JP2003012311A - Production method of polymer coated carbon material, negative-electrode material and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer-coated carbon material a surface of which is firmly and integrally coated with a polymer and provide a negative electrode material for a lithium ion secondary battery attaining high initial charge and discharge efficiency and high service capacity using the same and a lithium secondary battery. SOLUTION: The production method of the polymer-coated carbon material is as follows. A carbon material is mechanochemically treated in the presence of a polymer and/or a precursor of a polymer. A coated polymer induced from the polymer and/or the precursor of the polymer is adhered to and integrated with a surface of the carbon material.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a polymer-coated carbon material, a polymer-coated carbon material as a negative electrode material for a lithium ion secondary battery obtained by the production method, and a carbon material. The present invention relates to a lithium ion secondary battery having high initial charge / discharge efficiency and high discharge capacity.

[0002]

2. Description of the Related Art In recent years, with the miniaturization and higher performance of electronic devices, there has been an increasing demand for higher energy density of batteries. Under such circumstances, a lithium secondary battery using lithium as a negative electrode has a high energy density, and has been attracting attention because it has an advantage that a high voltage can be achieved. In this lithium secondary battery, it is known that when lithium metal is used as it is as a negative electrode, lithium is deposited in a dendrite state during charging, so that the negative electrode is deteriorated and the charge / discharge cycle is short. In addition, lithium deposited in a dendrite form may penetrate the separator to reach the positive electrode and cause a short circuit.

Therefore, each material for the positive and negative electrodes is composed of two kinds of intercalation compounds having different redox potentials, each functioning as a carrier for lithium ions, so that a non-aqueous solvent may be transferred in and out between the layers during the charge and discharge process. The lithium-ion secondary battery that has been used is being studied. As this negative electrode material, it has been proposed to use a carbon material having the ability to insert and extract lithium ions and capable of preventing the precipitation of lithium metal, specifically, graphite or a carbon material having a turbostratic structure. However, among them, graphite having excellent charge / discharge characteristics and high discharge capacity and potential flatness is particularly promising (Japanese Patent Publication No. 62-23433).

On the other hand, in a lithium ion secondary battery using graphite as a negative electrode material, the irreversible capacity (hereinafter also referred to as "irreversible capacity") in the first cycle is remarkably increased, and several tens to several hundreds mAh / The discharge capacity loss at the g level is shown. That is, there is a problem that the initial charge / discharge efficiency is low. Although all the causes have not been clarified, one of them is that graphite is active in an electrolytic solution. Specifically, it is reported that the solvent or supporting electrolyte decomposes on the graphite surface. Has been done. This decomposition reaction is continued until the decomposition product is deposited and grown on the surface of graphite (carbon) and the thickness of electrons is such that electrons cannot directly move from the surface of graphite to a solvent or the like. In addition, the solvent molecules and lithium ions may be co-intercalated to peel off the graphite surface layer, and the newly exposed graphite surface may react with the electrolyte to increase the irreversible capacity (the initial charge / discharge efficiency is low. ) Has also been reported (Journal of Electrochemical Society, vol.137, 2009 (1990)).

Such an increase in irreversible capacity (low initial charge / discharge efficiency) can be compensated by adding a positive electrode material to the secondary battery, but the addition of an extra positive electrode material is referred to as a decrease in energy density. It creates new problems and should be avoided. In order to reduce the irreversible capacity (that is, to increase the initial charge / discharge efficiency), it has been proposed to dissolve the amine compound in the electrolytic solution to inactivate the surface of the carbon material (JP-A-8-236155, JP-A-5
-29019). However, it cannot be said that the irreversible capacity has been sufficiently reduced.

A technique for coating various carbon materials with a polymer or the like for the purpose of reducing the irreversible capacity is also disclosed. For example, graphitized powder of mesocarbon microbeads is added to a suspension of a solid polymer electrolyte such as tetrafluoroethylene / perfluorovinyl ether copolymer (trade name Nafion), and the solid polymer is coated on the powder. Method (JP-A-7-235328), artificial graphite powder added to a polyethylene oxide paste using a solvent, and vacuum dried (JP-A-8-213001),
Polypropylene glycol, polyethylene glycol
A method of immersing and adsorbing a carbon material such as artificial graphite in a polymer solution such as a polyether compound such as polypropylene glycol copolymer, and then crosslinking with a silane coupling agent (JP-A-9-161848), polyvinyl alcohol, polytetra A method in which a carbon material such as pitch coke particles is dispersed in a solution such as fluoroethylene, polyethylene, or styrene-butadiene rubber, and the dispersion is spray-dried (JP-A-9-219188), and an ion such as polyvinylidene fluoride is formed on the surface of the carbon negative electrode. A coating method in which a conductive polymer or a water-soluble polymer such as polyvinyl alcohol or hydroxyethyl cellulose is dissolved is applied (JP-A-11-120992).
If a carbon material coated with a polymer by each of the above methods is used as a negative electrode material for a lithium ion secondary battery, it is possible to reduce the irreversible capacity (that is, improve the initial charge / discharge efficiency).

[0007]

However, each of the above polymers does not have sufficient adhesiveness with the carbon material. For example, in order to coat the carbon material on the electrode, when the carbon material is mixed with a binder and a solvent and prepared into a paste to prepare a negative electrode mixture, the carbon material is homogeneously dispersed in the paste,
It is necessary to thoroughly stir the paste to homogenously disperse the carbon material in the paste, but if the adhesion between the coating polymer and the carbon material is insufficient, it may peel off when stirring the paste. Therefore, the effect of reducing the irreversible capacity by the polymer coating cannot be obtained. In particular, the effect of reducing the irreversible capacity may be impaired even when high-speed stirring that is usually performed is added, which is remarkable when using a polymer such as the above polyvinylidene fluoride or styrene-butadiene rubber,
In terms of initial charge and discharge efficiency, it is about 20-
It is reduced by 30%.

The present invention has been made in view of the above situation, and a method for producing a polymer-coated carbon material in which a polymer coating is firmly adhered and integrated on the surface of the carbon material, and a method for producing the same When used as a negative electrode material for a lithium ion secondary battery, the irreversible capacity in the first cycle is effectively reduced, and a high initial charge / discharge efficiency as well as a high discharge capacity is obtained. It is an object of the present invention to provide a polymer-coated carbon material that can obtain the above-mentioned battery characteristics in a stable manner, and a lithium-ion secondary battery having the above-mentioned battery characteristics.

