JPH06223830A - Lithium secondary battery - Google Patents

Abstract

PURPOSE:To provide a lithium secondary battery which has a high charging/ discharging capacity and which excels in the safety and cyclic characteristic, by using a negative electrode active material which is a combination of oxides as given by specific general expression and a Li-containing metal oxide as given by a specific expression and synthesized through baking of Li compound. CONSTITUTION:The negative electrode active material of a lithium secondary battery is prepared from a composite oxide, which is given by a general expression MxRyOz and consisting of metals of two or more sorts, and a Li-containing metal oxide which is given by a general expression LivL and which is obtained through baking of Li-containing compound. In the first expression, M and R are metal of 2-6 valence, i.e., M is one of the Mg, Mn, Fe, Co, Ni, Cu, Zn, Mo while R is a metal element belonging to the Va group, and (x), (y), (z) are conditioned as 0<x/y<=3, 2<=z/y<=7. In the second Exp., L is a radical of 1, 2, or 3 valence while containing one of the OH, CO3, NO3, SO3, SO4, DO4, B4O7, ClO3, ClO4, SCN, HCO2, CH3CO2, C2O4, C4H4O6, CF3SO2, PF6, F, Cl, Br, I, and (v) represents integer 1, 2, or 3.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In recent years, lithium secondary batteries have been receiving attention as secondary batteries that are lightweight, compact and have an energy density. Lithium metal or lithium alloy is typically used as the negative electrode active material for the lithium secondary battery. When they are used, the lithium metal grows in a dendritic manner during charge / discharge to cause an internal short circuit, or the dendritic metal itself. It is highly active and is at risk of catching fire.

On the other hand, recently, a sintered carbonaceous material capable of inserting and extracting lithium has been put into practical use. The disadvantage of this carbonaceous material is that it has conductivity so that lithium metal is deposited on the carbonaceous material during overcharging or rapid charging, and dendritic metal is eventually deposited. is there. In order to avoid this, a method of reducing the amount of the positive electrode active material to prevent overcharge is adopted. However, in this method, the amount of the active material is limited, so that the discharge capacity is limited. Further, since the carbonaceous material has a relatively small specific gravity, the discharge capacity is limited when it is used as a battery because the capacity per volume is low.

On the other hand, as the negative electrode active material other than lithium metal, lithium alloy or carbonaceous material, TiS2, LiTi capable of absorbing and desorbing lithium ions.
S2 (U.S. Pat. No. 983,476), WO2, lithium compound of Fe2O3 (JP-A-3-120070), Nb2O5
(Japanese Patent Publication No. 62-59412, JP-A-2-82447),
Iron oxide, FeO, Fe2O3, Fe3O4, cobalt oxide,
CoO, Co2O3, Co3O4 (JP-A-3-291,86
2) is known. None of these compounds has a low redox potential, and a lithium secondary battery having a high discharge potential of 3 V class cannot be realized. Also, the discharge capacity
I am not satisfied with what I am doing.

For the purpose of improving the above-mentioned drawbacks, it has been proposed to use a Li-containing transition metal oxide as a negative electrode active material in order to achieve a lithium secondary battery having a high discharge potential of 3 V class (Japanese Patent Application No. Hei 10-135242). 4-106642). By combining this Li-containing transition metal oxide with a certain kind of positive electrode, it is possible to give a Li secondary battery having a large discharge capacity of 3 V class, and it is hard to cause dendrites of lithium and is extremely safe. is there. Further, it has an advantage that it has a higher specific gravity and a higher capacity per unit volume than carbonaceous materials. However, when Li-containing transition metal oxide is used as the negative electrode active material, the initial cycle performance is good, but when the number of cycles is 50 or more, the cycle performance gradually decreases, and the performance as a lithium secondary battery is reduced. Was insufficient.

[0006]

The first object of the present invention relates to a lithium secondary battery having excellent safety.
The second object of the present invention relates to a lithium battery having a high charge / discharge capacity. Further, the third object of the present invention relates to a lithium secondary battery having excellent cycleability.

