JP2002237296A - Negative electrode material for lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To select and use a conductive material, preferably a recycling material, provide a negative electrode material for a lithium ion secondary battery using a carbonaceous material of large de-doping capacity and capable of efficiently drawing out the original discharge capacity of the carbonaceous material, as the electrode material. SOLUTION: A nickel-base alloy which is the waste material of a magnetic recording material is mixed in a carbon material to acquire the negative electrode material for the lithium ion secondary battery improved in conductivity and having large dedoping capacity, and the lithium ion secondary battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative electrode material for a lithium ion secondary battery, and more particularly, to a carbon electrode material having high capacity, high charge / discharge efficiency, and excellent cycle characteristics defined by a dope-undope capacity. The present invention relates to a used negative electrode material for a lithium ion secondary battery.

[0002]

2. Description of the Related Art In recent years, portable devices such as portable telephones, laptop computers, and camera-integrated VTRs have formed a large market. There is a strong demand for a lightweight, compact, and high energy density secondary battery as a power supply for these portable devices. Lithium-ion secondary batteries are superior to other secondary batteries in these respects,
Each company is actively developing. Secondary batteries using lithium metal for the negative electrode have been developed for consumer use at one time for communication equipment, but when charged, dendrites (resin-like crystals) that precipitate on the negative electrode surface or There has been an important problem that the safety and battery performance of the battery are impaired due to the generation of granular lithium and the like.

[0003] For this reason, measures such as using a lithium alloy for the negative electrode as disclosed in Japanese Patent Application Laid-Open No. 4-286864 and examining an electrolytic solution as disclosed in Japanese Patent Application Laid-Open No. 4-56078 are disclosed. Has been taken.

[0004] In order to improve this, it has been found that lithium is occluded between the layers during the charge / discharge process, and a carbonaceous material capable of preventing the deposition of lithium metal is used as the negative electrode. Among them, as shown in JP-A-4-237949, polymerized carbide, coke, carbon fiber, coal and petroleum pitch fired material, graphitic carbon such as mesocarbon microbeads, lower crystallinity and Carbonaceous materials defined by specific gravity, Raman spectroscopy, specific surface area and other properties have been proposed. JP-A-57-208079 discloses that graphite having the highest crystallinity should be used as a carbonaceous material. However, since graphite uses intercalation of lithium ions into graphite crystals as a principle of charge and discharge, there is a problem that a capacity of 372 mAh / g or more calculated from LiC _{6 as the} maximum lithium-introducing compound cannot be obtained. Was.

On the other hand, a carbonaceous material which is calcined at 950 ° C. or lower and has very few crystallized portions is a graphite having a theoretical capacity of 372 mAh.
It has been reported to show a capacity greater than / g, and is attracting attention as a capacity increase method. It is known that this carbonaceous material has different capacity, efficiency, irreversible capacity defined as the difference between dope capacity and undoped capacity, and potential characteristics during charge and discharge depending on the difference in firing temperature (Dahn et al., Science Magazine, Vol. 270, p. 590).

As described above, in the temperature range up to about 450 ° C., the carbonaceous material tends to have a larger initial lithium ion charge capacity as it is fired at a lower temperature. There has been a problem that the irreversible capacity defined as the difference in doping capacity also increases. That is, in the normal firing method, although a high lithium ion charge capacity is exhibited, the material also has a high irreversible capacity with a high resistivity, so that such a carbonaceous material is practically used as an electrode material for a lithium ion secondary battery. I couldn't do that.

Incidentally, nickel-based alloys, especially nickel-based alloys represented by permalloy, supermalloy, and super-permalloy, support today's information society as magnetic recording materials. Magnetic recording media using such materials include:
2. Description of the Related Art Various forms such as magnetic tapes and hard disks are widely used not only for recording images and sounds but also as external recording media for computers. The nickel-based alloy used in this manner is discarded in large quantities in the process of manufacturing the recording medium. Nickel is an expensive resource, but if it is alloyed for a specific purpose like this, a large amount of energy will be consumed to recover it again as a single item, so it is often discarded from the viewpoint of cost recovery. Is the current situation. However, there has been a long search for a way to utilize a nickel-based alloy alloyed as a magnetic recording medium for other purposes as it is or in a form close to the composition as it is.

