JPH10106540A - Lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high capacity lithium ion secondary battery in which the lithium ion permeation between an active material in a mixture material film and an electrolytic solution is enhanced. SOLUTION: A sheet-form electrode for use in a lithium secondary battery is made from a mixture material film which is prepared by binding active material particles 1 onto a conductive base using a polymer binder 2 and a high-polymer solid electrolyte 3. Favorable examples of the polymer binder 2 of meshing structure are polybinylidene fluoride or polytetrafluoroethylene, while preferable examples of the resin as a parent material for high-polymer solid electrolyte 3 are polyethylene glycol or polyethylene oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery having improved capacity by increasing the permeability of lithium ions between an active material in a mixture film and an electrolyte. Related to secondary batteries.

[0002]

2. Description of the Related Art In general, a sheet-like electrode obtained by applying a coating material in which an active material or a binder is dispersed in an organic solvent to a conductive substrate made of a metal foil or the like and drying it to form a mixture film is used. A spiral electrode body is produced by spirally winding the separator together with the separator, and the spiral electrode body is inserted into the battery case.
A lithium secondary battery manufactured by injecting and sealing an organic solvent-based electrolyte is characterized by a high energy density per unit capacity and a high energy density per unit weight.

[0003]

However, the active material contained in the mixture film is doped and undoped with lithium ions during charging and discharging through an electrolyte that has penetrated into the voids in the mixture film. If the binder covers the active material particles, the permeation of lithium ions into the active material is impaired, and the battery characteristics deteriorate. In addition, even if there are fine gaps on the surface of the active material particles covered with the binder, a sufficient amount of the electrolyte cannot penetrate into the gaps, so that the permeation of lithium ions is hindered and battery characteristics deteriorate. .

[0004] Therefore, if the amount of the binder to be added is reduced to increase the gap between the particle surfaces of the active material, the strength of the mixture film is reduced, and the active material and the electron are recharged while the battery is repeatedly charged and discharged. Adhesion between the conductive aid and the conductive substrate gradually decreases, and in this case, battery characteristics deteriorate due to a decrease in electron conductivity.

Accordingly, the present invention solves the above-mentioned problems in the conventional lithium secondary battery and allows a sufficient amount of lithium ions to pass between the active material in the mixture film and the electrolyte. Accordingly, an object of the present invention is to provide a high-capacity lithium secondary battery by preventing a decrease in battery characteristics.

[0006]

Means for Solving the Problems The present invention has been made as a result of conducting various studies in order to achieve the above-mentioned objects, and comprises the steps of forming active material particles by using a polymer binder having a network structure and a polymer solid electrolyte. To form a mixture film, thereby increasing the permeability of lithium ions between the active material and the electrolyte in the mixture film, preventing a decrease in battery characteristics due to the binder, and providing a high capacity. It is intended to obtain a lithium secondary battery.

The structure of the mixture film of the present invention will be described with reference to the drawings. As shown in FIG. 1, active material particles 1 are connected to adjacent active material particles 1 by a polymer binder 2 having a network structure. At the same time, the surface of the active material particles 1 is covered with a polymer binder 2 forming the network structure and a polymer solid electrolyte 3 arranged so as to fill gaps in the network. The gap of the mixture film is filled with an electrolyte (not shown).

In the thus-formed composite film, a sufficient amount of lithium ions permeate the polymer solid electrolyte 3 to allow the active material particles 1 in the composite film and the electrolyte outside the composite film to pass through. , The deterioration of battery characteristics due to the binder is prevented.

In addition, the active material particles 1 are bound by the polymer binder 2 having a network structure, and the solid polymer electrolyte 3 also functions as a binder. Even if charge and discharge are repeated, the adhesion between particles and the adhesion between the mixture film and the conductive substrate are maintained, and the electron conductivity between particles is also maintained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, examples of a polymer binder having a network structure include those which form a network bond as described below. For example, when polyvinylidene fluoride and solid particles are mixed and dispersed so as to give a shearing stress, preferably in the presence of a solvent, the polyvinylidene fluoride is entangled with the solid particles in a fibrous form to form a network-like bond.

In the present invention, the binder which is entangled with the solid particles and forms a network bond is referred to as a polymer binder having a network structure. Suitable examples of the polymer binder having such a network structure include a fluorine-based resin such as polytetrafluoroethylene and a tetrafluoroethylene-hexafluoropropylene copolymer in addition to the polyvinylidene fluoride described above.

