JPH087881A - Electrode plate for non-aqueous electrolyte secondary battery and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Object] To provide an electrode plate for a non-aqueous electrolyte secondary battery capable of preventing a decrease in conductivity (electron conductivity) inside a coating film and a decrease in capacity retention rate during charge / discharge cycles. A non-aqueous electrolyte secondary battery electrode plate having a coating film obtained by applying an electrode coating liquid containing an active material, a binder and a dispersion medium onto the surface of a metal foil current collector. An electrode plate for a non-aqueous electrolyte secondary battery, in which a coating film forms a raised structure including the binder and an active material bound by the binder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode plate for a non-aqueous electrolyte secondary battery which can prevent a decrease in capacity retention rate during charge / discharge cycles, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, electronic devices and communication devices have been rapidly reduced in size and weight. Secondary batteries used as power sources for driving these devices are also strongly required to have high energy density and high voltage. A non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery has been proposed instead of an alkaline storage battery.

Regarding the electrode plate, which has a great influence on the performance of the secondary battery, in order to extend the charge / discharge cycle life,
Further, it has been proposed to increase the area of the thin film in order to increase the energy density. For example, Japanese Patent Laid-Open No. 63-1045
6, JP-A-3-285262 discloses that a powder of a positive electrode active material such as a metal oxide, a sulfide and a halide, a conductive agent and a binder (binder) are dissolved in an appropriate wetting agent (solvent) to form a paste. A positive electrode plate obtained by preparing an active material coating solution, applying the coating solution to a metal foil current collector, and then removing the solvent is disclosed. As the binder, for example, a fluororesin such as polyvinylidene fluoride or a silicone = acrylic copolymer is used.

On the other hand, in the coating type electrode plate, the binder used for preparing the active material coating solution is electrochemically stable to the non-aqueous electrolytic solution, that is, the organic solvent and does not elute into the electrolytic solution. The applied active material coating film is required to be flexible so as not to be peeled off, dropped off, cracked or the like during the battery assembly process, and to have excellent adhesion to the metal foil current collector.

[0005]

However, in the conventional coating type electrode plate, the binder forms a continuous phase inside the coating film and coats the surfaces of the particulate active material and the conductive material, so that the ions are doped from the active material. Alternatively, since dedoping is hindered, there is a tendency that the conductivity (electron conductivity) inside the coating film is lowered or the capacity retention rate during charge / discharge cycles is lowered.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is possible to reduce the conductivity (electron conductivity) in the coating film and the capacity retention rate during charge / discharge cycles. In order to prevent, a nonaqueous electrolyte secondary battery electrode plate having a coating film formed by applying an electrode coating liquid containing an active material, a binder and a dispersion medium on the surface of a metal foil current collector,
The present invention provides an electrode plate for a non-aqueous electrolyte secondary battery, wherein the coating film comprises a binder and an active material bound by the binder to form a raised structure.

In the present invention, a step of kneading an active material, a granular binder and a dispersion medium to prepare an electrode coating liquid,
A step of applying the electrode coating liquid to a metal foil current collector to form a coating film in a state where the binder is dispersed in the form of particles, a step of removing the dispersion medium contained in the coating film, and the removing step. The present invention provides a method for producing an electrode plate for a non-aqueous electrolyte secondary battery, which comprises the step of subjecting the coating film to heat or ionizing radiation irradiation at the same time or thereafter.

That is, in the electrode plate for a non-aqueous electrolyte secondary battery according to the present invention, an adhesive force is generated between the surface of the particulate binder and the surfaces of the particulate active material and the conductive material, and the particulate active material. And, the active material coating film is formed while binding the conductive material, but at this time, the binder does not cover the surface of the particulate active material and the conductive material, that is, the surface of the active material and the conductive material is slightly By exposing and adhering to each other to form a wavy structure (for example, a structure that mimics milleting, lightning, etc.), it prevents the doping and dedoping of ions from the active material or the conductivity inside the coating film. (Electron conductivity) can be prevented from decreasing, and the capacity retention rate during charge / discharge cycles can be increased.

