JPH05135802A - Organic electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To get an organic secondary battery in which a negative electrode material of high capacity and excellent in charge and discharge cycle property is used, by using graphite which is mixed beforehand with inorganic or organic Li compound as a negative active material and then heating/baking process is applied. CONSTITUTION:This is a secondary battery comprising a positive pole active material consisting at least of transition metal chalcogenide containing Li, a negative pole active material, and organic electrolyte, and as the negative active material, graphite is used singly or being mixed, after being mixed with Li compound in advance and is subjected to heating/baking treatment. Hereby, the capacity loss at the first charge by exhalation can be reduced sharply, and an organic electrolyte secondary battery having high charge and discharge capacity and using a negative pole material excellent in charge and discharge cycle property can be obtained. In addition, the heating/baking treatment is performed at a temperature of 150 deg.C or more in inert gas atmosphere or vacuum, and also it is to be desired that the average grain diameter of graphite should be 5-150mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery having a high charge / discharge capacity and excellent charge / discharge cycle characteristics, and more particularly to a lithium secondary battery.

[0002]

2. Description of the Related Art In a lithium secondary battery, when lithium metal is used as a negative electrode active material, dendritic lithium metal (dendrites) and mossy lithium metal (moss), which have high activity, are generated by repeated charging and discharging. However, it may directly or indirectly fall into contact with the positive electrode active material to cause an internal short circuit, which not only has poor cycle characteristics, but also has a great risk in handling such as ignition. As a countermeasure, a lithium alloy (Al, Al-Mn (US
4,820,599), Al-Mg (JP-A-57-9).
8977), Al-Sn (JP 63-6,742),
Al-In, Al-Cd (JP-A-1-144,57)
A method using 3)) has been proposed, but since lithium metal is used, it is not an essential solution to the prevention of internal short circuit. In recent years, a method using a carbonaceous compound capable of inserting and extracting lithium ions or lithium metal has been proposed as a method that does not use lithium metal. The carbonaceous material seems to have almost no amorphous part by heat-treating various amorphous carbons having both an amorphous part and a crystalline part at a high temperature close to 3000 ° C. However, the two are greatly different in physical properties and properties and are treated as completely different materials (Michio Inagaki, Carbon Material Engineering, Nikkan Kogyo Shimbun Publishing (1985)). It is also well known that these carbonaceous materials are produced naturally or can be obtained by heating and burning various organic compounds. Many proposals have been made using the above-mentioned amorphous carbon for the negative electrode (Japanese Patent Laid-Open Nos. 58-209,864, 61-214,417, and 6).
2-88, 269, 62-90, 863, 62-21
6,170, 63-3,282, 63-24,5
55, 63-121, 247, 63-121, 25
7, 63-155,568, 63-276,87
3, same 63-314, 821, JP-A-1-204, 36.
1, the same 1-221, 859, the same 2-230, 660, the same 1-274, 360, the same 2-284, 354, the same 3-1
22, 974, WO 90/13, 924, etc.), but it is a well-known fact that amorphous carbon has a significantly smaller charge / discharge capacity than graphite (Physical Review B, Vol. 42,
6424 (1990)), there is a problem in using it for a secondary battery intended for high charge / discharge capacity. As a method of compensating for the above-mentioned drawbacks of amorphous carbon, amorphous carbon particles are treated with Li-A.
Japanese Patent Application Laid-Open No. 3-1.
No. 22,974 and a method of disposing a thin layer of Li on an amorphous carbon negative electrode are proposed in JP-A-2-230 and 660, respectively, but both have low charge / discharge capacity of amorphous carbon. However, there is a problem in applying the method to a secondary battery having a high charge / discharge capacity, which is not a method capable of overcoming the problem.