[0009]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above problems. As a result, by coating a polymer on the carbon material surface by mechanochemical treatment, the initial charge / discharge efficiency when high-speed stirring is applied. Even if it is a polymer such as polyvinylidene fluoride or styrene butadiene rubber, which is considered not to have high adhesion to the carbon material due to the phenomenon of deterioration of the carbon material, it can be firmly adhered and integrated with the carbon material,
The inventors have found that the initial charge / discharge efficiency can be maintained at a high level even when high-speed stirring is added, and that the polymer can be made into a thin film and a small amount, and thus the present invention has been completed. According to the present invention, the polymer is strongly adhered to the surface of the carbon material as a polymer film because the compression force and the shearing force are simultaneously imparted by the mechanochemical treatment to homogenize the polymer thin film and simultaneously It is considered to be integrated with the active part of the surface. At that time, there is a possibility that the active portion on the surface of the carbon material and the functional group in the polymer have reacted.

Therefore, the above problems can be solved by the present invention described below. The present invention uses a carbon material as a polymer and / or
Or mechanochemical treatment in the presence of polymer precursor,
A method for producing a polymer-coated carbon material, wherein a coating film made of a polymer derived from the polymer and / or a polymer precursor is adhered and integrated on the surface of the carbon material. In the above, the polymer and / or polymer precursor can be pre-deposited on the carbon material prior to the mechanochemical treatment.
Further, in the above, the polymer and / or the polymer precursor may be added during the mechanochemical treatment of the carbon material. As the polymer, a polymer amine compound is preferably used.

The polymer-coated carbon material obtained by the above manufacturing method has improved wettability, for example. Therefore, when a carbon material is used as a conductive filler for imparting conductivity, it is possible to impart equivalent conductivity with a small amount of use compared to conventional (before modification) carbon materials. Play. Further, reactivity is imparted by the action of the functional group of the polymer. Therefore, when the carbon material is used as a reinforcing filler for imparting mechanical properties, the interfacial adhesion with other matrix materials is higher than that of the conventional (before modification) carbon material, and the excellent mechanical properties This has the effect of exhibiting specific characteristics. As described above, the polymer-coated carbon material obtained in the present invention can be used in various applications, and is particularly suitable as a carbon material for a negative electrode of a lithium ion secondary battery. Therefore, in the present invention, the polymer-coated carbon material described above is used. There is provided a negative electrode material for a lithium ion secondary battery comprising Also provided is a lithium-ion secondary battery using the polymer-coated carbon material of the present invention as a negative electrode material. The lithium ion secondary battery of the present invention comprises the above negative electrode, positive electrode and non-aqueous electrolyte.

In the lithium ion secondary battery using the above polymer coated carbon material as an electrode material, high initial charge / discharge efficiency and high discharge capacity are obtained because decomposition reaction on the surface of the carbon material is significantly suppressed. It is thought to be for.
Specifically, by attaching a polymer to the surface of the carbon material, the active part of the surface of the carbon material, which is the starting point of the decomposition reaction of the electrolytic solution, is sealed and the decomposition reaction is suppressed or intervenes on the surface of the carbon material. It is also considered that the decomposition reaction of the electrolytic solution proceeded mildly by the polymer, and the decomposition products were formed as a uniform thin film, and excessive decomposition was suppressed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. In the method for producing a polymer-coated carbon material according to the present invention, the carbon material is subjected to mechanochemical treatment in the presence of a polymer and / or a polymer precursor, and the polymer film is adhered and integrated on the surface of the carbon material. Let <Carbon Material> The carbon material for coating the polymer varies depending on its purpose, but hereinafter, the case where it is mainly used as a negative electrode material of a lithium ion secondary battery will be described as an example.
The carbon material used as the negative electrode material of the lithium ion secondary battery is not particularly limited as long as it can store and release lithium ions as the negative electrode active material. It is desirable to use a graphite material having high crystallinity as the carbon material, but the characteristics of the present invention can be utilized even in an amorphous hard carbon material.

Specifically, coal-based and petroleum-based tars, mesophase calcined carbon (bulk mesophase) made from pitch, mesophase spheres, cokes (raw coke, green coke, pitch coke, needle coke, petroleum coke) Etc.) or a graphitized material thereof, pyrolytic carbon, graphite carbon fiber, thermal expansion carbon (vapor growth carbon), artificial graphite, natural graphite, carbon black, activated carbon and the like. Further, amorphous hard carbon made of phenol resin, oxygen-crosslinked petroleum pitch, heavy oil, naphthalene or the like can be used. These carbon materials are a mixture of multiple types, granules, coatings,
It may be a laminate. In addition, the liquid phase, the gas phase, or the solid phase may be subjected to various chemical treatments, heat treatments, oxidation treatments, and the like.

Among the above, in order to obtain a high discharge capacity, the lattice spacing d ₀₀₂ in X-ray diffraction is 0.34.
A graphitic material having a true specific gravity of 2.2 or more in nm or less is preferable. Here, the lattice spacing d ₀₀₂ means CuK as X-ray.
X-ray diffraction method using α-rays and high-purity silicon as a standard substance [Sugio Ohtani, carbon fiber, P733-742 (198)
6) Modern editorial company]. Although the particle size of the carbon material is not particularly limited, it is usually preferable that the number average particle size is about 10 nm to 50 μm. Further, if the specific surface area of the carbon material is too large, the amount of polymer required for obtaining the effect of reducing the irreversible capacity increases, leading to a decrease in the discharge capacity. Therefore, the nitrogen gas adsorption BET specific surface area is 5 m ² / g or less, preferably It is preferably 2 m ² / g or less.
The form of the carbon material is not particularly limited, and may be a pulverized product of the above materials, a fibrous material, a film material, or the like.

The polymer coated on the carbon material as described above can be used without any particular limitation, but it is desirable that the polymer is stable in each step during the production of the negative electrode. For example, a step of preparing a negative electrode mixture with a binder or a solvent, a step of kneading the negative electrode mixture after that, which is stable to the solvent and does not cause elution or peeling, after producing a secondary battery, It is desirable to use one that is chemically and electrochemically stable with respect to the electrolytic solution and the electrolyte. Specifically, polyvinylidene fluoride, fluorine-based resins such as polytetrafluoroethylene, polymer compounds used for solid electrolytes such as polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyvinyl alcohol, polyethylene glycol, polypropylene glycol, polyvinylpyrrolidone. , Styrene-maleic anhydride copolymer,
Water-soluble polymer compounds such as methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylic acid, cross-linkable polymer compounds such as styrene-butadiene rubber, olefin polymer compounds such as polyethylene and polypropylene, and polymer amine compounds can be used. Is. Furthermore, hydrolysates of these polymers,
Various reaction products and modified products such as crosslinking reaction products and acid modified products may be used, and salts such as neutral salts of acids or bases and metal salts may also be used.

