JP2001229917A - Method of producing negative electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simpler method of producing a negative electrode using a high-capacity amorphous carbon coating graphite, based carbonaceous material as the active material. SOLUTION: The method of producing the negative electrode comprises forming an amorphous carbon coating graphite based carbonaceous material, obtained by firing at 700 degrees C or higher a mixture, in which a 10-150 parts by weight of thermoplastic resin is mixed based on 100 parts by weight of a graphite carbonaceous material, and a binder into a dispersion coating, using a solvent capable of dissolving the binder, and applying the coating onto a collector and drying the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a negative electrode for a secondary battery, and more particularly, to a method for manufacturing a negative electrode for a secondary battery using a graphitic carbon material having a specific coating film as a negative electrode active material. Related to manufacturing method.

[0002]

2. Description of the Related Art In recent years, various devices such as a camera-integrated VTR device, an audio device, a portable computer, and a cellular phone have been reduced in size and weight, and there has been a demand for higher performance of a battery as a power supply for these devices. Is growing. In particular, lithium secondary batteries capable of realizing high voltage and high energy density have been actively developed. A lithium secondary battery includes a positive electrode capable of inserting and extracting lithium ions, a negative electrode, and an electrolyte layer containing a non-aqueous electrolyte. Conventionally, a liquid composed of a non-aqueous organic substance has been used as the non-aqueous electrolyte. However, a lithium secondary battery using such a non-aqueous electrolyte has a danger of liquid leakage and fire such as heat generation and fire resulting from an internal short circuit due to precipitation of lithium dendrite. Therefore, in recent years, in order to improve safety, development of a non-aqueous electrolyte, for example, a polymer electrolyte contained in a gel polymer and made non-fluidized has been performed.

[0003] In addition, lithium metal was first used as a negative electrode material. However, during repeated charging and discharging, dendritic lithium was deposited and penetrated through the separator, reached the positive electrode, and short-circuited. It was found that a fire accident could occur. Therefore, at present, attention has been paid to use of a carbon material capable of preventing the deposition of lithium metal by allowing a non-aqueous solvent to enter and exit during a charge / discharge process between layers, as a negative electrode material.

As this carbon material, Japanese Patent Application Laid-Open No. 57-20
No. 8079 proposes to use a graphite material. In particular, it has been known that when graphite having good crystallinity is used as a carbon anode material for a lithium secondary battery, a capacity close to 372 mAh / g, which is the theoretical capacity for absorbing lithium of graphite, is obtained, which is preferable as a material. . However, since the graphite material is active with respect to the electrolytic solution, it generally shows an irreversible capacity of several tens mAh / g or more due to film formation and side reactions during the first charge and discharge. JP-A-5-2990
No. 74 discloses that the charge and discharge cycle efficiency can be improved by subjecting a carbon material to a chemical pretreatment with an inorganic acid or heated sodium hydroxide, and then performing a vacuum heat treatment at a temperature of 800 ° C. or more. It is disclosed that it is possible. JP-A-6-20690 discloses a method for producing an amorphous carbonaceous material while oxidizing the surface by chemical liquid oxidation, electrolytic oxidation, or gas phase oxidation, and measuring the increase in negative electrode capacity. Furthermore, Japanese Patent Application Laid-Open No. 6-44959 discloses a method in which an acid is added to a carbonaceous material and heated to obtain a capacity (370 mAh / g) close to the theoretical capacity of graphite.

However, since graphite uses the intercalation of lithium ions into graphite crystals as the principle of charge and discharge, it has a capacity of at least 372 mAh / g calculated from the maximum lithium-introducing compound LiC ₆ at normal temperature and normal pressure. There is a problem that can not be obtained. Therefore, a capacity exceeding the theoretical capacity of graphite of 372 mAh / g has not been obtained by any of the methods. Moreover, the low wettability of the graphite material with the electrolytic solution is due to the fact that the lithium undoping capacity at the initial stage of charge / discharge is 350 mAh, which should be able to express the graphite material.
/ G or more. JP-A-7-022037 and the like disclose a carbonaceous material obtained by coating the surface of a graphitic carbonaceous material with an organic material capable of being carbonized and calcining. This material has the advantage that the potential at the time of charging and discharging is close to the oxidation-reduction potential of lithium metal, similar to that of graphite, and can obtain a higher capacity than that of the graphitic carbonaceous material.
A capacity exceeding 2 mAh / g has not been obtained. further,
Japanese Patent Application Laid-Open No. 10-284080 discloses an electrode material having a high capacity and excellent rate resistance characteristics. The surface of a graphitic carbonaceous material is coated with an organic substance capable of being carbonized, fired, pulverized, and then subjected to acid or alkaline treatment. A carbonaceous material treated with a solution is disclosed. However, the negative electrode containing the carbon material as an active material has a problem that gas is generated during charging.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a simpler method for producing a negative electrode using an amorphous carbon-coated graphite-based carbonaceous material as an active material and suppressing generation of gas during charging. is there.

