JP2001210329A - Manufacturing method of negative electrode material for nonaqueous lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a negative electrode material which has a high capacity, a long cycle life and in which an irreversible capacity in the first time charge is small as well, that is, this is friendly with an electrolyte. SOLUTION: In a manufacturing method of the negative electrode material for nonaqueous lithium secondary battery, it is characterized as follows; a metallic material M, a graphite material, and a carbonaceous matter precursor which is an organic compound are mixed and calcined at the inert atmosphere lower part; the metallic material M is composed of solid phase A, B; a part or the entire surface of periphery of nuclear particle consisting of solid phase A has a structure coated by the solid phase B5 further, the solid phase A at least contains silicon as a constituent element; the solid phase B is a solid solution or intermetallic compound between at least a kind of element selected from the group consisted of II group element, transition metal element, XII group element, XIII group element, XIV group element except for carbon and silicon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a negative electrode material for a non-aqueous lithium secondary battery, which is suitable as a power source for small and weighed electric devices and electric vehicles.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become smaller, high-capacity secondary batteries have been demanded. For this reason, non-aqueous lithium secondary batteries having higher energy density than nickel-cadmium batteries and nickel-metal hydride batteries have attracted attention.

[0003]

At first, the use of lithium metal as the negative electrode material was attempted. However, as charge and discharge were repeated, dendritic lithium was precipitated and penetrated through the separator to reach the positive electrode. As a result, it has been found that a short circuit may occur.

Japanese Patent Application Laid-Open No. 57-208079 has proposed that lithium be used as a negative electrode material and graphite having high crystallinity be used as an electrode plate. However, graphite
Since the intercalation into the graphite crystal is used for lithium occlusion, there is a drawback that a material exceeding its volume theoretical capacity of 820 mAh / cc cannot be obtained at normal temperature and normal pressure.

It is known that as a negative electrode material capable of exhibiting a higher capacity, a metal which combines with lithium, such as Al, Si, Sn, etc., may be used. There has been a problem that it is significantly reduced.

Japanese Patent Application Laid-Open No. 5-286763 discloses that the addition of a plurality of types of carbon to Al suppresses a decrease in capacity due to a charge / discharge cycle. The maximum capacity per unit is 2,839mA
Limited to h / cc. On the other hand, Si has a large capacity per volume as large as 4,648 mAh / cc, but has a large change in volume at the time of charge and discharge, and causes the above-mentioned problem. Therefore, Si has not been put to practical use as a negative electrode material.

In recent years, as a method for solving these drawbacks, Japanese Patent Laid-Open No. 7-240201 discloses a technique using silicide powder as a negative electrode material for a Li secondary battery. It has been found that these compounds have a large volume capacity and a long cycle life, but this material has a low electric conductivity, and when used alone, cannot be sufficiently combined with Li to exhibit a theoretical capacity. Therefore, Japanese Patent Application Laid-Open No. 8-153517 discloses a technique for forming a negative electrode material by adding a conductive agent such as acetylene black to the present material powder.

However, acetylene black generally has a very small particle size of less than 1 μm, and thus has a problem that the specific surface area is large and the irreversible capacity at the time of the first charge is increased.

Japanese Patent Laid-Open Publication No. Hei 10-199527 discloses the use of highly crystalline graphite particles as a conductive material together with silicide in order to solve such disadvantages. This improves the capacity compared to using silicide alone,
Although the cycle life is improved and the irreversible capacity at the time of the first charge is reduced, the capacity gradually decreases after a long cycle. This is presumably because the change in volume of the silicide caused by the charge and discharge of lithium changes the structure of the negative electrode made conductive with graphite, and destroys the structure with the charge and discharge cycle.

Although the main active material of the negative electrode is Si metal instead of silicide, in order to suppress the above-mentioned structural destruction, it is necessary to obtain a structure in which a graphite material as a conductive agent is brought closer to the main active material. Japanese Patent Application Laid-Open No. 9-249407 discloses an invention in which both active material powder and graphite are mechanically treated. If this technology is applied to silicide, the cycle life is expected to be further extended as in the case of Si, but on the other hand, mechanical treatment of graphite particles leads to an increase in the specific surface area of graphite, This causes an increase in the irreversible capacity at the time of the first charge.