Further, the coating may be a polymerized low molecular weight compound (polymer precursor) attached to the graphite particles, which has a high molecular weight in the process of mechanochemical treatment or the process of producing the negative electrode. The polymer precursor of this case, -OH in the molecule, -COOH, -NH -, - NH 2
Such as those having a functional group such as self-crosslinking by dehydration condensation or decarboxylation, isocyanate compounds, dihydrazide compounds, aziridine compounds, those forming a crosslinked structure by the combined use of a crosslinking agent such as an epoxy compound, There is no regulation on the combination. For example, γ-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane. Silane coupling agents such as methoxysilane undergo silanol groups (-Si-OH) due to hydrolysis reaction.
Is produced and self-crosslinking proceeds by dehydration condensation, and can be used in the present invention. In addition, functional group-containing acrylic monomers such as acrylic acid, methacrylic acid, hydroxyethyl methacrylate, and acrylic amide can also be used. The above-mentioned polymer and polymer precursor may be used in combination.

Among the above, a high molecular amine compound is preferably used. The polymer amine compound is not particularly limited as long as it is a polymer having an amino group in the molecule, and the type of amino group and the type of polymerization repeating unit are not limited. For example, the amino group may be any of primary amine, secondary amine, tertiary amine or quaternary ammonium, and may have a ring member. The amino group may form the main chain of the polymer or may be pendant. The high-molecular amine compound may be either a homopolymer or a copolymer, may be a copolymer of an amino group-containing monomer and another monomer, and may be a main chain of a polymer produced in advance. The amino group may be modified to have a pendant, and the manufacturing method thereof is not limited.

Examples thereof include polyvinylamine-based polymers, polyallylamine-based polymers, polydiallylamine-based polymers, diallylamine-maleic acid copolymers, and further polymers containing polyaniline units, polypyrrole units and the like. It These may be salts such as hydrochloride and ammonium salt. Among the above, it is preferable that the high molecular amine compound is capable of forming a film,
Those having a primary amine in the side chain exhibit high adhesion to the carbon material and are preferred. It is also preferable that the structure has a high charge density. Thermal decomposition temperature of high-molecular amine compounds is 12
It is preferably 0 ° C. or higher. The molecular weight is not particularly limited, but usually, the weight average molecular weight is usually 300 or more. The polymeric amine compounds may be used alone or in combination of two or more.

Of these, polyallylamine shown below is preferably used.

[Chemical 1]

In the present invention, the polymer and / or
Alternatively, when the carbon material is subjected to the mechanochemical treatment in the presence of the polymer precursor, the polymer and / or the polymer precursor may be present at the time of the mechanochemical treatment, and the order of addition and the location are not particularly limited. For example, the polymer and / or polymer precursor can be pre-deposited on the carbon material prior to the mechanochemical treatment. At this time, the polymer and / or polymer precursor is preferably used in a fluid state, and is used by melting, or if necessary, a polymer and / or polymer precursor solution (or dispersion liquid) with a solvent such as water. ) Can also be used. Specific methods include applying a molten polymer and / or polymer precursor to a carbon material, immersing the carbon material in the molten polymer and / or polymer precursor, applying a polymer to the carbon material and And / or a method of applying the polymer precursor solution by spraying, a method of immersing the carbon material in the polymer and / or the polymer precursor solution, and the like.

When the polymer and / or polymer precursor is used in a liquid state, it is also effective to depressurize and deaerate so that the solution or the dispersion liquid uniformly contacts the entire surface of the carbon material. The solution or dispersion of the polymer and / or polymer precursor is usually used at a solid content concentration of 10% or less. The solvent used above is dried and removed during the mechanochemical treatment, but the mechanochemical treatment may be performed after the drying. Drying of the solvent can be carried out according to a usual method, and uneven application of the polymer compound can be suppressed by applying the polymer and / or polymer precursor in a liquid state and then drying while stirring.

The carbon material and the polymer and / or polymer precursor may be dry blended and subjected to mechanochemical treatment. Further, the polymer and / or polymer precursor can be added during the mechanochemical treatment of the carbon material. The polymer and / or polymer precursor to be subjected to the mechanochemical treatment step may be in any form of solid, solution, and melt. For example, a method of spraying a solution of a polymer and / or a polymer precursor or a dispersion liquid of a polymer and / or a polymer precursor on a carbon material undergoing mechanochemical treatment and simultaneously removing the solvent by heating or the like is also effective. Is.

In the present specification, the mechanochemical treatment is a treatment in which a carbon material having a polymer and / or a polymer precursor attached thereto is simultaneously subjected to compressive force and shearing force.
The shearing force and compressive force applied here are usually larger than those of ordinary stirring, but these mechanical stresses are
Is preferably applied to the surface of the carbon material, and it is desirable that the particle skeleton of the carbon material is not essentially destroyed. When the particle skeleton of the carbon material is destroyed, the irreversible capacity tends to increase. Specifically, it is preferable that the reduction rate of the average particle diameter of the carbon material due to the mechanochemical treatment is suppressed to 20% or less.

The mechanochemical treatment may be any device as long as it can apply a compressive force and a shearing force to the object to be treated at the same time, and the device structure is not particularly limited. As such an apparatus, for example, a pressure kneader, a kneader such as a two-roll machine,
A rotary ball mill, a hybridization system (manufactured by Nara Machinery Co., Ltd.), a mechanomicros (manufactured by Nara Machinery Co., Ltd.), a mechanofusion system (manufactured by Hosokawa Micron Co., Ltd.) and the like can be used.

Among the above, an apparatus for simultaneously applying shearing force and compressive force by utilizing the difference in rotational speed is preferably used. Specifically, for example, a rotating drum and an internal member (inner piece having a different rotational speed from the drum) are used. ) And a circulation mechanism for the object to be treated (for example, FIG.
Hosokawa Micron Co., Ltd.'s mechanofusion system whose schematic mechanism is shown in (b) is used to apply centrifugal force to the object to be processed supplied between the rotating drum and the internal member, while The mechanochemical treatment can be performed by simultaneously and repeatedly applying the compressive force and the shearing force due to the speed difference. Also with a fixed drum,
A device may be used that applies a compressive force and a shearing force to the object to be processed by passing the object to be processed between the rotors that rotate at a high speed, the compression force and the shearing force being caused by the speed difference between the fixed container and the rotor. Hybridization system manufactured by Nara Machinery Co., Ltd.).

