JP3157079B2 - Manufacturing method of lithium secondary battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a lithium secondary battery.

[0002]

2. Description of the Related Art A secondary battery is used as a power source for driving a portable electronic device or the like for the purpose of economy and resource saving, and its use is rapidly expanding year by year. Also, with the miniaturization and high performance of electronic devices, batteries used are required to be small, light, and high in capacity. On the other hand, lead batteries, nickel cadmium batteries, and the like have been conventionally used as secondary batteries, but in recent years, non-aqueous lithium secondary batteries with a high energy density have been proposed or put into practical use.

In the above-mentioned lithium secondary battery, conventionally, when a metal oxide or metal sulfide such as manganese dioxide or molybdenum disulfide is used as an active material of the positive electrode, the metal oxide or metal sulfide is used. Is a non-conductive material, so that a powdery or fibrous conductive material is mixed as a component that performs a current collecting action.

As the above-mentioned conductor, a conductive material powder made of carbonaceous material such as carbon black and graphite is generally used. Further, as other conductors, there are those obtained by plating surfaces of graphite or the like with nickel, platinum, gold or the like, and granular or fibrous stainless steel materials are also used. In the gazette,
A technology using ferrite stainless steel together with graphite and carbon as a conductor has been proposed. However, a material such as graphite in which nickel, platinum, gold or the like is plated on the surface is added to the non-conductive active material as a conductive material to the last, and is not used as the active material itself.

[0005] Further, as the active material of the electrode of the above-mentioned lithium secondary battery, there is known a material using carbon, which is usually graphite. Conventionally, when carbon is used as an active material (usually a negative electrode), the electrode is composed of carbon and a binder, and a conductor is added or mixed as in the case of using a metal oxide as the active material as described above. I didn't. This is considered to be because it was thought that it was not necessary to further add a conductive aid because carbon is a conductive substance.

However, J. Electrochem. Soc., Vo
As disclosed in l.140, No.4, P922-927 (1993), when carbon, which is a conductive substance, is used for the electrode (negative electrode), the discharge capacity is reduced when high-rate discharge is performed. There are drawbacks. This document also discloses that the addition of carbon black to a graphite negative electrode improves high-rate discharge characteristics.

[0007]

However, when the high-rate discharge characteristics are improved by adding carbon black to a graphite electrode, the bulkiness of the carbon black and the current collector derived from the bulkiness are improved. In order to obtain the effect from the ease of slipping from the
36, pp. 517 to 527 (1991), the mixture consisting of the active material and the conductor must be kept on the current collector by applying pressure, etc. Is very difficult to realize. In fact, as described later in the Examples section, when the present inventors conducted experiments without applying pressure, carbon black was added even if the mixture was peeled off from the current collector or was not peeled off. The high-rate discharge characteristics were lower than those not performed.

Accordingly, an object of the present invention is to provide a method for manufacturing a lithium secondary battery in which a mixture is firmly bonded onto a current collector without applying pressure or the like, and the high-rate discharge characteristics are efficiently improved. It is assumed that.

[0009]

This and other objects are achieved by the present invention which is defined below as (1) to (3). (1) In producing a lithium secondary battery using a non-aqueous electrolyte containing a lithium-containing electrolyte, when a carbon coating comprising a carbon and a binder is formed on a current collector as carbon, the carbon in the carbon coating is Uses graphite that is oriented parallel to the current collector, mixes or coats the metal with carbon with this orientation, adds the metal, mixes it with the binder, and applies it to the current collector Then, using the carbon as an active material, a ratio of the carbon oriented in parallel is reduced, and a positive electrode or a negative electrode is obtained in which the ratio that the end face of the graphite faces the electrolyte side is increased, and the positive electrode and the negative electrode are used. For producing a lithium secondary battery having improved discharge characteristics. (2) The method for producing a lithium secondary battery according to the above (1), wherein the coating is performed by plating. (3) The method for producing a lithium secondary battery according to the above (1) or (2), wherein the amount of the metal added is 95/2 to 40/60 in terms of carbon / metal (weight ratio).

[0010]

In the lithium secondary battery of the present invention, since a metal is added as a conductive additive to carbon used for the negative electrode or the positive electrode active material, the contact resistance between the active materials is reduced or the current between the current collector and the active material is reduced. Can be reduced, and a decrease in capacity can be suppressed as much as possible even at a high rate discharge (large current discharge).

