JPH09161838A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a filling rate, capacity, and a cycle characteristic by using a conductive material, different from that of the other surface, to one surface of at least one electrode seat out of positive and negative battery seats. SOLUTION: Conductive material, containing carbon material, a transition metallic compound, and binding material is coated on one surface of a current collecting body to obtain a positive electrode sheet, and also the conductive material, containing carbonaceous material, is coated on one surface of a current collector to obtain a negative electrode sheet. And conductive material, having a different mean particle diameter, is coated on the other side surface of at least one electrode sheet of these positive and negative electrode sheets.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a battery using an electrode body in which a positive electrode, a negative electrode and a separator are spirally wound.

[0002]

2. Description of the Related Art In recent years, with the widespread use of portable devices such as video cameras, mobile phones, and notebook computers, there is an increasing demand for small, lightweight, high-capacity secondary batteries. Most of the secondary batteries currently used are nickel-cadmium batteries using an alkaline electrolyte, but it is difficult to increase the energy density because the average battery voltage is as low as 1.2V. Therefore, research on high energy secondary batteries using metallic lithium for the negative electrode has been conducted.

However, in a secondary battery using metallic lithium as a negative electrode, there is a risk that lithium will grow in a dendritic form due to repeated charging and discharging, causing a short circuit and ignition. In addition, since highly active metal lithium is used, the risk is inherently high, and there are many problems in using it for consumer use. In recent years, lithium ion secondary batteries using various carbonaceous materials have been devised as a device that solves such a safety problem and enables high energy peculiar to lithium electrodes. This method utilizes the fact that during charging, lithium ions are occluded (doping) in the carbonaceous material to have the same potential as that of metallic lithium, which can be used for the negative electrode instead of metallic lithium. In addition, doped lithium ions are released from the negative electrode during discharge.
(Dedoping) is performed to return to the original positive electrode material. When such a carbonaceous material that can be doped with lithium ions is used as the negative electrode, the problem of dendrite formation is small, and since there is no metallic lithium, it has excellent safety. Is being done.

As a secondary battery using an electrode using the above-mentioned carbonaceous material doped with lithium ions,
JP-A-57-208079, JP-A-58-93176, JP-A-58-192266,
JP-A-62-90863, JP-A-62-122066, JP-A-2-66856 and the like are known, and as the shape of the electrode body used in the lithium-ion secondary battery, a positive electrode, a negative electrode, and a separator are spirally wound. The shape is generally common.

However, when the spiral electrode body is used, the respective electrode sheets of the positive electrode and the negative electrode are deformed in a spiral shape, and a tensile force is applied to the electrode material on the outer peripheral surfaces of both the positive electrode sheet and the negative electrode sheet, and conversely The peripheral surface is compressed. Therefore, although the electrode material is applied in a flat plate state, the electrode material is stretched on the outer peripheral surface and the electrode material on the inner peripheral surface is contracted.

Further, in the spiral electrode body, when it is attempted to fill the constant volume with the electrode material as much as possible, it is necessary to increase the coating thickness of the electrode material, but as the thickness increases, the force applied to the outer peripheral surface and the inner peripheral surface is increased. Has a problem that the electrode material is cracked on the outer peripheral surface in the worst case.

Further, in the spiral electrode, the positive electrode in the spiral state,
Since it is necessary to optimize the charge / discharge characteristics of the negative electrode, especially the ion moving speed and the electric equivalence ratio (balance), a method is usually adopted in which the outer peripheral surface is coated more than the inner peripheral surface. However, in this method, after the electrode material is applied, the electrode sheet is liable to warp due to thermal expansion, thermal contraction, or pressure stretching in the steps of drying the electrode sheet at high temperature and pressing, etc., and then winding into a spiral shape. Occasionally, misalignment occurred, which eventually caused a short circuit due to the edge portions of the positive electrode sheet and the negative electrode sheet.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to obtain a battery having a high filling rate, a high capacity, good cycle characteristics, and high safety.

[0009]

The present inventors have achieved the present invention as a result of studying a battery having a high filling rate, a high capacity, good cycle characteristics, and high safety.