Japanese Patent Application Laid-Open No. 6-318454 discloses a negative electrode for a secondary battery containing a mixture of a flaky metal or alloy powder capable of reversibly occluding and releasing lithium, a flaky carbon powder and a binder. It has been disclosed. Also, JP-A-8-3
Japanese Patent Publication No. 06356 discloses a carbon electrode material composition for a secondary battery in which nickel particles are mixed with a carbonaceous material, but each of them has a different material configuration, object, and effect from the present invention.

[0009]

SUMMARY OF THE INVENTION A first object of the present invention is to provide a negative electrode material for a lithium ion secondary battery which has a large undoping capacity and can efficiently draw out the original discharge capacity of a carbonaceous material. Things. A second object of the present invention is to provide a negative electrode material for a lithium ion secondary battery which has excellent charge / discharge cycle characteristics and can express a large capacity without relying on a binder molding method which causes a decrease in operation reliability. is there. A third object of the present invention is to provide a negative electrode material for a high-performance lithium ion secondary battery by recycling nickel-based alloys used as magnetic materials that are disposed of as waste materials and blending them with carbon materials. Things.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, (1) forming a carbonaceous film mixed with a nickel-based alloy on a current collector. A negative electrode material for a lithium ion secondary battery,
(2) The method according to the above (1), wherein a carbonaceous film capable of electrochemically absorbing and releasing lithium ions mixed with a nickel-based alloy without a binder is provided on the current collector. (3) The negative electrode material for a lithium ion secondary battery according to the above (1) or (2), wherein the nickel-based alloy is a waste magnetic material. The inventors have found that the above-mentioned problems have been solved, and have completed the present invention.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The carbon materials used in the present invention include polymer carbide, coke, carbon fiber, coal and petroleum pitch fired products, mesocarbon microbeads, graphite and the like.
All known carbon materials conventionally used are mentioned and used. Among these carbon materials, a low-temperature fired carbon material, and a carbon material prepared by applying and heating a coating solution obtained by dissolving or dispersing a nonvolatile carbon-containing compound in an organic solvent on a current collector are preferably used. .

First, the low-temperature fired carbon material used in the present invention will be described. As the low-temperature fired carbon material used in the present invention, all materials manufactured by a known method using a known material can be used.

The organic substance for obtaining the carbon material of the present invention includes coal-based heavy oil such as coal tar pitch from soft pitch to hard pitch and dry distillation liquefied oil, and direct current such as atmospheric residual oil and vacuum residual oil. Petroleum heavy oil such as cracked heavy oil such as ethylene tar by-produced during thermal cracking of heavy crude oil, crude oil and naphtha. Furthermore, acenaphthylene, dekacyclen,
Aromatic hydrocarbons such as anthracene; N ring compounds such as phenazine and acridine; S ring compounds such as thiophene; alicyclic ring such as adamantane; polyphenylene such as biphenyl and terphenyl; Examples include polymers such as vinyl and polyvinyl alcohol. Further, natural polymers such as cellulose and saccharides, thermoplastic resins such as polyphenylene sulfide, and polyphenylene oxide, and thermosetting resins such as furfuryl alcohol resin, phenol-formaldehyde resin, and imide resin can also be used.

These organic substances are preferably used in an amount of 200 to 60.
0 ° C., 0.1 to 10 hours, more preferably 300 to 50
A treatment such as detarring and pitching is performed at 0 ° C. for 1 to 8 hours to obtain a carbonaceous material precursor. It is also useful and effective to use an industrially manufactured pitch.

[0015] These precursor materials are preferably
It is fired at 〜1000 ° C., more preferably at 600-900 ° C., and pulverized to obtain particles of preferably 5-100 μm. The volume resistivity of the powder is 10 ¹ Ω · c.
m, 10 ⁷ Ω · cm or less, a specific surface area of 1 m ² / g or more, 100 m ² / g or less, and an H / C (hydrogen / carbon atom existence ratio) of 0.1 to 0.5. Preferably it is carbon.

In another embodiment, carbon fiber is used and can be effectively used. In this case, a carbon material produced by a known method such as the method disclosed in JP-A-11-329434 can be preferably used.

It is known that a negative electrode carbonaceous material for a lithium ion secondary battery contains a conductive substance in order to improve the potential and charge / discharge characteristics. Nickel-based alloys are preferred because they have good conductivity and excellent oxidation resistance, and are preferably used because they have excellent contact between particles and easily form a conductive path.

As the nickel-based alloy that can be used here, any known nickel-based alloy can be used, but it is particularly useful as a waste material of a magnetic recording medium that can use a material containing expensive nickel as it is. As such a nickel-based alloy, all known alloys such as a nickel-iron alloy, a nickel-chromium alloy, and a nickel-molybdenum alloy can be used. These nickel-based alloys are partially or wholly oxidized,
Nitrided, sulfided, borated and the like also belong to the category of the present invention.

