JP2001283859A - Binder for electrode of lithium-ion secondary battery and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery with excellent charge/discharge cycle characteristics. SOLUTION: A battery electrode is manufactured by using a binder for an electrode of a lithium-ion secondary battery containing poly(metha)acrylic lithium salt, and a lithium-ion secondary battery is manufactured using this electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder used for a lithium ion secondary battery electrode and its use.

[0002]

2. Description of the Related Art In recent years, lithium such as coke and graphite has been absorbed and released as a negative electrode active material of a lithium ion secondary battery because of its excellent flexibility and no risk of electrodeposition of lithium metal. Possible carbon materials are being considered. A negative electrode using a carbonaceous material as an active material
Usually, a carbon powder and, if necessary, a conductive agent powder (such as acetylene black and carbon black) are dispersed in a binder composition containing a binder and a liquid substance to form a slurry, and the slurry is collected by a doctor blade method or the like. It is produced by a method of drying after coating on a metal. As the binder, a rubber-based binder such as styrene-butadiene rubber (hereinafter, referred to as SBR) is mainly used in addition to polyvinylidene fluoride (hereinafter, referred to as PVDF).

On the other hand, as a positive electrode active material, for example, Li
CoO₂, LiNiO₂, LiMn ₂O₄Etc. lithium
Containing composite metal oxides are being studied. These lithu
The positive electrode using the composite metal oxide containing the
Lithium-containing composite metal oxides instead of polar carbonaceous materials
Is used to produce an electrode in the same manner as the negative electrode. Vine for positive electrode
As the hopper, PDVF, polytetrafluoroethylene
(PTFE) Other rubbers such as SBR and acrylic rubber
A binder is used.

The rubber binder is usually used in the form of a latex, dispersion or emulsion in which rubber particles are dispersed in water (aqueous binder composition). Most commonly, carboxymethylcellulose or a salt thereof (hereinafter sometimes collectively referred to as CMC) is used for the aqueous binder composition. Such a high-polarity polymer itself functions as a binder, and in order to give a slurry obtained by mixing with an active material an appropriate viscosity, the surface of a current collector metal (hereinafter simply referred to as a current collector) It is said that since the slurry can be applied uniformly, an excellent electrode can be obtained. Proposals have been made to use sodium or potassium salts of polyacrylic acid in order to obtain higher adhesiveness (Japanese Patent Laid-Open No. 10-154).
No. 513).

[0005]

According to the study of the present inventors, CMC is slowly decomposed from a relatively low temperature of 120 ° C. at the stage of drying after the slurry is applied to the current collector in the electrode manufacturing process. Begins and decomposition continues for more than several hours. Since water was generated by this decomposition, it was found that water did not escape from the active material layer of the electrode forever. Further, it was also found that sufficient charge / discharge cycle characteristics could not be obtained even when sodium or potassium salts of polyacrylic acid were used. In a lithium ion secondary battery, the presence of moisture in the electrode also needs to be reduced as much as possible because the performance of the battery and the safety are reduced.

[0006] Therefore, the present inventors, after the application of the slurry,
As a result of intensive research to obtain a battery that easily removes moisture during the drying stage and has excellent charge-discharge cycle characteristics, the use of a lithium salt of polyacrylic acid as a binder for electrodes has resulted in poor applicability to the current collector. Excellent slurry is obtained,
The inventors have found that a lithium ion secondary battery having excellent charge / discharge cycle characteristics can be obtained, and have completed the present invention.

[0007]

Thus, according to the present invention, as a first invention, there is provided a binder for a lithium ion secondary battery electrode containing a lithium salt of poly (meth) acrylic acid, and as a second invention, A binder composition for a lithium ion secondary battery electrode containing the binder and a liquid substance having a boiling point at normal pressure of 50 ° C. or more and 350 ° C. or less is provided. As a third invention, the binder composition contains the binder and an active material. A slurry for a lithium ion secondary battery electrode (hereinafter, sometimes referred to as a slurry) is provided. As a fourth invention, a lithium ion secondary battery electrode manufactured using the slurry is provided, and a fifth invention is provided. The present invention also provides a lithium ion secondary battery manufactured using the electrode. Since the surface of the active material layer of the electrode of the present invention is smooth, good battery characteristics can be provided.