On the other hand, graphite (Physical Review B, Vol. 42, 6), which is originally known to have a high charge / discharge capacity,
Although some methods using 424 (1990)) as a negative electrode have been proposed, graphite has an irreversible capacity loss of more than the amount of Li necessary for charge / discharge during the first charging,
It is known to exhibit so-called exfoliation (Journal of Electrochemical Society, Vol. 137, page 2009 (1990)), and it is very important to overcome its capacity loss in order to use it as a negative electrode of a secondary battery. .. As a means for solving this problem, Japanese Patent Publication No. 62-23,433 proposes a method of previously synthesizing a lithium intercalation compound into a negative electrode and combining this with a positive electrode containing no lithium. It is extremely difficult to manufacture because of problems such as ignition and the lithium intercalation compound itself is prone to be easily decomposed even in the presence of a trace amount of water. Furthermore, using a positive electrode containing lithium,
Proposals have been made that combine this with a graphite negative electrode (Proceedings of the 31st Battery Symposium, p. 97 (1990), etc.), but the above-mentioned capacity loss due to exfoliation is compensated for by excessive capacity retention of the positive electrode. However, there is a big problem in improving the battery capacity. In addition to the carbonaceous material, a negative electrode in which a metal oxide containing Nb is used in combination with Li is proposed in JP-A-2-82,447, but this method has a problem that the battery voltage is low, that is, the energy density is low. There is. Further, JP-A-3-112,070 proposes a lithium secondary battery composed of a negative electrode containing ferric oxide and a positive electrode containing lithium, and this negative electrode also has a large capacity loss portion at the initial stage of charging like graphite. In addition, it is necessary to hold an excessive charge / discharge capacity in the positive electrode, and there is a big problem in securing a high capacity. As described above, there is nothing that can satisfy the indispensable performance required for the negative electrode active material for the lithium secondary battery such as charge / discharge capacity, charge / discharge cycle characteristics, handleability, and manufacturing suitability, and further improvement is desired. There is.

[0004]

SUMMARY OF THE INVENTION A first object of the present invention is to obtain an organic electrolyte secondary battery using a negative electrode material having a high charge / discharge capacity. The second object of the present invention is to
An object is to obtain an organic electrolyte secondary battery using a negative electrode material having excellent charge / discharge cycle characteristics. The third object of the present invention is to
An object is to obtain an organic electrolyte secondary battery using a negative electrode material that is excellent in handleability and manufacturing suitability. The fourth object of the present invention is to
An object is to obtain an organic electrolyte secondary battery using a negative electrode material having a significantly low degree of environmental pollution.

[0005]

An object of the present invention is a secondary battery comprising at least a positive electrode active material composed of a transition metal chalcogenide containing Li, a negative electrode active material, and an organic electrolyte. This can be achieved by using graphite that has been mixed with the compound and then subjected to heat-baking treatment, either alone or in combination.

The secondary battery of the present invention uses graphite as a negative electrode active material and is excellent in securing a high charge / discharge capacity. However, after the graphite is mixed with a Li compound, it is subjected to heating and firing treatment. As a result, surprisingly, the capacity loss during the first charge due to the above-mentioned exfoliation could be greatly reduced, and the charge / discharge capacity and charge / discharge cycle characteristics were remarkably good.

As the graphite used in the secondary battery of the present invention, both natural graphite and artificial graphite can be used, and the natural graphite is preferably scaly or flake graphite. Commercially available graphite may be used, or various organic materials may be fired and graphitized before use. The average particle size of graphite is preferably in the range of 5 to 150 μm, more preferably 7 to 150 μm.
It is in the range of 120 μm, more preferably 10 to 10
It is 0 μm.

As the Li compound used for premixing with graphite of the present invention, either an inorganic or organic Li compound can be used. As the inorganic Li compound, lithium chloride, lithium chlorate, lithium metasilicate, lithium silicofluoride, lithium oxide, lithium bromate, lithium nitrate, lithium hydroxide, lithium hydride, lithium carbonate, lithium thiocyanate, lithium boride. Preferred are lithium metaborate, lithium tetraborate, lithium fluoroborate, lithium iodate, lithium sulfide, lithium sulfate, lithium phosphide, lithium phosphate and the like. Examples of the organic Li compound include lithium amidated compounds (lithium diethylamide, lithium diisopropylamide, lithium dimethylamide, lithium dicyclohexylamide, etc.),
Lithium alkoxide (lithium methoxide, lithium ethoxide, lithium-n-propoxide, lithium-
Isopropoxide, lithium-n-butoxide, lithium-t-butoxide, etc.), alkyl lithium (n-butyl lithium, cumyl lithium, etc.), lithium formate,
Lithium acetate, lithium citrate, lithium lactate and the like are preferable.

As a method for mixing the inorganic or organic Li compound and the graphite, the inorganic or organic Li compound is dissolved in water or an organic solvent and graphite is added thereto and kneaded, or the inorganic or organic Li compound in a powdery state is used. The compound and graphite are kneaded. As a method of firing a mixture of an inorganic or organic Li compound and graphite, firing in an inert gas atmosphere or under vacuum is preferable. The inert gas is preferably argon or helium, more preferably argon. The degree of vacuum is preferably 2 mmHg or less, more preferably 0.5 mmHg or less. The firing temperature is 150
C. or higher is preferable, more preferably 200.degree. C. or higher, still more preferably 300.degree. C. or higher.