That is, according to the present invention, in a battery using an electrode body formed by spirally winding a positive electrode sheet and a negative electrode sheet, at least one surface of the positive electrode sheet and the negative electrode sheet has at least one surface different from the other surface. A battery characterized in that different conductive materials are used.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of intensive studies on high-performance batteries, the present inventors have found that a conductive material having different characteristics on the outer peripheral surface and the inner peripheral surface is formed without causing a difference in thickness between the front and back during coating. It has been found that, by using it, it becomes possible to make the balance between the outer peripheral surface and the inner peripheral surface of the positive electrode and the negative electrode in the spiral shape proper.

That is, the object of the present invention is to optimize the amount ratio (balance) of the active materials in the positive electrode and the negative electrode for electron transfer, in the part corresponding to the outer peripheral surface and the part corresponding to the inner peripheral surface of the conductive material. (2) The electric conductivity and ionic conductivity of the electrode material on the outer peripheral surface and the inner peripheral surface are controlled by changing the characteristics, preferably electric conductivity, to obtain an optimum battery.

In the battery of the present invention, a conductive material different in type from other surfaces is used on at least one surface of the electrode sheet.

Examples of the conductive material that can be used in the battery of the present invention include carbon materials and metal powders, and particularly preferable conductive materials include various carbon blacks and artificial graphite.

Further, in the case of a lithium-ion battery, a part of the lithium ions released from the positive electrode is occluded in the conductive material of the negative electrode and the amount of lithium ions contributing to the electric capacity is substantially reduced, so that the conductivity of the negative electrode is reduced. As the material, a carbon material is particularly preferable, and in order to better control the balance between the amount of the positive electrode and the amount of the negative electrode, it is more preferable to use a carbon material capable of absorbing lithium ions and releasing a small amount.

When controlling the balance between the positive and negative electrodes by occluding lithium ions, the conductive material is preferably fired as a preferable method for controlling the characteristics of the conductive material, depending on the firing temperature, time, atmosphere conditions, and the like. Therefore, it is possible to obtain a conductive material exhibiting optimum characteristics. Furthermore, it is more desirable to select a condition that does not impair the conductivity under these firing conditions.

In the conductive material of the present invention, in order to make the outer peripheral surface and the inner peripheral surface have the same thickness and change the charge / discharge characteristics, the outer peripheral surface of both the positive electrode sheet and the negative electrode sheet is more electrically conductive than the inner peripheral surface. It is preferable to use a high conductive material.

In the conductive material of the present invention, it is preferable to use a conductive material having different characteristics such as electric conductivity by changing the shape, the average particle diameter and the specific surface area which is the surface area per unit weight.

In the present invention, the conductive material is added in the positive electrode,
Material of negative electrode active material, shape, particle size, and type of binder,
Since the optimum value changes depending on the compounding amount and the like, it should be experimentally determined, but preferably 0.
5 to 30 wt%, more preferably 0.7 to 20 wt% is used. If the added amount is less than 0.5 wt%, the conductive effect is poor, and 20w
If it exceeds t%, the capacity per unit weight of the electrode tends to decrease.

In the present invention, the particle size of the conductive material varies depending on the material, shape, particle size of the positive electrode and negative electrode active material, and the kind and blending amount of the binder, so that it should be determined experimentally. However, preferably, the primary particle size is 1 nm ~ 1
Fine particles of 00 μm, more preferably 5 nm to 20 μm are used. If the primary particle size is less than 1 nm, stable production is difficult, and if the primary particle size exceeds 100 μm, the effect of addition tends to be small.

In the present invention, as the electrode material applied to the positive electrode, carbon fiber, carbonaceous material such as artificial or natural graphite powder, carbon fluoride, inorganic compound such as metal or metal oxide, organic polymer compound and the like are used. Can be used.