The mechanochemical treatment conditions as described above are as follows:
Although it depends on the apparatus used and cannot be generally stated, it is preferable to set the reduction rate of the average particle diameter of the carbon material due to the treatment to 20% or less. For example, when using an apparatus equipped with a rotating drum and an internal member, the peripheral speed difference between the rotating drum and the internal member is 5 to 50 m / sec, the distance between them is 1 to 100 mm, and the processing time is 5 to 60 minutes. Is preferable. In the case of an apparatus equipped with a fixed drum / high-speed rotating rotor, the peripheral speed difference between the fixed drum and the rotating rotor is 10 to 100 m / sec, and the processing time is 30 sec to
It is preferably carried out under the condition of 5 minutes. In the present invention, it is preferable that at least a part of the polymer is attached so as to cover the carbon material.

The amount of polymer adhering to the carbon material is
To obtain the effect of reducing the irreversible capacity of the on-secondary battery
And 0.01 mg / m with respect to the surface area of the carbon material²Degree
It is desirable that it is more than once. On the other hand, the amount of attached polymer is high.
If too much, the electron transfer between the carbon material particles is hindered and the carbon material particles are charged and discharged.
The upper limit is usually 10 mg because the electrical characteristics tend to deteriorate.
/ M²It is desirable that the degree be
0.01-10 mg / m ²Degree, preferably 0.5-5
mg / m²It is a degree. The amount of polymer attached to the carbon material is
The maximum mass ratio is 5% by mass, preferably 1% by mass or less.
Is desirable. Also, when preparing a carbon material
Is a polymer or polymer within a range that does not impair the effects of the present invention.
And / or known conductive materials with polymeric precursors,
Combined with various additives such as ion conductive materials and surfactants
can do. These additives are polymeric and / or
Or added when the polymer precursor is attached to the carbon material.
May also be used in combination with a carbon material with a polymer attached
Good.

As described above, the carbon material in which the surface of the carbon material is coated with a polymer has improved surface properties such as wettability. For example, a resin is used as a conductive filler for imparting conductivity to the carbon material. When added to and used in, it has an effect that equivalent conductivity can be imparted by using a small amount as compared with the carbon material before modification. Further, reactivity is imparted by the action of the functional group of the polymer. Therefore, when the carbon material is used as a reinforcing filler for imparting mechanical properties, the interfacial adhesion with other matrix materials is higher than that of the conventional (before modification) carbon material, and the excellent mechanical properties This has the effect of exhibiting specific characteristics. Especially when a carbon material is used as a negative electrode material of a lithium ion secondary battery,
The effect of reducing the irreversible capacity while maintaining a high discharge capacity (high charge / discharge efficiency) can be obtained.

The carbon material according to the present invention can be used in various applications and is not particularly limited, but is particularly suitable as a material for the negative electrode of the lithium ion secondary battery described above, and therefore The invention provides a lithium ion secondary battery negative electrode using the above carbon material, and further a lithium ion secondary battery.

<Lithium-ion secondary battery> A lithium-ion secondary battery usually has a negative electrode, a positive electrode and a non-aqueous electrolyte as main battery constituent elements. The positive and negative electrodes each comprise a lithium ion carrier, and are used in the charging / discharging process. The ingress and egress of the non-aqueous solvent is performed between the layers. Essentially, it is a battery mechanism in which lithium ions are doped into the negative electrode during charging and dedoped from the negative electrode during discharging. The lithium ion secondary battery of the present invention is not particularly limited except that the above-mentioned carbon material is used as the negative electrode material, and other battery constituent elements are in accordance with the elements of a general lithium ion secondary battery. A lithium ion secondary battery usually has a negative electrode, a positive electrode and a non-aqueous electrolyte as main battery components.

<Negative Electrode> A negative electrode is formed from the above carbon material.
Although it can be carried out in accordance with a usual molding method, as long as it is a method capable of sufficiently obtaining the performance of the carbon material, having a high moldability to powder, and obtaining a chemically and electrochemically stable negative electrode. There are no restrictions. When manufacturing the negative electrode, a negative electrode mixture obtained by adding a binder to a carbon material can be used. As the binder, it is desirable to use one having chemical stability and electrochemical stability with respect to the electrolyte. For example, polyvinylidene fluoride, fluororesins such as polytetrafluoroethylene, polyethylene, polyvinyl alcohol, and further Carboxymethyl cellulose or the like is used. These can also be used together. Usually, the binder is preferably used in an amount of about 1 to 20% by mass based on the total amount of the negative electrode mixture.

Specifically, for example, a carbon material is adjusted to have an appropriate particle size by classification or the like and mixed with a binder to prepare a negative electrode mixture, and this negative electrode mixture is usually used on one surface of a current collector. Alternatively, the negative electrode material mixture layer can be formed by coating on both surfaces. In this case, an ordinary solvent can be used, and the negative electrode mixture layer is uniformly and firmly collected by dispersing the negative electrode mixture in the solvent to form a paste, coating it on a current collector, and drying. Adhered to the body. More specifically, for example, a carbon material and a fluorine-based resin powder such as polytetrafluoroethylene may be mixed and kneaded in a solvent such as isopropyl alcohol, and then applied. In addition, a carbon material and a fluororesin powder such as polyvinylidene fluoride or a water-soluble binder such as carboxymethyl cellulose are mixed with a solvent such as N-methylpyrrolidone, dimethylformamide or water or alcohol to form a slurry, It can be applied.

The paste is 300 times with a blade type homomixer.
It can be prepared by stirring at about 500 rpm, but it is also possible to add high speed stirring at about 2000 to 3000 rpm in order to achieve uniform dispersion of this paste (carbon material). At this time, the polymer once adhered above has excellent adhesiveness to the carbon material and is difficult to be peeled off. Therefore, even if high-speed stirring is applied, the polymer is hardly peeled off.

When the mixture of the carbon material powder and the binder is applied to the current collector, the coating thickness is preferably 10 to 200 μm. It is also possible to dry mix a carbon material and a resin powder such as polyethylene or polyvinyl alcohol and perform hot press molding in a mold. After forming the negative electrode mixture layer, pressure bonding such as pressurizing can be performed to further increase the adhesive strength between the negative electrode mixture layer and the current collector.

The shape of the current collector used for the negative electrode is not particularly limited, but a foil shape, a mesh shape such as a mesh or an expanded metal, or the like is used. Examples of the current collector include copper, stainless steel, nickel and the like. In the case of foil, the thickness of the current collector is preferably about 5 to 20 μm.

