JP2001110407A - Anode material for lithium ion battery and lithium ion secondary battery using the same - Google Patents

Abstract

(57) Abstract: A negative electrode material for a lithium ion battery having high capacity and improved high-temperature stability by improving the adhesion between a SEI film formed on the negative electrode surface and a carbonaceous surface of the negative electrode. Providing lithium-ion secondary batteries using it. SOLUTION: A positive electrode and a negative electrode are composed of a simple substance or a compound capable of inserting and extracting lithium, and after at least contacting the simple substance or the compound constituting the negative electrode with a fluorinating agent, a polymerizable organic substance, an organometallic compound, an organic electrolyte and By reacting with at least one selected from inorganic electrolytes, 157 in the argon laser Raman spectrum
Peak intensity of 0~1620cm ^-1 13 for (I _A)
R value is the ratio of the peak intensity of _{^{50~1370cm -1 (I B) (I}} B / I A) is 0.18 or more, and characterized in that the grafted compound is formed so as to be 2.00 or less A negative electrode material for a lithium ion battery, and a lithium ion secondary battery using the negative electrode material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a negative electrode material for a lithium ion battery and a lithium ion secondary battery using the same. Specifically, after treating the surface of the negative electrode material with a fluorinating agent, it is reacted with a polymerizable organic substance or the like to form a specific amount of a grafted product on the surface thereof, and a lithium material using the same. It relates to an ion secondary battery. The secondary battery of the present invention has high capacity and improved high-temperature stability.

[0002]

2. Description of the Related Art In recent years, high-capacity secondary batteries have been desired to have higher capacities as electronic devices have become smaller. Therefore, compared to nickel-cadmium and nickel-metal hydride batteries,
Attention has been paid to lithium ion secondary batteries having higher energy density. As the negative electrode material, the use of lithium metal was first attempted, but as charge and discharge were repeated, lithium in the form of dendrites precipitated and penetrated the separator to the positive electrode, causing a short circuit and an ignition accident It turned out to be possible. Therefore, attention has been paid to the use of a carbon material capable of preventing lithium metal from being deposited and coming out of the interlayer in the charge / discharge process, as a negative electrode material.

As this carbon material, Japanese Patent Application Laid-Open No. 57-20
No. 8079 proposes to use a graphite material. JP-A-4-237949 proposes a carbonaceous material having a lower crystallinity than graphite, such as a polymerized carbide, coke, coal and a petroleum pitch fired product. Further, Japanese Patent Application Laid-Open Nos. 4-368778 and 4-370
As disclosed in Japanese Patent Publication No. 662, it has been proposed to use a composite carbonaceous material having an amorphous part and a highly crystalline graphite multiphase structure.

[0004] Carbonaceous and graphitic particles (carbonaceous, graphitic and multi-layered carbonaceous materials containing them) have higher crystallinity and higher true density than non-graphitizable carbon materials. Therefore, if an electrode is formed using these carbon materials such as carbon and graphite, high electrode filling properties can be obtained, and the volume energy density of the battery can be increased. However, their carbonaceous surfaces are inherently less wettable by polar electrolytes and the resulting S
The EI coating (an interfacial coating formed by the reduction of the electrolyte and the electrolytic solution by lithium ions) also has insufficient adhesion to the carbonaceous surface, and when the battery becomes hot, the S
When the EI coating peels off from the electrode surface, a new S
There is a problem that Li is consumed to form the EI coating and the high-temperature cycle characteristics deteriorate.

Conventionally, various proposals have been made to improve the adhesion between the negative electrode carbon and the electrolyte. The first relates to the surface modification of the negative electrode.
No. 5938, Japanese Patent Application Laid-Open No. 9-2457.
No. 93 is a method of treating with a gas containing fluorine. The second relates to improvement of the binder, for example,
Japanese Patent Application Laid-Open No. Hei 7-201315 proposes crosslinking polyvinylidene fluoride (PVDF). Part 3
Relates to the improvement of the composition of an electrolytic solution, and many proposals have been made particularly regarding combinations of solvents and additives.