As a result of our intensive studies, we have found that the negative electrode material for a lithium secondary battery prepared by the method described below has a very small capacity deterioration even after a long-term charge / discharge cycle with a high capacity. It has been found that the material has a reduced irreversible capacity.

That is, an object of the present invention is to produce a negative electrode material having a high capacity, a long cycle life, and a small irreversible capacity at the time of the first charge, that is, an electrolyte-friendly negative electrode material.

[0013]

In order to achieve the object of the present invention, a negative electrode material is prepared by mixing a metallic substance M, a graphite substance, and a carbonaceous precursor which is an organic substance, and firing the mixture under an inert atmosphere. Characteristically, the metallic substance M has a structure in which solid phases A and B are formed, and a part or the entire periphery of a core particle composed of the solid phase A is covered with a solid phase B. The solid phase B contains at least silicon as a constituent element, and the solid phase B is at least one element selected from the group consisting of Group 2 elements of the periodic table, transition elements, Group 12 and Group 13 and Group 14 elements excluding carbon and silicon. And a solid solution with silicon or an intermetallic compound.

The metal material M having a large volume capacity and the graphite, which is conductive particles, are integrally treated with a carbonaceous material to achieve both a high capacity and a long cycle life, and the presence of the carbonaceous material on the surface. The irreversible capacity generated at the time of initial charging can be suppressed.

[0015]

Next, the details of the present invention will be described. The method of compounding the metal material M, the graphite material, and the material obtained by firing the carbonaceous material precursor under an inert atmosphere, which constitutes the material of the present invention, includes (1) metal material M particles, graphite material particles, And carbonaceous material particles obtained by calcining the carbonaceous material precursor, a form in which each is mixed, and (2) a part or all of the surface of the metallic material M powder is contact-treated with the carbonaceous material precursor,
After firing, a suitable crushing or pulverizing step is performed to form a powder, and a graphite material powder is mixed therein. (3) A part or all of the surface of the metal material M is contact-treated with the carbonaceous precursor. ,
After firing, powdered in the above step, a part or all of the surface of the graphite material powder is contact-treated with a carbonaceous material precursor,
After firing, a form in which powdered materials are mixed. (4) A mixture of a graphite material and the carbonaceous precursor is contact-treated with a part or all of the surface of the metal material M, and after firing, the particles are treated in the above step. (5) A graphite material is previously coated on a part or all of the surface of the metal material M, and a carbonaceous material precursor is further subjected to contact treatment to prepare a material composed of two or more composite layers. After that, there is a form in which the powder is baked and formed into particles by the above process, and a form in which one or more of these forms are mixed.

The term "contact treatment of a carbonaceous material precursor" as used herein includes a concept from binding of particles by the substance to so-called coating, such as providing a layer made of the substance on the particle surface.

The order of mixing the above three types of constituent materials of the negative electrode material may be any as long as the scope of the claims is not impaired. However, the metallic substance M and the graphite substance are first mixed, and then the carbonaceous substance is added thereto. When the precursor is further added and further mixed, the graphite material as a conductive agent approaches the surface of the metal material M, so that the conductivity is preferably maintained even during the progress of the charge / discharge cycle.

As a means for compounding the respective materials for producing the active material, a conventionally known method can be used, for example, a powder mixer such as a V blender, an axial mixer, a disperser, a paddle mixer, a lathe. Stirrers such as digue mixers, planetary mixers, emulsifying and dispersing machines, kneaders such as KRC kneaders, kneaders, grinders, etc., crushers and crushers such as turbo mills, ball mills, jet mills, disk mills, impact mills, pin mills, hammer mills, etc. , Mechanofusion, hybridizer, theta composer, etc., granulation, surface modification, and coating devices can be used in combination.

Particularly, in the composite form of the above (4), it is preferable to use a grinder or a kneader, since the raw materials can be homogeneously mixed by using a grinder or a kneader. In the composite form of (5), it is preferable to use the above-mentioned mechanofusion or hybridizer since the surface of the metal material M can be efficiently coated with the graphite material by appropriately setting the operating conditions. Mechanical processing with mechanofusion and hybridizers is possible even in the atmosphere,
Since the surface of the graphite particles, which is a conductive material, is mainly damaged by oxidation and the electrical conductivity may be reduced, the treatment is preferably performed in an inert atmosphere such as nitrogen or argon. The processing intensity varies depending on the equipment, but the shear rate is 10
It is preferable to carry out at s ⁻¹ or more. If the shear rate is lower than this, the specific gravities of the metallic substance M and the graphite substance are different, so that the two materials are not sufficiently mixed and tend to be non-uniform. More preferably, it is performed at a shear rate of 1000 s ^-1 or more.