One of the objects of the present invention is to make effective use of waste materials and recycled materials. As a nickel-based alloy,
A magnetic recording material selected from permalloy, supermalloy and ultra-permalloy is valuable as one of the materials satisfying such a purpose.

When a magnetic recording material waste or recycled material is used as the nickel-based alloy, the magnetic recording material layer often contains a nickel-based alloy and a binder resin, and in many cases, on a support layer. Is formed with a thin layer. To peel off the nickel-based alloy layer from the support, a method of dissolving, dispersing, or swelling the recording layer in an appropriate solvent to remove it, or a method of mechanically peeling off the support using a scraper or the like, A method of heating and burning the body and / or the binder resin to collect the remaining alloy particles is exemplified. In some cases, a nickel-based alloy layer is directly provided on a support by a vacuum thin film forming method without using a binder resin. In this case, a target alloy can be recovered in the same manner. The recovered alloy can be mixed with a carbon material by an appropriate method as it is when there is no solvent, or when it is a dispersion containing a solvent, while containing the solvent, or after evaporating the solvent. .

In general, when a conductive filler is added to an insulating material or a high-resistance material, a so-called percolation phenomenon occurs in which the resistance rapidly decreases at a specific volume fraction. Therefore, the ratio of the conductive filler needs to be larger than the percolation threshold. The content of the nickel-based alloy and the carbon material in the present invention is preferably such that the carbon material is 95 to 60% by volume, the nickel-based alloy is 5 to 40% by volume, more preferably the carbon material in the final adjusted electrode. Is 90 to 70% by volume and the nickel-based alloy is 10 to 70% by volume.
30% by volume.

When the amount of the nickel-based alloy is less than the above range,
There is little improvement in low potential and rapid charge / discharge characteristics, and if it is higher than the above range, the volume energy density and the weight energy density may be reduced. The above range is not the raw material charge ratio but the content at the stage of the final carbonaceous material. Therefore, at the time of preparation, it is necessary to determine the compounding amount of the raw materials in consideration of the composition ratio at the final stage.

Next, a method for manufacturing these electrodes will be described. The raw material of the carbonaceous material and the nickel-based alloy are mixed in a mixer having a heating means at a charging ratio such that the final composition falls within the above range, and preferably calcined at 500 to 1000 ° C. for 0.5 to 3 hours, Obtain a conductive filler composite material.

Alternatively, a method of producing a carbon material via carbon fibers is also effective. In this case, in view of the performance as a negative electrode material for a battery, it is preferable that the pitch-based carbon fiber is carbonized in an appropriate temperature range. As the negative electrode material, a material pulverized after carbonization is preferably used. This is usually
It is manufactured by using a pitch as a raw material, spinning, infusibilizing, and carbonizing into carbon fibers by a conventional method, and then pulverizing the carbon fibers. The carbon material thus obtained can also be mixed with a nickel-based alloy to form a negative electrode material.

As a mixing method of these carbon materials and nickel-based alloys, it is possible to use a commonly used evaporation method, electroless plating method, immersion method, sputtering method, mechanical alloying, mechanical grinding, etc. The effect of the present invention can be obtained simply by mixing the two. These are produced by a method using a known device.

The carbon material having a nickel-based alloy thus obtained is pulverized preferably in a range of 1 to 100 μm, more preferably in a range of an average particle size of 5 to 50 μm, and a binder, a solvent and the like are added to the pulverized material. In addition, a slurry is formed, and the slurry is applied to a substrate of a metal current collector such as a copper foil and dried to form an electrode. Further, the electrode material can be directly formed into an electrode shape by a method such as roll forming or compression forming.

The binders usable for the above purpose include:
Solvent-stable, polyethylene, polypropylene,
Polyethylene terephthalate, aromatic polyamide, resin-based polymers such as cellulose, styrene-butadiene rubber,
Rubbery polymers such as isoprene rubber, butadiene rubber, and ethylene / propylene rubber, styrene / butadiene / styrene block copolymers, their hydrogenated products, styrene / isoprene / styrene block copolymers, and their thermoplasticity such as their hydrogenated products Elastomeric polymers, soft resinous polymers such as syndiotactic 12-polybutadiene, ethylene / vinyl acetate copolymer, propylene / α-olefin (2 to 12 carbon atoms) copolymer, polyvinylidene fluoride,
Fluoropolymers such as polytetrafluoroethylene and polytetrafluoroethylene / ethylene copolymers; and polymer compositions having ion conductivity of alkali metal ions, particularly lithium ions, may be mentioned.