[0007]

Means for Solving the Problems As a result of earnest research by the present inventors, the present invention relates to a lithium secondary battery comprising a positive electrode active material, a negative electrode active material, and an organic electrolyte containing a lithium salt. 2) A lithium-containing metal oxide obtained by firing a Li-containing compound represented by the following general formula (2) and a composite oxide composed of at least two metals represented by It has been surprisingly found that all of the above problems can be achieved with secondary batteries. General formula (1) MxRyOz (In the formula, M and R are each a divalent to hexavalent metal, and M is Mg, Mn, Fe, Co, Ni, Cu, Zn, M.
At least one selected from o and R represents a Va group metal element. x, y, z are 0 <x / y ≦ 3, 2 ≦ z / y ≦
The range is 7. ) General formula (2) LivL (wherein L represents a mono-, di- or trivalent group, and OH, CO3,
NO3, SO3, SO4, PO4, B4O7, ClO3, Cl
O4, SCN, HCO2, CH3CO2, C2O4, C4H4O
6, at least one of CF3SO3, PF6, F, Cl, Br, I and the like. v represents 1, 2, and 3. )

The compound represented by formula (1) will be described in more detail. In the general formula (1) and MxRyOz, M
And R are each a divalent to hexavalent metal, and M is M
At least one selected from g, Mn, Fe, Co, Ni, Cu, Zn and Mo, and particularly preferably M is C
o and Ni. R is a metal element of the Va group. Two or more kinds of Va group metal elements may be used in combination. Particularly preferably, R is V or Nb. x, y, z is 0 <
The ranges are x / y ≦ 3 and 2 ≦ z / y ≦ 7. It is preferably in the range of 0 <x / y ≦ 2, 2 ≦ z / y ≦ 6.

The synthesis method of the general formula (1) is not particularly limited, and a calcination method, a redox method, a thermal decomposition method as a solid phase synthesis method, and a gas phase reaction method or a gas phase synthesis method as a gas phase synthesis method. Oxidation method, vapor phase pyrolysis method, liquid phase synthesis method: homogeneous precipitation method, alkoxide method, coprecipitation method, sol-gel method, emulsion method,
Freeze-drying method, spray-drying method, etc. A method suitable for the material can be selected from the methods described in the Ceramics Synthesis Primer (Iwasaki and Kaneko, published by Agne Publishing, 1992), but the firing method is particularly preferable. Is.

The firing temperature of the compound of the general formula (1) is preferably 200 ° C. or higher and 2000 ° C. or lower. More preferably, it is 300 ° C. or higher and 1500 ° C. or lower.

The firing atmosphere of the compound of the general formula (1) is air, O2, N2, H2, CO, CO2, H2O, H.
e, Ar, etc. may be used alone or in combination of two or more.

Specific examples of the compound of the general formula (1) are shown below, but the compounds are not limited to these compounds unless the gist of the present invention is changed. Compound 1, Co2V2O7 JCPDS Grant-
in-Aid Report (1986) Compound 2, CoV2O6 Journal of
Solid State Chemistry 56, 8
4, (1985) Compound 3, CoV3O8 Journal of I
norganic and Nuclear Chem
istry31, 3049, (1969) Compound 4, Co3V2O8 Bulletin de
la Society Francais de M
ineralogie et de Cristall
o graphie 87, 47, (1964) Compound 5, Ni2V2O7 Acta Crystal
logicala Section B 30, 29
07, (1974) Compound 6, Ni7V5O17 Revue des H
autes Temperatures et des
Refractaires 10, 27, (197
3) Compound 7, Ni3V2O8 Chemical Scri
pta 25,212 (1985) Compound 8, Cu2V2O7 Acta Crystal
Ilographic Section B 29, 27
37, (1973) Compound 9, Mg2V2O7 Chemical Scri
pta 25,212 (1985) Compound 10, Mn2V2O7 Neues Jahrbu.
ch fuel Mineralogie Monat
shefte compound 11, MoVO5 Comptes Rend
us dellAcademie des Scien
ces 260, 3410, (1965) compound 12, CuNbO3 Inorganic an
d Nuclear Chemistry Lette
rs 13, 559, (1977) Compound 13, CoNb2O6 Acta Chemica
Scandin avica A32, 309, (1
978) Compound 14, MgNb2O6 JCPDS Grant
-In-Aid Report (1980) Compound 15, MnNb2O6 JCPDS Grant-
in-Aid Report (1980) Compound 16, ZnNb2O6 JCPDS Grant-
in-Aid Report (1986)

These may be used alone or in combination of two or more.