[0006]

However, the effects of these proposals are not sufficient, and further improvement is required. The present invention relates to a method for producing S
Provided is a negative electrode material for a lithium ion battery having high capacity and improved high-temperature stability by improving the adhesion between the EI coating and the carbonaceous surface of the negative electrode, and a lithium ion secondary battery using the same. The purpose is to:

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of such circumstances, and as a result, after treating the surface of a negative electrode material with a fluorinating agent, reacting it with a polymerizable organic substance or the like, and identifying the surface of the material. By forming a grafted product in an amount and using it as a negative electrode, it has been found that a lithium ion secondary battery having high capacity and improved high-temperature stability can be obtained, and the present invention has been completed. .

That is, the gist of the present invention is: The positive electrode and the negative electrode are composed of a simple substance or a compound capable of inserting and extracting lithium, and after contacting at least the simple substance or the compound constituting the negative electrode with a fluorinating agent, selected from a polymerizable organic substance, an organometallic compound, an organic electrolyte and an inorganic electrolyte. 1570-162 in the argon laser Raman spectrum
Peak intensity of 0 cm ^-1 1,350 to 13 for (I _A)
R value is the ratio of the peak intensity of _{^{70cm -1 (I B) (I}} B
/ I _A ), wherein the grafted product is formed so as to have a ratio of 0.18 or more to 2.00 or less. _A negative electrode material for a lithium ion battery, wherein the negative electrode material described in 2.1 is used. Lithium ion secondary battery.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. (Negative electrode material for lithium ion battery) As the negative electrode material used in the present invention, a carbonaceous material, particularly, a graphite material is preferable. Graphite materials include natural graphite, artificial graphite, graphitized mesocarbon microbeads, pitch type, polyacrylonitrile type, mesophase pitch type,
What processed the graphitized carbon fiber of a vapor phase growth type into a powder form can also be used. In addition, a single substance or a mixture of two or more of these substances may be used. Among them, the most preferred is purified natural graphite or artificial graphite. In addition, melt-soluble organic substances, thermosetting polymer or the like under an inert gas atmosphere,
1500-3000 ° C., preferably 20 in vacuum
It is also possible to use artificial graphite obtained by heating existing carbonaceous materials, such as artificial graphite and coke, obtained by heating at a temperature of 00 to 3000 ° C. to further advance the graphitization appropriately. These graphite materials have a (002) plane spacing d ₀₀₂ of 3.37 ° or less, preferably 3.36 ° or less, and a crystallite size (Lc) in the C-axis direction of 500 ° or more by X-ray diffraction. , Preferably at least 1000 °. These use the figures corrected based on the Gakushin method.

In Raman spectrum analysis using an argon ion laser beam having a wavelength of 5145 °, 157
When the intensity of a peak existing in the range of 1620 cm ^-1 from 0 the intensity of a peak existing from I _A, 1350 in the range of 1370 cm ^-1 was I _B, which is a ratio R value (= I
_B / I _A) is 0.50 or less, and preferably within 0.20 or less. The crystallinity of the carbonaceous powder can also be determined by electrochemical capacity using lithium ions. The carbonaceous powder used in the present invention has an electric capacity of 270 mAh / g or more, preferably 300 mAh, in terms of electric capacity of a half-cell having a charge / discharge rate of 0.2 mA / cm ^2.
/ G or more, and more preferably 330 mAh / g or more. That is, a highly crystalline carbon material having a carbon hexagonal network structure developed to some extent. When metal ions are intercalated, the composition is expressed as C ₆ Li. It is preferable that the material be capable of forming a stage 1 structure.