Further, as the polymer binder having a network structure in the present invention, those which form a network bond as described below are also exemplified. When a dispersion liquid in which spherical rubber particles of the order of submicrons are dispersed in an aqueous solution and solid particles are mixed and the mixture is dried, a network-like bond including a large number of fine gaps is formed. Such rubber dispersion liquids include styrene-butadiene rubber latex, carboxy-modified styrene-
Preferred examples include butadiene rubber latex.

The solid polymer electrolyte used in the present invention comprises a resin in which lithium ions are contained.
Examples of the resin serving as a matrix of such a solid polymer electrolyte include polyethylene glycol, polyethylene oxide, polypropylene oxide, a crosslinked isocyanate of polyethylene oxide, a crosslinked isocyanate of polypropylene oxide, and a copolymer of ethylene oxide and propylene oxide. And mixtures thereof.

In a typical polymer electrolyte battery, a polymer solid electrolyte is prepared by mixing a lithium salt with the above resin. In the present invention, however, the above-mentioned organic solvent-based electrolyte is used. In addition to the case where the polymer solid electrolyte is prepared in advance as described above, the electrode is manufactured using only the resin, the battery is assembled, and the voltage is applied, so that the lithium ions in the electrolyte enter the resin and It is thought that it can be a solid electrolyte.

If the lithium ion conductivity of the above-mentioned solid polymer electrolyte is too low, the battery characteristics may be degraded.
At 3 ° C., 3 × 10 ⁻⁸ S · cm ⁻¹ or more, especially 1 × 10
It is preferably at least ⁻⁷ S · cm ⁻¹ .

In order to increase the lithium ion conductivity of the solid polymer electrolyte, a lithium electrolyte salt may be added in advance. Such lithium electrolyte salts include, for example, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAs
F ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiC ₄ F ₉ SO and the like are suitable. However, even when the polymer solid electrolyte is prepared in advance outside the battery, even when the electrode is made using only the resin as described above and the polymer solid electrolyte is formed inside the battery, the lithium ion conductivity does not change significantly. It is considered something.

In the production of the sheet electrode of the present invention, when a polymer binder having a network structure dissolved in the same kind of solvent and a polymer solid electrolyte are used in combination, binding between solid particles such as an active material is performed. Can be further strengthened, and more favorable results can be obtained.

As a method for producing a sheet-like electrode according to the present invention, for example, active material particles and the like are mixed with polyvinylidene fluoride and the like while applying a shearing stress in the presence of a solvent such as N-methylpyrrolidone and dimethylacetamide. After dispersion, the mixture is mixed with a polyethylene oxide powder and a suitable solvent such as N-methylpyrrolidone and dimethylacetamide, and further mixed to form a coating. Alternatively, while mixing solid particles such as an active material, rubber latex, and polyethylene oxide powder, a suitable solvent such as alcohol, N-methylpyrrolidone, or water is added little by little and mixed to form a paint. Then, the paint is applied on a conductive substrate such as a metal foil and dried to form a mixture film.

The ratio of the polymer binder having the network structure to the solid polymer electrolyte is not particularly limited, but is 2:98 to 98: 2, preferably 5:95 by weight.
~ 95: 5 is preferred. If the proportion of the polymer solid electrolyte is less than the above range, the conductivity of lithium ions will not be sufficiently high, and if the proportion of the polymer solid electrolyte is greater than the above range, the solid binder between the solid particles due to the network binder There is a possibility that a sufficient binding force cannot be obtained.

The amount of addition of the polymer binder and the solid polymer electrolyte having the network structure is about 1 to 30 parts by weight in 100 parts by weight of each of the positive electrode mixture and the negative electrode mixture. It is preferable to do so.

The mixture film in which the active material particles of the present invention are bound by a polymer binder having a network structure and a solid polymer electrolyte can be applied to the production of both positive and negative electrodes. The types of the polymer binder and the solid polymer electrolyte having a network structure used for these may be the same for the positive electrode and the negative electrode, or may be different depending on the respective compositions of the positive electrode and the negative electrode. good.

In the present invention, as the active material, for example, a lithium-containing composite metal oxide, a material capable of doping / undoping lithium ions, or the like can be used.

Examples of the lithium-containing composite metal oxide include lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide and the like. These may be used alone or as a mixture of two or more kinds, or as a solid solution thereof. This lithium-containing composite metal oxide is particularly suitable for use as a positive electrode active material.