Further, by adding a metal, the orientation of graphite used as carbon can be prevented, and a reduction in capacity can be suppressed as much as possible even at a high rate of discharge. FIGS. 2, 3 and 4 show cross sections of electrodes in which an electrode coating consisting of only graphite and a binder resin is applied to a titanium plate by a metal mask printing method as in the prior art. As can be seen from the photographs of FIGS. 2, 3 and 4, when only graphite and a binder resin are used, the graphite is oriented parallel to the titanium plate as the current collector. The photographs of FIGS. 2, 3 and 4 are electron microscope photographs showing the same object at 500 times, 700 times and 1000 times, respectively.

On the other hand, according to the present invention, in the case of an electrode in which an electrode paint composed of graphite coated with nickel and a binder resin is applied to a titanium plate by a metal mask printing method, as shown in the photographs of FIGS. In addition, nickel-coated graphite is not oriented in a specific direction. The photographs in FIGS. 5 and 6 are electron microscope photographs showing the same object at 500 times and 700 times, respectively.

When carbon is used as an active material, an electrochemical reaction occurs at the end face of the carbon. Therefore, FIGS. 2, 3 and 4
In the case of the photograph (1), the diffusion of ions is slow and large-current discharge becomes impossible because the end face of the graphite does not face the electrolytic solution. In contrast, in the case of FIGS. 5 and 6, the ratio of the end face of the graphite facing the electrolytic solution is larger than in the case of FIGS. 2, 3 and 4, so that the diffusion of ions is facilitated and a large current discharge is possible. Becomes In the above description, only the case where graphite coated with nickel is used is shown, but the same operation and effect can be obtained when coating with another metal or simply adding a metal.

Japanese Patent Application Laid-Open No. 4-34870 discloses an organic electrolyte battery characterized in that carbon is used for a negative electrode and the negative electrode is bonded to a negative electrode current collector with a conductive paste containing Ni as a main component. Is disclosed. It is described that this reduces the internal resistance of the battery. However, there is no description about the relationship between the discharge current and the discharge capacity.
With the internal resistance, the relationship between the discharge current and the discharge capacity cannot be predicted. What can be known from the internal resistance value is about the closed circuit voltage.

Further, Japanese Patent Application Laid-Open No. 3-37968 discloses that
The negative electrode is basically composed of lithium and niobium pentoxide, and at least Pt, Ag, N
There is a description that by adding a corrosion-resistant metal powder such as i, Al, Cu, Mo, etc., the storage characteristics are improved while enduring overdischarge. However, this battery uses lithium and niobium pentoxide as active materials, and does not use carbon as in the present invention. In addition, the above publication describes that the discharge capacity retention rate after high-temperature storage of the battery and the discharge capacity retention rate after high-temperature overdischarge are improved, but the relationship between discharge current and discharge capacity is completely mentioned. Not.

[0016]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described in detail.

In the lithium secondary battery of the present invention, carbon to which a metal is added is used for a negative electrode or a positive electrode. Carbon acts as an electrode active material. As carbon, graphite capable of doping or intercalating lithium ions is used. For example, those described in JP-A-62-23433 and JP-A-3-137010 are exemplified. Carbon is usually used in the form of particles, in which case the average particle diameter of the carbon particles is 5 to 30 μm. If the particles are too small, the discharge capacity will be small, and if they are too large, the discharge capacity will be small.

As the negative electrode active material, in addition to the above-mentioned carbon, a conductive polymer material capable of doping or intercalating lithium ions, lithium metal or lithium alloy can be used.

The conductive polymer material may be selected from, for example, polyacetylene, polyphenylene, polyacene and the like, and examples thereof include those described in JP-A-61-77275.

As the positive electrode active material, a metal compound, metal oxide, metal sulfide, or conductive polymer material capable of doping or intercalating lithium ions, in addition to the above-mentioned carbon, may be used. For example, LiCoO ₂ , Li
NiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , V ₂ O ₅ ,
TiS ₂ , MoS ₂ , FeS ₂ , polyacetylene, polyaniline, polypyrrole, polythiophene, polyacene, and the like.
JP-A-3-59507 and the like can be mentioned.

When a metal oxide, metal sulfide, or the like is used as the positive electrode active material, a carbon material such as graphite, acetylene black, and Ketjen black may be used as the conductive agent, and the metal added to carbon according to the present invention described above. Is preferable.