Further, in the present invention, as an electrode material applied to the positive electrode, a positive electrode active material used in a usual secondary battery can be mentioned. Examples of such a positive electrode active material include inorganic compounds such as transition metal oxides and transition metal chalcogens containing an alkali metal, polyacetylene, polyparaphenylene, polyphenylene vinylene, polyaniline,
Examples thereof include conjugated polymers such as polypyrrole and polythiophene, crosslinked polymers having a disulfide bond, and thionyl chloride. In the present invention, a lithium salt is preferably used as the electrolyte, but in this case, cobalt, nickel, manganese, molybdenum, vanadium, chromium, iron,
Transition metal oxides such as copper and titanium and transition metal compounds such as transition metal chalcogens are preferably used. In particular, L
iCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , Li _y Ni _1-x M
_x O ₂ (M: Ti, V, Mn, or Fe), Li
_{1-xa A x Ni 1-} yb B y O 2 ( however, A is at least one alkali or alkaline earth metal element, particularly preferably, Mg, Sr can be mentioned, B is at least one transition metal element And preferably Co and Fe) are most preferably used because of their large energy density. Especially _{wherein, Li 1-xa A x Ni} 1-yb B y
O ₂ is 0 <x≤0.1, 0≤y≤0.3, -0.1≤a≤0.1, -0.15≤
b ≦ 0.15 (However, when A and B are composed of two or more elements, x is the total number of moles of alkali or alkaline earth metal excluding Li, and y is the total number of moles of all transition metal elements excluding Ni. In the case of y = 0, A contains at least one kind of alkaline earth metal) and a positive electrode material having excellent characteristics can be obtained. Further, in this case, it is possible to obtain active materials having different characteristics by changing the types, numbers, and compositions of A and B, or by using positive electrode materials with different x, y, a, and b. It is suitable.

When the positive electrode active material is an inorganic compound such as a metal or a metal oxide, a charge / discharge reaction occurs due to cation doping and dedoping, and when it is an organic polymer compound,
A charge / discharge reaction occurs due to anion doping and dedoping, but these are appropriately selected according to the required positive electrode characteristics of the battery and are not particularly limited.

In the present invention, as the electrode material applied to the negative electrode, carbon fiber, artificial or natural graphite powder, carbonaceous material such as fluorocarbon, inorganic compound such as metal or metal oxide, organic polymer compound, etc. Can be used.

In the present invention, carbon fiber is preferably used as the electrode material applied to the negative electrode. in this case,
The carbon fiber is not particularly limited, but a fibrous organic material is generally used. The carbon fiber used in the present invention, for example, PAN-based carbon fiber obtained from polyacrylonitrile (PAN), pitch-based carbon fiber obtained from pitch such as coal or petroleum, cellulose-based carbon fiber obtained from cellulose, low molecular weight Vapor grown carbon fibers obtained from organic gas, livinyl alcohol, lignin, polyvinyl chloride, polyamide, polyimide, phenol resin, carbon fibers obtained by firing furfuryl alcohol, etc., and the like, electrodes and batteries Depending on the characteristics, carbon fibers satisfying the characteristics are appropriately selected. Furthermore, among these carbon fibers, PAN
Carbon fibers and pitch carbon fibers are more preferably used. Especially when used as the negative electrode of a secondary battery using a non-aqueous electrolyte containing an alkali metal salt such as lithium, PAN
Carbon-based fibers are particularly preferred. The diameter of the carbon fiber preferably used in the present invention is appropriately determined depending on the form of each electrode or battery, but generally, the diameter is 1 to 100.
Carbon fibers having a diameter of 3 to 20 μm are preferably used, and carbon fibers having a diameter of 3 to 20 μm are more preferable. It is also possible to use several kinds of carbon fibers having different diameters, if necessary.

Further, the length of the carbon fiber preferably used in the present invention is not particularly limited, but it is usually preferably 10
The thickness is 0 μm or less, more preferably 50 μm or less. When the length of the carbon fiber exceeds 100 μm, it is difficult to apply the carbon fiber uniformly using a coater, which is not preferable. If the length of the carbon fiber is shorter than the diameter of the carbon fiber, there is a risk of breaking in the fiber direction. Therefore, the length of the carbon fiber is more preferably the carbon fiber diameter or more.

Further, these electrode materials can be used as active electrodes for various batteries, such as primary batteries and secondary batteries.
What kind of battery is used is not particularly limited.

When used in a non-aqueous electrolyte secondary battery containing an alkali metal salt, a carbonaceous material doped with an alkali metal or a cation is used for the negative electrode, and a material doped with an anion is used for the positive electrode.

The electrode material thus obtained can be used as an electrode of various batteries, and the type of the battery is not particularly limited, but it is preferably used as an electrode of a secondary battery. Particularly preferable secondary batteries include secondary batteries using a non-aqueous electrolyte solution containing an alkali metal salt such as lithium perchlorate, lithium borofluoride, and phosphorus hexafluoride / lithium.