As the substance capable of doping and undoping lithium ions, for example, lithium metal or a lithium-containing compound is used. Examples of the lithium-containing compound include a lithium alloy and other substances. Examples of the lithium alloy include alloys of lithium and other metals such as lithium-aluminum, lithium-lead, lithium-bismuth, lithium-indium, lithium-gallium, and lithium-indium-gallium. Examples of the lithium-containing compound other than the lithium alloy include a carbon material having a turbostratic structure, graphite, and the like. Some of them do not contain lithium at the time of manufacture, but when they act as an active material, they become lithium-containing by chemical means, electrochemical means, or the like.

The substance capable of being doped with or undoped with lithium ions can be used as both a positive electrode active material and a negative electrode active material, and is particularly suitable for use as a negative electrode active material.

In preparing the positive electrode, an electron conduction aid such as flake graphite and carbon black can be added to the positive electrode active material, if necessary. Also,
In the production of the negative electrode, as in the case of the positive electrode, if necessary, an electron conduction aid such as flaky graphite and carbon black can be added to the negative electrode active material.

In the present invention, as a coating method for forming a mixture film, any coating method such as an extrusion coater, a reverse roller and a doctor blade can be adopted.

In the present invention, as the conductive substrate of the sheet electrode, for example, a metal conductive material such as aluminum, stainless steel, titanium, copper, etc.
Foam metal and foil processed and formed into a plate shape are used.

In the present invention, the sheet-like electrode having a mixture film formed by binding active material particles with a polymer binder having a network structure and a solid polymer electrolyte is applied to both a positive electrode and a negative electrode. Although it is preferable to apply to both the positive electrode and the negative electrode, the present invention may be applied to only one of the positive electrode and the negative electrode. Further, in assembling a battery, the above-mentioned sheet electrode is usually spirally wound together with a separator, and inserted into a battery case as a spiral electrode body.

Examples of the electrolytic solution include 1,2-dimethoxyethane, 1,2-diethoxyethane, propylene carbonate, ethylene carbonate, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolan, diethyl carbonate, dimethyl carbonate, ethyl In a single solvent such as methyl carbonate or a mixed solvent of two or more kinds, for example, LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ ,
An organic solvent-based electrolyte prepared by dissolving an electrolyte such as LiClO ₄ , LiPF ₆ , or LiBF ₄ alone or by dissolving two or more of them is used.

As the separator, for example, a thickness of 10
A microporous polypropylene film or a microporous polyethylene film having a pore size of 50 μm and a porosity of 30 to 70% is preferably used.

The battery includes, for example, a spirally wound electrode body manufactured by spirally winding a sheet-shaped positive electrode and a sheet-shaped negative electrode manufactured as described above with a separator interposed therebetween.
It is inserted into a nickel-plated iron or stainless steel battery case, injected with an electrolytic solution, and then sealed. Further, the battery usually incorporates an explosion-proof mechanism for discharging the gas generated inside the battery to the outside of the battery when the pressure has risen to a certain pressure, thereby preventing the battery from bursting under high pressure.

[0033]

Next, an embodiment of the present invention will be described.
However, the present invention is not limited to only these examples. In the examples below,% indicating the concentration and the like is% by weight.

Example 1 (1) Preparation of Positive Electrode The preparation of the positive electrode will be described in the order of synthesis of lithium nickel oxide used as a positive electrode active material and formation of a mixture film.

Synthesis of Lithium Nickel Oxide Lithium hydroxide (LiOH.H ₂ O) and nickel oxide (III) (Ni ₂ O ₃ ) are subjected to a heat treatment to produce lithium nickel oxide (generally represented by LiNiO ₂ . Li and Ni
Is slightly deviated from the stoichiometric composition).
This synthesis was performed as follows.

Lithium hydroxide and nickel oxide are converted to Li /
After weighing so that Ni = 1 / 1.05 (molar ratio), the mixture was pulverized and mixed in an agate mortar. This was preheated in an oxygen (O ₂ ) stream at 500 ° C. for 2 hours, then heated to 700 ° C. at a heating rate of 50 ° C./h or less, and then heated at 700 ° C. for 20 hours and fired.
Since the synthesized lithium nickel oxide is weak against moisture, handling such as pulverization was performed in an argon gas atmosphere.