As the metal to be added to the carbon, any material may be used as long as it is a conductor in the case of a negative electrode. For example, in addition to a simple metal such as nickel, copper, silver, and aluminum, stainless steel may be used. Alloys such as steel and permalloy can also be used.

When carbon is used for the positive electrode, the metal to be added is a metal having high oxidation resistance, for example, aluminum, titanium,
It is necessary to use stainless steel or the like.

As the method of addition, a method of uniformly mixing and adding metal powder to carbon powder, a method of coating metal on carbon particles, and the like can be used.

When added as metal powder, there is no particular limitation on the shape of each particle, and for example, spherical, fibrous, flat or the like can be used. For example, when a spherical material is used, the average particle size is preferably 1 to 50 μm.

As a method for coating the metal on the carbon particles, electroless plating, vapor deposition, sputtering, immersion, a binder and the like can be used. The metal coating may not be applied to the entire carbon particles, but may be a part thereof.
The thickness of the coating film is preferably 10 μm or less. If the thickness is more than this, the energy density per volume or weight of the electrode decreases.

When a metal coating is applied to the entire carbon particles, the coating film is preferably porous in order to allow lithium ions to be doped or intercalated into carbon.

The amount of metal added is as follows: carbon: metal = 98: 2
40:60 (weight ratio), especially carbon: metal = 95: 5-4
5-55 (weight ratio) is preferable.

If the amount of the metal added is less than 2% by weight, the effect of reducing the contact resistance between the carbon powders or the contact resistance between the current collector and the carbon powder cannot be realized. On the other hand, when the amount of the metal exceeds 60% by weight, the energy density per weight or volume of the mixture is reduced.

The electrolyte is prepared by dissolving a lithium-containing electrolyte in a non-aqueous solvent. The lithium-containing electrolyte may be appropriately selected from, for example, LiClO ₄ , LiBF ₄ , and LiPF ₆ . Non-aqueous solvents include, for example, ethers, ketones, carbonates, etc.
Although it can be selected from the organic solvents exemplified in, for example, JP-A No. 1260, carbonates are particularly preferred in the present invention. Among the carbonates, it is particularly preferable to use a mixed solvent containing ethylene carbonate as a main component and one or more other solvents added. These mixing ratios are ethylene carbonate: another solvent-30 to 7
Preferably, the ratio is 0:70 to 30 (volume ratio). The reason for this is that the freezing point of ethylene carbonate is 36.4 ° C.
This is because ethylene carbonate alone cannot be used as an electrolytic solution for a battery because ethylene carbonate alone is high, and one or more other solvents having a low freezing point are added to lower the freezing point. Any other solvent may be used as long as it lowers the freezing point of ethylene carbonate. For example, diethyl carbonate, dimethyl carbonate, propylene carbonate, 1,2-dimethoxyethane, methylethyl carbonate, γ-butyrolactone, γ-palerolactone, γ-octanoic lactone, 1,2-diethoxyethane, 1,2-ethoxymethoxy Ethane, 1,2-dibutoxyethane, 1,3-dioxolanan, tetrahydrofuran, 2-methyltetrahydrofuran, 4,4-dimethyl-1,3-dioxane, butylene carbonate,
Methyl formate and the like. By using carbon as the active material and using the mixed solvent, the battery capacity is significantly improved.

The electrode according to the invention has a current density of 10.0 mA
/ cm ² large current discharge, discharge capacity 200g / g
It is preferably at least mAh.

To produce the secondary battery electrode of the present invention,
First, a coating composition for an electrode layer for forming an electrode layer on the current collector surface is prepared.

The material and shape of the current collector are not particularly limited in the case of a negative electrode, and aluminum, copper, nickel,
Titanium, stainless steel, etc., and in the case of a positive electrode, a band-like metal, alloy, such as aluminum, titanium, stainless steel, or the like may be used as a foil, perforated foil, mesh, or the like.

The active material, metal powder or metal-coated active material, binder resin and various additives are mixed and dispersed together with a solvent, if necessary, using a dispersion device such as a stirrer, a ball mill, a super sand mill, or a pressure kneader. To prepare an electrode coating composition.