[0008]

DETAILED DESCRIPTION OF THE INVENTION Binder The binder of the present invention is a lithium salt of polyacrylic acid or a lithium salt of polymethacrylic acid. Of course, both can be mixed and used. Polyacrylic acid and polymethacrylic acid (hereinafter sometimes referred to as poly (meth) acrylic acid) according to the present invention have a weight average molecular weight in terms of monodisperse polystyrene (hereinafter referred to as poly (meth) acrylic acid) calculated by gel permeation chromatography using tetrahydrofuran. , Simply referred to as weight average molecular weight) of 1000 to 5
Million, preferably 10,000 to 3,000,000. If the weight average molecular weight is too high, the viscosity becomes too high during lithium salification, which may cause a problem in operability. Conversely, if the weight average molecular weight is too low, only a slurry having poor coatability to the current collector is obtained. May not be possible. Further, the poly (meth) acrylic acid may be cross-linked.

The lithium salt of poly (meth) acrylic acid is
It is obtained by adding a lithium source such as an aqueous solution of lithium hydroxide to poly (meth) acrylic acid. Lithium chloride increases the viscosity of the lithium poly (meth) acrylate solution. As the lithium salt of poly (meth) acrylic acid, a 1% by weight aqueous solution having a viscosity at 25 ° C. (measured by a B-type viscometer) of 1 to 1,000,000 centipoise (cps) is preferably used, and more preferably. 1000-500,000 c
ps. When the viscosity is in this range, sufficient coating property of the slurry described later on the current collector is ensured.

[0010] 2. Binder composition The binder composition of the present invention is obtained by mixing the above-described binder of the present invention with water or a boiling point at normal pressure of 50 ° C. or more and 350 ° C.
The boiling point at normal pressure is preferably 100 ° C. or higher and 30
It is dissolved or dispersed in a liquid substance at 0 ° C. or lower.
The binder content of the present invention in the composition is usually 0.01 to
It is 50% by weight, preferably 0.05 to 20% by weight, more preferably 0.05 to 15% by weight. Within this range, a slurry having excellent paint properties can be obtained.

Specific examples of the liquid substance used in the present invention include water (100) and hydrocarbons such as n-dodecane (216) and tetralin (207);
Alcohols such as hexanol (184) and 1-nonanol (214); ketones such as holone (197), acetophenone (202) and isophorone (215); benzyl acetate (213), isopentyl butyrate (184),
γ-butyrolactone (204), methyl lactate (14
3), esters such as ethyl lactate (154) and butyl lactate (185); amines such as o-toluidine (200), m-toluidine (204) and p-toluidine (201); N-methylpyrrolidone (202) ), N, N-dimethylacetamide (194), amides such as dimethylformamide (153); dimethylsulfoxide (1
89) and organic liquid substances such as sulfoxides and sulfones such as sulfolane (287). The number in parentheses after the compound name is the boiling point at normal pressure (unit: ° C.), and the values after the decimal point are rounded or truncated. For compounds having a wide range of boiling points, the lower limit was confirmed to be 50 ° C. or higher, and the upper limit was described. Among these, water and N-methylpyrrolidone are particularly preferred liquid substances from the viewpoint of good handling in electrode production, and a small amount of alcohol such as methanol or ethanol can be further added thereto.

The binder composition of the present invention comprises a polymer other than a lithium salt of poly (meth) acrylic acid (hereinafter referred to as another polymer),
It is desirable to use them together at a ratio (weight ratio) of 0.5 to 30 times, preferably 1 to 10 times.

