JPH07296802A - Manufacture of lithium secondary battery electrode, and lithium secondary battery - Google Patents

Abstract

PURPOSE:To improve the binding property of a collector to an electrode layer which is capable of storing and releasing lithium and to enhance the cycle characteristic of a battery by forming the electrode layer after the application and drying of a silane coupling agent. CONSTITUTION:A sheet of conductor that is electrochemically stable against cathode and anode active materials and nonaqueous solutions is used as a collector, and the conductor material used is e.g. nickel, titanium, stainless steel, copper, or aluminum. A solution obtained when a silane coupling agent is partially or entirely hydrolyzed by reaction with water is applied to the collector surface and dried. In this case, the concentration of the silane coupling agent solution is about 0.01 to 5wt%. Prior to the application of the silane coupling agent, the collector surface is roughened in advance. The anode or cathode then becomes excellent in the binding property of its collector to its electrode layer which is capable of storing and releasing lithium, and the cycle characteristic of the battery can be enhanced without reduction in battery capacity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sheet electrode for a lithium secondary battery and a lithium secondary battery using the electrode obtained by the method.

[0002]

2. Description of the Related Art An electrode for a lithium secondary battery capable of inserting and extracting lithium is, for example, a positive electrode during charging in the case of a battery structure using an electrode containing lithium cobalt oxide in the positive electrode and an electrode containing a carbon material in the negative electrode. This utilizes an electrochemical reversible reaction in which lithium in the negative electrode is occluded in the negative electrode via the electrolytic solution, and during discharge, lithium in the negative electrode is released and occluded in the positive electrode via the electrolytic solution. The characteristics required for this electrode are that the capacity (capacity) and capacity (capacity) of lithium to be stored in the electrode are large, and that capacity deterioration during the storage / release cycle is small.

From this point of view, various proposals have been made for electrodes or batteries using a carbon material capable of inserting and extracting lithium. Specifically, as a negative electrode material, a battery using a graphite negative electrode in which lithium capable of charging and discharging is mixed in a crystal (Japanese Patent Laid-Open No. 57-208079) and a graphite material composed of easily graphitizable spherical particles are used as the negative electrode. (Japanese Patent Application Laid-Open No. 4-115457), a battery using a carbon material having a pseudo-graphite structure obtained by carbonizing an organic polymer compound or the like as a negative electrode (Japanese Patent Application Laid-Open No. 62-122066), and a specific structure. A battery using a carbon material for the negative electrode (Japanese Patent Laid-Open No. 62-9
No. 0863), a battery using a carbon material having a turbostratic structure as a negative electrode (Japanese Patent Laid-Open No. 2-66856) such as a battery using a wide range of carbon materials from a graphite material to a turbostratic carbon material as a negative electrode. ing. As the positive electrode material,
A battery using a carbon material having a specific structure obtained by carbonizing a metal chalcogen compound or an organic polymer compound (Japanese Patent Laid-Open No. 62-12).
2066), in addition to alkali metals and transition metals
A battery (Japanese Patent Laid-Open No. 62-90863) using a composite oxide in which 1, In, Sn, etc. are mixed has been proposed.

[0004]

As a result of experiments and studies using a wide range of carbon powders for electrodes, the present inventors have found that when forming a sheet-like electrode shape, an electrode layer containing a current collector, a carbon material, and a binder was used. Insufficient binding property causes peeling.
It has been found that it is difficult to form a sheet and it is difficult to form a battery as it is. It was also found that the battery using the sheet electrode having insufficient binding property has insufficient cycleability.

Further, in a battery using a sheet-shaped electrode having insufficient binding property, the mixed electrode layer repeatedly expands and contracts due to charge and discharge, and finally peels off from the current collector and is lost, resulting in charge and discharge. They have found a problem that they are not involved, that is, the amount of lithium that can be charged and discharged is reduced, resulting in a decrease in capacity and cycle deterioration.

The object of the present invention is to obtain a sheet-shaped negative electrode and a positive electrode for a lithium secondary battery, which are excellent in binding property between a current collector and an electrode layer capable of inserting and extracting lithium, and a method for obtaining the same. An object of the present invention is to provide a lithium secondary battery that uses electrodes and has excellent cycle characteristics.