The binder resin contained in the electrode layer is not limited. For example, polyvinylidene fluoride (PVD)
F), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE) ), Polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTF
E), fluorine resins such as polyvinyl fluoride (PVF),
Vinylidene fluoride-hexafluoropropylene fluororubber (VDF-HFP fluororubber), vinylidenefluoride-hexafluoropropylene-tetrafluoroethylene fluororubber (VDF-HFP-TFE)
Fluororubber), vinylidene fluoride-pentafluoropropylene fluororubber (VDF-PFP fluororubber), vinylidenefluoride-pentafluoropropylene-tetrafluoroethylene fluororubber (VDF
-PFP-TFE-based fluoro rubber), vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene-based fluoro rubber (VDF-PFMVE-TF)
E-based fluoro rubber), vinylidene fluoride-based fluoro rubber (VDF-CTFE-based fluoro rubber), vinylidene fluoride-based fluoro rubber, tetrafluoroethylene-propylene-based fluoro rubber (TFE-P-based fluoro rubber) ), A tetrafluoroethylene-perfluoroalkyl vinyl ether-based fluororubber and a thermoplastic fluororubber (for example, Daiel Thermoplastic manufactured by Daikin Industries) can be used.

The above-mentioned binder is usually used in a state of dissolving or dispersing a powdery binder material using a solvent, but it may be used as a powder without using a solvent. The solvent to be used is not particularly limited, and various solvents such as water, methyl ethyl ketone, cyclohexanone, isophorone, N-methylpyrrolidone, N, N dimethylformamide, N, N-dimethylacetamide and toluene may be selected according to the purpose.

The amount of the binder is preferably about 3 to 13 parts by weight based on 100 parts by weight of the electrode material. If the amount of the binder is too small, the adhesiveness becomes insufficient, and if the amount of the binder is too large, the battery capacity becomes insufficient.

An electrode is formed by applying the electrode coating composition as described above to the current collector. The coating method is not particularly limited, and a known method such as a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, a doctor blade method, a gravure coating method, and a screen printing method is used. Good. Thereafter, if necessary, a rolling process using a flat plate press, a calender roll, or the like is performed.

Although the structure of the lithium secondary battery of the present invention is not particularly limited, it is usually composed of a positive electrode, a negative electrode, and a separator provided as necessary, and is a paper-type battery, a button-type battery, a coin-type battery, Stacked battery,
Examples include a cylindrical battery.

[0040]

EXAMPLES Hereinafter, the present invention will be described in more detail by showing specific examples of the present invention.

Example 1 Nickel was coated on an artificial graphite powder (SFG25 manufactured by Lonza) having a 90% cumulative particle size of 25 μm by electroless plating.

The electroless nickel plating was performed under the following conditions.

30 g of nickel chloride, 10 g of sodium hypophosphite and 50 g of sodium hydroxyacetate were dissolved in water to make 1 liter. The plating bath was heated to 90 ° C., and 10 g of graphite was charged while stirring with a magnetic stirrer. Hold in this state for 30 minutes, then filter the graphite,
After washing, nickel-coated graphite was obtained. The nickel content in the nickel-coated graphite powder was 50.7% by weight. Nickel was randomly coated on the surface of the graphite powder (see the photograph in FIG. 7).

This nickel-coated graphite powder and an NMP (N-methylpyrrolidone) solution of PVDF (polyvinylidene fluoride) were mixed with nickel-coated graphite powder: PVDF = 87.
The mixture was mixed at a mixing ratio of 5: 12.5 (weight ratio) and an appropriate viscosity to prepare an electrode paint. This paint is 20mm wide on a titanium plate 24mm wide, 24mm long and 1mm thick.
It was applied by a metal mask printing method so as to be 20 mm long and 0.1 mm thick. The electrode was dried at 150 ° C. under atmospheric pressure for 30 minutes and further at 200 ° C. under vacuum for 30 minutes to remove NMP and moisture.

At this electrode, the electrolyte was 1M LiClO ₄ , and the solvent was a mixed solvent of EC (ethylene carbonate) and DMC (dimethyl carbonate) (EC: DMC = 1: 1 by volume) as a solvent. to prepare a charge-discharge characteristic measuring cell as in Figure 1 using a lithium metal reference electrode, at a current density of 0.25mA / cm ² 0V (vs.Li
/ Li ⁺ ) and 1 V at a current density of 10.0 mA / cm ²
(Vs. Li ^/ Li ⁺ ). The discharge capacity at this time was 353 mAh per gram of graphite. For the sake of clarity, Table 1 shows the discharge capacity per gram of graphite in each of Examples and Comparative Examples.