<Positive electrode> As a positive electrode material (positive electrode active material)
Is one that can be doped / dedoped with a sufficient amount of lithium.
It is preferable to select it. As such a positive electrode active material
Is a lithium-containing transition metal oxide, transition metal chalcogen
Compound, vanadium oxide (V₂O_Five, V ₆O₁₃, V₂O
_Four, V₃O₈Etc.) and its Li compounds, etc.
Compounds containing m, general formula M_XMo₆S_8-y(Where X is 0 ≦
X ≦ 4 and Y are numerical values in the range of 0 ≦ Y ≦ 1, M is a transition
Chebrel phase compound represented by (representing metal such as metal)
The thing, activated carbon, activated carbon fiber, etc. can be used.
The above-mentioned lithium-containing transition metal oxide includes lithium and transition gold.
It is a complex oxide with genus and has two or more transitions with lithium.
It may be a solid solution of metal. Lithium-containing transition
Specifically, the metal oxide is LiM (1)_1-XM (2)
_XO₂(Where X is a numerical value in the range of 0 ≦ X ≦ 1, and M
(1), M (2) is at least one transition metal element
Become. ) Or LiM (1)_2-yM (2)_yO_Four(formula
Medium Y is a numerical value in the range of 0 ≦ Y ≦ 1, and M (1), M
(2) consists of at least one transition metal element. )so
Shown. In the above, with a transition metal element represented by M
Then, Co, Ni, Mn, Cr, Ti, V, Fe, Z
n, Al, In, Sn and the like, and preferably C
Examples include o, Fe, Mn, Ti, Cr, V, and Al.

As the lithium-containing transition metal oxide,
More specifically, LiCoO₂, LixNi_yM_1-yO₂(M
Is a transition metal element other than Ni, preferably Co, F
At least one selected from e, Mn, Ti, Cr, V and Al
1 type, 0.05 ≦ x ≦ 1.10, 0.5 ≦ y ≦ 1.0
Is. ) Li composite oxide, LiNiO
₂, LiMnO₂, LiMn₂O_FourAnd so on.

The lithium-containing transition metal oxide as described above uses, for example, Li or a transition metal oxide or salt as a starting material, these starting materials are mixed according to the composition, and the mixture is heated to 600 ° C. to 1000 ° C. in an oxygen atmosphere. It can be obtained by firing in the temperature range of ° C. The starting material is not limited to oxides or salts, and can be synthesized from hydroxide or the like. In the present invention, as the positive electrode active material, the above compounds may be used alone or in combination of two or more kinds. For example, a carbon salt such as lithium carbonate can be added to the positive electrode.

In order to form a positive electrode with such a positive electrode material, for example, a positive electrode mixture composed of the positive electrode material, a binder, and a conductive agent for imparting conductivity to the electrode is applied to both surfaces of the current collector. A positive electrode material mixture layer is formed. As the binder, any of those exemplified for the negative electrode can be used. As the conductive agent, for example, a carbon material is used.

The shape of the current collector is not particularly limited, and a box shape, a mesh shape such as a mesh or an expanded metal, or the like is used. For example, examples of the current collector include aluminum foil, stainless steel foil, nickel foil and the like. The thickness is preferably 10 to 40 μm. Also in the case of the positive electrode, like the negative electrode, the positive electrode mixture is dispersed in a solvent to form a paste, and the paste-like positive electrode mixture is applied to a current collector and dried to form a positive electrode mixture layer. Alternatively, after forming the positive electrode mixture layer, pressure bonding such as pressurizing may be further performed. Thereby, the positive electrode material mixture layer is uniformly and firmly adhered to the current collector.

In forming the negative electrode and the positive electrode as described above, various additives such as conventionally known conductive agents and binders can be appropriately used.

<Electrolyte> As the electrolyte used in the present invention, an electrolyte salt used in a usual non-aqueous electrolytic solution can be used. For example, LiPF ₆ , LiBF ₄ , Li.
AsF ₆ , LiClO ₄ , LiB (C ₆ H ₅ ), LiC
l, LiBr, LiCF ₃ SO ₃ , LiCH ₃ SO ₃ ,
LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ S
O ₂ ) ₃ , LiN (CF ₃ CH ₂ OSO ₂ ) ₂ , LiN
(CF ₃ CF ₂ OSO ₂ ) ₂ , LiN (HCF ₂ CF ₂
CH ₂ OSO ₂ ) ₂ , LiN ((CF ₃ ) ₂ CHOSO
_{2) 2, LiB [(C} 6 H 3 ((CF 3) 2] 4, Li
A lithium salt such as AlCl ₄ or LiSiF ₆ can be used. Particularly, LiPF ₆ and LiBF ₄ are preferably used from the viewpoint of oxidation stability. The electrolyte salt concentration in the electrolytic solution is preferably 0.1 to 5 mol / liter, and is 0.1.
It is more preferably 5 to 3.0 mol / liter.

The above non-aqueous electrolyte may be a liquid non-aqueous electrolyte solution or a polymer electrolyte such as a solid electrolyte or a gel electrolyte. In the former case, the non-aqueous electrolyte battery is
It is configured as a so-called lithium ion battery, and in the latter case, the non-aqueous electrolyte battery is configured as a polymer electrolyte battery such as a polymer solid electrolyte battery and a polymer gel electrolyte battery.

When a liquid non-aqueous electrolyte solution is used, the solvent is ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate,
1,1- or 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, anisole, diethyl Ether, sulfolane, methylsulfolane, acetonitrile, chloronitrile, propionitrile, trimethyl borate, tetramethyl silicate, nitromethane, dimethylformamide, N-methylpyrrolidone,
Ethyl acetate, trimethyl orthoformate, nitrobenzene, benzoyl chloride, benzoyl bromide, tetrahydrothiophene, dimethyl sulfoxide, 3-methyl-2-
An aprotic organic solvent such as oxazolidone, ethylene glycol or dimethylsulfite can be used.

When the non-aqueous electrolyte is a polymer electrolyte such as a polymer solid electrolyte or a polymer gel electrolyte, it contains a matrix polymer gelled with a plasticizer (non-aqueous electrolyte solution),
Examples of the matrix polymer include ether polymers such as polyethylene oxide and cross-linked products thereof, polymethacrylate polymers, polyacrylate polymers, fluorine polymers such as polyvinylidene fluoride and vinylidene fluoride-hexafluoropropylene copolymer. Can be used alone or in combination. Among these, from the viewpoint of redox stability and the like, it is desirable to use a fluoropolymer such as polyvinylidene fluoride or vinylidene fluoride-hexafluoropropylene copolymer.