The graphitic substance can also be suitably used for a material obtained by mixing and firing an organic substance or the like, or forming amorphous carbon on the surface by using a CVD method or the like. As organic substances, coal-based heavy oils such as coal tar pitch from dry pitch to hard pitch and dry distillate liquefied oil, normal pressure residual oil,
Examples thereof include heavy oils such as direct current heavy oils such as vacuum residual oils, petroleum heavy oils such as cracked heavy oils such as ethylene tar which are by-produced during thermal decomposition of crude oil, naphtha and the like. In addition, these heavy oils are used in a quantity of 200 to 40.
The solid residue obtained by distillation at 0 ° C. is 1 to 100 μm
What has been ground can also be used. Further, vinyl chloride resins and precursors of these resins which become phenol resins and imide resins by firing are also used.

[0012] The mixing of the graphitic substance and the organic substance can be performed using a mixing type mixing device such as a stirring type mixing device using a rotary blade, a kneader, a paddle type mixing device, a roll type mixing device or the like. A V-type mixer, a cylindrical mixer, a double-cone mixer, a ribbon-type mixer using mixing blades, a paddle dryer using a rotary paddle, and the like that mix by rotating the container itself can also be used.

The thus obtained mixture of the graphitic substance and the organic substance is fired in an inert gas atmosphere to obtain a graphite material having amorphous carbon formed on the surface. As the inert gas, nitrogen, argon, or the like can be used. If necessary, pulverized, the multilayer carbon material of the present invention has a volume-based median diameter of 5 to 70 μm, preferably 10 to 4 μm.
0 μm, particularly preferably 13 to 30 μm. BET
The specific surface area measured using the method is preferably 1 to 10
m ² / g, more preferably 1 to 4 m ² / g, particularly preferably to fall in the range of 1 to 3 m ² / g. Further, the apparent density is further improved as compared with the nuclear graphite material used by the carbon coating, but preferably falls within a range of 0.7 to 1.2 g / cc.

In the present invention, these carbon materials are usually in the form of particles, and in some cases, after being molded as a negative electrode material and brought into contact with fluorine gas, polymerizable organic substances, organometallic compounds, organic electrolytes and inorganic electrolytes are obtained. 157 in the argon laser Raman spectrum by reacting with at least one simple substance or compound selected from
1350-1 for a peak intensity of 0-1620 cm ^-1
The R value which is the peak intensity ratio at 370 cm ^-1 is 0.18 or more and 2.00 or less, preferably 0.20 or more and 1.50 or more.
The following surface treatment is performed. When the R value is smaller than 0.18, an organic polymer in an amount sufficient to stabilize the SEI film formed on the negative electrode surface is not introduced, and sufficient high-temperature stability cannot be obtained. On the other hand, when the R value is 2.
If it is larger than 00, the processing is excessive, the irreversible capacity increases, and the reversible capacity decreases.

Various methods are known as a surface treatment method for introducing a graft polymer on a carbon surface. For example, as in the case of graft copolymerization on a polymer surface,
There are catalytic methods, chain transfer methods, radiation polymerization methods, photopolymerization methods, mechanical cleavage methods, coupling methods, and the like. In each case, the activated graft origin is the end face of graphite crystals with a large amount of sp ³ carbon. Mostly, little activation of the bottom is made. As an example in which a polymer is grafted to the negative electrode carbon of a lithium ion battery, JP-A-11-40163 describes an effect of preventing a decrease in cycle capacity by reducing an impedance at an electrode interface by grafting a vinyl compound. Is. On the other hand, the present inventors have found that not only the end face but also the bottom face part is activated even in a treatment that does not lead to significant destruction of the graphite crystal when fluorine gas is used. As the active point, a C radical, a COO radical, or the like can be considered. As an example of grafting a polymer onto a carbon material using fluorine gas, JP-A-6-305858 discloses a radical polymerizable monomer having an e-value of Alfrey-Price of a monomer of -1.0 <e <1.7. It is shown that a new polymer layer is formed on the surface of the carbon material by contacting the surface of the carbon material. However, in the case of this treatment, the amount of the adhered polymer is at most a few weight%, and it is difficult to form the layer. However, although it is considered that a layer is partially formed, it is basically observed by SEM or the like that the polymer is stretched like a beard from an active point.