[0046]

[Table 1]

In FIG. 1, reference numeral 1 denotes a 100 cc beaker, 2 denotes a silicon stopper, 3 denotes a working electrode, 4 denotes a counter electrode, and 5 denotes a counter electrode.
Denotes a reference electrode, 6 denotes a Luggin tube, and 7 denotes an electrolytic solution.

Example 2 Artificial graphite powder having a 90% cumulative particle size of 25 μm (SFG25 manufactured by Lonza) and an average particle size of 2.
2 to 2.8 µm nickel powder (Type 2 manufactured by INCO)
55) NMP of PVDF (polyvinylidene fluoride)
(N-methylpyrrolidone) solution has an appropriate viscosity, and the weight ratio of graphite: nickel: PVDF is 43.1: 4.
It mixed so that it might be set to 4.4: 12.5, and the electrode coating material was produced. At this time, graphite: nickel = 49.3: 50.7
(Weight ratio). This electrode paint is 24mm wide and 24m long.
It was applied to a 1 mm thick titanium plate having a width of 20 mm, a length of 20 mm and a thickness of 0.1 mm by a metal mask printing method.
The titanium plate electrode was dried at 150 ° C. under atmospheric pressure for 30 minutes and further at 200 ° C. under vacuum for 30 minutes to remove NMP and moisture.

[0049] to prepare a cell as in FIG. 1 in the electrode was charged at a current density of 0.25 mA / cm ² until 0V (vs.Li/Li ^+), a current density of 10.0mA / cm ² 1V (vs .Li
/ Li ⁺ ). The discharge capacity at this time was graphite 1
It was 336 mAh per g. Then the current density is 0.25mA
/ cm ² to 0 V (vs. Li / Li ⁺ ), and discharged at a current density of 0.5 mA / cm ² to 1 V (vs. Li / Li ⁺ ). The discharge capacity at this time was 350 mAh per gram of graphite.

Example 3 Graphite: Nickel: PVDF =
Except that 78.75: 8.75: 12.5 (weight ratio), that is, graphite: nickel = 90: 10 (weight ratio), an electrode paint was prepared in the same manner as in Example 2, and a cell was further prepared. The discharge capacity was measured. The results are shown in Table 1.

Example 4 Graphite: Nickel: PVDF =
83.125: 4.375: 12.5 (weight ratio), that is, graphite: nickel = 90: 5 (weight ratio), except that an electrode paint was prepared in the same manner as in Example 2, and a battery was further prepared. The discharge capacity was measured. The results are shown in Table 1.

Example 5 An electrode was prepared in exactly the same manner as in Example 2 except that a copper powder having an average particle size of 10 μm (Wako Pure Chemical Reagent First Class) was used instead of the nickel powder. The composition is graphite: copper: PVDF = 43.1: 44.4: 12.5 (weight ratio), that is, graphite: copper = 49.3: 50.7 (weight ratio). Thereafter, the same operation as in Example 2 was performed to form the cell of FIG. 1 and the discharge capacity was measured. The results are shown in Table 1.

Example 6 Instead of nickel powder, stainless steel fibers (Stainless steel microfiber SMF-S manufactured by Kawasaki Steel, diameter 5 to 10 μm, length 50 to 100 μm)
An electrode was prepared in exactly the same manner as in Example 2 except that (2) was used. Composition: graphite: stainless steel fiber: PVDF = 43.
1: 44.4: 12.5 (weight ratio), that is, graphite: stainless fiber = 49.3: 50.7 (weight ratio). Thereafter, the same operation as in Example 2 was performed to prepare the battery of FIG. 1, and the discharge capacity was measured. The result is shown in FIG.

[Comparative Example 1] An electrode paint was prepared by using an artificial graphite powder (SFG25 manufactured by Lonza) having a 90% cumulative particle size of 25 µm as it was. At this time, the weight ratio between the graphite powder and PVDF is 87.5: 12.5. Except for the above, the same procedure was performed as in Example 1.

When discharged at a current density of 0.5 mA / cm ² , the discharge capacity was 355 mAh / g of graphite and the current density was 10.0 m / g.
A / cm ² , the discharge capacity when discharged is 2 per g of graphite.
20 mAh.