[0007]

Means for Solving the Problems The inventors of the present invention have intensively studied a method for manufacturing a negative electrode using an amorphous carbon-coated graphite-based carbonaceous material as an active material, and as a result, have found that a method for producing a negative electrode has been proposed. It has been found that a negative electrode can be manufactured without using a pulverizing step after firing by using a plastic resin, and the present invention has been completed. That is, the gist of the present invention is to provide an amorphous carbon-coated graphite-based carbonaceous material obtained by calcining a mixture containing 10 to 150 parts by weight of a thermoplastic resin at 700 ° C. or higher with respect to 100 parts by weight of a graphitic carbonaceous material. Binder, and a dispersion paint using a solvent capable of dissolving the binder,
The method for producing a negative electrode is characterized in that the paint is applied on a current collector and dried.

In a preferred embodiment of the present invention, the above-mentioned production method characterized by heating a mixture of a graphitic carbonaceous material and a thermoplastic resin, and melting the thermoplastic resin. , Polyvinyl chloride, polyvinyl alcohol or polyvinylpyrrolidone.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The amorphous carbon-coated graphite-based carbonaceous material which is the active material of the negative electrode in the present invention means a graphite-based carbonaceous material having an amorphous carbon film on a surface layer. Examples of the graphitic carbonaceous material used for producing the amorphous carbon-coated graphite-based carbonaceous material in the present invention include highly crystalline natural graphite, highly crystalline artificial graphite, and natural graphite and artificial graphite. A heat-treated product, a re-heat-treated product of expanded graphite, or a high-purity purified product of these graphites is preferable.

Examples of the type of the graphitic carbon substance include the following (1) to (4), which can be selected from these. (1) Highly crystalline natural graphite or artificial graphite; (2) Natural graphite, artificial graphite, or expanded graphite reheated at 2000 ° C. or higher; (3) Graphitization of graphitizable organic raw materials Graphite having the same performance as (1) and (2), such as coal tar pitch, coal-based heavy oil, atmospheric residual oil, petroleum-based heavy oil, aromatic hydrocarbon, nitrogen-containing cyclic compound, At least one selected from a sulfur-containing cyclic compound, polyphenylene, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, natural polymer, polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin 250 organics
Graphitized at a firing temperature of 0 ° C. or more and 3200 ° C. or less,

(4) The graphitizable organic substance of (3) is lithium, beryllium, boron, magnesium, aluminum, silicon, potassium, calcium, titanium, vanadium, chromium, manganese, copper, zinc, nickel, platinum,
Palladium, cobalt, ruthenium, tin, lead, iron, germanium, zirconium, molybdenum, silver, barium,
In the presence of a catalyst such as at least one powder or thin film selected from tantalum, tungsten and rhenium,
400 ° C. or more and 2500 ° C. or less, more preferably 100 ° C.
Graphitized by firing at 0 ° C or more and 2000 ° C or less.

The average particle size of the graphitic carbonaceous material is usually 4 μm.
Or more, preferably 10 μm or more, and usually 40 μm or less.
Lower, preferably 30 μm or less. Particle size is too small
It is difficult to increase the packing density of the coating and the electrode
The surface properties are reduced, and the adhesiveness with the separator is reduced. graphite
The specific surface area of the carbonaceous material is the specific surface area of the BET method.
0.1m^Two/ G or more, preferably 1 m^Two/ G or more,
Normal 20m^Two/ G or less, preferably 10 m ^Two/ G or less
You. If the specific surface area is too small, the rapid charge / discharge characteristics decrease,
If it is too large, the strength of the coating film decreases, and the safety also decreases.