Formation of Mixture Film The lithium nickel oxide synthesized above, flaky graphite as an electron conduction aid, polyvinylidene fluoride as a polymer binder, and polyethylene oxide as a resin serving as a matrix of a polymer solid electrolyte were prepared as follows. A paint containing the proportions was prepared.

Lithium nickel oxide 90 parts by weight Flake graphite 6 parts by weight Polyvinylidene fluoride 3.2 parts by weight Polyethylene oxide 0.8 parts by weight

In preparing this paint, first, polyvinylidene fluoride was dissolved in N-methylpyrrolidone in advance to prepare a solution having a concentration of 12%, and the above-mentioned lithium nickel oxide, flaky graphite and polyethylene oxide powder were added to After mixing and stirring at a temperature of 60 ° C. while adding N-methylpyrrolidone so that the coating viscosity becomes 6000 mPa · s, the above-mentioned 12% N-
By adding a methylpyrrolidone solution and further stirring, a coating material for forming a positive electrode mixture film was prepared. Then, this paint is applied on an aluminum foil having a thickness of 20 μm and dried to form a mixture film. Similarly, the above paint is applied to the back side of the aluminum foil and dried to form a mixture film. Then, roll pressing was performed to produce a sheet-shaped positive electrode having a total thickness of 220 μm. The polyethylene oxide forms a matrix of the polymer solid electrolyte by applying a voltage after assembling the battery. This polymer solid electrolyte has a lithium ion conductivity at 25 ° C. of about 1 × 10 ⁻⁷ S · cm ^−1. become.

(2) Preparation of Negative Electrode First, artificial graphite (synthesized at 2800 ° C.) as an active material for negative electrode, polyvinylidene fluoride as a polymer binder, and polyethylene oxide as a resin serving as a matrix of a polymer solid electrolyte were prepared in the following proportions. Was prepared.

Artificial graphite (synthesized at 2800 ° C.) 90 parts by weight Polyvinylidene fluoride 8 parts by weight Polyethylene oxide 2 parts by weight

The paint was prepared in the same manner as the above-mentioned paint for forming a mixture film of the positive electrode.
m, coated on both sides of the copper foil in the same manner as when forming the mixture film of the positive electrode, dried to form a mixture film, and then roll-pressed to produce a 250-μm-thick sheet-shaped negative electrode did.
The coating density was adjusted so that the weight ratio of the active materials of the positive electrode and the negative electrode was 2: 1.

(3) Preparation of electrolyte solution LiPF ₆ was added to a mixed solvent of ethylene carbonate and ethyl methyl carbonate (mixing ratio was 1: 1 by volume).
The resulting solution was dissolved in mol / l to prepare an organic solvent-based electrolytic solution.

(4) Assembly of Cylindrical Battery The above sheet-shaped positive electrode was cut into a band having a width of 28 × 220 mm and the sheet-shaped negative electrode was cut into a band having a width of 30 × 260 mm. Then, a part of the coating film at the end of each sheet-like electrode was peeled off, and a lead made of aluminum was resistance-welded to a portion where the metal foil was exposed. A strip-shaped separator made of a porous polypropylene film is interposed between the sheet-shaped positive electrode and the sheet-shaped negative electrode and spirally wound to produce a spirally wound electrode body, and the spirally wound electrode body is made of a stainless steel battery case. Inserted in.

Then, the tip of the lead body on the negative electrode side is welded to the bottom of the battery case by penetrating the insulator, and the insulator is inserted into the opening of the battery case to form a groove. The lead body on the positive electrode side was welded. Then, after the can body manufactured through such a process is vacuum-dried at 60 ° C. for 10 hours, 2 ml of an electrolyte is injected in a dry atmosphere, sealed, and sealed to form a cylindrical R5 battery (FIG. 2). Outer diameter: 1
4.95 mm, height: 39.7 mm).

The battery shown in FIG.
Is a positive electrode, and 12 is a negative electrode. However, FIG. 2 does not show a metal foil or the like as a conductive substrate used for manufacturing the positive electrode 11 or the negative electrode 12 in order to avoid complication. Reference numeral 13 denotes a separator, and reference numeral 14 denotes an electrolytic solution.

Reference numeral 15 denotes a battery case made of stainless steel, and this battery case 15 also serves as a negative electrode terminal. An insulator 16 made of a polytetrafluoroethylene sheet is arranged at the bottom of the battery case 15, and an insulator 17 made of a polytetrafluoroethylene sheet is also arranged at the inner periphery of the battery case 15. The spiral electrode body composed of the negative electrode 12 and the separator 13 and the electrolyte 1
4 and the like are housed in the battery case 15.