Comparative Example 2 An artificial graphite powder having 90% cumulative particle size of 25 μm (SFG25 manufactured by Lonza) and carbon black (Toka Black 4500 manufactured by Tokai Carbon Co.)
VDF (polyvinylidene fluoride) has an appropriate viscosity in an NMP (N-methylpyrrolidone) solution, and the weight ratio of graphite: carbon black: PVDF is 43.1: 44.
It mixed so that it might be set to 4: 1: 2.5 (weight ratio), and the electrode coating material was produced. At this time, graphite: carbon black = 49.
3: 50.7 (weight ratio). Apply this electrode paint horizontally
mm, length 24mm, thickness 1mm, width 20mm, height 20mm
mm and a thickness of 0.1 mm by a metal mask printing method. This titanium plate electrode is heated at 150 ° C. under atmospheric pressure for 30 minutes.
And dried under vacuum at 200 ° C. for 30 minutes to remove NMP and moisture.

As for the electrode after drying, ten electrodes were produced, but the adhesion was poor such that all of the electrodes were cracked or the mixture was partially peeled off from the titanium plate. The cell of FIG. 1 was fabricated using this electrode in the same manner as in Example 1, and the discharge capacity was measured.

Comparative Example 3 Graphite: carbon black: P
VDF = 78.75: 8.75: 12.5 (weight ratio), ie, graphite: carbon black = 90: 10 (weight ratio)
1 except that the cell of FIG.
Each of them was prepared and the discharge capacity was measured. Observation of the electrodes during charging and discharging revealed that some of the mixture was peeled off from the titanium plate. Table 1 shows the discharge capacity of the best cell. In the case where the mixture was partially peeled from the titanium plate, the discharge capacity was 0%.
mAh.

Comparative Example 4 Graphite: Carbon Black: P
1 except that VDF = 83.125: 4.375: 12.5 (weight ratio), that is, graphite: carbon black = 95: 5 (weight ratio). It was prepared and the discharge capacity was measured. Observation of the electrodes during charging and discharging revealed that some of the mixture was peeled off from the titanium plate. Table 1 shows the discharge capacity of the best cell. In the case where the mixture was partially peeled off from the titanium plate, the discharge capacity was 0 mAh.

[0060]

As can be seen from Table 1, the discharge capacities at a small discharge current density of 0.5 mA / cm ² were considerably reduced in Examples and Comparative Examples (the ones with the addition of carbon black of Comparative Example 2 and thereafter). ), But 10 mA / cm ²
The discharge capacity at a large discharge current density of 220 mAh /
However, as in Example 4, the amount was increased to 249 mAh / g even by adding a small amount of 5 wt% of nickel as in Example 4.

As described above, according to the present invention, it is possible to provide a battery having a large discharge capacity even when a large current is discharged.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a cell for measuring charge and discharge characteristics.

FIG. 2 is a drawing substitute photograph showing a particle structure, and is an electron microscope image showing a cross section of a conventional electrode.

FIG. 3 is a drawing substitute photograph showing a particle structure, and FIG.
5 is an electron microscope image showing the cross section of the conventional electrode shown in FIG.

FIG. 4 is a drawing substitute photograph showing a particle structure, and FIG.
3 is an electron microscope image showing the cross section of the conventional electrode shown in FIG.

FIG. 5 is a drawing substitute photograph showing a particle structure, and is an electron microscope image showing a cross section of an example of an electrode according to the present invention.

6 is a drawing substitute photograph showing a particle structure, and FIG.
4 is an electron microscope image showing the cross section of the electrode according to the present invention shown in FIG.

FIG. 7 is a drawing substitute photograph showing a grain structure, and is an electron microscope image showing an example of graphite coated with nickel according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Beaker 2 Stopper 3 Working electrode 4 Counter electrode 5 Reference electrode 6 Luggin tube 7 Electrolyte

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01M 10/40 H01M 4/02-4/04 H01M 4/36-4/62

Claims (3)

(57) [Claims] In producing a lithium secondary battery using a non-aqueous electrolyte containing a lithium-containing electrolyte, a carbon film formed of a carbon and a binder is formed on a current collector as carbon. Using graphite in which carbon is oriented parallel to the current collector, a metal is added to the carbon having this orientation by mixing or coating a metal, and then mixing with a binder to form a current collector. The positive electrode or the negative electrode is obtained by applying the carbon as an active material, reducing the proportion of the carbon oriented in parallel, and increasing the proportion of the end face of the graphite facing the electrolyte. A method for producing a lithium secondary battery in which a lithium secondary battery with improved discharge characteristics is obtained using the method. 2. The method according to claim 1, wherein the coating is performed by plating. 3. The method for producing a lithium secondary battery according to claim 1, wherein the amount of the metal added is 95/2 to 40/60 in terms of carbon / metal (weight ratio).