Other polymers that can be used in combination are:
For example, diene-based polymers, olefin-based polymers, styrene-based polymers, acrylate-based polymers, amide- or imide-based polymers, ester-based polymers, cellulose-based polymers, and the like are specifically exemplified. Specific examples include polybutadiene, polyisoprene, and isoprene-isobutylene. Copolymer, natural rubber, styrene-1,3-butadiene copolymer, styrene-isoprene copolymer, 1,3-
Butadiene-isoprene-acrylonitrile copolymer, styrene-1,3-butadiene-isoprene copolymer, 1,3-butadiene-acrylonitrile copolymer, styrene-acrylonitrile-1,3-butadiene-methyl methacrylate copolymer, styrene-acrylonitrile-1,3- Butadiene-itaconic acid copolymer, styrene-acrylonitrile-1,3-butadiene-methyl methacrylate-fumaric acid copolymer, styrene-1,3-butadiene-itaconic acid-methyl methacrylate-acrylonitrile copolymer, acrylonitrile-
1,3-butadiene-methacrylic acid-methyl methacrylate copolymer, styrene-1,3-butadiene-itaconic acid-methyl methacrylate-acrylonitrile copolymer, styrene-acrylonitrile-1,3-butadiene-methyl methacrylate-fumaric acid copolymer, etc. A diene polymer; ethylene-propylene copolymer, ethylene-propylene-diene copolymer, polystyrene,
Olefin polymers such as polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene ionomer, polyvinyl alcohol, vinyl acetate polymer, ethylene-vinyl alcohol copolymer, chlorinated polyethylene, polyacrylonitrile, polyacrylic acid, polymethacrylic acid, and chlorosulfonated polyethylene Styrene-ethylene-butadiene copolymer, styrene-butadiene-propylene copolymer, styrene-
Styrene-based polymers such as n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile copolymer, styrene-n-butyl acrylate-itaconic acid-methyl methacrylate-acrylonitrile copolymer;

Polymethyl methacrylate, polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, ethyl acrylate-acrylonitrile copolymer,
(Meth) acrylate-based polymers such as 2-ethylhexyl acrylate-methyl acrylate-acrylic acid-methoxypolyethylene glycol monomethacrylate; polyamide 6, polyamide 66, polyamide 11,
Amide- or imide-based polymers such as polyamide 12, aromatic polyamide and polyimide; ester condensation-based polymers such as polyethylene terephthalate and polybutylene terephthalate; carboxymethyl cellulose, carboxyethyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, carboxyethyl methyl cellulose Cellulose compounds (including salts such as ammonium salts and alkali metal salts thereof); polystyrene-polybutadiene block copolymer, styrene-butadiene-styrene block copolymer, styrene-ethylene-butylene-styrene block copolymer, styrene-isoprene block copolymer , Styrene-ethylene-propylene-styrene block copolymer Block copolymers and the like; fluorine rubber, PVDF or PTFE, tetrafluoroethylene -
Fluorinated polymers such as hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, polychlorotrifluoroethylene, ethylene-chlorotrifluoroethylene copolymer; and other methyl methacrylate polymers. These polymers may be used alone or in combination of two or more.

Among the specific examples described above, preferred are diene-based polymers and (meth) acrylate-based polymers. In addition, those in which these polymers are in the form of particles and the outer layer of the polymer particles have ( Homopolymer or copolymer of (meth) acrylic acid monomer or (meth) acrylic acid ester monomer, (meth)
Composite polymer particles (core-shell structure, composite structure, localized structure, daruma-like structure, Idoko-like) having a polymer layer such as a copolymer of an acrylic acid-based monomer or a (meth) acrylate-based monomer and a copolymerizable monomer. Particularly preferred examples include structures referred to as structures, raspberry-like structures, multi-particle composite structures and the like ("Adhesion", Vol. 34, No. 1, pages 13 to 23, particularly FIG. 6 on page 17). .

These other polymers may be dissolved or dispersed in the liquid medium described above. In particular, it is desirable that most or all of the other polymer is dispersed in the slurry in the form of particles. In this case, the particle diameter of the other polymer (after drying the dispersion medium, measuring the major axis and minor axis of 100 particles with an electron microscope and taking the average value) is usually 0.005 to 100 μm, preferably 0 to 100 μm. .01-50
μm, and more preferably 0.05 to 30 μm.

3. Battery Electrode Slurry The slurry of the present invention contains the above-described binder of the present invention and an active material. Usually, such a slurry is prepared by mixing the above-described binder composition of the present invention and an active material. Further, in the slurry, other polymers that can be used in combination with the binder composition described in detail, or a viscosity modifier or a fluidizing agent may be added, and further, as a conductive agent, conductive graphite or activated carbon. Carbon or metal powder can be added. (Active Material) The active material used in the slurry of the present invention may be any material as long as it can absorb and release lithium ions. Examples of the negative electrode active material include various carbonaceous materials. Examples of the active material include metal composite oxides, particularly metal composite oxides containing lithium and at least one metal selected from the group consisting of iron, cobalt, nickel, and manganese.