The non-aqueous electrolyte secondary battery in the present invention is represented by a lithium secondary battery. That is, as the positive electrode active material, for example, a combination of one or more of lithium oxides such as LiCoO ₂ and LiMn ₂ O ₄ and chalcogen compounds such as TiS ₂ , MnO ₂ , MoO ₃ and V ₂ O _5. Is used as the negative electrode active material, lithium,
A lithium alloy or a carbonaceous material such as graphite, carbon black or acetylene black is preferably used. In particular, LiCoO ₂ is used as the positive electrode active material,
It is preferable to use a carbonaceous material as the negative electrode active material,
A high discharge voltage of about 4 V can be obtained.

In the electrode plate of the present invention, the active material coating solution is prepared by kneading or dispersing the above powdery active material, binder (binder) and an appropriate dispersion medium. It is obtained by coating a metal foil current collector such as stainless steel. Further, it is preferable to mix graphite, carbon black, acetylene black, metal powder, or the like into the active material coating liquid as a conductive agent.

What characterizes the present invention is that the binder is present as dispersed particles at least in the active material coating solution, and it is in the form of particles at the same time as or after the step of coating the metal foil current collector and removing the dispersion medium. When the binder exhibits thermoplasticity or thermosetting property, heat treatment is performed, while when the particulate binder exhibits ionizing radiation curing property, irradiation of ionizing radiation causes irradiation of the surface of the particulate binder with the particulate active material or conductivity. By fixing the particulate active material and the conductive material by generating an adhesive force with the surface of the material,
That is, an electrode plate is obtained by forming an active material coating film. That is, when the particulate binder is composed of a thermoplastic resin, after applying the active material coating liquid to the current collector and removing the dispersion medium, or at the same time,
By performing a heat treatment at a temperature higher than the softening point of the thermoplastic resin to soften or melt the surface of the particles, an adhesive force between the particulate active material and the conductive material surface is generated to form an active material coating film. It can be formed to obtain an electrode plate.

The thermoplastic resin constituting the particulate binder is, for example, polyester resin, polyamide resin, polyacrylic ester resin, polycarbonate resin, polyurethane resin, cellulose resin, polyolefin resin, polyvinyl resin, fluorine resin, polyimide resin. , Etc., but considering the adhesive strength during heat softening and the ease of forming into particles, polyacrylic acid ester resins and polyvinyl resins, especially polymethyl (meth) acrylate, polybutyl (meth) Clerate,
Poly-2-hydroxyethyl (meth) acrylate, poly (meth) acrylamide, polystyrene, polyvinyl chloride, polyvinyl acetate and copolymers thereof,
Further, it is preferable to use a crosslinked product (microgel) obtained by partially copolymerizing a polyfunctional monomer such as divinylbenzene, methylenebisacrylamide, (poly) ethylene glycol diacrylate, or trimethylolpropane trimethacrylate.

If the softening point of the thermoplastic resin constituting the particulate binder is too high, the heat treatment temperature must be high, which is not preferable in the manufacturing process, and if it is too low, the softening point will be in a softened state even at room temperature. Both are not preferable because peeling or particle dropout occurs due to film flow. A preferred softening point is, for example, 30 ° C to 200 ° C, more preferably 50 ° C to 150 ° C. Further, in order to prevent the coating of the active material and the conductive material particles by maintaining the particle shape after the active material coating film is formed by softening and melting the particulate binder,
It is necessary that the elastic modulus of the thermoplastic resin at the time of softening is high to some extent.

When the particulate binder is made of a thermosetting resin, the active material coating liquid is applied to the current collector to remove the dispersion medium, as in the case of being made of a thermoplastic resin. After or at the same time, heat treatment is carried out to cause an adhesive force between the particulate active material and the surface of the conductive material by reacting the thermosetting resin to form an active material coating film, whereby an electrode plate can be obtained. .

The thermosetting resin that constitutes the particulate binder must be a thermoreactive prepolymer, oligomer or monomer (hardening agent). For example, urethane, epoxy, melamine, phenol = formaldehyde, amide, urea, imide, prepolymers such as acrylic reaction system, oligomers, and monomers, and if they are urethane prepolymers, isocyanate groups ( -NCO) is required, and in the case of an epoxy-based prepolymer, it is necessary to include a glycidyl group in the molecule. If necessary, they can be used in appropriate combination with an initiator, a catalyst and the like.

When the particulate binder is composed of an ionizing radiation-curable resin, the current collector is coated with the active material coating liquid, the dispersion medium is removed, and then the ionizing radiation is irradiated to cure the ionizing radiation-curable resin. By reacting the resin, the adhesive force between the particulate active material and the surface of the conductive material is generated to form the active material coating film, and the electrode plate can be obtained.