The separator used in the present invention is not particularly limited as long as it prevents short circuit between the positive electrode and the negative electrode. It is desirable that the electrolyte has good permeability and does not become a resistance to transfer of electrons and ions. Typical materials include polyester, polyamide, polyolefin, polyacrylate, polymethacrylate, polysulfone, polycarbonate, and polytetrafluoroethylene. To be Among these, polypropylene, polyethylene, polysulfone and the like are particularly preferable because they are excellent in strength and safety. The shape of the separator is generally a porous film or a non-woven fabric, but a porous film is preferable because the filling rate in the battery can is easily increased. Further, the porous membrane is generally a symmetric membrane or an asymmetric membrane, but the strength,
In order to improve safety, it is also possible to use a composite membrane in which a plurality of types of membranes are laminated. The porosity of the porous film is preferably as high as possible in order to enhance the permeability of electrons and ions, but it may cause a decrease in the strength of the film and is therefore determined according to the material and the film thickness. Generally, the film thickness is 20-100 μm,
A porosity of 30-80% is desirable. Further, the diameter of the pores is preferably a range in which the active material detached from the electrode sheet, the binder, and the conductive material do not permeate, and specifically, the average pore diameter is 0.01
It is preferably about 1 μm.

The binder used in the battery of the present invention may be either a thermoplastic resin or a thermosetting resin, and is not particularly limited. It is also possible to use the binder in the form of a solution or emulsion. The amount of the binder added is usually 0.01 wt% to 40 wt% in the electrode material. Examples of the binder include various epoxy resins, cellulose resins, organic fluorine-based polymers, and copolymers, acrylic resins, organic chloro-based resins, polyimides,
Examples thereof include polyamide and polycarbonate. In particular, organic fluorine-based polymers and copolymers are preferable from the viewpoint of stability, and among them, polytetrafluoroethylene, polyvinylidene fluoride, propylene hexafluoride polymer and copolymers are preferable binders.

The method for applying the positive electrode material and the negative electrode material to the current collector to prepare an electrode sheet is not particularly limited, but in view of the properties of the present invention, a solution dispersed in a solvent is applied together with a binder, a conductive material and the like. After that, a general method is to dry or attach the active material to the current collector using a conductive binder or a mixture of a conductive material and a binder.

In the current collector of the present invention, metal may be used in the form of foil, mesh, lath, etc., but these are not particularly limited.

The positive electrode sheet and the negative electrode sheet can be obtained by applying an electrode material on one side or both sides of the current collector. If the electrode material is applied to one side of the current collector,
It is preferable to take the same form as in the case where two current collectors are overlapped with each other to coat both surfaces. However, in the case of single-sided coating, it is difficult to heat or press the electrode sheet due to the difference in expansion and contraction characteristics between the current collector and the electrode material, and winding is likely to occur when spirally wound. It is desirable to apply the electrode material to both surfaces of the electric body.

The electrolyte contained in the electrolytic solution used in the battery of the present invention includes alkali metal halides, perchlorates, thiocyanates, borofluorides, and phosphorus fluorides.
Arsenic fluoride, aluminum fluoride, trifluoromethyl sulfate, etc. are preferably used. Lithium salt, in particular, has the lowest standard electrode potential, and therefore a large potential difference can be obtained. Therefore, as the electrolyte contained in the electrolytic solution,
More preferably, a lithium salt is used.

The solvent used in the electrolytic solution used in the present invention is not particularly limited, and a conventional solvent is used, and examples thereof include an acid or alkaline aqueous solution, or a non-aqueous solvent. Among these, as the solvent of the electrolytic solution of the secondary battery comprising a non-aqueous electrolytic solution containing an alkali metal salt, propylene carbonate, ethylene carbonate, dimethyl carbonate, γ-butyrolactone, N-methylpyrrolidone, acetonitrile, N, N- Dimethylformamide, dimethylsulfoxide, tetrahydrofuran, 1,3-dioxolane,
Methyl formate, sulfolane, oxazolidone, thionyl chloride, 1,2-dimethoxyethane, diethylene carbonate,
And derivatives and mixtures of these are preferably used.

The battery used in the present invention is not particularly limited as long as it is a battery using an electrode body wound in a spiral shape, but as a battery for mounting on portable equipment requiring a high energy density, a negative electrode is used. A battery using an alkali metal as a material and a secondary battery using cation or anion doping to a carbonaceous material are effective.