As the fluorinating agent used in the fluorination treatment,
A substance that emits fluorine atoms such as fluorine gas and NF ₃ is used. The treatment temperature with the fluorinating agent is -100 to 200
° C, preferably a temperature range of 0 to 50 ° C. Further, the treatment time with the fluorinating agent may be a short treatment if fluorine or the like is uniformly supplied to the carbon material.
Minutes, preferably 30 minutes or less. The fluorine partial pressure of the fluorine gas is not particularly limited from pressurization to decompression, but it is preferable that the treatment is performed at 100 to 760 mmHg. Further, the fluorine gas may be used alone, or may be used by mixing an inert gas such as nitrogen and argon.
The concentration is not particularly limited, but is usually 0.1.
A range of 1 to 100%, preferably a range of 50 to 100% is selected.

Next, the surface of the carbonaceous material contacted with fluorine gas is reacted with at least one kind or compound selected from a polymerizable organic substance, an organic metal compound, an organic electrolyte and an inorganic electrolyte. As the polymerizable organic substance and the organometallic compound, for example, a radical polymerizable monomer having an Alfrey-price e value of -1.0 <e <1.7, which is a measure of the reactivity of the monomer, is also preferably used. From an industrial viewpoint, a monomer that can be handled in a gaseous state is preferable. Examples of radically polymerizable monomers having an e-value of Alfrey-Price of −1.0 <e <1.7 are disclosed in, for example, “Polymer Data Handbook” (Baifukan, 1986) and the like. Monomers.

(1) Olefins Acenaphthylene, sodium ethylene sulfonate, butyl ethylene sulfonate, P-oxathiene, chlorotrifluoroethylene, 2-chloro-1-propylene, propylene, 1-hexene, etc. (2) Fluorine-containing olefin tetra Fluoroethylene, hexafluoropropylene,
Vinylidene fluoride, vinyl fluoride, 3,3,3-trifluoropropylene, octafluoroisobutylene, chlorotrifluoroethylene, etc.

(3) Styrene and its derivatives p-acetoxystyrene, chlorostyrene, p-chloromethylstyrene, p-cyanostyrene, 2,4-dibromostyrene, butyl styrenesulfonate, stilbene,
(4) vinyl halide vinylidene chloride, vinyl chloride, vinyl bromide, vinyl iodide, etc.

(5) Vinyl esters: Vinyl benzoate, vinyl isocyanate, vinyl formate, vinyl chloroacetate, vinyl cinnamate, vinyl acetate, ethyl vinyl oxalate, divinyl carbonate, p-vinyl benzoic acid, vinyl propionate, etc. Vinylpyridines 2-isopropenylpyridine, 2-vinylpyridine, 4
-Vinyl pyridine, 2-vinyl pyridine oxide, etc.

(7) Acrylic acid derivative Acrylamide, ethyl acrylate, acrylic acid 2,3
-Epoxypropyl, octadecyl acrylate, acrylate, phenyl acrylate, butyl acrylate, propyl acrylate, benzyl acrylate, methyl acrylate, N-acryloylpyrrolidone, acrylonitrile, acrolein, acrylic acid, methoxypolyethylene glycol acrylate, etc.

(8) Methacrylic acid derivative 1,2-dimethacryloyloxyethane, methacrylic acid,
Methacrylamide, zinc methacrylate, isopropyl methacrylate, ethyl methacrylate, methacrylic acid 2,3
-Epoxy propyl, methacrylic chloride, dodecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, furfuryl methacrylate, propyl methacrylate, methyl methacrylate, methacrylonitrile,
Methoxy polyethylene glycol methacrylate, etc. (9) Dienes Butadiene, isoprene, chloroprene, etc.