Reference numeral 18 denotes a sealing plate made of stainless steel, and a gas vent 18a is provided in the center of the sealing plate 18. 19 is a circular packing made of polypropylene, 2
Reference numeral 0 denotes a flexible thin plate made of titanium, and reference numeral 21 denotes an annular, thermally deformable member made of polypropylene.

The above-mentioned heat-deformable member 21 has an effect of changing the breaking pressure of the flexible thin plate 20 by being deformed by the temperature.

Reference numeral 22 denotes a nickel-plated terminal plate made of rolled steel. The terminal plate 22 is provided with a cutting blade 22a and a gas exhaust hole 22b. When the internal pressure rises and the flexible thin plate 20 is deformed by the increase in the internal pressure, the flexible thin plate 20 is broken by the cutting blade 22a, and gas inside the battery is discharged from the gas discharge hole 22b to the outside of the battery. In addition, the battery is designed so as to prevent the battery from being destroyed under high pressure.

Reference numeral 23 denotes an insulator, 24 denotes an aluminum lead, and the lead 24 electrically connects the positive electrode 11 and the sealing plate 18.
8 acts as a positive electrode terminal. Reference numeral 25 denotes a lead body for electrically connecting the negative electrode 12 and the battery case 15.

Example 2 In place of polyvinylidene fluoride in the material for forming a mixture film of the positive electrode and the negative electrode in Example 1, carboxy-modified styrene-
Using a butadiene rubber latex, a 60% aqueous dispersion of the carboxy-modified styrene-butadiene rubber was added in place of the 12% N-methylpyrrolidone solution of polyvinylidene fluoride in the preparation of the paint, and a roll press was performed. The R5 type battery was produced in the same manner as in Example 1 except that the pressure was changed from 23 kg / cm ³ to 15 kg / cm ³ .

Example 3 Polytetrafluoroethylene was used in place of polyvinylidene fluoride in the material for forming a mixture film of the positive electrode and the negative electrode in Example 1, and 12% N-methylpyrrolidone of polyvinylidene fluoride was used for preparing a coating material. Instead of the solution, a 60% aqueous dispersion of polytetrafluoroethylene was added and the pressure of the roll press was increased to 23 kg /
Besides changing from cm ³ to 15 kg / cm ³ was prepared R5 form batteries in the same manner as in Example 1.

Example 4 In the material for forming a mixture film of the positive electrode in Example 1, 3.2% of polyvinylidene fluoride was changed to 3.6%, and 0.8% of polyethylene oxide was changed to 0.4%. Then, an R5 type battery was fabricated in the same manner as in Example 1, except that 8% of polyvinylidene fluoride in the material for forming a mixture film of the negative electrode was changed to 8% and 2% of polyethylene oxide was changed to 1%. did.

Example 5 In the material for forming a mixture film of the positive electrode in Example 1, 3.2% of polyvinylidene fluoride was changed to 3.8%, and 0.8% of polyethylene oxide was changed to 0.2%. In the same manner as in Example 1, except that 8% of polyvinylidene fluoride in the material for forming a mixture film of the negative electrode was changed to 9.5% and 2% of polyethylene oxide was changed to 0.5%. A battery was fabricated.

Comparative Example 1 In the material for forming a mixture film of the positive electrode in Example 1, 3.2% of polyvinylidene fluoride was changed to 4%, and 0.8% of polyethylene oxide was changed to 0% (that is, Polyethylene oxide was not used), 8% of polyvinylidene fluoride in the material for forming a mixture film of the negative electrode was changed to 10%, and 2% of polyethylene oxide was changed to 0% (that is,
An R5-type battery was fabricated in the same manner as in Example 1 except that polyethylene oxide was not used.

Comparative Example 2 3.2% of latex of carboxy-modified styrene-butadiene rubber in the material for forming a mixture film of a positive electrode in Example 2 was added to 4%.
To 0.8% and polyethylene oxide 0.8% to 0%
(That is, polyethylene oxide is not used), the latex of carboxy-modified styrene-butadiene rubber in the material for forming a mixture film of the negative electrode was changed from 8% to 10%, and the polyethylene oxide from 2% to 0%. (I.e. did not use polyethylene oxide)
Otherwise, the procedure of Example 2 was repeated to fabricate an R5 battery.
In addition, the above-mentioned latex concentrations are all concentrations as solids.