In order to produce the negative electrode material of the present invention, it is necessary to mix the raw materials using the above-mentioned means and then to perform further firing, but this temperature must be in the range of 700 to 1500 ° C. Is preferred. Below this temperature, the aromaticity of the carbonaceous material does not sufficiently develop, so that the electric conductivity is low and irreversible capacity is likely to be generated during lithium charge and discharge. At a temperature higher than this temperature, the melting point of the metallic material as a raw material is close to the melting point, so that the metal portion is melted, making it difficult to use the active material as an active material.
This temperature range is more preferably 800 to 1300 ° C.,
Most preferably, it is 800 to 1100 ° C.

Next, raw materials necessary for producing the present negative electrode material will be described.

The metallic substance M is composed of solid phases A and B.
Has a structure in which a part or the entire surface of a core particle composed of is covered with a solid phase B, further, the solid phase A contains at least silicon as a constituent element, and the solid phase B corresponds to 2 of the periodic table.
It is preferably a solid solution or an intermetallic compound of silicon and at least one element selected from the group consisting of a group 14 element, a transition element, groups 12 and 13 and a group 14 element excluding carbon and silicon. For example, the solid phase A is made of Si, and the solid phase B is made of NiSi ₂ , CoSi ₂ , VSi ₂ , TiS
Examples of the metal material include i ₂ , MnSi _1.8 , and / or Mg ₂ Si.

As the graphite material, its crystal plane (002)
It is preferable to use a highly crystalline graphite powder in which the interplanar spacing d ₀₀₂ is 0.348 nm or less and the thickness Lc of the graphite layer is 10 nm or more. d ₀₀₂ is 0.338 nm or less,
And those thicknesses Lc of the laminated layer is 20nm or more and more preferably, d ₀₀₂ is 0.337nm or less and those thicknesses Lc of the laminated layer is 40nm or more is most preferred.

Further, the graphite pledge Raman spectroscopy using an argon ion laser beam having a wavelength 514.3Nm, the intensity of the peak appearing in the range of ^{1580cm -1 ~1620cm -1 IA, 1350cm -1} ~1370cm -1 The graphitic material having a peak intensity ratio R (= IB / IA) of 0.4 or less, where IB is the peak intensity appearing in the range described above, is preferable. More preferably, R is 0.3 or less,
Those having a value of 0.25 or less are most preferred.

The average particle size of the graphite used is preferably 1 μm or more and 1 mm or less. If the average particle diameter is larger than this, it is difficult to uniformly mix with the metallic substance M, and if it is smaller than this, the specific surface area is too large and the irreversible capacity at the time of initial charge / discharge becomes large. This average particle size is 1 to
More preferably, the average particle diameter is 1 to 40 μm.
25 μm is most preferred. Even if the average particle diameter is out of the above range, such a particle can be used as long as the average particle diameter can be kept in the range at the stage of the mechanical treatment according to claims 3 and 4.

Such a graphite-like material is suitable natural graphite, artificial graphite, a high-purity purified product thereof, and a reheat treatment thereof, in which the interplanar spacing d ₀₀₂ of the crystal plane (002) is 0.348 nm or less. Or a powder of a mixture of these.

The carbonaceous material precursor includes coal-based heavy oil such as coal tar pitch from soft pitch to hard pitch or dry-distilled liquefied oil, normal-pressure residual oil, DC-based heavy oil of reduced-pressure residual oil, crude oil, Petroleum heavy oil such as ethylene tar, which is a by-product of thermal decomposition such as naphtha, and other aromatic hydrocarbons such as acenaphthylene, decacyclene, anthracene, and phenanthrene; S-ring compounds such as bithiophene, polyphenylenes such as biphenyl and terphenyl, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, insolubilized products thereof, organic polymers such as nitrogen-containing polyacrylonitrile and polypyrrole, sulfur-containing Organic polymers such as polythiophene and polystyrene,
Cellulose, lignin, mannan, polygalacturonic acid, chitin, chitosan, natural polymers such as polysaccharides represented by saccharose, thermoplastic resins such as polyphenylene sulfide, polyphenylene oxide, furfuryl alcohol resin, phenol-formaldehyde resin, imide One or more carbonizable organic compounds selected from thermosetting resins such as resins, and mixtures of the above with low molecular weight organic solvents such as benzene, toluene, xylene, quinoline, and n-hexane are used.