(10) Others Allyl alcohol, 2-allyl pyrrole, allyl phenyl ether, allyl benzene, isopropyl vinyl ketone, isopropenyl methyl ketone, itaconic acid, diethyl itaconate, ethyl vinyl ketone, ethyl vinyl sulfide, octadecyl vinyl ether, croton Aldehyde, methyl crotonate, phenyl cinnamate, methyl cinnamate, isopropenyl acetate, diethylene glycol monovinyl ether, diphenylvinyl phosphine, methyl sorbate, sorbonitrile, vinylene carbonate, triethoxyvinylsilane, tributylvinyltin, trimethylvinylsilane, m-vinyl Phenol, diethyl vinyl phosphate, phenyl vinyl ketone, diallyl phthalate, diethyl fumarate, diisopropyl fumarate, mu Conic acid, dimethyl mesaconate, methyl vinyl sulfone, etc.

Among these monomers, particularly, acrylic acid and methacrylic acid having a relatively large value of e and high reactivity are preferable from the viewpoint of industrialization. As other polymerizable organic substances, there are cyclic carbonates such as spiro compounds. For example, 1,6-dioxaspiro [4.4] nonane-2,7-dione and the like can be suitably used.

Examples of the organic electrolyte include polyether polymers such as polyethylene oxide and polypropylene oxide, crosslinked polymers of polyether compounds, polyepichlorohydrin, polyphosphazene, polysiloxane, polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile and the like. A high molecular compound, a lithium salt, or a system in which a lithium-based alkali metal salt is compounded, or a system in which an organic compound having a high dielectric constant such as propylene carbonate, ethylene carbonate, and γ-butyrolactone is added thereto Is mentioned. Examples of the inorganic electrolyte include LiClO ₄ , LiPF ₆ ,
LiBF ₄ , LiAsF ₆ , LiCl, LiBr, Li
CF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (S
O ₂ C ₂ F ₅ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiN
And a lithium salt such as (SO ₃ CF ₃ ) ₂ .

These polymerizable organic substances, organometallic compounds,
The organic electrolyte and the inorganic electrolyte may be used alone or in a combination of two or more. After activation with fluorine gas, radicals may be deactivated when exposed to oxygen or air before polymerization is performed. Therefore, it is necessary to control the oxygen concentration before and after polymerization and during polymerization. The contact pressure of the polymerizable organic substance or the organometallic compound can be any condition from reduced pressure to increased pressure, and is usually selected from the range of 1 Torr to 10 atm. Preferably, the range is 0.5 to 2 atm.

The contact temperature of the polymerizable organic substance or the organometallic compound varies depending on the monomer used.
To 200 ° C, preferably 20 to 90 ° C. The contact time is appropriately selected from a wide range.
The range is from seconds to 10 days, preferably from 1 minute to 5 hours.
Even outside these ranges, conditions can be appropriately selected.

In the present invention, after the polymerization reaction, a different polymer can be formed at the polymerization terminal by using another polymerizable gas. Assuming that the formed polymer has a weight increase of several percent by weight and a uniform film, a polymer of several angstroms to several tens of angstroms can be formed. It is considered that the organic polymer produced in such a beard-like (or film-like) form improves the adhesion between the produced SEI and the carbonaceous material, and contributes to high capacity and high-temperature stability.

An electrode is obtained by adding a binder, a solvent, and the like to the above carbon material to form a slurry, and applying and drying the slurry on a metal current collector substrate such as a copper foil. Further, the electrode material can be directly formed into an electrode shape by a method such as roll molding or compression molding. Examples of the binder that can be used for the above-mentioned purposes include, but are not limited to, solvents, polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, resin polymers such as cellulose, styrene / butadiene rubber, isoprene rubber, butadiene rubber, and ethylene.・ Rubber-like polymers such as propylene rubber, styrene / butadiene / styrene block copolymers, hydrogenated products thereof, styrene / isoprene / styrene block copolymers, thermoplastic elastomeric polymers such as hydrogenated products, syndiotactic Tic 12-polybutadiene, ethylene-vinyl acetate copolymer, soft resin-like polymer such as propylene / α-olefin (2 to 12 carbon atoms) copolymer, polyvinylidene fluoride, polytetrafluoroethylene, polytetrafluoroethylene Fles such as ethylene copolymer Motokei polymer, an alkali metal ion, the polymeric composition may be mentioned in particular has an ionic conductivity of lithium ions.