The thermoplastic resin used in the present invention is preferably a resin which becomes molten at 200 ° C.
Specifically, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyvinyl alcohol (PVA),
Examples include polyethylene (PE), polyethylene terephthalate (PET), and polyvinyl pyrrolidone (PVP). Particularly preferred are polyvinyl chloride (PVC), polyvinyl alcohol (PVA), and polyvinyl pyrrolidone (P
VP).

[0014] The mixing ratio of the graphitic carbonaceous material and the thermoplastic resin is such that if the amount of the thermoplastic resin is too small, the effect of suppressing gas generation is reduced. Usually at least 10 parts by weight,
Preferably, it is used in an amount of at least 20 parts by weight, more preferably at least 40 parts by weight. Also, if the amount is too large, a voltage drop and a capacity decrease at the time of discharge may occur. It is usually used in an amount of 150 parts by weight or less, preferably 80 parts by weight or less, more preferably 60 parts by weight or less. Depending on the type of thermoplastic resin used, it is appropriately selected from these ranges, but generally,
10 to 150 parts by weight, preferably 20 to 100 parts by weight, particularly preferably 4 to 100 parts by weight, per 100 parts by weight of the graphitic carbonaceous material.
0 to 60 parts by weight.

The mixing of the graphitic carbonaceous material and the thermoplastic resin may be performed in a dry manner using a known mixing device such as a V-type mixer, and a shearing force can be applied from the viewpoint of performing more precise mixing. It is preferable to use a device such as a ball mill or a hammer mill. When mixing the graphitic carbonaceous material and the thermoplastic resin, the mixture of the graphitic carbonaceous material and the thermoplastic resin is heated to 180 to 220 ° C. so that the thermoplastic resin is uniformly distributed around the circumference of the graphitic carbonaceous material. Heat treatment with
It is preferable to melt the thermoplastic resin.

The firing of the mixture is usually carried out in an atmosphere of an inert gas such as nitrogen or argon. The firing temperature may be at least the temperature at which carbonization is completed, and is usually 700 ° C. or higher, preferably 750 ° C. or higher, and preferably 110 ° C. or higher.
The temperature is 0 ° C or lower, more preferably 1000 ° C or lower, particularly preferably 950 ° C or lower. If the temperature is too low, carbonization is insufficient and sufficient performance as an electrode active material cannot be obtained.
If the temperature is too high, the crystallinity of the graphite may be too high. If the crystallinity is too high, gas may be generated. The heating rate is not particularly limited, but may be 10 to 50.
0 ° C./h, preferably 20 to 100 ° C./h.

The amorphous carbon-coated graphite-based carbonaceous material obtained by calcination is formed into a dispersion coating using a binder and a solvent capable of dissolving the binder without passing through a crushing step after calcination. Usually, graphitic carbonaceous material powder and synthetic resin,
When a binder mainly composed of hydrocarbons such as pitches and oils is mixed, the graphitic carbonaceous material powders are strongly bonded to each other.
By the way, when using a graphite-based carbonaceous material as a negative electrode material, it is necessary to use a graphite-based carbonaceous material as a powder, so it is usually necessary to grind using a crusher or the like,
When the pulverizing step is used, there is a problem that the yield is reduced due to generation of the fine particle component, and a new interface not covered with the surface is generated. In the fired amorphous carbon-coated graphite-based carbonaceous material obtained by the method of the present invention, without using a pulverizer,
Specifically, it can be easily crushed only by applying a gentle force such as a vibration sieve or the like, and the obtained amorphous carbon-coated graphite-based carbonaceous material can be used as it is in the next step.

As the binder in the present invention, it is necessary to be stable to an electrolytic solution or the like, and various materials are used from the viewpoint of weather resistance, chemical resistance, heat resistance, flame retardancy and the like. Specifically, inorganic compounds such as silicate and glass, polyethylene, polypropylene, poly-1,1-
Alkane-based polymers such as dimethylethylene; unsaturated polymers such as polybutadiene and polyisoprene; polystyrene, polymethylstyrene, polyvinylpyridine,
Polymers having a ring structure in a polymer chain such as poly-N-vinylpyrrolidone; polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyacrylic acid, polymethacrylic acid , Polyacrylamides and other acrylic derivative polymers; polyvinyl fluoride, polyvinylidene fluoride, polytetrafluoroethylene and other fluorine resins; CN-containing polymers such as polyacrylonitrile and polyvinylidene cyanide; polyvinyl acetate and polyvinyl alcohol Polyvinyl alcohol-based polymer;
Halogen-containing polymers such as polyvinyl chloride and polyvinylidene chloride; conductive polymers such as polyaniline can be used.