The above carbonaceous material precursor is H / C (atomic ratio)
Is preferably 0.4 or more and 1.8 or less, because it is easy to mix with the metallic substance M or the graphite substance. It is more preferably 0.6 or more and 1.2 or less, and most preferably 0.8 or more and 1.1 or less. If the H / C is more than this, the carbonization yield after firing is deteriorated, and if it is more than this, it is difficult to mix the materials.

The proportion of the carbonaceous material in the negative electrode material produced by firing the metallic material M, the graphite material, and the carbonaceous material precursor is 5% when the whole is 100% by weight.
0-95 wt%, 4.9-30 wt%, and 0.1-2
When the content is 0% by weight, a negative electrode material having a large capacity per volume, an excellent cycle life, and a small irreversible capacity at the time of initial charge / discharge can be produced, which is preferable. However, since the above numerical range is a weight ratio after firing, it is necessary to consider a change in weight caused by firing in the material mixing stage.

Next, a method of forming a negative electrode body using the negative electrode material of the present invention will be described.

As the negative electrode body, a conventionally known method can be adopted without any limitation as long as the above-mentioned negative electrode material prepared from the above-mentioned metal substance M, graphite substance and carbonaceous substance precursor can be used. M and the graphite are mixed with a grinder until homogenous, and a carbonaceous material precursor is added thereto and kneaded with a mixer or the like. This is fired under an inert atmosphere, and then cooled to around room temperature, taken out, preferably ground or crushed to a range of 8 to 25 μm, more preferably 8 to 20 μm, and most preferably 10 to 15 μm to obtain a powdery material. And Add conductive agent, binder, solvent, etc. to this,
An electrode is formed by applying a slurry to a current collector substrate such as a copper foil, a nickel mesh, or a stainless steel mesh and drying the slurry. The current collector for binding the particles can be used without limitation, and examples thereof include a metal cylinder, a metal coil, a metal plate, a metal thin film, a carbon plate, and a carbon cylinder. And the like. Copper foil is more preferred. Further, the electrode material in which the negative electrode material is adhered to these current collectors can be directly formed into an arbitrary electrode shape by a method such as roll forming or compression forming.

The conductive agent that can be used for the above purpose includes:
Highly crystalline artificial graphite having a conductivity of 1 S / cm or more, natural graphite, high-purity refined products thereof, and fine metal powder of, for example, copper, nickel, stainless steel, iron, etc., having a particle diameter of 25 μm or less, or Mixtures of these are mentioned.

Examples of the binder include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, and cellulose, styrene / butadiene rubber, isoprene rubber,
Butadiene rubber, rubbery polymers such as ethylene / propylene rubber, styrene / butadiene / styrene block copolymer, hydrogenated products thereof, styrene / ethylene / butadiene / styrene copolymer, styrene / isoprene / styrene block copolymer, Soft resinous materials such as thermoplastic elastomeric polymers such as hydrogenated products thereof, syndiotactic 1,2-polybutadiene, ethylene / vinyl acetate copolymer, and propylene / α-olefin (2 to 12 carbon atoms) copolymer Fluorinated polymer such as polymer, polyvinylidene fluoride, polytetrafluoroethylene, polytetrafluoroethylene / ethylene copolymer, polymer composition having ion conductivity of alkali metal ion, especially lithium ion, and the above-mentioned binding And mixtures of agents.

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, a polymer compound such as polyacrylonitrile, a lithium salt, or a system in which an alkali metal salt mainly composed of lithium is combined, or propylene carbonate, ethylene carbonate, high dielectric constant and ions such as γ-butyrolactone -A system containing an organic compound having a dipole interaction force can be used.

Examples of the solvent include water, acetone, dimethyl ether, alcohols such as methanol, ethanol, butanol, and isopropanol, and N.
-Methylpyrrolidinone, dimethylformamide, dimethylacetamide, hexamethylphosphoramide, dimethylsulfoxide, benzene, toluene, xylene, quinoline, pyridine, methylnaphthalene, hexane and the like can be used.