As the electrolyte salt and the non-aqueous solvent constituting the plasticizer contained in these polymer solid electrolytes and polymer gel electrolytes, any of the above can be used. In the case of a gel electrolyte, the concentration of the electrolyte salt in the non-aqueous electrolytic solution which is a plasticizer is preferably 0.1 to 5 mol / liter, and 0.5 to
2.0 mol / liter is more preferable. The method for producing such a solid electrolyte is not particularly limited, but, for example,
A method of mixing a polymer compound forming a matrix, a lithium salt and a solvent, and heating and melting the polymer compound, a lithium salt and a solvent in an appropriate organic solvent for mixing, and then mixing an organic solvent And a method of mixing a monomer, a lithium salt and a solvent, and irradiating the mixture with an ultraviolet ray, an electron beam or a molecular beam to form a polymer. Further, the addition ratio of the solvent in the solid electrolyte is preferably 10 to 90% by mass, and more preferably 30 to 80% by mass. When the content is 10 to 90% by mass, the conductivity is high, the mechanical strength is high, and a film is easily formed.

A separator may be used in the lithium ion secondary battery of the present invention. The separator is not particularly limited, and examples thereof include woven cloth, non-woven cloth, and synthetic resin microporous film. In particular, a synthetic resin microporous film is preferably used, and among them, a polyolefin microporous film is preferable in terms of thickness, film strength and film resistance. Specifically, it is a microporous membrane made of polyethylene and polypropylene, or a microporous membrane obtained by combining these.

In the lithium ion secondary battery of the present invention, it is possible to use a gel electrolyte because the initial charge / discharge efficiency is improved. The gel electrolyte secondary battery is configured by stacking a negative electrode containing a carbon material, a positive electrode, and a gel electrolyte in the order of, for example, a negative electrode, a gel electrolyte, and a positive electrode, and accommodating them in a battery exterior material. In addition to this, a gel electrolyte may be further arranged outside the negative electrode and the positive electrode. In a gel electrolyte secondary battery using such a carbon material as a negative electrode, even if propylene carbonate is contained in the gel electrolyte and a carbon material powder having a small particle size such that impedance can be sufficiently lowered is used, it is irreversible. The capacity can be kept small. Therefore, a large discharge capacity can be obtained and a high initial charge / discharge efficiency can be obtained.

Further, the structure of the lithium-ion secondary battery according to the present invention is arbitrary, and its shape and form are not particularly limited, and any of cylindrical, rectangular, coin-shaped, button-shaped, etc. can be selected. Can be selected. In order to obtain a more safe sealed non-aqueous electrolyte battery, it is desirable to provide a means for detecting an increase in the battery internal pressure and shutting off the current when an abnormality such as overcharge occurs. In the case of a polymer solid electrolyte battery or a polymer gel electrolyte battery, it may have a structure of being enclosed in a laminate film.

[0051]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited to these examples.
In the following examples and comparative examples, the carbon material is
Although a button type secondary battery for evaluation having a configuration as shown in (1) above was manufactured and evaluated, an actual battery can be manufactured according to a known method based on the concept of the present invention.

[Example 1] <Preparation of carbon material> Polyallylamine (PA manufactured by Nitto Boseki Co., Ltd.
A-01, weight average molecular weight 1000) was dissolved in distilled water to prepare an aqueous solution having a concentration of 0.07% by mass. Graphite particles of the mesophase carbonaceous material (bulk mesophase) obtained by heat treatment of pitch were added to 100 parts by mass of the obtained 0.07% by mass polyallylamine aqueous solution (average particle size by laser diffraction type particle size distribution meter (hereinafter simply referred to as average Particle diameter): 20 μm, BET specific surface area by nitrogen gas adsorption: 0.70 m ² / g, density: 2.257 g / cm ³ ,
Lattice plane spacing in X-ray diffraction d ₀₀₂ : 0.3359n
m) 100 parts by mass was immersed, depressurized and degassed. Next, this mixture was put into a Henschel mixer (manufactured by Mitsui Mining Co., Ltd.), and the inside of the mixer was heated to 120 ° C. with stirring to remove the solvent (water). Thus, graphite particles to which polyallylamine was attached at 1 mg / m ² were obtained.

Then, the polyallylamine-adhered graphite particles were subjected to mechanochemical treatment using a treating apparatus having a schematic structure as shown in FIG. 2 (Hybridization System manufactured by Nara Machinery Co., Ltd.). That is, by treating the rotating rotor at a peripheral speed of 50 m / sec for a treatment time of 3 minutes, the polyallylamine-adhered graphite particles charged in the apparatus are dispersed, and mainly impact force and intermolecular interaction are included. Mechanical effects such as compressive force, frictional force, and shearing force were repeatedly applied. The average particle size of the polyallylamine-adhered graphite particles after the mechanochemical treatment was 19 μm.

<Preparation of Negative Electrode Mixture Paste> (1) 90% by mass of polyallylamine-adhered graphite particles after the mechanochemical treatment obtained above and 10% by mass of polyvinylidene fluoride as a binder were mixed, and N-
Methylpyrrolidone (solvent) was added, and the mixture was stirred at 500 rpm for 5 minutes using a homomixer to prepare a negative electrode mixture paste (A). (2) Negative electrode mixture paste (A) prepared in the above (1)
A negative electrode mixture paste (B) was prepared by further stirring the mixture at 3000 rpm for 3 hours using a homomixer.

<Preparation of Working Electrode (Negative Electrode)> (3) The above negative electrode mixture paste (A) or (B) is applied on a copper foil (current collector 7b) to a uniform thickness, and further in vacuum. The solvent was evaporated at 90 ° C. and dried. Next, the negative electrode mixture applied on the copper foil is pressed by a roller press and punched into a circular shape having a diameter of 15.5 mm, so that the working electrode (negative electrode) 2 is formed from the paste (A) or (B), respectively. Was produced. <Production of Counter Electrode> The counter electrode 4 was formed by pressing a lithium metal foil against a nickel net and punching it out into a circular shape having a diameter of 15.5 mm to collect a current (7a) made of the nickel net and a lithium metal in close contact with the current collector. A counter electrode 4 made of foil was produced.

<Electrolyte> 50 mol of ethylene carbonate
%, And 50 mol% of diethyl carbonate, LiClO ₄ was dissolved at a concentration of 1 mol / dm ³ to prepare a non-aqueous electrolyte. A polypropylene porous body was impregnated with the obtained non-aqueous electrolytic solution to prepare a separator 5 impregnated with the electrolytic solution.