Further, a mixture of the above-mentioned polymers and the like, a modified product, a derivative, a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer and the like can also be used. The weight average molecular weight of these resins is usually 10,000
0 to 3,000,000, preferably 100,000 to 1,
It is about 1,000,000. If it is too low, the strength of the coating tends to decrease. On the other hand, if it is too high, the viscosity becomes high, and it may be difficult to form an electrode. Preferred examples of the binder resin include a fluorine-based resin and a CN group-containing polymer, and more preferably polyvinylidene fluoride.

The amount of the binder used is usually at least 0.1 part by weight, preferably at least 1 part by weight, and usually at most 30 parts by weight, based on 100 parts by weight of the amorphous carbon-coated graphite-based carbonaceous material. Is 20 parts by weight or less. If the amount of the binder is too small, the strength of the electrode tends to decrease, and if the amount of the binder is too large, the ion conductivity tends to decrease. As the solvent in the present invention, a solvent capable of dissolving the binder to be used may be appropriately selected, and examples thereof include N-methylpyrrolidone and dimethylformamide, and N-methylpyrrolidone is preferable. The solvent concentration in the paint is at least greater than 10% by weight, but is usually at least 20% by weight, preferably at least 30% by weight, more preferably at least 35% by weight. The upper limit is usually 90% by weight or less, preferably 8% by weight.
0% by weight or less. If the solvent concentration is too low, application may be difficult, and if it is too high, it may be difficult to increase the thickness of the applied film and the stability of the coating may deteriorate.

A commonly used dispersing machine can be used for the dispersion coating, and a ball mill, a sand mill, a twin-screw kneader or the like can be used. In the present invention, the negative electrode is manufactured by applying the dispersion paint prepared as described above on a current collector and drying it. There is no particular limitation on the coating apparatus for applying the paint on the current collector, and examples include slide coating and extrusion type die coating, reverse roll, gravure coater, knife coater, kiss coater, microgravure coater, rod coater, blade coater, and the like. However, the extrusion method is most preferable in consideration of the viscosity of the coating material and the thickness of the coating film. After the above-mentioned paint is applied on the current collector, the paint film is applied, for example, at 120 ° C. for 10 minutes.
Let dry for minutes. When the drying temperature is low, the crystallization of the binder hardly occurs, and the strength of the coating film decreases. If the drying time is short and drying is insufficient, the residual solvent adversely affects the battery characteristics.
Conversely, if the temperature is high or the drying time is too long, the current collector is oxidized and battery characteristics deteriorate. Usually 80-140 ° C,
Dry for 5-20 minutes.

In order to improve the conductivity and mechanical strength of the electrode, the electrode may contain additives, such as conductive materials and reinforcing materials, which exhibit various functions, powders, fillers, and the like. The conductive material is not particularly limited as long as it can impart conductivity by mixing an appropriate amount with the amorphous carbon-coated graphite, but usually, acetylene black, carbon black, carbon powder such as graphite, and various types of Metal fiber,
Foil and the like. The carbon powder conductive material preferably has a DBP oil absorption of 120 cc / 100 g or more, and
cc / 100 g or more is preferable because it holds the electrolytic solution. As the additives, trifluoropropylene carbonate, 1,6-dioxaspiro [4,4] nonane-2,7-dione, 12-crown-4-ether, vinylene carbonate, catechol carbonate, and the like can improve the stability and life of the battery. Can be used to enhance. As the reinforcing material, various inorganic or organic spherical or fibrous fillers can be used.

The thickness of the negative electrode is generally 0.05 to 200.
It is about μm. Within this range, it is usually at least 10 μm, preferably at least 20 μm, and usually at most 200 μm, preferably at most 150 μm. If it is too thin, the capacity of the battery may be too small. On the other hand, if the thickness is too large, the rate characteristics may be too low. Note that the negative electrode in the above description means a layer containing an active material (amorphous carbon-coated graphite) and does not include a current collector.