[0007]

Means for Solving the Problems As a result of intensive investigations, the present inventors have found that an electrode layer is formed after applying a silane coupling agent and drying, and thereby forming a current collector and a mixed electrode layer. It was found that the binding property with can be greatly improved, and the present invention has been completed.

That is, the present invention comprises the following inventions. (1) In a method for producing a sheet-shaped negative electrode for a lithium secondary battery, in which an electrode layer containing a carbon powder capable of inserting and extracting lithium and a binder is formed on the current collector, before forming the electrode layer, the current collector A method for producing a sheet-shaped negative electrode for a lithium secondary battery, which comprises a step of applying a silane coupling agent on the surface and drying. (2) In a method for producing a sheet-shaped negative electrode for a lithium secondary battery, in which an electrode layer containing a carbon powder capable of inserting and extracting lithium and a binder is formed on the current collector, the current collector is formed before the electrode layer is formed. A method for producing a sheet negative electrode for a lithium secondary battery, comprising the steps of roughening the surface, then applying a silane coupling agent to the surface, and drying.

(3) In a method for producing a sheet-shaped positive electrode for a lithium secondary battery, in which an electrode layer containing a compound capable of inserting and extracting lithium, a conductive material and a binder is formed on a current collector, before forming the electrode layer And a step of applying a silane coupling agent to the surface of the current collector and drying the same, the method for producing a sheet-shaped positive electrode for a lithium secondary battery. (4) In a method for producing a sheet-shaped positive electrode for a lithium secondary battery, which comprises forming an electrode layer containing a compound capable of inserting and extracting lithium, a conductive material and a binder on a current collector, before forming the electrode layer, A method for producing a sheet-shaped positive electrode for a lithium secondary battery, comprising the steps of roughening the surface of an electric body, then applying a silane coupling agent to the surface, and drying the surface. (5) In a lithium secondary battery comprising a positive electrode capable of inserting and extracting lithium, a negative electrode and a non-aqueous electrolyte solution, at least one of the electrodes was obtained by the production method described in (1) or (2). A lithium secondary battery, which is a sheet-shaped negative electrode or a sheet-shaped positive electrode obtained by the manufacturing method according to (3) or (4).

The present invention will be described in detail below. As the current collector used in the present invention, a positive electrode / negative electrode active material and a sheet-shaped conductor that is electrochemically stable with respect to the non-aqueous electrolyte can be used. Examples of the sheet-shaped conductor include nickel, titanium, stainless steel, copper, aluminum and the like. The shape may be a sheet shape, for example, a foil shape, and usually the film thickness is 5 μm to 5 μm.
It is preferably about 0 μm.

The carbon powder used in the method for producing a sheet-shaped negative electrode for a lithium secondary battery of the present invention (hereinafter, sometimes referred to as the first invention) absorbs lithium by charging and discharging.
Any material that can be released, such as natural graphite, artificial graphite, coke, carbon black, vapor grown carbon, carbon fiber,
Examples thereof include a material obtained by carbonizing an organic polymer compound, or a material obtained by heat-treating or mixing these. Particularly, as the carbon powder for the negative electrode, those close to the lithium potential are preferable,
A carbon powder containing graphite as a single component or a main component is preferable. Further, the graphite used in the first invention is preferably graphite having a lattice spacing d ₀₀₂ in X-ray diffraction of 3.4 angstroms or less and a true specific gravity of 2.2 or more. here,
The lattice spacing d ₀₀₂ uses CuKα rays as X-rays,
It means a value measured by an X-ray diffraction method [Shiro Otani, carbon fiber, P733-742 (1986) Modern Editing Company] using high-purity silicon as a standard substance. The particle size of the carbon powder used in the first invention is not particularly limited,
Usually, those having a number average particle size of about 10 nm to 50 μm are preferable. The binder used in the first invention has a binding effect of binding the powders to each other, and may be one having resistance to the potential of the non-aqueous electrolyte used or the positive electrode or the negative electrode, for example, fluororesin powder or polyethylene powder. And so on. The amount of the binder is preferably about 0.1 to 20 parts by weight with respect to 100 parts by weight of the total amount of powder used.