The compound represented by formula (2) will be described in more detail. General formula (2) LivL In the formula, L represents a mono-, di-, or trivalent group, such as OH and C
O3, NO3, SO3, SO4, PO4, B4O7, ClO3,
ClO4, SCN, HCO2, CH3CO2, C2O4, C4
It contains at least one of H4O6, CF3SO3, PF6, F, Cl, Br and I. v represents 1, 2 and 3.

Examples of the compound of the general formula (2) include lithium hydroxide, lithium carbonate, lithium nitrate, lithium tetraborate, lithium chlorate, lithium perchlorate, lithium formate, lithium acetate, lithium oxalate and citric acid. Examples include lithium, lithium lactate, lithium tartrate, lithium pyruvate, and lithium iodide. Particularly preferred are lithium acetate, lithium hydroxide, lithium carbonate, lithium oxalate, lithium citrate, lithium lactate, lithium tartrate, lithium pyruvate, and lithium iodide.

The combination of the compound of the general formula (1) and the compound of the general formula (2) is not particularly limited and can be appropriately selected and combined depending on the materials.

The firing temperature of the compound of the general formula (1) and the compound of the general formula (2) is preferably 150 ° C. or higher and 600 ° C. or lower. More preferably, it is 200 ° C. or higher and 500 ° C. or lower. The mixing ratio of the compound of the general formula (1) and the compound of the general formula (2) is preferably such that Li / R is 0.1 or more and 5 or less. More preferably,
It is 0.1 or more and 4 or less.

The particle size of the compound of the general formula (1) and the compound of the general formula (2) before firing is such that the firing reaction proceeds smoothly.
It is preferably 0.1 μm or more and 2 mm or less. A particularly preferable particle size is 5 μm or more and 500 μm or less. The firing atmosphere for the compound of the general formula (1) and the compound of the general formula (2) is
Air, O2, N2, CO2, H2O, He, Ar and the like can be used alone or in combination of two or more.

The oxide of the general formula (1) and the compound of the general formula (2) may be washed and dried after firing. The washing method is not particularly limited, and the synthesized lumps or those crushed by a crusher or the like may be washed. The cleaning method is not particularly limited, but examples of typical methods include a dipping method, a stirring method, and an ultrasonic cleaning method. Moreover, you may heat if needed at the time of washing. The cleaning liquid may be neutral, acidic or basic, but preferably has pH = 4 to 8, and more preferably pure water or ion-exchanged water having pH = 7, or an organic solvent. The amount of the cleaning liquid is not particularly limited, and is preferably an amount at which the lithium-containing transition metal oxide is immersed or more. The cleaning time and the number of times of cleaning are appropriately selected depending on the Li-containing metal oxide, but it is often preferable to perform the cleaning twice or more in 1 hour or more. The treatment method after washing is not particularly limited, and the washing solution is removed by a decantation method, a filtration method, a centrifugation method, or the like, and the washing solution is dried. Further, in the case of a water-based cleaning liquid, it is effective to accelerate the drying by cleaning with an organic solvent such as acetone, methanol, ethanol, isopropyl alcohol and the like. The drying method is not particularly limited, and any method such as an air drying method, a heat drying method, a vacuum drying method and an infrared drying method can be used.

The fired product of the oxide of the general formula (1) and the compound of the general formula (2) is preferably ground. The crushing method is not particularly limited, and a vibration mill, ball mill, sand mill, tube mill, conical mill, rod mill, jaw crusher, roll crusher, edge runner, ring roll mill, etc. can be used. Particularly preferable is pulverization with a vibration mill, a ball mill or a sand mill.

The particle size of the calcined product of the oxide of the general formula (1) and the compound of the general formula (2) is preferably 0.1 μm or more and 200.
μm or less is preferable. A particularly preferable particle size is 0.3 μm or more and 100 μm or less.

The specific surface area of the calcined product of the oxide of the general formula (1) and the compound of the general formula (2) is 0.1 m 2 / g −5.
0 m2 / g is preferred. More preferable specific surface area is
It is 0.5 m2 / g-10 m2 / g.