The negative electrode material particles and the binder used in the present invention may be mixed in various forms. That is, a form in which two kinds of particles are mixed and bound, a form in which a fibrous binder is mixed in a form entangled with the above-mentioned invention particles and a conductive agent, or a form in which a layer of a binder is attached to the particle surface, and the like. Can be

The mixing ratio of the negative electrode material particles and the conductive agent is such that the negative electrode material is at least 60% by weight or more and the conductive agent is 1% by weight or more, when the whole constituent material of the negative electrode is 100% by weight.
The content is preferably 0% by weight or less. If the conductive agent is added in an amount greater than this, the charge / discharge capacity that the electrode can generate per unit volume decreases, and if the amount is less than this, the effect of the addition cannot be formed because conductive paths between the conductive agents cannot be formed in the electrode. Not fully expressed.

The mixing ratio of the binder to the negative electrode material particles and the conductive agent is preferably 0.1 to 30% by weight, more preferably 0.1 to 30% by weight, based on the total weight of the negative electrode material particles and the conductive agent.
0.5 to 5% by weight. If the binder is added in an amount larger than this, the internal resistance of the electrode increases, which is not preferable.
If the amount is less than this, the binding property between the current collector and the electrode powder is inferior.

A case where a battery is manufactured using this negative electrode body will be described below. Electrolyte, positive electrode plate, other battery components such as separator, gasket, current collector, sealing plate,
A secondary battery is configured by combining with a cell case and the like. The batteries that can be created are not particularly limited, such as a cylindrical type, a square type, a coin type, but basically, a current collector and a negative electrode body are placed on a cell floor plate, and an electrolytic solution and a separator are further placed thereon. The positive electrode body is placed so as to face the negative electrode body, 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, 2-methyltetrahydrofuran, sulfolane, 1,3-dioxolan, dimethyl sulfide, propylene sulfide, ethylene sulfide An organic solvent such as vinylene carbonate, polyepichlorohydrin, polyphosphazene, polysiloxane, polyvinylpyrrolidone, polyvinylidene carbonate, a polymer compound such as polyacrylonitrile, a lithium salt, or an alkali metal salt mainly composed of lithium was compounded. System or high dielectric constants such as propylene carbonate, ethylene carbonate, γ-butyrolactone, and ion-dipole Organic compounds having an interaction force can be used alone or in combination of two or more.

In these solvents, about 0.5 to 2.0 M of L
iClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ ,
An electrolyte such as LiAsF ₆ , LiCl, LiBr, Li trifluorosulfonimide, or Li bis (tetrafluoromethanesulfonyl) imide is dissolved to form an electrolyte.

Also, ether-based polymer solid electrolytes such as polyethylene oxide, polypropylene oxide, and poly (methacryloyl ethylene oxide), which are conductors of alkali metal cations such as lithium ions, cross-linked polymers of polyether compounds; The hydrogen group at the terminal of the structure is replaced with an alkyl group such as a methyl group or an ethyl group, an ω-alkyl polyether such as polyethylene oxide dimethyl ether, polyacrylonitrile or a polyvinyl alcohol having a high degree of saponification, and the above organic solvent and the above electrolyte. Mixed gel electrolytes can also be used.

As the positive electrode material, any conventionally known one can be used and is not particularly limited. Specifically, LiFeO ₂ , LiCoO ₂ , LiNiO ₂ , Li
Mn ₂ O ₄ and their non-stoichiometric compounds, MnO ₂ , Ti
S ₂ , FeS ₂ , Nb ₃ S ₄ , Mo ₃ S ₄ , CoS ₂ , V
₂ O ₅ , P ₂ O ₅ , CrO ₃ , V ₆ O ₁₃ , TeO ₂ , GeO _{2 and the} like can be used.

The positive electrode body is prepared, for example, by adding a conductive agent such as acetylene black or graphite to the above-mentioned positive electrode material, mixing tetrafluoroethylene or the like as a binder, applying the mixture on an aluminum foil, molding and drying. Can be obtained by

[0045]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the present invention.

Evaluation Method of Electrode Material All evaluations were performed as follows. The negative electrode material of the present invention and a binder were applied and bound on a copper foil current collector, and then formed into a pellet. This together with the separator and electrolyte,
A half-cell with a lithium metal counter electrode was assembled in 2016 coin cells. The charge / discharge capacity was evaluated using a cell as described above using a charge / discharge tester. Similar effects can be expected with a lithium ion battery assembled with a positive electrode body.