In the present invention, a binder and a reinforcing agent which are usually used can be added to the negative electrode mixture containing graphite which has been preliminarily mixed with a Li compound and then subjected to heating and firing treatment. As the binder, natural polysaccharides, synthetic polysaccharides, synthetic polyhydroxy compounds, synthetic polyacrylic acid compounds, fluorine-containing compounds and synthetic rubbers are mainly used. Among them, starch, carboxymethyl cellulose, diacetyl cellulose, hydroxypropyl cellulose, ethylene glycol, polyacrylic acid, polytetrafluoroethylene and polyvinylidene fluoride, ethylene / propylene / diene copolymer and Acrylonitrile-butadiene copolymer and the like are preferable. A fibrous material that does not react with lithium is used as the reinforcing agent. For example, synthetic polymers such as polypropylene fiber, polyethylene fiber, Teflon fiber and carbon fiber are preferable. The size of the fiber is 0.1-4m in length
m and the thickness is preferably 0.1 to 50 denier. Especially 1
-3 mm and 1-6 denier are preferred. In the case of coin-type batteries or button-type batteries, the negative electrode mixture is used as pellets by applying pressure, or is applied on a current collector and then rolled, or the press sheet of the mixture is rolled together with the current collector. Or, see
A sheet-shaped electrode can be prepared and the sheet-shaped electrode can be wound up and used for a cylindrical battery. Further, in the negative electrode mixture of the present invention containing graphite surface-treated with a Li compound in advance, acetylene black, Ketjen black, silver (Japanese Patent Laid-Open No. 63-148,554) or a polyphenylene derivative ( JP-A-59-20,971) and the like can be added, and the addition amount is preferably 15% or less, more preferably 10% or less.

As the positive electrode active material composed of a transition metal chalcogenide containing Li which can be used in the present invention, Mn is used.
O ₂ , Mn ₂ O ₄ , Mn ₂ O ₃ , CoO ₂ , Co _x Mn
_1-x O _y , Ni _x Co _1-X O _y , V _X Mn _1-X O _y , F
e _X Mn _1-x O _y , V ₂ O ₅ , V ₃ O ₈ , V ₆ O ₁₃ , C
Li compounds such as o _x V _1-x O _y , MoS ₂ , MoO ₃ , and TiS ₂ are preferable. Particularly preferably Li _a Co _b V _c
It is O _d . Here, a = 0 to 1.1, b = 0.12
0.9, c = 1-b, d = 2-2.5. The transition metal chalcogenite Li compound is mainly used by a method of mixing with a compound containing lithium and firing, or an ion exchange method. The method for synthesizing the transition metal chalcogenide may be a well-known method, but especially in air or in an inert gas atmosphere, the amount of 200 to 150
Baking at 0 ° C is preferred.

As the electrolyte, propylene carbonate
G, ethylene carbonate, diethyl carbonate, γ
-Butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, ethyl monoglyme, phosphate triester 60-23,973), trimethoxymethane (JP-A-61-4,170), dioxolane derivative (JP-A-62-15,771, JP-A-62-22,37).
2, pp. 62-108, 474), sulfolane (Japanese Patent Laid-Open Publication No. 6-68, pp.
2-31,959), 3-methyl-2-oxazolidinone (JP-A-62-44,961), propylene carbonate derivative (JP-A-62-290,069, JP-A-62-2).
90,071), tetrahydrofuran derivative
3-32,872), ethyl ether (JP-A-63-6)
2,166), 1,3-propane sultone (Japanese Patent Application Laid-Open No. 63-63242).
-102,173) aprotic organic least one or more of the mixed solvent and lithium salt soluble in the solvent of a solvent such as, for _{^{example, ClO 4 -, BF 6 -}} , PF 6 -, C
F ₃ SO ₃ ⁻ , CF ₃ CO ₂ ⁻ , AsF ₆ ⁻ , SbF _{6
^{-, (CF 3 SO 2)}} 2 N -, B 10 Cl 10 2- ( JP 5
7-74,974), (1,2-Simethoxyethane) ₂
ClO ₄ ^- (JP 57-74,977), lower aliphatic carboxylic acid salt (JP-60-41,773), AlCl
_{^{4 -, Cl -, Br -}} , I - ( JP 60-247,2
65), chloroborane compounds (JP-A-61-165, 9
57), tetraphenyl boric acid (JP-A-61-214,37).
6) and the like. Of these, an electrolytic solution containing LiClO ₄ or LiBF ₆ in a mixed solution of propylene carbonate and 1,2-dimethoxyethane is typical.