Examples of the polymer having ion conductivity include polyether polymer compounds such as polyethylene oxide and polypropylene oxide, crosslinked polymers of polyether compounds, polyepichlorohydrin, polyphosphazene, polysiloxane, polyvinylpyrrolidone, and the like. Polyvinylidene carbonate, high molecular compound such as polyacrylonitrile, lithium salt, or a system in which an alkali metal salt mainly composed of lithium, or a high dielectric constant such as propylene carbonate, ethylene carbonate, γ-butyrolactone A system containing an organic compound can be used. The ionic conductivity of such an ion-conductive polymer composition at room temperature is preferably 10 ^-5 S / cm or more, and more preferably 10 ^-3 S / cm or more.

The carbon material having a nickel-based alloy used in the present invention may be mixed with the above-mentioned binder in various forms. That is, a form in which both particles are mixed, a form in which a fibrous binder is entangled with the carbonaceous material particles, or a form in which a binder layer is attached to the surface of the carbonaceous material particles, and the like. The mixing ratio of the carbon material having a nickel-based alloy and the binder is preferably 30% by weight or less, more preferably 10% by weight or less. If the binder is added in an amount larger than this, the internal resistance of the electrode increases, which is not preferable.

In the present invention, it is possible to use a carbonaceous film capable of electrochemically occluding and releasing lithium ions mixed with a nickel-based alloy without containing a binder. Such a carbonaceous film can be produced by applying and heating a coating solution obtained by dissolving or dispersing a nonvolatile carbon-containing compound and a metal compound in an organic solvent on a current collector.

As such a nonvolatile carbon-containing compound,
Co-produced heavy oil such as coal tar pitch from dry pitch to hard pitch, dry distillation liquefied oil, heavy duty direct current oil such as atmospheric residual oil and vacuum residual oil, crude oil, naphtha etc. Petroleum heavy oil such as cracked heavy oil such as ethylene tar. Aromatic hydrocarbons such as acenaphthylene, decacyclene and anthracene; N-ring compounds such as phenazine and acridine; S-ring compounds such as thiophene;
Pressurizing more than MPa is required, but alicyclic ring such as adamantane, polyphenylene such as biphenyl and terphenyl,
Examples include polymers such as polyvinyl chloride and polyvinyl alcohol. Also, natural polymers such as cellulose and saccharides, thermoplastic resins such as polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin,
Thermosetting resins such as phenol-formaldehyde resins and imide resins can also be mentioned. In particular, an easily graphitizable carbon body is suitably used as such a non-volatile carbon-containing compound. Mesophase pitch carbon is most preferably used as a non-volatile carbon-containing compound.

As the metal to be doped into the carbonaceous negative electrode, a nickel-based alloy as described above can be used.

Each of the above materials may be formed on a current collector by a vacuum thin film forming method such as a vacuum vapor adsorption method, a sputtering method, or a chemical vapor deposition (CVD) method, or may be dissolved or dispersed in an organic solvent. Thus, a coating liquid may be prepared, and this may be coated on a current collector and subjected to a heat treatment to prepare a carbon thin film electrode containing the desired nickel-based alloy. Again,
Industrially, the latter is preferred.

Although all known organic solvents can be used,
In particular, when an organic solvent containing at least pyridine, quinoline, pyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, and cyclohexanone is used, a coating liquid in which the above-mentioned nonvolatile carbon-containing compound is suitably dissolved or dispersed can be prepared. Organic solvents that may be used in combination with these organic solvents include alcohols represented by methanol, ethanol, ketones represented by acetone, 2-butanone, esters represented by ethyl acetate, butyl acetate, and diethyl. Ethers such as ether, tetrahydrofuran and dioxane, amines such as triethylamine and ethylenediamine, and the like are used.

The desired coating solution can be obtained by mixing, stirring or dispersing the above-mentioned nonvolatile carbon-containing compound and nickel-based alloy with the above-mentioned organic solvent. When mixing both, heating and stirring may be performed, or mixing and dispersion may be performed using a dispersing device represented by a ball mill, an attritor, and a planetary mill.

The coating solution thus prepared is applied to the current collector using a known coating method such as blade coating, wire bar coating, spin coating, spray coating, dip coating, or bead coating. Can be applied. An electrostatic spray deposition (ESD) method in which an electric field is applied between a heated current collector and a nozzle containing a coating liquid to simultaneously perform film formation and heat treatment is preferably used.