(Example 1) Metallic material 40 having an average particle diameter of 12.5 µm containing Si on the surface and inside of NiSi ₂
g and 4 g of artificial graphite having an average particle diameter of 1.6 μm with d ₀₀₂ of 0.336 nm and an R value of 0.2 obtained from the Raman spectrum were uniformly mixed in the air for 2 minutes in a MRK molder grinder. did. The mixture has an H / C of about 1.
0 and 5 g of tar pitch having an aromaticity index fa of about 0.5 were added and further mixed. This was heated to 900 ° C. at a rate of 8 ° C./min.
Hold for hours. After cooling to around room temperature, the fired product was crushed in an agate mortar, classified with a sieve having openings of 45 μm, and sized to an average particle size of 14.1 μm to obtain a sample. The metallic material M of the particles obtained from the yield at the time of firing and elemental analysis,
The proportions of the graphite substance and the carbonaceous substance were 90% by weight, 9% by weight, and 1% by weight, when the whole particles were 100% by weight. When the sample particles were observed by SEM, a structure in which the surface of the metallic substance M particles was coated with a mixture of graphite and carbonaceous substance was observed. This sample particle 6
g of artificial graphite having an average particle diameter of 1.6 μm having d ₀₀₂ of 0.336 nm as a conductive agent, and carboxymethyl cellulose (CMC) and styrene butadiene rubber (100% by weight) as a binder. SBR)
A total of 2.46% by weight was mixed together, applied on a copper foil having a thickness of 19 μm, and then pre-dried at 80 ° C. Furthermore, the diameter 1
It was punched out into a 2.5 mm disc and heated and dried under reduced pressure at 110 ° C. for 24 hours to form an electrode. A coin-shaped cell having a polyethylene separator impregnated with an electrolyte interposed between the obtained electrodes and facing a lithium metal electrode was prepared, and a charge / discharge test was performed. Ethylene carbonate (E
C) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 1: 3, and a solution prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) at a ratio of 1.25 mol / L was used. In the reference charge / discharge test, doping was performed at a current density of 0.32 mA / cm ² until the potential difference between the electrodes became 0 V, and undoping was performed at the same current density until the voltage reached 1.5 V. The capacity value was obtained by conducting a charge / discharge test on each of the three coin-type cells, and averaging the undoped capacity in the first charge / discharge cycle, the irreversible capacity obtained by subtracting the undoped capacity from the dope capacity in the same cycle, and Evaluation was made as a percentage (capacity retention /%) of a value obtained by dividing the twentieth discharge capacity by the first discharge capacity.

[0048]

(Equation 1)

As the specific gravity of the negative electrode material, the true specific gravity of the sample before lithium doping was used.

(Example 2) Using 40 g, 4 g, and 10 g of the metallic substance M, artificial graphite, and tar pitch of Example 1, respectively, were mixed and fired in the same manner as in Example 1. After cooling to around room temperature, crush it with an agate mortar and
The mixture was classified with a 5 μm sieve and sized to an average particle diameter of 14.1 μm to obtain a sample. The yield of the particles during firing and the ratio of the metallic substance M, the graphite substance, and the carbonaceous substance obtained from the elemental analysis were 89% by weight, 9% by weight, and 2% by weight, assuming that the whole particles were 100% by weight. %Met. When the sample particles were observed by SEM, a structure in which the surface of the metal material M particles was coated with the carbon material was observed. With respect to 6 g of the sample particles, d ₀₀₂ was 0.33 as a conductive agent.
0.7 g of artificial graphite having an average particle diameter of 3.7 μm, which is 6 nm
And carboxymethylcellulose (CMC) and styrene-butadiene rubber (SBR) in total of 2.46% by weight with respect to 100% by weight of the particles as a binder, and mixed together to prepare an electrode in the same manner as in Example 1, and charge and discharge. The test was performed.