The battery can loaded with the spiral electrode body is not particularly limited, but a battery can plated with iron for corrosion resistance, a stainless steel battery can and the like have strength, corrosion resistance, It is preferable because it is excellent in workability. Further, it is possible to reduce the weight by using various engineering plastics, and it is also possible to use various engineering plastics and metal together.

Further, the shape of the spiral in the present invention does not necessarily have to be a true cylindrical shape, and may be a long cylinder shape having an elliptical spiral cross section or a prismatic shape such as a rectangular spiral cross section. . In this case, the battery can can also take a shape corresponding to the shape of the electrode body. As a typical use form, a spirally-shaped electrode body and an electrolytic solution are loaded into a cylindrical battery can having a bottom, and leads taken out from the electrode sheet are sealed in a state of being welded to the cap and the battery can. The form is mentioned as the most common form, but is not limited to this form.

[0040]

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited by this.

Example 1 A positive electrode material for the outer peripheral surface was made of LiCoO ₂ as a positive electrode active material.
80 wt%, polyvinylidene fluoride as a binder (Kureha Chemical Co., Ltd., KF1100) 5 wt%, average particle size as a conductive material
It was prepared by mixing 15 wt% of artificial graphite (SP-270, manufactured by Nippon Graphite Industry Co., Ltd.) having 1 μm and a specific surface area of 270 m ² / g. The positive electrode material for the inner peripheral surface is 80 wt% of LiCoO ₂ as a positive electrode active material,
5 wt% polyvinylidene fluoride (Kureha Chemical Co., Ltd., KF1100) as a binder, artificial graphite with an average particle diameter of 6 μm and a specific surface area of 20 m ² / g as a conductive material (Nippon Graphite Industry Co., Ltd., SP-2
0) was mixed by using 15 wt%. Aluminum foil (thickness 20 μm) is used as a current collector, and the positive electrode material is applied to the current collector on both the outer peripheral surface and the inner peripheral surface at 250 g / m ² at 150 ° C.
After performing the heat treatment of 1., it was pressed at a pressure of 500 kgf / cm to obtain a positive electrode sheet.

Next, as a negative electrode active material, PAN-based carbon fiber
(Toray Industries, Inc., trading card T300) 75 wt% made into short fibers with an average length of 30 μm, polyvinylidene fluoride as a binder
(Kureha Chemical Co., Ltd., KF1100) 5 wt%, conductive material having an average particle size of 6 μm, specific surface area of 20 m ² / g artificial graphite (Nippon Graphite Industry Co., Ltd., SP-20) 15 wt% for the outer peripheral surface, Kneading was carried out at the same ratio for both the peripheral surfaces. Copper foil (thickness 10 μm) as current collector
Using the above, the above negative electrode material was applied onto a current collector so that both the outer peripheral surface and the inner peripheral surface had a weight of 80 g / m ^2, and heat treatment and pressing were performed in the same manner as the positive electrode sheet to obtain a negative electrode sheet.

A porous polypropylene film (manufactured by Daicel Chemical Co., Ltd.,
A cylindrical electrode body was obtained by stacking as a separator of Celguard # 2500) and winding. No cracks occurred in these electrode bodies.

Further, this electrode body was loaded into a battery can having an internal volume of 5 cc, and a battery was prepared by using a 1: 1 mixed solution of dimethyl carbonate and ethylene carbonate containing 1M lithium borofluoride as an electrolytic solution. This battery, charging current
400mA, constant voltage value 4.2V, constant current constant voltage charging with a charging time of 2 hours, capacity test with discharge current 200mA, discharge end voltage 2.5V, initial discharge capacity 390mAh, capacity retention at 100 charge / discharge cycles The rate was 80.9%.

Example 2 As a conductive material for the positive electrode material for the outer peripheral surface, artificial graphite having an average particle size of 6 μm and a specific surface area of 20 m ² / g (manufactured by Nippon Graphite Industry Co., Ltd., SP-
20) 3 wt%, average particle size 1 μm, specific surface area 270 m2 / g artificial graphite (Nippon Graphite Industry Co., Ltd., SP-270) was mixed in the same manner as in Example 1 except that 12 wt% was mixed. It was created.