The ionizing radiation-curable resin which constitutes the particulate binder is mainly composed of a prepolymer such as a (meth) acryloyl compound, an allyl compound or a vinyl compound, which reacts with ultraviolet rays, electron beams or γ rays, oligomers and monomers. To do. For example, prepolymers and oligomers such as urethane (meth) acrylate, epoxy (meth) acrylate, polyester (meth) acrylate and styrene, (meth) acrylic acid, methyl (meth) acrylate, butyl (meth) acrylate, 2-hydroxyethyl acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, hexamethylene glycol diacrylate, neopentyl glycol diacrylate, ethylene glycol diglycidyl ether diacrylate, diethylene glycol diglycidyl ether diacrylate, hexamethylene glycol diglycidyl ether diacrylate , Neopentyl glycol diglycidyl ether diacrylate, trimethylolpropane triacryl Over DOO, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate,
A small amount of monofunctional and polyfunctional monomers such as dipentaerythritol hexaacrylate can be mixed and used.

Furthermore, it is possible that the present particulate binder has a multilayer structure. Multilayer structured particles are generally called core = shell particles, and the material and physical properties are different between the inner part (core) and outer part (shell) of the particle.
It is a particle composed of a plurality of layers, which is more than one layer. In that case, at least only the outermost layer may be made of the resin having the above-mentioned thermoplasticity, thermosetting property, and ionizing radiation curability. Therefore, the other layers including the core may be either inorganic fine particles or organic fine particles.

When the inorganic fine particles are the inner layer, the outermost layer (surface layer) is made of a thermoplastic, thermosetting, and ionizing radiation-curable resin by a conventionally known synthesis method or the like. be able to. For example, Polymer Journal,
vol.21, No.6, p425 (1989) and Journal of Polymer Sc
ience, A, vol.29, p697 (1992) and surface, vol.28, No.
4, p286 (1990), surface, vol. 30, No. 1, p74 (1992) and the like. Further, as a method for obtaining the organic multilayer particles, there is a method of synthesizing the organic layer particles by a multistage emulsion polymerization method. Macrolekuare as a known method
Chemie. Vol.181, p2517 (1980) and Polymer Journal,
vol.17, p179 (1985) and Journal of Coatings Tecnol
ogy, vol.60, No.776, p69 (1988), surface, vlo.25, N
O.2, p86 (1987) and Japanese Patent Publication No. 3-42312. The monomers, oligomers, and prepolymers that can be polymerized by these methods are mainly acrylic and building materials. For example, styrene, vinyl acetate, (meth) acrylic acid, methyl (meth) acrylate,
Butyl (meth) acrylate, 2-hydroxyethyl acrylate, (meth) acrylamide, divinylbenzene, (poly) ethylene glycol diacrylate, trimethylolpropane triacrylate and the like can be polymerized or copolymerized.

The average particle size of these particulate binders is
Depending on the active material used and the average particle size of the conductive material, it is about 0.01 to 100 μm, preferably about 0.1 to 50 μm.
Is. If the average particle size of the particulate binder is extremely smaller than the average particle size of the active material and conductive material used, the interconnected particulate binder coats the surface of the active material and conductive material particles, and the active material Since it impedes the doping and dedoping of ions from the solution, the conductivity (electron conductivity) inside the coating film may decrease, and the charge / discharge capacity and cycle characteristics may decrease, which is not preferable. On the other hand, if the average particle diameter of the particulate binder is excessively large, it becomes difficult for the particulate binders to adhere to each other or the particulate binder and the active material or conductive material particles, and the coating film forming ability decreases, which is not preferable.

In addition to the particulate binder, if necessary, a polyester resin, a polyamide resin, a polyacrylic acid ester resin, a polyurethane resin, a cellulose resin, a polyolefin resin, a fluororesin or other thermoplastic resin, or a wax or a surface active agent. Agents may be added to the dispersion medium, whereby the stability of the active material coating liquid, coating suitability, and
The adhesion, heat resistance, mechanical strength, etc. of the active material coating film can be improved.