More specifically, as a particularly preferable negative electrode active material, carbonaceous materials such as hard carbon, graphite, natural graphite, mesocarbon microbeads (MCMB), pitch-based carbon fiber, and polyacene are generally used. Although used, composite metal oxides and other metal oxides can also be used.

Particularly preferred cathode active materials include:
LixMO ₂ (where M represents one or more transition metals, preferably at least one of Co, Mn and Ni.
10>x> 0.05) or LixM ₂ O
₄ (where M represents one or more transition metals, preferably Mn, and 1.10>x> 0.05), for example, LiCoO ₂ , LiNiO ₂ , LiLi
xNiyCo _(1-y) O ₂ (However, 1.10>x>
0.05, 1>y> 0) and a composite oxide represented by LiMn ₂ O ₄ .

4. Lithium ion secondary battery electrode The electrode of the present invention is manufactured by applying the slurry of the present invention to a current collector such as a metal foil, drying and fixing the active material on the current collector surface. The electrode of the present invention may be either a positive electrode or a negative electrode. The current collector is not particularly limited as long as it is made of a conductive material, but is usually made of a metal such as iron, copper, aluminum, nickel, and stainless steel.
The shape is not particularly limited, but usually, the thickness is 0.001 to 0.001.
It has a sheet shape of about 0.5 mm.

The method of 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,
It is applied by an extrusion method, immersion method, brush painting, or the like. The amount to be applied is not particularly limited, but the thickness of the active material layer formed after removing water or the organic dispersion medium by a method such as drying is 0.005 to 5 mm, preferably 0.01 to 2 mm. General. The drying method is not particularly limited, and examples thereof include drying with warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams. Drying conditions are adjusted so that water and the organic dispersion medium can be removed as soon as possible within a speed range in which the active material layer is not cracked by stress concentration or the active material layer does not peel off from the current collector. . Further, the density of the active material of the electrode may be increased by pressing the dried current collector. As the pressing method, a method such as a die press or a roll press is used.

5. Lithium-ion secondary battery The lithium-ion secondary battery of the present invention includes an electrolyte and an electrode for a lithium-ion secondary battery of the present invention, and is manufactured according to a conventional method using components such as a separator as necessary. It is. For example, the following method can be mentioned. That is, the positive electrode and the negative electrode are overlapped via a separator, rolled or folded according to the battery shape, and put in a battery container.
Inject electrolyte and seal. Battery shape is coin type,
Any of a button type, a sheet type, a cylindrical type, a square type, a flat type and the like may be used.

The electrolyte may be any one which is usually used for a lithium ion secondary battery.
What has the function as a battery should just be selected according to the kind of positive electrode active material. As the electrolyte, for example, any of conventionally known lithium salts can be used.
₄ , LiBF ₆ , LiPF _{6 and the} like.

The solvent for dissolving this electrolyte (electrolyte solvent) is not particularly limited. Preferred specific examples are propylene carbonate, ethylene carbonate,
Carbonates such as butylene carbonate, dimethyl carbonate, and diethyl carbonate; lactones such as γ-butyl lactone; and in addition, ethers, sulfoxides, oxolanes, organic acid esters, inorganic acid esters, diglymes, Triglymes, sulfolane, oxazolidinones, sultones and the like can also be used. A single solvent or a mixed solvent of two or more solvents can be used.

[0025]

When the binder composition of the present invention is used for producing an electrode of a lithium ion secondary battery, lithium having excellent properties of a slurry, excellent charge / discharge cycle characteristics of a battery, and excellent safety without blistering of the battery is obtained. A secondary battery can be manufactured.

[0026]

The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In the examples, parts and percentages are by weight unless otherwise specified.

The evaluation conditions in the examples and comparative examples are as follows. <Evaluation of Slurry Properties> Dispersibility: 50 μm according to JIS K 5400
The degree of dispersion was measured using a crush gauge of m.
When it was less than μm, it was judged as good, and when the measured value was more than 20 μm, it was judged as bad. Mixability: Evaluated according to JIS K 5400. It was determined to be good when mixed evenly, and to be poor when mixed poorly. Storage stability: Storage stability for 10 days was evaluated in accordance with JIS K 5400 paint storage stability at room temperature.
If no change was observed in the slurry state, it was stable.
When the state of the slurry was changed, gelation or two-phase separation was determined based on the changed state (described in the table as "gel" and "two-phase", respectively). Coating property: The positive electrode slurry is coated on the following aluminum foil,
The negative electrode slurry was coated on the following copper foil with a gap of 200 μm each.
JIS K 5400 using a film applicator
The coating was performed in accordance with the above, and whether or not the coating was uniformly performed was visually evaluated. Slurries that could be applied uniformly and easily were good, and those that were difficult to apply uniformly were determined to be poor.