After obtaining a negative electrode sheet in the same manner as in Example 1, these positive electrode sheet and negative electrode sheet were obtained in the same manner as in Example 1 to obtain a cylindrical electrode body. No cracks occurred in these electrode bodies.

After preparing a battery in the same manner as in Example 1,
When a capacity test was conducted under the same conditions as in Example 1, the initial discharge capacity was 385 mAh, the capacity retention ratio was 100 times when the number of charge and discharge was 100 times, and the capacity retention rate was 82.1.
%Met.

Example 3 As a conductive material for the positive electrode material for the outer peripheral surface, artificial graphite having an average particle size of 6 μm and a specific surface area of 20 m ² / g (manufactured by Nippon Graphite Industry Co., Ltd., SP-
20) 6 wt%, average particle size 1 μm, specific surface area 270 m ² / g artificial graphite (manufactured by Nippon Graphite Industry Co., Ltd., SP-270) was mixed in the same manner as in Example 1 except that 9 wt% was mixed. Created a sheet.

After obtaining a negative electrode sheet in the same manner as in Example 1, these positive electrode sheet and negative electrode sheet were obtained in the same manner as in Example 1 to obtain a cylindrical electrode body. No cracks occurred in these electrode bodies.

After producing a battery in the same manner as in Example 1,
When a capacity test was performed under the same conditions as in Example 1, the initial discharge capacity was 383 mAh, and the capacity retention rate was 100% when the number of charge / discharge cycles was 100 times.
%Met.

Example 4 As a conductive material of the positive electrode material for the outer peripheral surface, artificial graphite having an average particle size of 6 μm and a specific surface area of 20 m ² / g (manufactured by Nippon Graphite Industry Co., Ltd., SP-
20) 9 wt%, average particle size 1 μm, specific surface area 270 m ² / g artificial graphite (manufactured by Nippon Graphite Industry Co., Ltd., SP-270) was mixed in the same manner as in Example 1 except that 6 wt% was mixed. Created a sheet.

After obtaining the negative electrode sheet in the same manner as in Example 1, the positive electrode sheet and the negative electrode sheet were obtained in the same manner as in Example 1 to obtain a cylindrical electrode body. No cracks occurred in these electrode bodies.

After producing a battery in the same manner as in Example 1,
When a capacity test was performed under the same conditions as in Example 1, the initial discharge capacity was 376 mAh, and the capacity retention rate was 81.5 after 100 times of charge and discharge.
%Met.

Example 5 As a conductive material of the positive electrode material for the outer peripheral surface, artificial graphite having an average particle size of 6 μm and a specific surface area of 20 m ² / g (manufactured by Nippon Graphite Industry Co., Ltd., SP-
20) in an amount of 12 wt%, an average particle size of 1 μm, and a specific surface area of 270 m ² / g artificial graphite (manufactured by Nippon Graphite Industry Co., Ltd., SP-270) in the same manner as in Example 1 except that 3 wt% was mixed. Created a sheet.

After obtaining a negative electrode sheet in the same manner as in Example 1, these positive electrode sheet and negative electrode sheet were obtained in the same manner as in Example 1 to obtain a cylindrical electrode body. No cracks occurred in these electrode bodies.

After producing a battery in the same manner as in Example 1,
When a capacity test was performed under the same conditions as in Example 1, the initial discharge capacity was 376 mAh, the capacity retention rate was 100 times, and the capacity retention ratio was 79.9.
%Met.

Example 6 The positive electrode material for the outer peripheral surface was LiCoO ₂ as the positive electrode active material.
85 wt%, polyvinylidene fluoride (Kureha Chemical Co., Ltd., KF1100) 10 wt% as a binder, and acetylene black (Denka Black, manufactured by Denki Kagaku Kogyo) as a conductive material is baked at 2000 ° C. for 4 hours in a nitrogen atmosphere. Graphitized 5 wt%
Was prepared by mixing. The positive electrode material for the inner peripheral surface was composed of 85 wt% LiCoO ₂ as a positive electrode active material, 10 wt% polyvinylidene fluoride (KF1100 manufactured by Kureha Chemical Co., Ltd.) as a binder,
5 wt% of unfired acetylene black was mixed as a conductive material, and a positive electrode sheet was obtained in the same manner as in Example 1.