The active material coating solution is prepared by a conventional dispersion method such as a homogenizer, a ball mill, a side mill, a roll mill or the like, which comprises a particulate binder, a powdery active material, water or an organic solvent such as methyl alcohol, toluene or methyl ethyl ketone. It is possible to mix and disperse a composition in which a dispersant and, if necessary, a conductive material are mixed.

The active material coating liquid thus prepared is
Gravure coat, gravure reverse coat, roll coat, Meyer bar coat, blade coat, knife coat, air knife coat, comma coat, slot die coat, slide die coat, dip coat, etc. It is applied to the metal foil current collector so as to have a thickness of 200 μm, preferably 50 to 150 μm.

The dispersion medium is removed after the active material coating liquid has been applied to the metal foil current collector, and at the same time as or after the removal of the dispersion medium, a heat treatment using a dryer, an electric furnace or the like, or an ultraviolet lamp. It is possible to obtain an active material coating film by irradiating ionizing radiation with an electron beam irradiation device, a γ-ray irradiation device or the like to generate an adhesive force between the particulate binder and the particle surface of the active material or the conductive material.

Further, in order to improve the homogeneity of the coating film, it is also preferable to obtain the electrode plate of the present invention by performing a press treatment using a metal roll, a heating roll, a sheet press machine or the like.

Further, before proceeding to a battery assembling process using this electrode plate, it is also preferable to further perform heat treatment, decompression treatment or the like in order to remove water in the electrode plate active material coating film.

A non-aqueous electrolytic solution prepared by dissolving a lithium salt in an organic solvent is used for the secondary battery constituted by the obtained electrode plate.

As the organic solvent, cyclic esters, chain esters, cyclic ethers, chain ethers, etc. are used. Specifically, as the cyclic esters, propylene carbonate, butylene carbonate, γ-butyrolactone are used. , Vinylene carbonate, 2 methyl-γ-butyrolactone, acetyl-γ-butyrolactone, γ-valerolactone, etc. As chain esters, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl butyl Carbonate, methyl propyl carbonate, ethyl butyl carbonate, ethyl propyl carbonate, butyl propyl carbonate, propionic acid alkyl ester, malonic acid dialkyl ester, acetic acid alkyl ester In addition, as cyclic ethers,
Tetrahydrofuran, alkyltetrahydrofuran, dialkylalkyltetrahydrofuran, alkoxytetrahydrofuran, dialkoxytetrahydrofuran,
1,3-dioxolane, alkyl-1,3-dioxolane, 1,4-dioxolane and the like, and as chain ethers, 1,2-dimethoxyethane, 1,2-ethoxyethane, diethyl ether, ethylene glycol dialkyl ether , Diethylene glycol dialkyl ether, triethylene glycol dialkyl ether, tetraethylene glycol dialkyl ether and the like are used.

The lithium salt includes LiClO ₄ ,
LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCl, L
Inorganic lithium salts such as iBr, and LiB (C
₆ H ₅ ) ₄ , LiN (SO ₂ CF ₃ ) ₂ , LiC (SO
_{2 CF 3) 3, LiOSO 2} CF 3, LiOSO 2 C 2
_{F 5, LiOSO 2 C 3 F} 7, LiOSO 2 C 4 F 9,
LiOSO ₂ C ₅ F ₁₁ , LiOSO ₂ C ₈ F ₁₃ , L
An organolithium salt such as iOSO ₂ C ₇ F ₁₅ is used.

[0030]