<Evaluation of Electrode> Production of Electrode and Coin Battery A positive electrode slurry was uniformly applied to an aluminum foil (thickness: 20 μm) and a negative electrode slurry was applied to a copper foil (thickness: 18 μm) by a doctor blade method. 1 at 120 ° C
Dry with a dryer for 5 minutes, and then 5 torr with a vacuum dryer.
After 2 hours drying under reduced pressure at r, 120 ° C., the active material density of the positive electrode 3.2 g / cm ³ by roll press biaxial, compressed so that the negative electrode 1.5 g / cm ^3, the thickness of the active material layer An electrode of 80 μm is obtained. This electrode was cut out into a circle having a diameter of 15 mm, and a separator made of a circular polypropylene porous membrane having a diameter of 18 mm and a thickness of 25 μm was interposed.
Stainless steel with active materials facing each other, placed so that the aluminum foil or lithium metal of the positive electrode is in contact with the bottom of the outer container, and further expanded metal is placed on the copper foil or lithium metal of the negative electrode, and polypropylene packing is installed. -Made coin-shaped outer container (diameter 20 mm, height 1.
8 mm, stainless steel thickness 0.25 mm). Here, for the negative electrode test, the positive electrode was metallic lithium,
For the positive electrode test, lithium metal is used for the negative electrode. An electrolytic solution is injected into the coin-shaped outer container so that no air remains, and the outer container is fixed with a 0.2 μm-thick stainless steel cap via a polypropylene packing, and the battery can is sealed. Then, a coin-type battery having a diameter of 20 mm and a thickness of about 2 mm is manufactured. As the electrolytic solution, a solution in which LiPF ₆ is dissolved at a concentration of 1 mol / liter in ethylene carbonate / diethyl carbonate = 50/50 (volume ratio at 20 ° C.) is used. Bending test: Electrode length 100 mm, width 20 mm
The test piece was cut into fifty test pieces, and the active material layer of the electrode was placed inside, and a stainless steel rod having a diameter of 2 mm was used as a core and bent until the electrode surfaces were in contact with each other (inward bending). Was folded in the same manner (outside bending), the number of cracks in the active material layer and the number of test pieces (electrodes) from which the active material layer was separated from the current collector were counted. The larger this value is, the more the electrode has many defects.

[0029] Adhesion test: The adhesion test between the current collector and the active material layer was performed on 10 electrode test pieces each using JI.
According to the grid test method specified in SK 5400,
It was measured. The results were visually evaluated on a 10-point scale. The value was the average value of 10 test pieces, and the decimal part was rounded off. If this value is 8 or more, it can be determined that there is practically good binding property.

<Evaluation of Battery> Charge / discharge capacity retention ratio: The electric capacity of a 20-cell battery was measured. The discharge capacity (unit = mAh / g) at the end of the 50th cycle and at the end of the 5th cycle was measured, and the charge / discharge capacity retention ratio expressed by the ratio (%) of the capacity at the 50th cycle to the capacity at the 5th cycle was obtained. , 20 cells were averaged. The higher this value, the better the cycle characteristics. After the charge / discharge capacity retention rate measurement of the blister test: that is, after the completion of 50 cycles, the battery thickness of the 20-cell coin battery was measured, and the number of batteries in which blisters were recognized was indicated. It can be said that the smaller the value, the safer the battery without blisters.

In the following Examples and Comparative Examples, parts and%
Are by weight unless otherwise noted. Example 1 2 parts of polyacrylic acid (weight average molecular weight about 1,000,000)
After dissolving in 998 parts of ion-exchanged water, 12 parts of a 13% aqueous solution of lithium hydroxide was added to obtain an aqueous solution of a lithium salt of polyacrylic acid. The obtained aqueous solution was adjusted to a concentration of 1%,
Its viscosity was measured at 25 ° C. and found to be 80,000 cps. To 100 parts of natural graphite, 0.5 parts of solids equivalent of the aqueous solution of lithium salt of polyacrylic acid and 2 parts of solids of 40% styrene butadiene rubber latex (styrene content 36%) were added. Furthermore, the solid content is 33.2%
Until water is obtained, and the mixture is sufficiently stirred.
I got A negative electrode was manufactured using the obtained slurry A, and a battery was manufactured using the negative electrode. slurry,
The electrode and the battery were evaluated as described above. Table 1 shows the results.