In addition to the electrolytic solution, the following solid electrolytes can be used. Solid electrolytes are classified into inorganic solid electrolytes and organic solid electrolytes. Well-known inorganic solid electrolytes include Li nitrides, halides, and oxyacid salts. Among them, Li ₃ N, LiI, Li ₅ N
_{I 2, Li 3 N-LiI} -LiOH, LiSiO 4, L
iSiO ₄ -LiI-LiOH (JP-A-49-81,8)
_{99), xLi 3 PO 4 -} (1-x) Li 4 SiO
₄ (JP-A-59-60,866), Li ₂ SiS ₃ (JP-A-60-501,731), phosphorus sulfide compound (JP-A-62-82,665) and the like are effective. In the organic solid electrolyte, a polyethylene oxide derivative or a polymer containing the derivative (JP-A-63-135,447), a polypropylene oxide derivative or a polymer containing the derivative, a polymer containing an ionic dissociation group (JP-A-62-135). 254,30
2, ibid. 62-254, 303, ibid. 63-193, 95
4), a mixture of a polymer containing an ionic dissociative group and the aprotic electrolyte (US Pat. Nos. 4,792,504, 4,
830,939, JP-A-62-22,375, and JP-A-62-1.
22, 376, 63-22, 375, 63-22.
776, JP-A-1-95,117), phosphoric acid ester polymer (JP-A-61-256,573), and a polymer matrix material containing an aprotic polar solvent (US Pat. No. 4,822,701; 4,830,939, JP-A-63-239,779, Japanese Patent Application No. 2-30,318, and 2
-78,531) is effective. Furthermore, there is also a method of adding polyacrylonitrile to the electrolytic solution (Japanese Patent Laid-Open No. 62-62).
278,774). Also known is a method of using an inorganic and organic solid electrolyte in combination (JP-A-60-1,768).

The separator has a large ion permeability,
An insulating thin film having a predetermined mechanical strength. Olefin-based nonwoven fabrics such as polypropylene and glass fibers are used because of their resistance to organic solvents and hydrophobicity.

It is also known to add the following compounds to the electrolyte for the purpose of improving discharge and charge / discharge characteristics. For example, pyridine (JP-A-49-108,52)
5), triethyl phosphite (JP-A-47-4,3)
76), triethanolamine (JP-A-52-72,4).
25), cyclic ether (JP-A-57-152,68)
4), ethylenediamine (JP-A-58-87,77)
7), n-glyme (JP-A-58-87,778), hexaphosphoric acid triamide (JP-A-58-87,779),
Nitrobenzene derivative (JP-A-58-214, 28)
1), sulfur (JP-A-59-8,280), quinoneimine dye (JP-A-59-68,184), N-substituted oxazolidinone and N, N ^, -substituted imidazolidinone (JP-A-59-68).
-154,778), ethylene glycol dialkyl ether (JP-A-59-205,167), quaternary ammonium salt (JP-A-60-30,065), polyethylene glycol (JP-A-60-41). 773), pyrrol (JP-A-60-79,677), 2-methoxyethanol (JP-A-60-89,075), AlCl ₃ (JP-A-6-79,677).
1-88,466), a monomer of a conductive polymer electrode active material (JP-A-61-161,673), triethylenephosphoramide (JP-A-61-208,758), and a trialkylphosphine (JP-A-61-167). 62-80,976), morpholine (JP-A-62-80,977), aryl compounds having a carbonyl group (JP-A-62-86,673),
Crown ethers such as 12-crown-4 (Physical Review)
B, 42, 6424 (1990)), hexamethylphosphoric triamide and 4-alkylmorpholine (JP 62-217,575), bicyclic tertiary amine (JP 62-217). , 578), oil (JP-A-62-62)
-287,580), a quaternary phosphonium salt (JP-A-63-63)
-121,268), a tertiary sulfonium salt (JP-A-63 / 1988)
-121, 269) and the like.