<Production of Evaluation Battery> A button type secondary battery shown in FIG. 1 was produced as an evaluation battery. The outer cup 1 and the outer can 3 have a hermetically sealed structure in which they are caulked at their peripheral portions with an insulating gasket 6 interposed therebetween.
In order from the inner surface of the current collector 7a made of nickel net,
A battery system in which a disk-shaped counter electrode 4 made of a lithium foil, a separator 5 impregnated with an electrolyte solution, a disk-shaped working electrode (negative electrode) 2 made of a negative electrode mixture, and a current collector 7b made of a copper foil are laminated. .

The evaluation battery was laminated by sandwiching the separator 5 impregnated with the electrolyte solution between the working electrode 2 which was in close contact with the current collector 7b and the counter electrode 4 which was in close contact with the current collector 7a. 2 is housed in the outer cup 1, the counter electrode 4 is housed in the outer can 3, the outer cup 1 and the outer can 3 are combined, and the peripheral portions of the outer cup 1 and the outer can 3 are caulked with the insulating gasket 6 interposed therebetween. It was sealed and prepared. This evaluation battery includes a working electrode (negative electrode) 2 containing a carbon material that can be used as a negative electrode active material in an actual battery, and a counter electrode 4 made of a lithium metal foil.
It is a battery composed of and. With respect to the evaluation battery manufactured as described above, the following charge / discharge test was performed at a temperature of 25 ° C.

<Charging / Discharging Test> Constant current charging is performed at a current value of 0.9 mA until the circuit voltage reaches 0 mV, and when the circuit voltage reaches 0 mV, switching to constant voltage charging is performed, and the current value becomes 20 μA. After continuing to charge until, it rested for 120 minutes. Next, at a current value of 0.9 mA, the circuit voltage is 2.
Constant current discharge was performed until it reached 5V. At this time, the charge capacity and the discharge capacity are obtained from the energization amount in the first cycle,
The initial discharge efficiency was calculated from the following formula. Initial charge / discharge efficiency (%) = (discharge capacity / charge capacity) × 10
0 In this test, the process of doping lithium ions into the carbon material was charged and the process of dedoping the carbon material was discharged.

Table 1 shows the measured values of the discharge capacity (mAh / g) and the initial charge / discharge efficiency (%) per 1 g of the carbon material powder.
Shown in. As shown in Table 1, the lithium-ion secondary battery using the carbon material of the present invention as the working electrode (corresponding to the negative electrode of the actual battery) exhibits a high discharge capacity and a high initial charge / discharge efficiency (that is, a small irreversible capacity). ) Has. In addition, paste (B) obtained by adding long-term stirring to normal paste (A)
It was confirmed that even in the working electrode prepared from, a high initial charge / discharge efficiency was obtained and the adhesion of the coated polymer to the carbon material was excellent.

[Examples 2 to 7] Carbon materials were prepared in the same manner as in Example 1 except that the amounts of carbon materials and polyallylamine deposited were changed as shown in the table to prepare lithium secondary batteries. Table 1 shows the measurement results of the discharge capacity and the initial charge / discharge efficiency. As shown in Table 1, the lithium secondary battery using the carbon material of the present invention has a high discharge capacity and a high initial charge / discharge efficiency. In addition, a working electrode prepared from a paste (B) obtained by stirring a paste (A) for a long time also has a high initial charge / discharge efficiency and excellent adhesion of the coated polymer to a carbon material. Was confirmed.

Comparative Examples 1 to 5 In Examples 1 to 7,
Lithium ion secondary batteries were produced using carbon materials that were not treated with polyallylamine. Table 1 shows the measurement results of the discharge capacity and the initial charge / discharge efficiency. Table 1
As shown in, when each carbon material is used as a material for the working electrode (negative electrode) without treatment with polyallylamine, the initial charge / discharge efficiency is low.

[Example 8] <Preparation of carbon material> Polyallylamine (PA manufactured by Nitto Boseki Co., Ltd.
A-H10C, weight average molecular weight 60,000) was dissolved in distilled water to prepare an aqueous solution having a concentration of 4.2 mass%. The same graphitized particles as in Example 1 (average particle diameter: 20 μm, BET specific surface area by nitrogen gas adsorption: 0.70 m ² / g, density: 2.257 g / cm ³ , lattice spacing d ₀₀₂ : 0 in X-ray diffraction) 100 parts by mass of bulk mesophase graphitized particles obtained by heat treatment with a pitch of 3359 nm) is a processing device having a schematic structure as shown in FIGS. 3 (a) and 3 (b) (mechanofusion system manufactured by Hosokawa Micron Corporation). The mixture was placed in a container and subjected to mechanochemical treatment by applying a shearing force and a compressing force under the conditions of a peripheral speed of the rotating drum of 15 m / sec, a processing time of 30 minutes, and a distance of 5 mm between the rotating drum and the internal member. During the treatment, 4.2% by mass of polyallylamine aqueous solution was added to 5
At the same time as adding by mass spraying, the inside of the apparatus was heated to 120 ° C. to remove the solvent (water). Thus, graphite particles to which 3 mg / m ^{2 of} polyallylamine was attached were obtained. Further, it was vacuum dried at 200 ° C. for 6 hours to completely remove water. The average particle size of the polyallylamine-adhered graphite particles after the mechanochemical treatment was 20 μm.

A working electrode (negative electrode) was prepared in the same manner as in Example 1 except that the above carbon material was used. The evaluation results are shown in Table 1. As shown in Table 1, the lithium ion secondary battery using the carbon material of the present invention exhibits a high discharge capacity,
In addition, it has high initial charge and discharge efficiency. In addition, a working electrode prepared from a paste (B) obtained by stirring a paste (A) for a long time also has a high initial charge / discharge efficiency and excellent adhesion of the coated polymer to a carbon material. Was confirmed.

[Examples 9 to 19] A carbon material was prepared in the same manner as in Example 8 except that the kind and deposition amount of the polymer or the polymer precursor were changed as shown in Table 1. A secondary battery was produced. The evaluation results are shown in Table 1. As shown in Table 1, the lithium secondary battery using the carbon material of the present invention has a high discharge capacity and a high initial charge / discharge efficiency. In addition, a working electrode made from a paste (B) obtained by adding a long time stirring to a normal paste (A),
It was confirmed that a high initial charge / discharge efficiency was obtained and the adhesion of the coated polymer to the carbon material was excellent.