(Example 3) Metallic substance 15 having an average particle diameter of 12.5 μm containing Si on the surface and inside of NiSi ₂
0 g, d ₀₀₂ is 0.336 nm, R of Raman spectrum
Artificial graphite 28 having an average particle size of 1.6 μm having a value of 0.2
g was treated with Mesofusion manufactured by Hosokawa Micron at room temperature under a nitrogen atmosphere for 15 minutes. This sample 4
To 0 g, 8 g of the tar pitch used in Example 1 was added and further mixed in the atmosphere. This was fired in the same manner as in Example 1, crushed with a hammer mill, classified with a sieve having an opening of 38 μm, and sized to an average particle diameter of 14.1 μm to obtain a sample. The yield of the particles during firing and the ratio of the metallic substance M, the graphite substance, and the carbonaceous substance obtained from the elemental analysis were 83% by weight, 16% by weight, and 1% by weight when the whole particles were 100% by weight. %Met. When the sample particles were observed by SEM, the surface of the metallic substance M particles was
A structure coated with a mixture of graphite and carbonaceous material was observed.
For 6 g of the sample particles, d ₀₀₂ was used as a conductive agent.
0.2 g of artificial graphite having an average particle size of 3.7 μm having a particle size of 0.336 nm, and carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) totaling 2.46% by weight based on 100% by weight of the particles as a binder. Were mixed together to form an electrode in the same manner as in Example 1, and a charge / discharge test was performed.

(Example 4) A metallic material 80 containing Si on the surface and inside of NiSi ₂ and having an average particle diameter of 12.5 μm
g and, d ₀₀₂ is 0.336 nm, artificial graphite 1g having an average particle diameter of 1.6 [mu] m R value is 0.2 of the Raman spectra
Was treated at room temperature under an argon atmosphere for 3 minutes using a hybridizer manufactured by Nara Machinery. 7 g of the tar pitch used in Example 1 was added to 40 g of this sample, and further mixed in the air. This was fired in the same manner as in Example 1, crushed with an agate mortar, and classified with a sieve having an opening of 45 μm to obtain a sized sample having an average particle diameter of 14.1 μm. From the yield and the elemental analysis at the time of calcination, the ratios of the metallic substance M, the graphite substance, and the carbonaceous substance of the obtained particles were 97% by weight, 1% by weight, and 100% by weight of the whole particle. 2% by weight
Met. When the sample particles were observed by SEM, a structure in which the surface of the metallic substance M particles was coated with a mixture of graphite and carbonaceous substance was observed. 1.3 g of artificial graphite having an average particle diameter of 1.6 μm having a d ₀₀₂ of 0.336 nm as a conductive agent, carboxymethylcellulose (CMC) and carboxymethyl cellulose (CMC) as a binder were used for 100 g of the particles. Styrene butadiene rubber (SB
R) A total of 2.46% by weight was mixed together to prepare an electrode in the same manner as in Example 1, and a charge / discharge test was performed.

(Comparative Example 1) An average particle diameter of 3.7 μm where d ₀₀₂ is 0.336 nm and R value of Raman spectrum is 0.1
m artificial graphite and carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR) as binders
Was mixed together with a total of 2.46% by weight with respect to 100% by weight of the graphite, an electrode was prepared in the same manner as in Example 1, and a charge / discharge test was performed.

(Comparative Example 2) Metal substance M used in Example 1
With carboxymethylcellulose (CM as a binder)
C) and styrene butadiene rubber (SBR) were mixed with a total of 2.46% by weight based on 100% by weight of the metal,
An electrode was prepared in the same manner as in Example 1, and a charge / discharge test was performed.

(Comparative Example 3) Metallic substance M used in Example 1
1.2 g of the artificial graphite used in Comparative Example 1 with respect to 4.8 g
Add and mix homogeneously. With respect to 100% by weight of this mixture, carboxymethylcellulose (CM
C) and styrene butadiene rubber (SBR) 2.4 in total
6% by weight were mixed together to prepare an electrode in the same manner as in Example 1, and a charge / discharge test was performed.

Hereinafter, a comparative study with Examples 1 to 4 and Comparative Examples 1 to 3 in which the lithium secondary battery manufactured according to the present invention was specifically charged and discharged will be described. Table 1 shows the undoped capacities of the lithium secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 3,
The irreversible capacity and capacity maintenance rate are summarized.

