secondary battery incorporating the negative electrode (8) and the positive electrode metallic lithium.
Note.

[Comparative Example 3] The polymer dispersion liquid (G) was used in place of the binder composition 4.8 parts obtained in Example 1 by mixing the polymer dispersion liquid (A) and the polymer dispersion liquid (B). A negative electrode (9) was obtained in the same manner as in Example 1 except that (1) was used. The particle size distribution of the binder composition is 0.01 μm or more,
100% by volume of particles less than 0.25 μm, 0.25 μm
As described above, 0% by volume of particles less than 3 μm was used. The negative electrode slurry had a solid content concentration of 34% and a viscosity of 3700 mPa · s. The characteristics of the binder composition used for the production of the negative electrode (9), the binder binding force of the negative electrode (9), and the battery capacity and rate characteristics of the secondary battery incorporating the negative electrode (9) and metallic lithium as the positive electrode are shown. Note 1.

Comparative Example 4 Polymer dispersion liquid (E) 3 was used instead of 3 parts of the binder composition obtained by mixing the polymer dispersion liquid (E) and the polymer dispersion liquid (F) in Example 3. A positive electrode (10) was obtained in the same manner as in Example 3 except that parts were used. Regarding the particle size distribution of the binder composition, particles having a particle size of 0.01 μm or more and less than 0.25 μm are 99.7% by volume, 0.2
Particles having a size of 5 μm or more and less than 3 μm were 0.3% by volume. The positive electrode slurry has a solid content concentration of 79% and a viscosity of 3000.
It was mPa · s. The characteristics of the binder composition used to manufacture the positive electrode (10), the binder binding force of the positive electrode (10), and the battery capacity and rate characteristics of a secondary battery incorporating the positive electrode (10) and metallic lithium as the negative electrode are shown. Note 1.

[Comparative Example 5] In Example 3, the polymer dispersion liquid (E) was replaced with 3 parts of the binder composition obtained by mixing the polymer dispersion liquid (E) and the polymer dispersion liquid (F). A positive electrode (11) was obtained in the same manner as in Example 3 except that 2 parts were used. The particle size distribution of the binder composition is 0.01 μm.
m or more and less than 0.25 μm, 0.2% by volume, 0.
The particles having a size of 25 μm or more and less than 3 μm were 99.8% by volume. The positive electrode slurry has a solid content concentration of 79% and a viscosity of 270.
It was 0 mPa · s. Shows the characteristics of the binder composition used to manufacture the positive electrode (11), the binder binding force of the positive electrode (11), and the battery capacity and rate characteristics of a secondary battery incorporating the positive electrode (11) and metallic lithium as the negative electrode. Note 1.

[Comparative Example 6] In Example 3, instead of 3 parts of the binder composition obtained by mixing the polymer dispersion liquid (E) and the polymer dispersion liquid (F), the polymer dispersion liquid (G) 3 was used. A positive electrode (12) was obtained in the same manner as in Example 3 except that 0.8 part was used. The particle size distribution of the binder composition is 0.01 μm.
m or more and less than 0.25 μm is 100% by volume, 0.
Particles of 25 μm or more and less than 3 μm were 0% by volume.
The positive electrode slurry has a solid content concentration of 79% and a viscosity of 3100 mP.
It was a.s. Characteristics of the binder composition used for producing the positive electrode (12), binder binding force of the positive electrode (12),
In addition, Table 1 shows the battery capacity and rate characteristics of the secondary battery incorporating the positive electrode (12) and the negative electrode metallic lithium.

[0066]

[Table 1]

The following can be seen from Table 1. Comparative Examples 1, 3, 4 and 6 in which the polymer dispersion liquid (II) having a primary particle mode particle size of 0.25 μm or more and less than 3 μm was not mixed.
The binder composition of (1) had a small binding force to the collector at the electrode, the battery capacity of the obtained battery was small, and the rate characteristics were poor. The most frequent particle size of the primary particles is 0.01 μm or more,
The binder compositions of Comparative Examples 2 and 5 in which the polymer dispersion (I) having a size of less than 0.25 μm was not mixed, the binding force to the current collector at the electrode was small, the battery capacity of the obtained battery was small, and the rate was low. The characteristics have also deteriorated.

On the other hand, Examples 1 to 1 obtained in the present invention
It can be seen that the binder composition of No. 6 has a large binding force to the current collector at the electrode, a large battery capacity of the obtained battery, and excellent rate characteristics.

[0069]

When an electrode is produced using the binder composition of the present invention, a secondary battery having a large binding property between the current collector and the active material, a large battery capacity and an excellent rate characteristic can be obtained.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuya Nakamura             1-2-1, Yokou, Kawasaki-ku, Kawasaki-shi, Kanagawa               Zeon Corporation, General Development Center F-term (reference) 5H050 AA00 AA08 BA14 BA17 CA02                       CA07 CA11 CB03 CB07 CB16                       DA11 EA23 FA17 GA02 GA10                       HA01 HA05 HA14

Claims (7)

[Claims] 1. A liquid medium dispersion (I) of a polymer having a modal particle size of primary particles of 0.01 μm or more and less than 0.25 μm is added in an amount of 70 to 99 parts by weight in terms of polymer, and A binder composition for a secondary battery electrode, which is obtained by mixing a liquid medium dispersion liquid (II) of a polymer having a frequent particle size of 0.25 μm or more and less than 3 μm with 1 to 30 parts by weight of the polymer (however, The total amount of the polymer after mixing the dispersion liquid (I) and the dispersion liquid (II) is 100 parts by weight). 2. A binder composition for secondary battery electrodes, comprising a polymer dispersed in a liquid medium in the form of particles, wherein the primary particles of the polymer are 0.01 μm or more and 0.25.
70-99% by volume in the particle size range of less than μm, and 0.
1 to 30% by volume in the particle size section of 25 μm or more and less than 3 μm
An existing binder composition for secondary battery electrodes. 3. The binder composition for a secondary battery electrode according to claim 1, wherein the liquid medium has a normal boiling point of 80 to 350 ° C. 4. A slurry for a secondary battery electrode, comprising the binder composition for a secondary battery electrode according to claim 1, and an electrode active material. 5. The secondary battery electrode slurry according to claim 4, wherein the amount of the polymer adsorbed on the electrode active material is 1 to 50 mg per 1 g of the electrode active material. 6. A secondary battery electrode comprising a current collector and a mixed layer containing a polymer and an electrode active material bound to the current collector, wherein the polymer primary particles have a particle size of 0.01 μm or more. 25 μm
70-99% by volume in the particle size range of less than, and 0.25
A secondary battery electrode, characterized in that 1 to 30% by volume is present in a particle size section of ≧ 3 μm and <3 μm. 7. A secondary battery having the secondary battery electrode according to claim 6.