Example 2 In place of the 40% styrene butadiene rubber latex of Example 1, a 40% acrylic latex (80/5/15 (component content weight ratio) of 2-ethylhexyl acrylate / acrylic acid / methacrylonitrile) A negative electrode slurry B was obtained in the same manner as in Example 1 except that the above was used. Using the obtained slurry B, a negative electrode is manufactured,
A battery was manufactured using this negative electrode. The above evaluation was performed for the slurry, the electrode, and the battery. Table 1 shows the results.

Example 3 LiCoO ₂ was used instead of 100 parts of the natural graphite of Example _2.
A positive electrode slurry P was obtained in the same manner as in Example 2, except that 95 parts and 5 parts of conductive carbon were used, and the solid content of the slurry was 65%. A positive electrode was manufactured using the obtained slurry P, and a battery was manufactured using the positive electrode. The above evaluation was performed for the slurry, the electrode, and the battery. Table 1 shows the results.

Comparative Example 1 2 parts of polyacrylic acid (weight average molecular weight: about 1,000,000)
An aqueous solution of polyacrylic acid dissolved in 998 parts of ion-exchanged water was obtained. To 100 parts of natural graphite, 0.5 parts by weight of the solid content of the polyacrylic acid aqueous solution and 2 parts by weight of the solid content of 40% styrene butadiene rubber latex (styrene content: 36%) were added. Further, water was added until the solid content became 33.2%, and the mixture was sufficiently stirred to obtain a negative electrode slurry C.
A negative electrode was manufactured using the obtained slurry C, and a battery was manufactured using the negative electrode. The above evaluation was performed for the slurry, the electrode, and the battery. Table 1 shows the results.

Comparative Example 2 2 parts of polyacrylic acid (weight average molecular weight: about 1,000,000)
After dissolving in 998 parts of ion-exchanged water, 12 parts of a 13% aqueous sodium hydroxide solution was added to obtain a sodium salt aqueous solution of polyacrylic acid. The obtained aqueous solution was adjusted to a concentration of 1%, and its viscosity was measured at 25 ° C.
Met. To 100 parts of natural graphite, a solid content equivalent to 0.5 part of the aqueous solution of the sodium salt of polyacrylic acid, and 40%
Styrene butadiene latex (styrene content 36%)
And the solid content of 2 parts. Further, the solid content is 33.
Water was added until the concentration became 2%, and the mixture was sufficiently stirred to obtain a negative electrode slurry D. A negative electrode was manufactured using the obtained slurry D, and a battery was manufactured using the negative electrode. The above evaluation was performed for the slurry, the electrode, and the battery. Table 1 shows the results.

Comparative Example 3 A positive electrode slurry Q was obtained in the same manner as in Example 3, except that the aqueous solution of polyacrylic acid used in Comparative Example 1 was used instead of the lithium salt of polyacrylic acid. A positive electrode was manufactured using the obtained slurry Q, and a battery was manufactured using the negative electrode. About slurry, electrode and battery
The above evaluation was performed. Table 1 shows the results.

[0037]

[Table 1]

From these results, in Examples 1 to 3 using a binder composition containing a lithium salt of poly (meth) acrylic acid, a good slurry was obtained, and the electrode obtained by using the slurry was subjected to a bending test. Gives a good electrode without cracks. The yield can be increased in an actual production line, leading to an improvement in production efficiency.

Claims (5)

[Claims] 1. A binder for a lithium ion secondary battery electrode comprising a lithium salt of poly (meth) acrylic acid. 2. A binder composition for a lithium ion secondary battery electrode comprising the binder according to claim 1 and a liquid substance having a boiling point at normal pressure of 50 ° C. to 350 ° C. 3. A slurry for a lithium ion secondary battery electrode, comprising the binder according to claim 1 and an active material. 4. An electrode for a lithium ion secondary battery produced using the slurry according to claim 3. 5. A lithium ion secondary battery having the electrode according to claim 4.