【Example】

Example 1 An active material, a conductive material and a particulate binder shown below were stirred and dispersed by a homogenizer at a rotation speed of 8000 rpm for 10 minutes to obtain a positive electrode and negative electrode active material coating liquid. In addition, unless otherwise specified, the following% is based on weight. << Cathode active material coating liquid >> Particulate binder: Polymethyl acrylate fine particles, average particle size of about 2 μm (MP-1400, Soken Chemical Co., Ltd., softening point 90 ° C.) 5% Cathode active material powder: average particle size of about 10 μm LiCoO ₂ powder 85% Conductive material powder: Graphite powder with an average particle size of about 3 μm 10% Dispersion medium: Isopropyl alcohol 30% << Negative electrode active material coating liquid >> Particulate binder: Polymethyl acrylate fine particles, average particle size about 2 μm (MP -1400, Soken Chemical Co., Ltd., softening point 90 ° C.) 10% Negative electrode active material powder: Graphite powder with an average particle size of about 3 μm 90% Dispersion medium: Isopropyl alcohol 50% Obtained positive electrode active material coating liquid, negative electrode activity The material coating liquid is dried on a current collector made of aluminum foil with a thickness of 20 μm and copper foil with a thickness of 10 μm using a slot die coater. After applying to both sides so that the thickness of the state is about 100 μm, the dispersion medium is removed by heating in an oven at 120 ° C., and at the same time, the particulate binder is softened to generate an adhesive force and thereby each positive and negative electrode plate. Got Further, this was compressed using a roller press machine to homogenize the applied coating film. Example 2 An active material, a conductive material, and a particulate binder shown below were stirred and dispersed by a homogenizer at a rotation speed of 8000 rpm for 10 minutes to obtain a positive electrode and negative electrode active material coating liquid. << Cathode active material coating liquid >> Particulate binder: Fine particles shown in Synthesis Example (1) 5% Cathode active material powder: LiCoO ₂ powder with an average particle size of about 10 μm 85% Conductive material powder: Graphite powder with an average particle size of about 3 μm 10% Dispersion medium: Isopropyl alcohol 30% Curing catalyst: Triethylamine 0.1% << Negative electrode active material coating liquid >> Particulate binder: Fine particles shown in Synthesis Example (1) 5% Negative electrode active material powder: Average particle size of about 3 μm Graphite powder 90% Dispersion medium: Isopropyl alcohol 50% Curing catalyst: Triethylamine 0.1% * Synthesis example (1) Methyl methacrylate 15%, Divinylbenzene 2%,
Glycidyl methacrylate 3% and pure water 79.5%
And 0.5% sorbitan acid monolaurate as an emulsifier
And add 1 with a homogenizer at a rotation speed of 6000 rpm.
The mixture was stirred for 0 minutes to emulsify the monomer in pure water. To this emulsion, 0.5% of potassium persulfate was added as an initiator,
Polymerization was carried out at 60 ° C. for 8 hours with stirring to obtain acrylic ester particles. The obtained particles were filtered, washed thoroughly with water, and then dried. The particles had glycidyl groups on the surface. The average particle size of the particles was about 1 μm.

The positive electrode active material coating liquid thus obtained,
Apply the negative electrode active material coating liquid to an aluminum foil with a thickness of 20 μm,
A current collector made of a copper foil having a thickness of 10 μm was coated on both sides with a slot die coater so that the dry thickness was about 100 μm, and then heated in an oven at 120 ° C. to remove the dispersion medium. At the same time, an adhesive force was generated by thermosetting the particulate binder to obtain positive and negative electrode plates, respectively. Further, this was compressed using a roller press machine to make the applied coating uniform. Example 3 The active material, conductive material and particulate binder shown below were stirred and dispersed for 10 minutes at a rotation speed of 8000 rpm by a homogenizer to obtain a positive electrode and negative electrode active material coating liquid. << Cathode active material coating liquid >> Particulate binder: (meth) acrylic acid ester-based particles having unsaturated double bonds on the surface, average particle size of about 5 μm (“Microcryl”, manufactured by Toyo Ink Mfg. Co., Ltd.) 5% Positive electrode active material powder: LiCoO ₂ powder with an average particle diameter of about 10 μm 85% Conductive material powder: Graphite powder with an average particle diameter of about 3 μm 10% Dispersion medium: Isopropyl alcohol 30% << Negative electrode active material coating liquid >> Particulate binder: on the surface (Meth) acrylic acid ester-based particles having unsaturated double bonds, average particle size of about 5 μm (“Microcryl”, manufactured by Toyo Ink Mfg. Co., Ltd.) 10% Negative electrode active material powder: Graphite powder of average particle size of about 3 μm 90% Dispersion medium: Isopropyl alcohol 50% The positive electrode active material coating liquid and the negative electrode active material coating liquid thus obtained were each made into an aluminum foil having a thickness of 20 μm, Thickness 10 μm
The current collector made of copper foil was coated on both sides with a slot die coater so that the dry thickness was about 100 μm, and the dispersion medium was removed by heating in an oven at 120 ° C. Using an electron beam irradiation device (Curetron, manufactured by Nissin High Voltage Co., Ltd.) for these
Adhesive force was generated by irradiating an electron beam of 5 Mrad from both sides with an accelerating voltage of 200 KV to react and cure the particulate binder to obtain positive and negative electrode plates. Further, the applied coating film was homogenized by compressing it using a roller press. Example 4 An active material, a conductive material, and a particulate binder shown below were stirred and dispersed by a homogenizer at a rotation speed of 8000 rpm for 10 minutes to obtain a positive electrode and negative electrode active material coating liquid. << Cathode active material coating liquid >> Particulate binder: Fine particles shown in Synthesis Example (2) 5% Cathode active material powder: LiCoO ₂ powder with an average particle size of about 10 μm 85% Conductive material powder: Graphite powder with an average particle size of about 3 μm 10% Dispersion medium: Isopropyl alcohol 30% Curing catalyst: Triethylamine 0.1% << Negative electrode active material coating liquid >> Particulate binder: Fine particles shown in Synthesis Example (2) 5% Negative electrode active material powder: Average particle size of about 3 μm Graphite powder 90% Dispersion medium: Isopropyl alcohol 50% Curing catalyst: Triethylamine 0.1% * Synthesis example (1) Macromolekuare Chemie. Vol.181, p2517 (1980), Po
lymer Journal, vol.17, p179 (1985) and Journal of C
oatings Tecnology, vol.60, No.776, p69 (1988), surface, vlo.25, No.2, p86 (1987), and Japanese Patent Publication No. 3-4231
According to the method described in JP-A-2, the following inner layer (core layer) and outer layer (shell layer) monomers were polymerized to prepare an organic multilayer particle having a two-layer structure.