The liquid applied on the current collector is heated to form a carbonaceous film containing a nickel-based alloy capable of electrochemically absorbing and releasing lithium ions. Good results are obtained when the heat treatment temperature at this time is in the range of 500 to 2000 ° C, and even better results are obtained when the temperature is in the range of 700 to 1200 ° C. The heat treatment may be performed in an air atmosphere, but better results can be obtained by performing the heat treatment in an inert gas atmosphere represented by nitrogen, argon, helium, or the like.

As the current collector, any known materials may be used as long as they have electron conductivity, but non-corrosive materials are particularly preferable. Examples of such a material include conductive carbon, gold, platinum, and stainless steel, and stainless steel is preferably used. The shape of the current collector is practically a foil or a porous body.

The thus prepared negative electrode plate, the electrolyte and the positive electrode plate described below are combined with other battery components such as a separator, a gasket, a current collector, a sealing plate, a cell case, and the like to form a lithium ion secondary battery. Constitute. The battery that can be manufactured is not particularly limited, such as a cylindrical type, a square type, a coin type, but basically, a current collector and a negative electrode material are placed on a cell floor plate, and an electrolyte and a separator are further placed thereon. A positive electrode is placed so as to face the negative electrode, and caulked together with a gasket and a sealing plate to form a secondary battery.

Non-aqueous solvents that can be used for the electrolyte include:
Propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, γ-butyrolactone, tetrahydrofuran, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, 1,
A single organic solvent such as 3-dioxolane or a mixture of two or more organic solvents can be used.

In these solvents, L of about 0.5 to 2.0 M is added.
iCLO_Four , LiPF₆ , LiBF _Four , LiCF_Three SO
_Three , LiAsF₆ Are dissolved to form an electrolyte.
In addition, the conductivity of alkali metal cations such as lithium ions
A solid polymer electrolyte which is a body can also be used. Correct
The material of the polar body is not particularly limited.
Which alkali metal cations can be stored and released during charge and discharge
It is preferable that the metal chalcogen compound be composed of a metal chalcogen compound. That
Oxidation of vanadium as a similar metal chalcogen compound
Material, vanadium sulfide, molybdenum oxide, molybdenum
Den sulfide, manganese oxide, chromium oxide, titanium
Oxide of tan, sulfide of titanium and their complex oxidation
And complex sulfides. Preferably, Cr_Three O
₈ , V_Two O _Five , V_Five O₁₃, VO_Two, Cr_Two O_Five , MnO_Two
 , TiO_Two , MoV_Two O₈ , TiS_Two V_Two S_Five Mo
S_Two, MoS_Three VS_Two , Cr_0.25V_0.75S_Two , Cr_0.5 
V_0.5S_Two And so on. Also, LiMY_Two (M is Co,
Transition metals Y such as Ni are chalcogen compounds such as O and S),
LiM_Two Y_Four (M is Mn, Y is O), WO_Three Oxidation of etc.
Material, CuS, Fe_0.25V_0.75S_Two , Na_0.1 CrS_Two etc
Sulfide, NiPS_Three , FePS_Three Phosphorus and sulfur compounds
Thing, VSe_Two , NbSe_Three Use selenium compounds such as
You can also. These are mixed with a binder similarly to the negative electrode material.
To form a positive electrode plate. Holds electrolyte
Separator is generally a material with excellent liquid retention,
For example, polyolefin resin nonwoven fabric or porous
Function by impregnating the above electrolyte with a
Is expressed.

[0042]

Next, the present invention will be described in detail with reference to examples, but it is needless to say that the present invention is not limited by these examples. However, parts referred to here are parts by weight.

Example 1 Mesophase pitch carbon was pulverized in a mortar, filled into a Soxhlet cylindrical filter paper, and extracted with a Soxhlet continuous extraction device for 24 hours using toluene as an extraction solvent. Thereafter, the extraction residue was air-dried, and then heat-treated at 700 ° C. for 1 hour in a batch heating furnace under an inert atmosphere. This was pulverized, and the particle size was adjusted to 8 to 25 μm by a vibrating sieve to obtain a carbon material used in the present invention.