The negative electrode active material of the present invention can be used in combination with other active materials. Examples of the negative electrode active material that can be used in combination with the present invention include lithium metal and lithium alloy (Al, Al-
Mn (US Pat. No. 4,820,599), Al-Mg
(JP-A-57-98977) and Al-Sn (JP-A-63-98977).
-6, 742), Al-In, Al-Cd (JP-A-1-
144, 573) and the like, and calcined carbonaceous compounds capable of inserting and extracting lithium ions or lithium metal (for example, JP-A-58-209,864, 61-214,417,
62-88, 269, 62-216, 170, 6
3-13, 282, same 63-24, 555, same 63-1
21,247, 63-121,257, 63-15
5,568, 63-276, 873, 63-31.
4,821, JP-A-1-204,361, and 1-22.
1,859, 1-254,360, etc.).

The electrode mixture can usually contain a conductive material such as carbon, silver (JP-A-63-148,554) or polyphenylene derivative (JP-A-59-20,971). .

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, methyl formate, methyl acetate, phosphate triester ( JP-A-60-23,973), trimethoxymethane (JP-A-61-4,170), dioxolane derivative (JP-A-62-15,771, JP-A-62-22,3).
72, 62-108,474), sulfolane (JP 62-31959), 3-methyl-2-oxazolidinone (JP 62-44,961), propylene carbonate derivative (JP 62-290,069, 62-2
290,071), tetrahydrofuran derivative (JP-A-63-32,872), ethyl ether (JP-A-63-87).
62,166), 1,3-propane sultone (Japanese Patent Laid-Open Publication No.
3-102, 173) and a mixture of at least one aprotic organic solvent and a lithium salt soluble in the solvent, for example, ClO4-, BF6-, PF6-, CF3.
SO3-, CF3CO2-, AsF6-, SbF6-, B10Cl1
0- (JP-A-57-74,974), (1,2-dimethoxyethane) 2ClO4- (JP-A-57-74,977),
Lower aliphatic carboxylic acid salt (JP-A-60-41,77
3), AlCl4-, Cl-, Br-, I- (JP-A-60-
247,265), a chloroborane compound (JP-A-61-
165, 957), tetraphenyl boric acid (JP-A-61-2
14, 376) and the like. Among them, a mixture of propylene carbonate and 1,2-dimethoxyethane or ethylene carbonate or diethyl carbonate is mixed with LiCF3SO3 and LiClO4.
An electrolytic solution containing LiBF6 or LiPF6 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. Li-nitrides, halides, oxyacid salts, and the like are well known as inorganic solid electrolytes. Among them, Li3N, LiI, Li5NI
2, Li3N-LiI-LiOH, LiSiO4, Li
SiO4 -LiI-LiOH (JP-A-49-81,89
9), xLi3PO4-(1-x) Li4SiO4 (JP-A-59-60,866), Li2SiS3 (JP-A-60).
-501, 731), a phosphorus sulfide compound (JP-A-62-8)
2,665) is 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 ion dissociating group (JP-A-62-254,302, the same). 6
2-254,303, 63-193,954), 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-62-22,3.
76, 63-22, 375, 63-22, 776,
JP-A-1-95, 117), phosphoric acid ester polymer
(JP-A 61-256,573) is effective. Furthermore, there is also a method of adding polyacrylonitrile to the electrolytic solution (JP-A-62-278,774). Also, a method of using an inorganic and organic solid electrolyte in combination (Japanese Patent Laid-Open No. 60-1,768).
Is also known.

The separator has a large ion permeability,
An insulating thin film having a predetermined mechanical strength. Sheets and nonwoven fabrics made of olefinic polymers such as polypropylene or glass fibers or polyethylene 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), triethylphosphite (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-5-280).
9-154,778), ethylene glycol dialkyl ether (JP-A-59-205,167), quaternary ammonium salt (JP-A-60-30,065), polyethylene glycol (JP-A-60-41). , 773), pyrrole (JP-A-60-79,677), 2-methoxyethanol-
(JP-A-60-89,075), AlCl3 (JP-A-61-88,466), conductive polymer-monomer of electrode active material (JP-A-61-161,673), triethylenephosphoramide. (JP 61-208,758), trialkylphosphine (JP 62-80,976), morpholine (JP 62-80,977), aryl compound having a carbonyl group (JP 62-86, 67
3), hexamethylphosphoric triamide and 4-alkylmorpholine (JP 62-217,575), bicyclic tertiary amine (JP 62-217,578), oil (JP 62 -287,580), a quaternary phosphonium salt (JP-A-63-121268), a tertiary sulfonium salt (JP-A-63-121269), 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, carbon dioxide gas can be included in the electrolytic solution in order to have suitability for high temperature storage. (JP-A-59-
134,567)

Further, the positive electrode active material and the negative electrode active material can contain an electrolytic solution or an electrolyte. For example, the ion-conductive polymer or nitromethane described in JP-A-48-3
6,633), and addition of an electrolytic solution (JP-A-57-124,8).
70) is known.