[0057]

[Table 1]

[0058]

According to the present invention, it is possible to manufacture a negative electrode material for a lithium secondary battery having a high capacity, a small capacity deterioration in a long-term cycle, and a small irreversible capacity generated at the time of initial charging.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideharu Sato 8-3-1 Chuo, Ami-cho, Inashiki-gun, Ibaraki Prefecture Inside the Tsukuba Research Laboratory, Mitsubishi Chemical Corporation (72) Keiko Nishioka 8-cho, Chuo, Ami-cho, Inashiki-gun, Ibaraki Prefecture No. 3-1 Mitsubishi Chemical Corporation Tsukuba Research Laboratory (72) Inventor Shinji Kasamatsu 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Yoshiaki Nitta 1006 Odaka Kadoma Kadoma, Osaka Matsushita Electric F-term (reference) in Sangyo Corporation 5H029 AJ03 AJ05 AK03 AL01 AL07 AM03 AM04 AM05 BJ13 CJ02 CJ28 DJ12 DJ16 DJ17 HJ01 HJ02 HJ13 HJ14 5H050 AA07 AA08 BA17 CA08 CA09 CB01 DA09 EA09 EA10 EA24 FA05

Claims (12)

[Claims] 1. A method for producing a negative electrode material for a non-aqueous lithium secondary battery, comprising mixing a metal substance M, a graphite substance, and a carbonaceous precursor which is an organic substance, and firing the mixture under an inert atmosphere. Characterized in that the metallic substance M is composed of solid phases A and B, and has a structure in which a part or the whole of the core particles composed of the solid phase A is covered with the solid phase B. At least silicon as a constituent element, and the solid phase B is at least selected from the group consisting of Group 2 elements, transition metal elements, Group 12 elements, Group 13 elements, and Group 14 elements excluding carbon and silicon in the periodic table. A method which is a solid solution or an intermetallic compound of one kind of element and silicon. 2. The method according to claim 1, wherein the surface of the metal material M is coated in advance with a graphite material and a carbonaceous material precursor which is an organic material, and is calcined. 3. The surface of the metallic substance M is coated by mechanically treating the metallic substance M and the graphite substance under an inert atmosphere, and the treated substance is contact-treated with a carbonaceous substance precursor, and then fired. The method of claim 1. 4. The method according to claim 3, wherein the mechanical treatment is performed in an inert atmosphere at a shear rate of 10 s ⁻¹ or more. 5. The method for producing a negative electrode material according to claim 1, wherein the firing temperature is 700 to 1500 ° C. 6. A plane distance d of a crystal plane (002) of a graphite material.
₀₀₂ is 0.348 nm or less, and the thickness Lc of the graphite layer is 10 nm or more.
The method described in. 7. Graphite pledge is, in the Raman spectrum analysis using an argon ion laser beam having a wavelength 514.3Nm, the intensity of the peak appearing in the range of ^{1580cm -1 ~1620cm -1 IA, 1350cm -1} ~1370cm The negative electrode material according to any one of claims 1 to 6, wherein the negative electrode material has a peak intensity ratio R (= IB / IA): 0.4 or less, where IB is a peak intensity appearing in the range of ^-1. Manufacturing method. 8. The graphite material has an average particle diameter of 1 μm or more and 1 m.
The method according to any one of claims 1 to 7, wherein m is equal to or less than m. 9. The graphite material is natural graphite, artificial graphite, a high-purity purified product thereof, or a mixture thereof, wherein the interplanar spacing d ₀₀₂ of the crystal plane (002) is 0.348 nm or less. 9. The method according to any one of claims 1 to 8. 10. The carbonaceous material precursor is coal tar pitch, coal-based heavy oil, DC-based heavy oil, petroleum-based heavy oil, aromatic hydrocarbon, nitrogen-containing heterocyclic organic compound, sulfur-containing heterocyclic organic. The method according to any one of claims 1 to 5, wherein the method is one or more carbonizable organic compounds selected from a compound, a nitrogen-containing organic polymer, a sulfur-containing organic polymer, and a natural polymer. 11. The method according to claim 1, wherein the carbonaceous material precursor has an H / C ratio of 0.4 or more and 1.8 or less. 12. When the total amount of the negative electrode material is 100% by weight, the ratio of the carbonaceous material obtained by heat-treating the metal material M, the graphite material, and the carbonaceous material precursor, which is an organic material, is 50 to 50%, respectively.
The method according to any one of claims 1 to 11, wherein the amount is 95% by weight, 4.9 to 30% by weight, and 0.1 to 20% by weight.