Inner layer: styrene 20%, methyl methacrylate 60%, divinylbenzene 20% Outer layer: methyl methacrylate 100% The obtained particles were filtered, washed thoroughly with water, and then dried.
The average particle size of the particles was 3 μm.

The positive electrode active material coating liquid and the negative electrode active material coating liquid thus obtained were applied to a current collector made of an aluminum foil having a thickness of 20 μm and a copper foil having a thickness of 10 μm, respectively, to obtain a dry thickness of about 100 μm using a slot die coater. After being applied on both sides so as to be respectively, the dispersion medium was removed by heating in an oven at 120 ° C., and at the same time, an adhesive force was produced by softening the outer layer of the particulate binder to obtain positive and negative electrode plates. Further, these were compressed by using a roller press machine to homogenize the applied coating film. Comparative Example 90 parts by weight of LiCoO ₂ powder having an average particle size of about 10 μm, 5 parts by weight of graphite powder, 5 parts by weight of polyvinylidene fluoride resin (Neoflon VDF, manufactured by Daikin Industries, Ltd.) and 20 parts by weight of N-methylpyrrolidone were used as a homogenizer. At 8000 rpm for 10 minutes with stirring and dispersion,
A positive electrode active material coating liquid was obtained. Further, 90 parts by weight of graphite powder, 10 parts by weight of polyvinylidene fluoride resin (Neotron VDF, manufactured by Daikin Industries, Ltd.) and N-methylpyrrolidone 2
0 part by weight was stirred and dispersed under the same conditions as the positive electrode active material coating liquid to obtain a negative electrode active material coating liquid.

The positive electrode active material coating liquid and the negative electrode active material coating liquid thus obtained were respectively applied to an aluminum foil having a thickness of 20 μm and a thickness of 10 μm.
m of the copper foil current collector using a slot die coater so that the dry thickness is about 100 μm, and then dried in an oven at 200 ° C. to remove the solvent and remove the positive and negative electrode plates. Got The applied coating was homogenized by compressing this coating using a roller press.

Between the positive and negative electrode plates prepared in Examples 1 to 4 and Comparative Example, a polyolefin-based (polypropylene, polyethylene or their co-weight) having a three-dimensional pore structure (sponge-like structure) wider than the positive and negative electrode plates. The electrode plate group was formed by spirally winding it through a separator made of a microporous film (combined). Next, this electrode plate group was inserted into a cylindrical stainless steel container having a bottom and also serving as a negative electrode terminal,
A battery having an AA size and a rated capacity of 500 mAh was assembled.

As the electrolytic solution, EC (ethylene carbonate): PC (propylene carbonate): DME (dimethoxyethane) were mixed in a volume ratio of 1: 1: 2 to a total volume of 1 liter, and the mixed solvent was used as a supporting salt. 1 mol of LiPF ₆ was dissolved to prepare an electrolytic solution, and a predetermined amount of this electrolytic solution was injected into the above battery.