The compound capable of inserting and extracting lithium used in the method for producing a sheet-like positive electrode for a lithium secondary battery of the present invention (hereinafter sometimes referred to as the second invention) is:
Transition metal oxides, composite oxides of lithium and transition metals,
Examples include transition metal sulfides. Here, examples of the transition metal include Co, Ni, Mn, and Fe. Specifically, transition metal oxide powders such as MnO ₂ , MoO ₃ , V ₂ O ₅ , and TiO ₂ , composite oxide powders of lithium and transition metals such as lithium nickel oxide and lithium cobalt oxide, TiS ₂ , FeS. And transition metal sulfide powders. The conductive material used in the second invention is not particularly limited as long as it can impart conductivity by mixing an appropriate amount with a compound powder capable of inserting and extracting lithium, acetylene black, carbon black, carbon powder such as graphite, and the like, Examples thereof include metal powders that are stable at the electrode potential used. The binder used in the second invention may be the same as that used in the first invention.

The silane coupling agent used in the first and second inventions preferably has a chemical structure of YRSiX ₃ . Here, X is -OR or -OC.
OR (however, R is a lower alkyl group), a chlorine atom etc. are mentioned, and Y is an epoxy group, an amino group, a vinyl group, a mercapto group, a chlorine atom etc. are mentioned.

Specifically as X, -OCH₃, -OC
₂H_Five, -OCOCH₃, -OC₂H_FourOCH₃, -N
(CH₃)₂, -Cl and the like. Also, Y
Specifically, CH₂= CH-, CH₂= C (CH
₃) COOC ₃H₆-, NH₂C₃H₆-, NH₂C₂
H_FourNHC₃H₆-, NH₂COCHC₃H₆-, CH
₃COOC₂H_FourNHC₂H_FourNHC₃H₆-, NH₂
C₂H _FourNHC₂H_FourNHC₃H₆-, SHC₃H
₆-, ClC₃H₆-, CH₃-, C₂H_Five-, C₂H
_FiveOCONHC₃H₆-, OCNC₃H₆-, C₆H_Five
-, C₆H_FiveCH₂NHC₃H₆-, C₆H_FiveNHC₃
H₆Groups such as-.

Further, as the silane coupling agent used in the present invention, specifically, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltrichlorosilane, vinyltris (2-methoxyethoxy) silane,
γ-methacryloxypropyltrimethoxysilane, γ
-Methacryloxypropyltriethoxysilane, γ-
Aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-
Aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltriethoxysilane, γ-
Ureidopropyltriethoxysilane, γ-ureidopropyltrimethoxysilane, β- (3,4epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4
Epoxycyclohexyl) ethyltriethoxysilane,
γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropyltriethoxy Silane, methyltriethoxysilane, methyltrimethoxysilane,
Examples thereof include phenyltriethoxysilane and phenyltrimethoxysilane.

Preferably, vinyltriethoxysilane,
Vinyltrimethoxysilane, vinyltris (2-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β-
(Aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltriethoxysilane, γ-ureidopropyltriethoxysilane, γ-ureidopropyltrimethoxysilane, β
-(3,4 epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4epoxycyclohexyl) ethyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane.

More preferably, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (2-
(Methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, β- (3,4 epoxy cyclohexyl)
Examples thereof include ethyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane.