Further, in order to make the electrolytic solution nonflammable, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride chloride can be contained in the electrolytic solution. (JP-A-48-36,
632) Further, the electrolytic solution may contain carbon dioxide gas in order to have suitability for high temperature storage. (JP-A-59-
134,567)

Further, the positive electrode active material may contain an electrolytic solution or an electrolyte. For example, the ion conductive polymer or nitromethane (Japanese Patent Laid-Open No. 48-36,633),
It is known to add an electrolytic solution (JP-A-57-124,870). Moreover, the surface of the positive electrode active material can be modified. For example, the surface of a metal oxide is treated with an esterifying agent (JP-A-55-163,779) or a chelating agent (JP-A-55-163,780), and a conductive polymer (JP-A-55-163). 58-163, 188, 59-14, 27
4), polyethylene oxide, etc. (JP-A-60-9)
7, 561). Also, the surface of the negative electrode active material can be modified. For example, an ion conductive polymer or a polyacetylene layer is provided (Japanese Patent Laid-Open No. 5-5120).
8-111,276), LiCl (JP-A-58-14)
2,771), ethylene carbonate (JP-A-59-3)
1, 573) and the like.

As a carrier for the electrode active material, in addition to ordinary stainless steel, nickel, and aluminum for the positive electrode, a porous metal foam for conductive polymers (JP-A-59-18,
578), titanium (JP-A-59-68,169), expanded metal (JP-A-61-264,686), punched metal, and negative electrode, in addition to ordinary stainless steel, nickel, titanium, and aluminum, Porous nickel (JP-A-58-18,883), porous aluminum (JP-A-58-38,466), aluminum sintered body (JP-A-59-130,074), molded body of aluminum fiber group ( JP-A-59-148,277), silver-plated stainless steel surface (JP-A-60-41,761), fired carbonaceous material such as phenol resin fired body (JP-A-60-11).
2, 254), Al-Cd alloy (JP-A-60-212,
779), a porous metal foam (JP-A-61-74, 26).
8) etc. are used.

The current collector may be any electron conductor that does not undergo a chemical change in the constructed battery. For example, in addition to commonly used stainless steel, tachin and nickel, nickel plated bodies of copper (Japanese Patent Application Laid-Open No. 48-36,62).
7), a titanium-plated body of copper, and a positive electrode active material of sulfide, which is obtained by subjecting stainless steel to copper treatment (JP-A-60-17).
5, 373) and the like are used. The shape of the battery is a coin,
It can be applied to any of buttons, sheets and cylinders.

[0020]

EXAMPLES The present invention will be described in more detail with reference to specific examples below, but the present invention is not limited to the examples as long as the gist of the invention is not exceeded. Example 1 Graphite (KS-6 manufactured by Lonza Co.) 1 was added to 10 ml of a 1M lithium methoxide / methanol solution under an argon gas atmosphere.
After adding 0 g and stirring at room temperature for 2 hours, methanol was distilled off under reduced pressure. The remaining lithium methoxide / graphite mixture was fired at 750 ° C. for 2 hours under an argon gas atmosphere. A pellet (15 mmΦ) obtained by compression-molding a mixture containing 90% by weight of this fired product and 10% by weight of polytetrafluoroethylene (manufactured by Wako Pure Chemical Industries, Ltd.) as a binder was prepared as a negative electrode material. As a positive electrode material, Li _0.5 Co _0.5 V _0.5 O _2.5
Was mixed at a mixing ratio of 84% by weight, acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive agent by 10% by weight, and polytetrafluoroethylene (manufactured by Wako Pure Chemical Industries, Ltd.) as a binder by 6% by weight, and a mixture was compression molded. Pellets (13 mmΦ) were used. The capacity ratio between the positive electrode and the negative electrode was 1.5. As an electrolyte, 1M LiBF ₄ (propylene carbonate and 1,2-
Using an equal volume mixture of dimethoxyethane) and a microporous polypropylene nonwoven fabric as the separator,
The electrolytic solution was used by impregnating a non-woven fabric. And FIG.
A coin-type lithium battery such as the one described above was created (Battery 1).
Further, batteries 2 to 7 were prepared as shown in Table 1. These lithium batteries have a current density of ² mA / cm ²
The charge and discharge of 0 mAH / g were carried out under the conditions of cutting at 3.2 V and the discharge condition at the 25th cycle, the discharge capacity at the 25th cycle, and the dendrite formation on the surface of the negative electrode after 25 cycles (using a scanning electron microscope). (Observation) was evaluated. Example 2 10 g of graphite (SP-20 manufactured by Nippon Graphite Co., Ltd.) was added to 15 ml of a 1 M aqueous lithium hydroxide solution, and the mixture was stirred at room temperature for 1 hour, and then water was distilled off under reduced pressure. Residue under argon gas atmosphere,
It was baked at 400 ° C. for 5 hours. 92% by weight of this baked product, ethylene / propylene / diene copolymer EP as a binder
DM (manufactured by Sumitomo Chemical Co., Ltd., trade name ESPRENE) A negative electrode pellet (15 mmΦ) was prepared by coating (solvent toluene), drying and compression molding a mixture mixed at a mixing ratio of 8% by weight, and used as a negative electrode material. A coin-type lithium battery was produced in the same manner as in Example 1 except for this (battery 8). Further, batteries 9 to 12 were prepared as shown in Table 1. A charge / discharge test was performed on these lithium batteries in the same manner as in Example 1.