After a negative electrode sheet was obtained in the same manner as in Example 1, these positive electrode sheet and negative electrode sheet were obtained in the same manner as in Example 1 to obtain a cylindrical electrode body. No cracks occurred in these electrode bodies.

After producing a battery in the same manner as in Example 1,
When a capacity test was performed under the same conditions as in Example 1, the initial discharge capacity was 375 mAh, the capacity retention rate was 100 times when the number of charge / discharge cycles was 100, and the capacity retention rate was 87.1.
%Met.

Comparative Example 1 As the positive electrode conductive material, artificial graphite (SP-20 manufactured by Nippon Graphite Industry Co., Ltd.) having an average particle size of 6 μm and a specific surface area of 20 m ² / g was used for both the outer peripheral surface and the inner peripheral surface. A battery was produced in the same manner as in Example 1 except for the above. When a capacity test was performed under the same conditions as in Example 1, the capacity retention rate was 75.1% at an initial discharge capacity of 365 mAh and a charge / discharge count of 100 times, and both the initial discharge capacity and the capacity retention rate were low.

Comparative Example 2 A battery was prepared in the same manner as in Example 6 except that unfired acetylene black (Denka Black, manufactured by Denki Kagaku Kogyo) was used as the conductive material for the positive electrode on both the outer and inner peripheral surfaces. It was made. When a capacity test was conducted under the same conditions as in Example 1, the initial discharge capacity was 367 mAh, the capacity retention rate was 100 times, and the capacity retention rate was 8
It was 3.5%, and the initial discharge capacity was low.

[0062]

EFFECTS OF THE INVENTION By using a conductive material of a kind different from the other surface on one surface of at least one of the positive electrode sheet and the negative electrode sheet, the filling rate is high, the capacity is high, the cycle characteristics are good, and the safety is high. A highly reliable battery can be obtained.

By using a conductive material having different characteristics on the outer peripheral surface and the inner peripheral surface, the charge and discharge characteristics of the positive electrode and the negative electrode in the spiral state, especially the ion moving speed and the electric equivalence ratio (balance) can be optimized. Therefore, a high performance battery can be manufactured.

Claims (18)

[Claims] 1. A battery using an electrode body formed by spirally winding a positive electrode sheet and a negative electrode sheet, wherein at least one electrode sheet of the positive electrode sheet and the negative electrode sheet has one surface different in conductivity from the other surface. Batteries characterized by using materials. 2. A conductive material having an average particle size different from that of the other surface is used on one surface of at least one electrode sheet of the positive electrode sheet and the negative electrode sheet.
The battery according to 1. 3. The battery according to claim 1, wherein one surface of at least one electrode sheet of the positive electrode sheet and the negative electrode sheet is made of a conductive material having a different electrical conductivity from the other surface. 4. The battery according to claim 3, wherein a conductive material having higher electrical conductivity than the inner peripheral surface is used for the outer peripheral surface. 5. The battery according to claim 1, wherein a conductive material having a specific surface area different from that of the other surface is used on one surface of at least one of the positive electrode sheet and the negative electrode sheet. 6. The battery according to claim 1, wherein a conductive material having a shape different from that of the other surface is used for one surface of at least one electrode sheet of the positive electrode sheet and the negative electrode sheet. 7. The battery according to claim 1, wherein the conductive material is a carbon material. 8. The conductive material is carbon black, or
The battery according to claim 1, which contains graphite. 9. The battery according to claim 1, wherein the conductive material is a mixture of two or more kinds of conductive materials. 10. The battery according to claim 1, wherein a conductive material having a primary particle diameter of 1 nm to 100 μm is used. 11. The battery according to claim 1, wherein a fired conductive material is used. 12. The battery according to claim 1, wherein a lithium salt is used as an electrolyte. 13. The battery according to claim 1, wherein the electrode material applied to the positive electrode contains a transition metal compound. 14. The battery according to claim 1, wherein the electrode material applied to the negative electrode contains a carbonaceous material. 15. The battery according to claim 14, wherein the carbonaceous material is carbon fiber. 16. The battery according to claim 15, wherein the carbon fiber is a polyacrylonitrile-based carbon fiber. 17. The carbon fiber has a diameter of 1 μm to 100 μm,
A length of 100 μm or less, characterized in that
The battery according to 5. 18. The battery according to claim 17, wherein the length of the carbon fiber is not less than the diameter of the carbon fiber.