Next, the method for producing the lithium secondary battery electrode of the present invention will be described in detail. The method of applying the silane coupling agent to the surface of the current collector is not particularly limited, but, as an example, a solution obtained by reacting the silane coupling agent with water to hydrolyze a part or the whole amount of the current is collected. A method of drying after applying to the body surface can be mentioned. The concentration of the silane coupling agent solution used here is 0.01
The amount is preferably about 5% to 5% by weight, more preferably about 0.1% to 3% by weight. Further, it is preferable to roughen the surface of the current collector in advance before attaching the silane coupling agent, because the binding effect is further enhanced. Examples of the roughening treatment include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method. Examples of the mechanical polishing method include a method of polishing the surface of the current collector with a polishing cloth paper to which abrasive particles are fixed, a grindstone, an emery buff, a wire brush equipped with a steel wire, or the like. Generally, it is preferable to use a polishing machine such as a buff polishing machine, a portable grinder or a sander. As the abrasive, emery, fused alumina, silicon carbide, boron carbide or the like is used. As the electrolytic polishing method,
Examples of the method include electrolysis in an electrolytic solution using a current collector as an anode. Examples of the electrolytic solution include phosphoric acid, sulfuric acid, oxalic acid, citric acid, acetic anhydride, and mixed solutions thereof. The chemical polishing method is a method in which a current collector is immersed in a polishing solution, and the polishing solution includes an electrolytic solution used in an electrolytic polishing method.

Next, an electrode material powder capable of occluding and releasing lithium and a paste formed by a known method using a binder for binding the powders and an organic solvent are used as the silane coupling material of the present invention. Apply on the treated current collector,
A sheet electrode can be manufactured by drying and then pressing.

The lithium secondary battery of the present invention constitutes a lithium secondary battery by combining an electrode capable of storing and releasing lithium and an electrode containing lithium and capable of storing and releasing lithium. Here, the high potential electrode is the positive electrode and the low potential electrode is the negative electrode, but the lithium secondary battery of the present invention uses the electrode obtained by the method of the present invention as at least one electrode.

The non-aqueous electrolyte used in the lithium secondary battery of the present invention is preferably a solution prepared by dissolving a lithium salt in an organic solvent having a high dielectric constant. The type of lithium salt is not particularly limited, and examples include LiClO ₄ , LiPF ₆ , and L
iBF ₄ , LiCF ₃ SO ₃ or the like can be used. The concentration of the lithium salt is usually selected to be about 0.5 mol / l to 1.5 mol / l. In addition, the organic solvent is
Any material may be used as long as it dissolves a lithium salt to give electric conductivity and is electrochemically stable with respect to the constituent negative electrode and positive electrode materials. Examples thereof include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, tetrahydrofuran, acetonitrile, sulfolane, and γ-butyrolactone. These may be used alone or in combination of two or more as a non-aqueous electrolyte, but it is preferable to mix two or more to use as a mixed solvent.

In the lithium secondary battery of the present invention, in addition to the positive electrode, the negative electrode and the non-aqueous electrolyte, contact between both electrodes is prevented,
In addition, it is preferable to combine and use a separator that holds a non-aqueous electrolyte and has a function of passing lithium ions. Examples of the separator include polyethylene,
Examples thereof include porous films such as polypropylene or polytetrafluoroethylene, non-woven fabrics and woven fabrics.
The thickness of the separator is preferably about 10 to 200 μm.

The lithium secondary battery of the present invention can be formed into various shapes such as a cylindrical shape, a box shape, a paper shape and a card shape by a known method.

[0024]

EXAMPLES Hereinafter, the effects of the present invention will be specifically described by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples. In order to obtain the effect of the present invention, a cylindrical battery having an AA type battery shape was manufactured, and a cycle property when charging and discharging was tested. Where A
The A-type battery is an AA-type battery according to the American ANSI designation and corresponds to R6 in JIS C8500. The tape peeling test was performed to evaluate the binding property.

Evaluation method of binding property (tape peeling test): 11 sheet electrodes were cut into an appropriate size and the active material layer was cut at 1 mm intervals using a cutter knife in the horizontal and vertical directions, respectively. Make a score for 1m
Make 100 squares. Then 10 pieces of Sellotape
The tape is peeled off after pressure bonding to the 0th cell. The tape peeling is continuously performed 5 times. The active material layer remaining on the sample side is counted every peeling, and the binding property is evaluated.