Comparative Example 6 A lithium ion secondary battery was prepared in the same manner as in Example 1 except that the carbon material was treated with triethylamine (low molecular weight) instead of polyallylamine (high molecular weight). Was produced. The evaluation results are shown in Table 1. As shown in Table 1, the effect of improving the initial charge / discharge efficiency is small when the carbon material is treated with a low molecular weight compound.

[Comparative Example 7] The carbon material was not treated with a polymer, and 0.01 mol of triethylamine was added to the electrolyte.
/ Liter was added. The evaluation results are shown in Table 1. As shown in Table 1, instead of treating the carbon material with a polymer,
When the amine compound is added to the electrolytic solution, the effect of improving the initial charge / discharge efficiency is small.

Comparative Example 8 The same amount as in Example 8 was applied with the polyallylamine prepared in Example 8 on the surface of the working electrode (negative electrode) prepared from the graphite particles not treated with polyallylamine. Was coated. After coating with polyallylamine, the product was vacuum dried at 200 ° C. for 6 hours to completely remove water. The evaluation results are shown in Table 1. As shown in Table 1, the effect of improving the initial charge / discharge efficiency is smaller when the surface of the working electrode is coated, as compared with the example in which the polymer is coated on the surface of the graphite particles.

[Comparative Example 9] In a Henschel mixer, the stirring rotation speed was 700 rpm and the treatment time was 30 minutes.
At the same time as adding by mass spraying, the inside of the apparatus was heated to 120 ° C. to remove the solvent (water). In this way, graphite particles having 0.05 mg / m ^{2 of} polyethylene oxide attached were obtained. Further, it was vacuum dried at 200 ° C. for 6 hours to completely remove water. The average particle size of the polyallylamine-adhered graphite particles obtained above was 20 μm. Other than using the graphite particles treated above as the carbon material,
A working electrode (negative electrode) was prepared in the same manner as in Example 1. The evaluation results are shown in Table 1. As shown in Table 1, when the polymer coated on the graphite particles is polyethylene oxide, even if the coating treatment using a Henschel mixer is carried out, the ordinary negative electrode mixture paste (A) is treated with mechanochemical treatment. Although almost the same high discharge capacity and initial charge / discharge efficiency can be obtained, when high-speed stirring is applied for a long time (paste (B)), the polymer coating effect decreases as compared with the case where mechanochemical treatment is applied, and the initial charge is increased. Discharge efficiency decreases.

[Comparative Examples 10 to 17] A carbon material was prepared in the same manner as in Comparative Example 9 except that the kinds and amounts of the polymers shown in Table 1 were changed, and lithium ion secondary batteries were produced. The evaluation results are shown in Table 1. In these examples not subjected to the mechanochemical treatment, the adhesiveness of the polymer to the graphite particles was insufficient and the polymer coating effect was deteriorated as compared with the examples, so that the paste (B) to which high-speed stirring was added for a long time was used. In this case, the initial charge / discharge efficiency is significantly reduced.

[0071]

[Table 1]

[0072]

[Table 2]

Although the use as the negative electrode of the lithium ion secondary battery has been described above, the polymer-coated carbon material of the present invention is not limited to the use. For example, the polymer-coated carbon material of the present invention has improved surface properties such as wettability. For example, when the carbon material is used as a conductive filler for imparting conductivity to a resin, before modification. Compared with the carbon material of (1), it is possible to provide the same conductivity with a small amount of use.

[0074]

EFFECTS OF THE INVENTION The carbon material of the present invention has surface properties such as wettability modified, and the adhesion of the polymer to the carbon material is large, so that the carbon material does not easily peel off even if stirring is applied. It is possible to maintain the modification effect such as. The lithium-ion secondary battery using the carbon material of the present invention as the negative electrode material makes it possible to reduce the irreversible capacity while maintaining a high discharge capacity, and further, without causing a delay in the charging speed, the initial charge / discharge. The efficiency can be significantly improved, and the cycle characteristics can be improved. Further, the lithium ion secondary battery of the present invention has a high discharge capacity and an initial charge / discharge efficiency, and has excellent cycle characteristics without causing a delay in charging speed. Therefore, the lithium ion secondary battery of the present invention satisfies the recent demand for higher energy density of the battery, and is effective for downsizing and high performance of the mounted device.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an evaluation battery for evaluating the characteristics of a carbon material.

FIG. 2 is a schematic explanatory diagram of a structure of a mechanochemical treatment device used in an example.

3 (a) and 3 (b) are schematic explanatory views of the structure of another mechanochemical treatment apparatus used in Examples.

[Explanation of symbols]

1 exterior cup 2 Working electrode 3 exterior cans 4 opposite poles 5 Electrolyte solution impregnated separator 6 Insulation gasket 7a, 7b Current collector

Continued front page    (72) Inventor Hitomi Hatano             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Technical Research Institute of Iron Co., Ltd. (72) Inventor Makiko Ijiri             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Technical Research Institute of Iron Co., Ltd. (72) Inventor Toshihide Suzuki             1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Made in Kawasaki             Technical Research Institute of Iron Co., Ltd. F-term (reference) 4G046 CA04 CB03 CB09 CC05                 5H029 AJ02 AJ03 AJ05 AK02 AK03                       AK05 AK08 AL06 AL07 AL08                       AM00 AM02 AM03 AM04 AM05                       AM07 AM16 CJ22 DJ08 DJ16                       EJ12 EJ14                 5H050 AA02 AA07 AA08 BA17 BA18                       CA02 CA08 CA09 CA11 CA16                       CB07 CB08 CB09 DA03 DA09                       EA00 EA22 EA23 EA24 EA28                       FA17 FA18 GA00 GA22

Claims (6)

[Claims] 1. A carbon material is mechanochemically treated in the presence of a polymer and / or a polymer precursor, and the surface of the carbon material is composed of a polymer derived from the polymer and / or the polymer precursor. A method for producing a polymer-coated carbon material in which a coating is adhered and integrated. 2. The method for producing a polymer-coated carbon material according to claim 1, wherein the polymer and / or the polymer precursor is previously attached to the carbon material prior to the mechanochemical treatment. 3. During the mechanochemical treatment of the carbon material,
The method for producing a polymer-coated carbon material according to claim 1, wherein the polymer and / or the polymer precursor is added. 4. The method for producing a polymer-coated carbon material according to claim 1, wherein the polymer is a polymer amine compound. 5. A negative electrode material for a lithium ion secondary battery, comprising a polymer-coated carbon material obtained by the production method according to claim 1. 6. A lithium ion secondary battery using the polymer-coated carbon material obtained by the method according to any one of claims 1 to 4 as a negative electrode material.