As the current collector in the present invention, various kinds of materials which do not cause problems such as elution electrochemically and can function as a current collector of a battery can be used, and usually, metals and alloys are used. For example, a copper foil is often used as the current collector of the negative electrode. Preliminarily roughening the surface of the current collector is a preferable method because the effect of binding to the electrode material layer can be improved. Examples of the surface roughening method include a method such as blasting and rolling with a rough roll, a polishing cloth paper to which abrasive particles are fixed, a grindstone, an emery buff, a wire brush provided with a steel wire, or the like. A mechanical polishing method for polishing the surface, an electrolytic polishing method, a chemical polishing method, and the like can be given.

Further, in order to reduce the weight of the secondary battery, that is, to improve the weight energy density, a perforated substrate such as an expanded metal or a punched metal can be used. In this case, the weight can be freely changed by changing the aperture ratio. When contact layers are formed on both surfaces of such a perforated type substrate, the peeling of the coating film tends to be less likely to occur due to the rivet effect of the coating film through this hole, but the aperture ratio becomes too high. In such a case, the contact area between the coating film and the base material becomes small, so that the adhesive strength may be rather lowered. The thickness of the current collector is usually 1 μm or more, preferably 5 μm or more, and usually 100 μm or less, preferably 5 μm or less.
0 or less. If it is too thick, the overall capacity of the battery will be too low, and if it is too thin, handling may be difficult.

An undercoat primer layer may be formed on the current collector. The function of the primer layer is to improve the adhesiveness of the negative electrode to the current collector.As compared with the case where no primer layer is provided, the internal resistance of the battery is reduced by improving the adhesiveness, This is to prevent a rapid decrease in capacity due to detachment of the coating film.
The undercoat primer layer can be formed, for example, by applying an undercoat primer material paint containing a conductive material, a binder, and a solvent on a current collector and then drying the paint. The conductive material used for the undercoat primer layer includes carbon black,
Examples of the material include a carbon material such as graphite, a metal powder, and a conductive organic conjugated resin. However, a material such as carbon black and graphite which can also function as an active material of an electrode is preferable.

The binder and the solvent used for the undercoat primer layer may be the same as the binder and the solvent used for the coating of the electrode material. In addition, conductive resins such as polyaniline, polypyrrole, polyacene, disulfide-based compounds, and polysulfide-based compounds can have both functions of the conductive material and the binder. It can also be used for the undercoat primer layer. Of course, the binder and the solvent used for the undercoat primer layer may be the same as or different from those used for the coating of the electrode material.

When the conductive material and the binder are used, the ratio of the binder to the conductive material is usually at least 1% by weight, preferably at least 5% by weight, and usually at most 300% by weight, preferably 100% by weight. % Or less. If the temperature is too low, peeling during the process is likely to occur during use of the battery, while if it is too high, the conductivity may decrease and the battery characteristics may deteriorate. The thickness of the undercoat primer layer is generally 0.05 to 200 μm.
m. Within this range, it is usually at least 0.05 μm, preferably at least 0.1 μm, and usually at most 10 μm, preferably at most 1 μm. If it is too thin, it is difficult to ensure uniformity, and if it is too thick, the volume capacity of the battery may be too low.

[0029]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by these examples unless it exceeds the gist thereof.

Example 1 Graphite powder (average particle size: 15 μm, specific surface area: 5 m ² / g)
With respect to 00 parts by weight, 50 parts by weight of powdery polyvinyl chloride was dry-mixed at room temperature for 30 minutes using an Al ₂ O ₃ ball mill, and the mixed powder was transferred to a graphite crucible and covered with a lid. The temperature was raised to 900 ° C at 300 ° C / h,
C. for 1 hour to obtain graphite coated with amorphous carbon. With respect to 100 parts by weight of the obtained amorphous carbon-coated graphite (the amorphous carbon-coated graphite was used without being crushed after firing), 10 parts by weight of polyvinylidene fluoride (binder), N-methyl-2- Mix 100 parts by weight of pyrrolidone (solvent),
The mixture was kneaded with a kneader for 2 hours to obtain a dispersion paint for a negative electrode. The negative electrode dispersion paint was applied on a 20 μm thick copper current collector base material by extrusion die coating,
It dried at 10 degreeC for 10 minutes, and produced the negative electrode.

Example 2 A negative electrode was produced in the same manner as in Example 1 except that the blending amount of polyvinyl chloride was changed to 100 parts by weight with respect to 100 parts by weight of the graphite powder. Example 3 A negative electrode was produced in the same manner as in Example 1 except that polyvinyl alcohol was used instead of polyvinyl chloride.