Comparative Example 3 In the material for forming a mixture film of the positive electrode of Example 3, 3.2% of polyvinylidene fluoride was changed to 4%, and 0.8% of polyethylene oxide was changed to 0% (that is, Polyethylene oxide was not used), 8% of polyvinylidene fluoride in the material for forming a mixture film of the negative electrode was changed to 10%, and 2% of polyethylene oxide was changed to 0% (that is,
An R5 type battery was fabricated in the same manner as in Example 3, except that polyethylene oxide was not used.

The batteries of Examples 1 to 5 and Comparative Examples 1 to 3 produced as described above were subjected to the following charge / discharge tests, and the capacities were measured.

Method of Measuring Charge / Discharge Capacity When the charge / discharge current was indicated by C, charge / discharge was performed with R5 type at 560 mA of 1C. Charging was performed at a constant voltage of 4.2 V provided with a current limiting circuit of 1 C, and discharging was performed until the voltage between the electrodes of the battery dropped to 2.75 V. The discharge capacity of the battery manufactured in Comparative Example 1 was set to 100%, and the respective battery capacities were compared. The results are shown in Table 1 and Table 2 by "% by volume".

In Tables 1 and 2, polymer binders having a network structure are simplified and referred to as "network binders", and the specific examples are indicated by abbreviations. The relationship between the abbreviation and the name of the polymer binder forming the network structure is as follows. In addition, the resin that is the base of the solid polymer electrolyte is also indicated by an abbreviation. The relationship between the abbreviation and the name of the resin that is the parent of the polymer solid electrolyte is also as follows. Further, Table 1 concerning Examples 1 to 5 also shows the polymer ratio (weight ratio) of the binder. The polymer ratio of the binder means a ratio (weight ratio) between a network binder (that is, a polymer binder having a network structure) and a resin serving as a matrix of the solid polymer electrolyte. In Tables 1 and 2, the resin that is the base of the solid polymer electrolyte is simplified and indicated as “polymer solid electrolyte”.

Name of polymer binder forming network structure: PVdF: polyvinylidene fluoride XSBR: carboxy-modified styrene-butadiene rubber PTFE: polytetrafluoroethylene

Name of resin to be the base of solid polymer electrolyte: PEO: polyethylene oxide

FIG. 3 shows Examples 1, 4 and 5 using polyvinylidene fluoride as a polymer binder having a network structure and a solid polymer electrolyte using polyethylene oxide as a base resin. Regarding Comparative Example 1 in which no polymer solid electrolyte was used, the polymer ratio of the binder [PEO (polyethylene oxide) / P
VdF (polyvinylidene fluoride) (weight ratio)].

[0065]

[Table 1]

[0066]

[Table 2]

As is clear from the comparison between the capacities (%) of the batteries of Examples 1 to 5 shown in Table 1 and the capacities (%) of the batteries of Comparative Examples 1 to 3 shown in Table 2, The battery of (1) had a larger capacity (%) and a higher capacity than the batteries of Comparative Examples 1 to 3.

Also in FIG. 3, the batteries of Examples 1 and 4 using polyvinylidene fluoride as a polymer binder having a network structure, and a solid polymer electrolyte using polyethylene oxide as a base resin were used. It was revealed that the battery of Example 5 had a larger capacity (%) and a higher capacity than the battery of Comparative Example 1 not using the solid polymer electrolyte.

[0069]

As described above, according to the present invention, a sheet formed by forming a mixture film in which active material particles are bound on a conductive substrate by a polymer binder having a network structure and a polymer solid electrolyte. By using the shape electrode, a high capacity lithium secondary battery could be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a main part of a mixture film in which active material particles of the present invention are bound by a polymer binder having a network structure and a polymer solid electrolyte.

FIG. 2 is a cross-sectional view schematically showing one example of the lithium secondary battery of the present invention.

FIG. 3 is a diagram showing the difference in capacity (%) between the battery of Example 1, the battery of Example 4, the battery of Example 5, and the battery of Comparative Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Active material particle 2 Polymer binder which forms network structure 3 Polymer solid electrolyte 11 Positive electrode 12 Negative electrode 13 Separator 14 Electrolyte

Claims (1)

[Claims] 1. A sheet-like electrode comprising a mixture film formed by binding active material particles with a polymer binder having a network structure and a solid polymer electrolyte on a conductive substrate. Rechargeable lithium battery.