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, lithium salt, or a system in which a lithium-based alkali metal salt is combined, or propylene carbonate, ethylene carbonate, high dielectric constant such as γ-butyrolactone A system in which an organic compound having the same is blended can be used. The ionic conductivity of such an ion-conductive polymer composition at room temperature is preferably 10
5 S / cm or more, more preferably 10-3 S / cm or more.

The mixing mode of the polymer-modified graphite material used in the present invention and the above-mentioned binder can take various forms. That is, a form in which both particles are mixed,
Examples include a form in which a fibrous binder is entangled with the particles of the carbonaceous material or a form in which a layer of the binder is attached to the surface of the particles of the carbonaceous material. The mixing ratio of the carbonaceous material and the binder is preferably 0.1 to 30% by weight, more preferably 0.5 to 10% by weight, based on the carbonaceous material. If the binder is added in an amount larger than this, the internal resistance of the electrode is increased, which is not preferable. If the amount is smaller than this, the binding property between the current collector and the carbonaceous powder is poor.

(Lithium ion secondary battery) The thus prepared negative electrode plate, the electrolyte and the positive electrode plate described below are combined with other battery components such as a separator, a gasket, a current collector, a sealing plate, and a cell case. A secondary battery was constructed to evaluate high temperature stability. The batteries that can be produced are not particularly limited, such as a cylindrical type, a square type, a coin type, but basically, a current collector and a negative electrode material are placed on a cell floor plate,
An electrolytic solution and a separator were further placed thereon, and the positive electrode was further placed so as to face the negative electrode, and caulked together with a gasket and a sealing plate to obtain a coin-type secondary battery.

Non-aqueous solvents that can be used for the electrolyte include:
Propylene carbonate, ethylene carbonate, chloroethylene carbonate, trifluoropropylene carbonate, butylene carbonate, vinylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, isopropyl methyl carbonate, ethyl propyl carbonate, isopropyl ethyl carbonate, butyl methyl carbonate , Butyl ethyl carbonate, dipropyl carbonate, 1,2-dimethoxyethane, γ
-Butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, 1,3-dioxolane, methyl acetate, ethyl acetate, methyl formate, ethyl formate alone or an organic solvent alone, or A mixture of two or more types can be used. CO ₂ , N ₂ O, CO,
SO ₂ and the like of the gas or polysulfide SX, vinylene carbonate, catechol carbonate in any ratio may be added to the single or mixed solvent.

In these solvents, about 0.5 to 2.0 M
LiClO_Four, LiPF₆, LiBF_Four, LiAs
F₆, LiCl, LiBr and other inorganic lithium salts, Li
CF_ThreeSO_Three, LiN (SO_TwoCF_Three)_Two, LiN (S
O_TwoC_TwoF_Five)_Two, LiC (SO _TwoCF_Three)_Three, LiN
(SO_ThreeCF_Three)_TwoAnd other organic lithium salts as electrolyte
And dissolved in the above solvent to form an electrolyte. In addition, lithium ion
Polymer solids, which are conductors of alkali metal cations such as on
Body electrolytes can also be used.

The material of the positive electrode body is not particularly limited, but is preferably made of a metal chalcogen compound which can occlude and release alkali metal cations such as lithium ions during charge and discharge. Examples of such metal chalcogen compounds include vanadium oxides, sulfides, molybdenum oxides, sulfides, chromium oxides, titanium oxides, sulfides, and composite oxides and sulfides thereof. No. Also,
LiMY ₂ (M is a transition metal such as Co or Ni, and Y is
Chalcogen compounds such as O and S), LiM ₂ Y ₄ (M is M
n and Y are O), oxides such as WO ₃ , CuS, Fe _0.28 V
Sulfides such as _0.75 S ₂ , Na _0.1 CrS ₂ , NiPS ₃ ,
Phosphorus such as FePS ₃ , sulfur compound, VSe ₂ , NbSe
Selenium compounds such as ₃ can also be used. Like the negative electrode material, these are mixed with a binder and applied on a current collector to form a positive electrode plate. The separator for holding the electrolyte is generally a material having excellent liquid retention properties. For example, the separator is impregnated with a nonwoven fabric or a porous film of a polyolefin resin.