Example 4 A negative electrode was prepared in the same manner as in Example 1 except that polyvinylpyrrolidone was used instead of polyvinyl chloride. Comparative Example 1 A negative electrode was produced in the same manner as in Example 1 except that polyvinyl chloride was not blended.

Formation of Battery First, the following paints were prepared. [Positive electrode paint] Composition : lithium cobalt oxide 90 parts Acetylene black 5 parts Polyvinylidene fluoride 5 parts N-methyl-2-hydroxylithone 80 parts All the above-mentioned raw materials were kneaded for 2 hours by a kneader to prepare a paste for a positive electrode.

[Electrolyte paint] Composition Tetraethylene glycol diacrylate 14 parts Polyethylene oxide triacrylate 7 parts Lithium perchlorate 21 parts Polymerization initiator 1 part Additive (spirodilactone) 14 parts Electrolyte (propylene carbonate) 120 parts Electrolyte (ethylene carbonate) 120 parts All of the above components were mixed, stirred and dissolved to obtain an electrolyte paint.

Next, a positive electrode paint is applied on an aluminum current collector base material having a thickness of 20 μm by extrusion die coating and dried to form a porous film in which an active material is bound on the current collector by a binder. did. Then
100kgf / c linear pressure using a roll press (calendar)
A positive electrode was produced by compacting under the condition of m.

An electrolyte coating is applied to the positive electrode and the negative electrodes manufactured in Examples 1 to 4 and Comparative Example 1, and a polymer porous film having a slightly larger area than the electrode immersed in the electrolyte coating is interposed therebetween and laminated. A flat unit battery element having a positive electrode, a negative electrode, and a non-fluidized electrolyte component by non-fluidizing the electrolyte by heating at 90 ° C. for 10 minutes with the electrolyte paint added and sandwiched. Was formed. Thereafter, a tab for taking out a current was connected to the unit battery element, and a laminated film composed of an aluminum film and a polymer film was vacuum-sealed and stored in a bag-shaped case formed oppositely to obtain a flat battery.

Battery Performance Test The obtained flat battery was charged to 4.2 V at 0.5 mA / cm ² , and the presence or absence of gas generation was visually confirmed. If there is gas generation, the case will bulge. The results are shown in the table below.

[0038]

[Table 1]

[0039]

According to the present invention, a negative electrode using an amorphous carbon-coated graphite-based carbonaceous material useful as a carbonaceous negative electrode for a high-capacity battery, particularly a secondary battery, is used as a graphitic carbonaceous material. After baking the mixture of the thermoplastic resins, the mixture can be manufactured by a simpler process without going through a pulverizing process.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01M 10/40 H01M 10/40 Z (72) Inventor Unaka Tanaka 2181 Nakahime, Onohara-cho, Mitoyo-gun, Kagawa Prefecture -2 Toyo Carbon Co., Ltd. Technology Development Center (72) Inventor Tetsuro Tojo Tono Carbon Co., Ltd. 21-21-2 Nakahime, Onohara-cho, Mitoyo-gun, Kagawa Prefecture (72) Inventor Toshiya Naruto Aoba-ku, Yokohama, Kanagawa 1000 Kamoshita-cho Mitsubishi Chemical Corporation Yokohama Research Laboratory F-term (reference) 4G046 EA03 EA05 EB02 EB06 EC06 5H029 AJ03 AJ14 AK03 AL06 AL07 AM03 AM04 AM05 AM07 CJ02 CJ22 CJ28 DJ08 DJ16 DJ18 EJ12 HJ01 HJ14 5H050 AA08 DAB EA23 EA24 FA17 FA18 FA20 GA02 GA22 HA01 HA14

Claims (3)

[Claims] 1. A mixture of 10 to 150 parts by weight of a thermoplastic resin with respect to 100 parts by weight of a graphitic carbonaceous material,
The amorphous carbon-coated graphite-based carbonaceous material and the binder obtained by firing at 00 ° C. or more are made into a dispersion paint using a solvent capable of dissolving the binder, and the paint is applied on a current collector and dried. A method for producing a negative electrode, comprising: 2. The method for producing a negative electrode according to claim 1, wherein a mixture of the graphitic carbonaceous material and the thermoplastic resin is subjected to a heat treatment to melt the thermoplastic resin. 3. The method for producing a negative electrode according to claim 1, wherein the thermoplastic resin is polyvinyl chloride, polyvinyl alcohol, or polyvinylpyrrolidone.