[0021]

[Table 1]

[0022]

[Table 2]

Comparative Example 1 Example 1 except that graphite (KS-6 manufactured by Lonza Co., Ltd.) which was not surface-treated with a Li compound was used as the negative electrode material.
A battery similar to that was prepared (battery a). Further, as shown in Table 1, a battery b in which the treatment condition with the Li compound was changed was prepared, and a charge / discharge test was conducted in the same manner as in Example 1.

Comparative Example 2 The same as Example 1 except that the negative electrode material used was a carbonaceous negative electrode composed of mixed particles of calcined carbonaceous particles of crystalline cellulose and a lithium-aluminum alloy described in JP-A-3-122,974. A different battery was prepared (battery c) and a charge / discharge test was conducted.

Comparative Example 3 A battery similar to that of Example 1 was prepared except that the negative electrode material used was a negative electrode obtained by laminating a fired carbonaceous material of cresol novolac resin described in JP-A-2-230,660 and a lithium foil. (Battery d) and a charge / discharge test was performed.

Comparative Example 4 A battery was prepared in the same manner as in Example 1 except that the fired furan resin described in JP-A-2-66,856 was used as a negative electrode material (Battery e), and a charge / discharge test was conducted.

Comparative Example 5 A battery was prepared in the same manner as in Example 1 (Battery f), except that a negative electrode obtained by laminating niobium pentoxide and lithium foil described in JP-A-2-82,447 was used as a negative electrode material (Battery f). A charge / discharge test was conducted. Table 1 shows the configurations of the batteries prepared in Examples and Comparative Examples.
Table 2 shows the results of the charge / discharge test in Tables 3 and 4. From Tables 3 and 4, it is clear that the lithium secondary battery of the present invention is superior to the batteries of Comparative Examples in discharge capacity, charge / discharge cycle characteristics, and dendrite suppressing ability. Regarding the battery capacity, the discharge capacity per battery was comparatively evaluated in both Examples and Comparative Examples with the volume of the negative electrode being constant.

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

EFFECTS OF THE INVENTION As in the present invention, by using graphite, which has been preliminarily mixed with an inorganic or organic Li compound and then subjected to heating and firing treatment, as the negative electrode active material, the charge / discharge capacity, charge / discharge cycle characteristics, and dendrite suppressing ability can be improved. It is possible to obtain an improved lithium secondary battery.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a coin battery used in an example.

[Explanation of symbols]

 1 Negative Electrode Sealing Plate 2 Negative Electrode Mixture Pellet 3 Separator 4 Positive Electrode Mixture Pellet 5 Current Collector 6 Positive Electrode Case 7 Gasket

Claims (4)

[Claims] 1. A secondary battery comprising a positive electrode active material composed of at least a Li-containing transition metal chalcogenide, a negative electrode active material, and an organic electrolyte, which is preliminarily mixed with a Li compound as a negative electrode active material and then subjected to a heating and baking treatment. An organic electrolyte secondary battery, wherein the treated graphite is used alone or as a mixture. 2. The organic electrolyte secondary battery according to claim 1, wherein the heating and baking treatment is a baking treatment at a temperature of 150 ° C. or higher in an inert gas atmosphere or under vacuum. Production method. 3. The organic electrolyte secondary battery according to claim 1, wherein the graphite has an average particle size of 5 to 150 μm. 4. The transition metal chalcogenide containing Li is L
i _a Co _b V _c organic electrolyte secondary battery according to claim 1, characterized in that the O _d. (In the formula, a = 0 to 1.1,
b = 0.15-0.9, c = 1-b, d = 2-2.5)