[0036]

Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples unless it exceeds the gist thereof. In addition, the measuring method of a Raman spectrum, electric capacity, and high temperature stability is as follows. (1) Raman spectrum The Raman spectrum was measured using NR-1800 manufactured by JASCO Corporation.
Irradiation at an intensity of The intensity of the peaks present in the range of 1570～1620Cm ^-1 and, 1350 ^-1
Was measured, and the R value obtained from these peaks was determined.

(2) Electric Capacity by Half-Battery 2-1) Preparation of Half-Battery A slurry is prepared by adding 5% by weight of PVDF as a binder to a carbonaceous material, and is coated on a silver foil by a doctor blade method to form a sheet electrode. did. This electrode has a diameter of 15.4m.
Then, a coin cell was punched out into a disk shape of m, and the separator was impregnated with an electrolyte, and a coin cell was made to face the lithium metal electrode with a center therebetween, and a charge / discharge test was performed. As the electrolyte, ethylene carbonate and diethylene carbonate were used in a weight ratio of 3:
A solution obtained by dissolving LiPF ₆ at a ratio of 1 mol / liter in a solvent mixed at a ratio of 7 was used. 2-2) Measurement of electric capacity In the charge / discharge test, charge / discharge is performed at a current density of 0.17 mA / cm ² until the potential difference between the two electrodes becomes 0 V, and discharge is performed at 0.33 mA / cm ² until the potential becomes 1.5 V. And the undoping capacity in the third cycle was determined as the reversible capacity.

(3) High temperature stability test 3-1) Production of secondary battery As a positive electrode, a Ni positive electrode (theoretical capacity: 200 mAh /
g) and a Mn positive electrode (theoretical capacity: 110 mAh / g). Assuming that the positive electrode / negative electrode capacity ratio is 1 / 1.2.
A coin cell was prepared using an electrolyte solution of 1M LiPF ₆ / EC + DEC (3: 7). As a separator, Celgard 3401 was used. 3-2) Measurement of High-Temperature Cycle Retention In the case of a Ni positive electrode, charge / discharge (3.0 to 4.1 V) is performed at room temperature for 2 cycles at a charge of 0.2 C / discharge of 0.2 C after manufacturing a 2032 coin cell. After that, the temperature was raised to 50 ° C.
Charging / discharging was performed for 100 cycles at C / 1C, and the ratio of the discharge capacity at the 100th cycle to the first cycle was calculated, and the ratio was defined as the high-temperature cycle retention rate. In the case of a Mn positive electrode,
In a similar test, charging and discharging were performed at 60 ° C. with a potential width of 3.0 to 4.2 V, and the high-temperature cycle retention was calculated.

(Example 1) 40 g of artificial graphite (particle diameter: 17 microns, Raman R value = 0.15) powder was placed in a reactor for fluorination treatment, the vessel was kept in a vacuum, and fluorine gas (F ₂ 100% by volume) at room temperature under atmospheric pressure.
The fluorination treatment was performed while rotating at 15 rpm for minutes. After the fluorination treatment, the fluorine gas was degassed, and 0.5% by weight of methoxypolyethylene glycol methacrylate (CH _{3-
CH = CH-CO- (OCH 2} CH 2) 23 -OCH 3)
Was dissolved in ethanol, and 200 g of the monomer solution was poured in while being careful not to put air thereinto. The solution was transferred to a beaker, and polymerized at 50 ° C. for 1 hour while stirring with a stirrer. After completion of the reaction, graphite was filtered under reduced pressure, washed with ethanol, and dried at 80 ° C. to obtain a sample. The weight increase due to the treatment was about 1% by weight. The R value by Raman measurement is
0.39. When a half-cell was prepared and its reversible capacity was measured, a undoped capacity of 333 mAh / g was obtained. The 50 ° C. cycle maintenance ratio for the Ni positive electrode was 88%. 60 ° C when a Mn positive electrode is used
A value of 40% was obtained for the cycle maintenance rate.