Further, the surface of the positive electrode active material can be modified. For example, the surface of the metal oxide may be treated with an esterifying agent (JP-A-55-163,779),
Treatment with a photocatalyst (JP-A-55-163,780), conductive polymers (JP-A-58-163,188, 59-14).
274), polyethylene oxide, etc. (JP-A-60-
97, 561). Also, the surface of the negative electrode active material can be modified. For example, an ion conductive polymer or polyacetylene layer is provided (Japanese Patent Laid-Open No. 58-111,276), LiCl (Japanese Patent Laid-Open No.
8-142, 771) and ethylene carbonate (JP-A-59-31573).

As a carrier for the electrode active material, in addition to the usual foil of stainless steel, nickel, aluminum, etc. for the positive electrode, a porous metal foam for conductive polymers (Japanese Patent Laid-Open No. 59-18578). ), Titanium (JP-A-59-68,
169), expanded metal (JP-A-61-26)
4, 686), punched metal, and negative electrodes, in addition to usual foils of stainless steel, nickel, copper, titanium, aluminum, etc., porous nickel (Japanese Patent Laid-Open No. 58-18 / 1983).
883), porous aluminum (JP-A-58-38,4).
66), an aluminum sintered body (JP-A-59-130,0).
74), a molded product of an aluminum fiber group (JP-A-59-1)
48,277), silver-plated stainless steel surface (JP-A-60-41,761), fired carbonaceous material such as phenol resin fired body (JP-A-60-112,264), Al
-Cd alloy (JP-A-60-212,779), porous foam metal (JP-A-61-74,268), 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, titanium and nickel, nickel-plated copper (Japanese Patent Laid-Open No. 48-36,62).
7), the titanium-plated body of copper and the positive electrode active material of sulfide are treated with copper on stainless steel (JP-A-60-175,3).
73) and the like are used. In the spiral type battery, it is generally used to serve as both an electrode carrier and a current collector. The shape of the battery can be any of coins, buttons, sheets, cylinders, corners and the like.

Specific synthetic examples of the negative electrode active material will be given below. Synthesis Example 1 (Synthesis of Compound 1) CoO (Wako Pure Chemicals Reagent) 14.
9 g and V2O5 (Wako Pure Chemical Industries, Ltd. reagent), 18.2 g were mixed in a porcelain mortar with 10 cc of methanol, and then vacuum dried at 5 * 10 −2 torr at room temperature. Next, the temperature was raised to 800 ° C. at a temperature rising rate of 15 ° C./min in air, and the mixture was fired at 800 ° C. for 12 hours in an electric furnace and naturally cooled. (Using Yamato Scientific Muffle Furnace FP-31)

The powder X-ray pattern (using a powder X-ray diffractometer manufactured by Rigaku Denki, using CuKα ray) of the obtained substance is JC.
PDS (US Joint Committee on
Power Diffraction Standard
ds) was used to identify the product by comparing it with the card index, and the above burned product was substantially Co2V2O7 (card number 2).
9-519) was confirmed. Table 1 shows the correspondence with the JCPDS card index.

[0036]

[Table 1]

When the content ratio of Co and V of the above-mentioned fired product was examined by an inductively coupled plasma (ICP) emission spectrometry, Co was found to be Co.
/V=1.01, which supports the identification result of X-ray diffraction.

(Synthesis of Compound A) Next, 13.2 g of anhydrous lithium acetate (reagent manufactured by Wako Pure Chemical Industries, Ltd.) and the above compounds 1, 33.
After mixing 1 g in a porcelain mortar, the mixture was placed in an electric furnace (using a muffle furnace FP-31 manufactured by Yamato Scientific Co., Ltd.) which was previously kept at 335 ° C. and baked at 335 ° C. for 3 hours. Immediately after firing, the fired product was taken out of the furnace and cooled in air. Next, a vibration mill (TI-100 manufactured by Hirako Seisakusho)
Compound A having an average particle size of 15 μm was obtained by pulverizing for 5 minutes.