Example 1 A rolled copper foil having a thickness of 10 μm was used as the negative electrode current collector, and # 12 was used.
After roughening both surfaces of the foil with 00 water resistant paper,
It was washed with ethanol. After drying with ethanol, a silane coupling agent [manufactured by Nippon Unicar Co., product name A110
0, H ₂ NCH ₂ CH ₂ CH ₂ Si (OC
₂ H ₅ ) ₃ )] in advance with a silane coupling agent: pure water:
A solution mixed with ethanol = 1: 1: 98 (parts by weight) is applied on one side of a copper foil, dried with warm air at 50 ° C., the surface is treated with a silane coupling agent, and then the remaining one side is treated in the same manner. Then, a current collector foil material having both surfaces treated with a silane coupling material was obtained.

The negative electrode material has a specific surface area of 9 m ² / g by a nitrogen adsorption method, a number average particle diameter of 10 μm, and a true specific gravity of 2.2.
6. 95 parts by weight of natural graphite (made in Madagascar) powder having a lattice spacing d ₀₀₂ of 3.36 in X-ray diffraction and 2800 ° C.
Specific surface area of 30m ²
/ G, true specific gravity is 2.04, number average primary particle size is 66 nm
Pseudo-graphitic carbon black powder [Tokai Carbon Co., Ltd.
Manufactured by trade name TB3800] 5 parts by weight mixed carbon material was used. Next, 10 parts by weight of polyvinylidene fluoride using N-methylpyrrolidone as a binder as a solvent was added to 90 parts by weight of the mixed carbon material and sufficiently mixed by a ball mill to obtain a paste mixture (negative electrode paste).

A sheet coated with a negative electrode paste on a silane-treated copper foil with a doctor blade on one side and then dried at 50 ° C. under vacuum, and also on the back side after drying, with the electrode material coated on both sides. Got Next, a sheet pressure negative electrode (1) having a film thickness of 150 μm and a density of 1.75 g / cc was obtained by pressing with a roll press at a pressing pressure of 700 kgf / cm ² . Table 1 shows the binding test results for this sheet.

The positive electrode sheet electrode was made of lithium cobalt oxide powder, and scaly graphite (trade name: KS1 manufactured by the company) as a conductive material.
5), using polyvinylidene fluoride as a binder, in the same manner as for the negative electrode, film thickness 150 μm, density 3.5.
A sheet-like positive electrode (2) having g / cc was obtained.

Next, the sheet-shaped negative electrode (1) obtained here
Using a sheet-shaped positive electrode (2) and a sheet-shaped positive electrode (2), the sheets were laminated on a polypropylene separator having a thickness of 25 μm, and then spirally wound, and lithium hexafluorophosphate (LiP) was used as an electrolytic solution.
F ₆ ) was impregnated with a solution (concentration 1 mol / l) obtained by dissolving F ₆ ) in an equal volume mixture of ethylene carbonate (hereinafter sometimes referred to as EC) and diethyl carbonate (hereinafter sometimes referred to as DEC). To produce an AA type cylindrical battery. The initial discharge capacity and cycleability of the obtained battery were measured. Here, the initial discharge capacity was calculated by the discharge capacity per positive electrode weight. The cycleability was evaluated by the capacity retention rate (%) at 40 cycles when the initial discharge capacity was 1. The obtained results are shown in Table 2. The cycle test results are shown in FIG.

Example 2 The same as Example 1 except that the current collector which was treated with the silane coupling agent was used instead of the current collector which was roughened and treated with the silane coupling agent. After the sheet-shaped negative electrode was prepared as described above, a tape peeling test was performed for comparison with the binding property. The results are shown in Table 1.

Example 3 Instead of the mixed carbon material of natural graphite and pseudo-graphitic carbon black powder as the material for forming the negative electrode layer, the average particle diameter was 6 μm.
A sheet-like negative electrode was prepared in the same manner as in Example 1 except that the mesophase pitch spherical graphite of m was used, and then a tape peeling test was performed for comparison with the binding property. The results are shown in Table 1.

Example 4 Instead of the mixed carbon material of natural graphite and pseudo-graphitic carbon black powder as the material for forming the negative electrode layer, the average particle size was 15
A sheet-like negative electrode was prepared in the same manner as in Example 1 except that coke having a thickness of μm was used, and then a tape peeling test was performed for comparison with the binding property. The results are shown in Table 1.