On the other hand, only the recording layer was recovered by a scraper from a magnetic recording material waste material obtained by applying Supermalloy on polyethylene terephthalate together with a binder resin, to obtain a mixed material containing a nickel-based alloy used in the present invention. At this time, the ratio of the metal to the binder was 1: 1 in terms of volume ratio.
The analysis revealed that

4 g of the carbon material, 3 g of a mixed material made of a nickel alloy and a resin were added to polyvinylidene fluoride (PVd).
A solution obtained by adding 10% by weight of a dimethylformamide solution of F) in terms of solid content was stirred to obtain a slurry. This slurry was applied on a nickel foil and preliminarily dried at 80 ° C. After being further pressurized and pressed, it was dried at 110 ° C. under reduced pressure to form electrodes. The obtained electrode was sandwiched with a polypropylene separator impregnated with an electrolytic solution, and a cell facing the lithium metal electrode was prepared, and a charge / discharge test was performed. As the electrolytic solution, a solution prepared by dissolving lithium perchlorate at a rate of 1 mol / L in a solvent in which ethylene carbonate and propylene carbonate were mixed at a volume ratio of 1: 1 was used.

The charge / discharge test was performed by a constant current charge / discharge method. Current density of 0.1 mA / cm ² and potential difference between electrodes is 0 V
, And then undoped until the potential difference between the electrodes reached 1.5 V. Table 1 shows the measurement results of the doping capacity and the undoping capacity.

On the other hand, the slurry prepared above was applied on a polyethylene terephthalate thin film, preliminarily dried at 80 ° C., and then dried at 110 ° C. under reduced pressure. Table 1 shows the results of measuring the resistivity by the four-terminal method.

(Comparative Example 1) A test was conducted in the same manner as in Example 1, except that no magnetic recording material was used. Table 1 shows the results.

Example 2 7 parts of the carbon material obtained in Example 1 were put into a ball mill pot filled with balls together with 3 parts of Ni ₈₀ Fe ₂₀ alloy powder and subjected to mechanical milling for 3 hours. To this ball mill pot, a 2-butanone solution of a vinylidene fluoride-trifluoroethylene copolymer in an amount of 10% by weight in terms of solid content was added and dispersed well.
A dispersion was obtained. Using the obtained dispersion, a sample exactly the same as that of Example 1 was produced, and a similar test evaluation was performed.
Table 1 shows the results.

Comparative Example 2 In Example 2, Ni
₈₀ by using pure nickel powder in place of the Fe ₂₀ alloy was tested in the same manner as in Example -1. Table 1 shows the results.

Example 3 Example 2 was repeated except that a high-temperature fired carbon (Mitsubishi Gas Chemical: 2800 ° C.) was used instead of the carbon material obtained by firing an organic substance at a low temperature.
The test was performed in the same manner as described above. Table 1 shows the results.

(Example-4) 5 parts of mesophase pitch carbon (manufactured by Petka Co., Ltd.) was pulverized well with a mortar, and then put into a soxhlet extraction thimble filter paper. Extraction was performed by an extraction device. Take out the extract and average particle size 2μm
And 0.5 part of Permalloy powder was added and stirred well. This liquid was put into a syringe and sprayed on a stainless steel foil heated to 1000 ° C. by a spray method. The film was formed in the nitrogen gas at this time. The thickness of the carbon thin film mixed with permalloy thus obtained was 35 μm.
Using the obtained electrode, a sample exactly the same as that of Example 1 was produced, and a similar test evaluation was performed. Table 1 shows the results.

[0053]

[Table 1]

From the above test results, it is clear that the negative electrode material for a lithium ion secondary battery of the present invention has a small irreversible capacity and a small resistance.

[0055]

According to the negative electrode material for a lithium ion secondary battery of the present invention, a nickel-based alloy is added to a carbonaceous material.
An object of the present invention is to provide a high-efficiency, high-performance carbon electrode material which is a carbon material, has a large undoping capacity, and can improve the conductivity inherent in the material. In addition, the negative electrode material for a lithium ion secondary battery of the present invention has a high capacity and is not only excellent in charge / discharge cycle characteristics, but also novel as an effective use of nickel-based alloy waste material as a magnetic material, It has high application value and excellent effect.

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Claims (3)

[Claims] 1. A negative electrode material for a lithium ion secondary battery, comprising a current collector and a carbonaceous film in which a nickel-based alloy is mixed. 2. A current collector comprising a carbonaceous film capable of electrochemically occluding and releasing lithium ions mixed with a nickel-based alloy without containing a binder. The negative electrode material for a lithium ion secondary battery according to 1. 3. The negative electrode material for a lithium ion secondary battery according to claim 1, wherein the nickel-based alloy is a waste magnetic material.