The powder X-ray diffraction pattern (using a powder X-ray diffractometer manufactured by Rigaku Denki Co., using CuKα ray) for Compound A is shown in FIG. The substance obtained is substantially JCP
Li described in DS card index No. 38-1396
It is CoVO4. Table 2 shows the correspondence between the JCPDS card index and this substance.

[0040]

[Table 2]

Synthesis Example 2 (Synthesis of Compound B) In the same manner as in Synthesis Example 1, except that the firing temperature of Compound 1 and anhydrous lithium acetate was 550 ° C.
A compound B having an average particle size of 17 μm was obtained.

The obtained substance is substantially the same as LiCoVO4 described in JCPDS Card Index, 38-1396.
Is. Table 2 shows the correspondence between the JCPDS card index and this substance.

Synthesis Example 3 (Synthesis of Compound C) As in Synthesis Example 1, except that the firing temperature was 9
At 00 ° C., Compound C having an average particle size of 17 μm was obtained.

The obtained substance is substantially LiCoVO 4 described in JCPDS Card Index, 38-1396.
Is. Table 2 shows the correspondence between the JCPDS card index and this substance.

Synthesis Example 4 (Synthesis of Comparative Compound B) CoO, 14.9 g and V 2
O5, 18.2g and anhydrous lithium acetate, 13.2g
After mixing in a porcelain mortar, add 3
Electric furnace maintained at 35 ° C (Yamato Scientific Muffle Furnace F
(Using P-31) and baked at 335 ° C. for 3 hours. Immediately after firing, the fired product was taken out of the furnace and cooled in air. Next, using a vibration mill (TI-100 manufactured by Hirako Seisakusho), 5
After pulverizing for a minute, Comparative Compound A having an average particle size of 15 μm was obtained.

Powder X-ray diffraction pattern (using powder X-ray diffractometer manufactured by Rigaku Denki Co., Ltd., CuK
2 is shown in FIG. Most of the obtained substances are substantially JCPDS card index 38-13.
LiCoVO4 described in No. 96. Table 2 shows JCPDS
The correspondence between the card index and this substance is shown.

Synthesis Example 5 (Synthesis of Comparative Compound (b)) Similar to the synthetic procedure of Synthesis Example 4, except that the firing temperature was 900 ° C., a comparative compound (b) having an average particle size of 17 μm was obtained.

The main substance obtained is essentially JC.
L in PDS card index, 38-1396
iCoVO4. Table 2 shows the correspondence between the JCPDS card index and this substance.

From the X-ray diffraction patterns of FIGS. 1-2, single-phase LiCoVO4 was obtained in the compounds A to C of the present invention, while this LiCoVO4 was obtained in the comparative compounds A and B.
Other impurities are recognized. In particular, many peaks indicating the presence of substances other than LiCoO4 are observed in the comparative compound B synthesized at low temperature.

Synthesis Example 6 (Synthesis of Compound 5) NiO (Wako Pure Chemicals Reagent), 14.
8 g and V2O5 (Wako Pure Chemical Industries, Ltd. reagent), 18.2 g were mixed in a porcelain mortar with 10 cc of methanol, and then vacuum dried at 5 * 10 −2 torr at room temperature. Next, the temperature was raised to 800 ° C. at a temperature rising rate of 15 ° C./min in air, and the mixture was fired in an electric furnace at 800 ° C. for 12 hours and naturally cooled. (Using Yamato Scientific Muffle Furnace FP-31) Powder X-ray pattern of the obtained substance (Rigaku Denki Powder X
The line diffractometer is used and CuKα line is used by JCPDS (Joint Committee on Power, USA)
Identification was performed by collating with the card index of Diffraction Standards), and it was confirmed that the above-mentioned fired product was substantially Ni2V2O7 (card number 38-285). Table 3 shows the correspondence with the JCPDS card index.

[0051]

[Table 3]

(Synthesis of Compound D) Next, 13.2 g of anhydrous lithium acetate (a reagent manufactured by Wako Pure Chemical Industries, Ltd.) and Ni2V2O described above were used.
After 7 and 33.1 g were mixed in a porcelain mortar, the mixture was put in an electric furnace (using a muffle furnace FP-31 manufactured by Yamato Scientific Co., Ltd.) which was previously kept at 335 ° C. and baked at 335 ° C. for 3 hours. Immediately after firing, the fired product was taken out of the furnace and cooled in air. Next, a vibrating mill (TI
-100) for 5 minutes to obtain a compound D having an average particle size of 15 μm.