Comparative Example 1 In the same manner as in Example 1 except that a current collector not subjected to roughening treatment or silane coupling agent treatment was used in place of the current collector subjected to roughening treatment or silane coupling agent treatment. After the sheet-shaped negative electrode was prepared, a tape peeling test was performed for comparison with binding properties. The results are shown in Table 1. Further, the initial discharge capacity and the cycle property of the AA type cylindrical battery manufactured according to Example 1 were measured. The obtained results are shown in Table 2. The cycle test results are shown in FIG.

Comparative Example 2 A sheet-shaped negative electrode was prepared in the same manner as in Example 1 except that a roughening-treated current collector was used in place of the roughening-treated and silane coupling agent-treated current collector. A tape peeling test was performed to compare the binding properties. The results are shown in Table 1.

Comparative Example 3 The procedure of Example 3 was repeated, except that a current collector which was not roughened and treated with a silane coupling agent was used in place of the current collector which was roughened and treated with a silane coupling agent. After the sheet-shaped negative electrode was produced by the above, a tape peeling test was performed for the purpose of comparing binding properties. The results are shown in Table 1.

Comparative Example 4 The same as Example 4 except that a current collector which was not roughened and treated with a silane coupling agent was used in place of the current collector which was roughened and treated with a silane coupling agent. After the sheet-shaped negative electrode was produced by the above, a tape peeling test was performed for the purpose of comparing binding properties. The results are shown in Table 1.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

The negative electrode or positive electrode obtained by the method for producing a sheet negative electrode or positive electrode for a lithium secondary battery of the present invention is
It has excellent binding properties between the current collector and the electrode layer capable of inserting and extracting lithium, and the lithium secondary battery obtained by the production method of the present invention has excellent cycleability without impairing the battery capacity. , Has great industrial value.

[0041]

[Brief description of drawings]

FIG. 1 is a diagram showing cycleability.

[Explanation of symbols]

1. The curve which shows the cycleability of the lithium secondary battery obtained in Example 1. 2. The curve which shows the cycleability of the lithium secondary battery obtained in Comparative Example 1.

Claims (5)

[Claims] 1. A method for producing a sheet-shaped negative electrode for a lithium secondary battery, comprising forming an electrode layer containing a carbon powder capable of inserting and extracting lithium and a binder on a current collector, before forming the electrode layer. A method for producing a sheet-shaped negative electrode for a lithium secondary battery, which comprises a step of applying a silane coupling agent to the surface of an electric body and drying. 2. A method for producing a sheet-shaped negative electrode for a lithium secondary battery, comprising forming an electrode layer containing a carbon powder capable of inserting and extracting lithium and a binder on a current collector, before forming the electrode layer. A method for producing a sheet-shaped negative electrode for a lithium secondary battery, comprising the steps of roughening an electric body surface, then applying a silane coupling agent to the surface, and drying the surface. 3. A method for producing a sheet-shaped positive electrode for a lithium secondary battery, comprising forming an electrode layer containing a compound capable of inserting and extracting lithium, a conductive material and a binder on a current collector, before forming the electrode layer. A method for producing a sheet-shaped positive electrode for a lithium secondary battery, comprising the steps of applying a silane coupling agent to the surface of a current collector and drying. 4. A method for producing a sheet-shaped positive electrode for a lithium secondary battery, comprising forming an electrode layer containing a compound capable of inserting and extracting lithium, a conductive material and a binder on a current collector, before forming the electrode layer. A method for producing a sheet-shaped positive electrode for a lithium secondary battery, comprising the steps of roughening the surface of the current collector, then applying a silane coupling agent to the surface and drying. 5. A lithium secondary battery comprising a positive electrode capable of inserting and extracting lithium, a negative electrode and a non-aqueous electrolyte, at least one of the electrodes being obtained by the method according to claim 1 or 2. A lithium secondary battery, which is a sheet-shaped negative electrode or a sheet-shaped positive electrode obtained by the method according to claim 3 or 4.