(Example 2) 40 g of artificial graphite (particle diameter: 17 microns, Raman R value = 0.15) powder was placed in a reactor for fluorination treatment, and the inside of the vessel was kept at a vacuum. ₂ 100% by volume) at room temperature under atmospheric pressure.
The fluorination treatment was performed while rotating at 15 rpm for minutes. After the fluorination treatment, the fluorine gas was degassed, and 0.5% by weight of methoxypolyethylene glycol methacrylate (CH ₃ -C
200 g of a monomer solution obtained by dissolving H = CH-CO- (OCH ₂ CH ₂ ) ₂₃ -OCH ₃ ) in ethanol was poured while being careful not to put air thereinto, and the solution was transferred to a beaker and stirred with a stirrer. The polymerization was carried out at a temperature of 1 ° C. for 1 hour. After completion of the reaction, graphite was filtered under reduced pressure, washed with ethanol, and dried at 80 ° C. to obtain a sample. The weight increase due to the treatment was about 0.5% by weight. The R value by Raman measurement was 0.38. Further, when a half-cell was prepared and its reversible capacity was measured, a de-doping capacity of 330 mAh / g was obtained. The 50 ° C. cycle maintenance ratio for the Ni positive electrode was 90%. 6 when using a Mn positive electrode.
A value of 43% was obtained for the 0 ° C. cycle maintenance rate.

Comparative Example 1 Untreated artificial graphite (particle size: 17)
For a micron and Raman R value = 0.15), a half-cell was prepared and its reversible capacity was measured to be 320 mAh / g.
Was obtained. In addition, in the case of the Ni positive electrode, 5
The 0 ° C. cycle maintenance was 80%. When the Mn positive electrode was used, a value of 23% was obtained for the 60 ° C. cycle maintenance ratio.

[0042]

According to the present invention, S formed on the surface of the negative electrode
Since the adhesion between the EI coating and the carbonaceous surface of the negative electrode is improved, a negative electrode material for a lithium ion battery having high capacity and improved high-temperature stability and a lithium ion secondary battery using the same can be obtained. .

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Claims (6)

[Claims] The positive electrode and the negative electrode are each composed of a simple substance or a compound capable of inserting and extracting lithium, and after at least bringing the simple substance or the compound constituting the negative electrode into contact with a fluorinating agent, a polymerizable organic substance, an organometallic compound, and an organic electrolyte are formed. And 157 in the argon laser Raman spectrum by reacting with at least one selected from
Peak intensity of 0~1620cm ^-1 13 for (I _A)
R value is the ratio of the peak intensity of _{^{50~1370cm -1 (I B) (I}} B / I A) is 0.18 or more, and characterized in that the grafted compound is formed so as to be 2.00 or less Negative electrode material for lithium ion batteries. 2. The negative electrode material for a lithium ion battery according to claim 1, wherein the simple substance or the compound constituting the negative electrode is a carbonaceous material. 3. The negative electrode material for a lithium ion battery according to claim 1, wherein the simple substance or the compound constituting the negative electrode is graphite. 4. The negative electrode material for a lithium ion battery according to claim 1, wherein the fluorinating agent is a fluorine gas. 5. The negative electrode material for a lithium ion battery according to claim 1, wherein the polymerizable organic substance is at least one selected from the group consisting of a methacrylic acid derivative, an acrylic acid derivative, and a cyclic carbonate. . 6. A lithium ion secondary battery using the negative electrode material according to claim 1.