The substance obtained from the powder X-ray diffraction pattern (using a powder X-ray diffractometer manufactured by Rigaku Denki Co., Ltd. and using CuKα ray) of the above compound D is substantially the journal of the Chemical Society of Japan 1
1, 1483 (1979), LiNiVO4. Table 4 shows the correspondence between literature values and this substance.

[0054]

[Table 4]

Synthesis Example 7 (Synthesis of Comparative Compound D) NiO, 14.8 g and V 2
O5, 18.2g and anhydrous lithium acetate, 13.2g
After mixing in a porcelain mortar, add 3
Electric furnace maintained at 35 ° C (Yamato Scientific Muffle Furnace F
(Using P-31) and baked at 335 ° C. for 3 hours. Immediately after firing, the fired product was taken out of the furnace and cooled in air. Next, using a vibration mill (TI-100 manufactured by Hirako Seisakusho), 5
Grinding for minutes gave a comparative compound D having an average particle size of 15 μm.

The main substances obtained from the powder X-ray diffraction patterns (using a powder X-ray diffractometer manufactured by Rigaku Denki Co., Ltd. and using CuKα rays) for Comparative Compound D are essentially those of the Chemical Society of Japan 11, 1483 (1979). LiNiV described
It is O4. Table 4 shows the correspondence between literature values and this substance.

Synthesis Example 8 (Synthesis of Compound E) As in Synthesis Example 1, except that CoO was replaced by Cu
O was added to 15.9 g to obtain Compound 8. Further, 34.1 g of this compound 8 was used in place of the compound 1 of Synthesis Example 1 to obtain a compound E having a particle size of 18 μm.

Synthesis Example 9 (Synthesis of Compound F) As in Synthesis Example 1, except that CoO was replaced by Zn
Compound F having a particle diameter of 17 μm was obtained by using 33.2 g of the calcined product of CoO, ZnO and V2O5 instead of the compound 1 of Synthesis Example 1 with 1.6 g of O and 13.4 g of CoO.

Synthesis Example 10 (Synthesis of Compound G) As in Synthesis Example 1, except that CoO was replaced by Mg.
O, 0.8 g, CoO, 13.4 g were further used instead of the compound 1 of Synthesis Example 1 by using 31.7 g of the calcined product of CoO, MgO and V2O5 to obtain a compound G having a particle size of 15 μm.

Synthesis Example 11 (Synthesis of Compound H) As in Synthesis Example 1, except that CoO was replaced with Mn.
O, 1.4 g, CoO, 13.4 g were further used in place of the compound 1 of Synthesis Example 1 by using 32.9 g of the calcined product of CoO, MnO and V2O5 to obtain a compound H having a particle size of 14 μm.

Synthesis Example 12 (Synthesis of Compound I) As in Synthesis Example 1, except that CoO was replaced with Fe.
O, 1.4 g, CoO, 13.4 g were further used in place of the compound 1 of Synthesis Example 1 by using 32.9 g of the calcined product of CoO, FeO and V2O5 to obtain a compound I having a particle size of 16 μm.

Synthesis Example 13 (Synthesis of Compound J) As in Synthesis Example 1, except that V 2 O 5 was replaced with Nb
2O5, 2.66 g, V2O5 16.3 g, and Nb2O5, V2O5 and Co were used instead of the compound 1 of Synthesis Example 1.
Using 33.9 g of a calcined product of O, a compound J having a particle size of 16 μm
Got

Synthesis Example 14 (Synthesis of Compound K) In the same manner as in Synthesis Example 2, except that lithium acetate was used as 4.7 g of lithium hydroxide to obtain Compound K having a particle size of 16 μm.

Synthesis Example 15 (Synthesis of Compound L) In the same manner as in Synthesis Example 2, except that lithium acetate was 7.4 g and lithium acetate was used to obtain a compound L having a particle size of 17 μm.