In the measurement of the battery characteristics, at a temperature of 25 ° C., with respect to each of 20 cells, the battery voltage becomes 4.3 V at a current value of a maximum charging current density of 1.0 mA / cm ² by a charge / discharge measuring device. The charging / discharging cycle was repeated 100 times, in which the battery was charged for 10 minutes, was discharged for 10 minutes, was then discharged at the same current value until 2.75 V, and was then stopped for 10 minutes and returned to charging again.

FIG. 1 shows an average charge / discharge curve at the end of 100 cycles of charge / discharge of batteries of 20 cells using the electrode plates obtained in Examples 1 to 4 and Comparative Example. Is shown as 100%. As is clear from FIG. 1, the charging / discharging curves of the batteries using the electrode plates obtained in Examples 1 to 4 were compared with the charging / discharging characteristics of the batteries using the electrode plates obtained in Comparative Examples. The rise of the potential immediately after discharge was small, that is, the polarization was small, and the charge / discharge capacity ratio also showed a large value of 90% or more as compared with 60% of the comparative example.

FIG. 2 shows the capacity retention rate at each cycle number, with the average value of the initial capacity being 100%, as a maintenance rate against it. The batteries formed using the electrodes manufactured in Examples 1 to 4 have a capacity retention rate of 80% or more even after 100 cycles, whereas the batteries formed using the electrodes manufactured in Comparative Examples have a capacity maintenance ratio of 20% or more. The capacity begins to decrease after about 30 cycles have passed, and is below 60% at the time of 100 cycles.

As is apparent from FIGS. 1 and 2, the electrode plate obtained according to the present invention has less polarization during charge and discharge and less decrease in capacity retention rate as compared with the electrode plate of the comparative example.

[0041]

As described above in detail, according to the electrode plate for a non-aqueous electrolyte secondary battery of the present invention, an electrode coating liquid containing an active material, a binder and a dispersion medium is used as a metal foil current collector. In an electrode plate for a non-aqueous electrolyte secondary battery having a coating film obtained by coating the surface thereof, the coating film contains the binder and an active material bound by the binder. Therefore, it is possible to prevent a decrease in conductivity (electron conductivity) inside the coating film and a decrease in capacity retention rate during charge / discharge cycles.

[Brief description of drawings]

FIG. 1 is a graph showing charge / discharge curves (average) of batteries using the electrode plates of Examples 1 to 4 and Comparative Example.

FIG. 2 is a graph showing a capacity retention rate (average) of batteries using the electrode plates of Examples 1 to 4 and Comparative Example.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuru Tsuchiya 1-1-1, Tanikaga-cho, Shinjuku-ku, Tokyo Dai Nippon Printing Co., Ltd. Pile production 23-6 Furukawa Battery Co., Ltd. Iwaki Plant (72) Inventor Toru Mangahara Joban Shimo-Funao-cho, Iwaki City, Fukushima Prefecture 23-6 Furukawa Battery Co., Ltd. Iwaki Plant

Claims (7)

[Claims] 1. An electrode plate for a non-aqueous electrolyte secondary battery, which has a coating film formed by coating a coating liquid for an electrode containing an active material, a binder and a dispersion medium on the surface of a metal foil current collector. An electrode plate for a non-aqueous electrolyte secondary battery, wherein the film forms a wake-like structure containing the binder and the active material bound by the binder. 2. A step of preparing an electrode coating solution by kneading an active material, a granular binder and a dispersion medium, wherein the electrode coating solution is applied to a metal foil current collector in a state where the granular binder is dispersed in a particulate form. A coating film forming step, a step of removing the dispersion medium contained in the coating film, and a step of subjecting the coating film to heat or ionizing radiation irradiation, simultaneously with or after the removing step. A method of manufacturing an electrode plate for a non-aqueous electrolyte secondary battery, comprising: 3. The method of claim 2, wherein the particulate binder is thermoplastic. 4. The method of claim 2, wherein the particulate binder is thermosetting. 5. The method of claim 2, wherein the particulate binder is ionizing radiation curable. 6. The method of claim 2, wherein the particulate binder is a multilayer structure composed of a core material and a shell material. 7. The granular binder is about 0.01-100.
μm, preferably about 0.1-50 μm,
The method according to claim 2.