[0065]

The present invention will be described in more detail with reference to the following examples, but the invention is not limited to the examples as long as the gist of the invention is not exceeded. Example 1 (Preparation and Evaluation of Lithium Secondary Battery) Above Synthesis Examples 1 to 1
82% by weight of each of the compounds A to C obtained in Example 3, 12% by weight of scaly graphite as a conductive agent, and 6% by weight of polyvinylidene fluoride as a binder are mixed, and the mixture is dried, followed by compression molding. Negative electrode pellets (13 mmφ, 6
0 mg) was used. The weight, thickness and diameter of this pellet were measured to obtain the pellet specific gravity. This negative electrode and LiCoO
Coin type batteries a to c together with a positive electrode composed of 2, polyvinylidene fluoride and graphite, a separator using a microporous polypropylene non-woven fabric, and 1 mol / l LiBF4 (equal volume mixture of propylene carbonate and 1,2-dimethoxyethane) as an electrolyte. And 1mA / cm2
A charging / discharging test was conducted under the conditions of charging 3.5 V and discharging 1.8 V at a current density of 10 to determine the discharge capacities of the 10th, 50th and 100th cycles. As a result of disassembling the battery after the charge / discharge cycle and observing the negative electrode pellet, deposition of Li metal was not observed. The results obtained are shown in Table 5.

[0066]

[Table 5]

Comparative Example 1 (Preparation and Evaluation of Rechargeable Lithium Battery) Using the comparative compounds a and b obtained in Synthesis Examples 4 and 5, coin type batteries d and e were prepared in the same manner as in Example 1, and negative electrode pellets were prepared. Production,
Negative electrode pellet specific gravity measurement, battery preparation, and charge / discharge test were performed. As a result of disassembling the battery after the charge / discharge cycle and observing the negative electrode pellet, deposition of Li metal was not observed. The results obtained are shown in Table 5.

Comparative Example 2 (Preparation and Evaluation of Rechargeable Lithium Battery) As a comparative compound C, a commercially available coal-based coke (manufactured by Nippon Steel Chemical Co., Ltd., trade name L) is used.
PC-u, Lc (crystal thickness in the C-axis direction in X-ray diffraction) = 41 Å, d002 (plane spacing of 002 planes) = 3.47 Å, ρ = 2.09 g / c
m3) 84% by weight, commercially available acetylene black (Denka Black Co., Ltd., trade name Denka Black) 8% by weight, ethylene-propylene-diene copolymer EP as a binder
DM (manufactured by Sumitomo Chemical Co., Ltd., trade name ESPRENE) is applied with a mixture mixed at a mixing ratio of 8% by weight (solvent toluene),
Negative electrode pellets (diameter 13
mm) was prepared as a negative electrode material. The weight, thickness and diameter of this pellet were measured to obtain the pellet specific gravity. With this negative electrode,
A positive electrode composed of LiCoO2, polyvinylidene fluoride, and graphite, a separator using a microporous polypropylene nonwoven fabric, and 1 mol / l LiBF4 as an electrolyte.
A coin type battery f was prepared together with (equal volume mixture of propylene carbonate and 1,2-dimethoxyethane) at 1 mA /
A charge / discharge test was carried out under the condition of charging 3.95 V and discharging 3.2 V at a current density of cm 2, and the discharge capacities of the 10th, 50th and 100th cycles were obtained. The battery after the cycle was disassembled, and it was confirmed that deposition of Li metal did not occur even after the cycle at this charge potential. The results obtained are shown in Table 5.

Example 2 (Preparation and Evaluation of Lithium Secondary Battery) Synthesis Example 6,
Using the compounds D to L obtained in Synthesis Examples 8 to 15 as coin type batteries g to o in the same manner as in Example 1, as in Example 1, negative electrode pellet preparation, negative electrode pellet specific gravity measurement, battery preparation, charging. A discharge test was conducted. As a result of disassembling the battery after the charge / discharge cycle and observing the negative electrode pellet, deposition of Li metal was not observed. The obtained results are shown in Table 6.

[0070]

[Table 6]

Comparative Example 3 (Preparation and Evaluation of Rechargeable Lithium Battery) Using Comparative Compound D obtained in Synthesis Example 7 as in Example 1, a coin-type battery p was obtained in the same manner as in Example 1. Pellet preparation, negative electrode pellet specific gravity measurement, battery preparation, and charge / discharge test were performed. As a result of disassembling the battery after the charge / discharge cycle and observing the negative electrode pellet, deposition of Li metal was not observed.
The obtained results are shown in Table 6.

Results Batteries using the active material synthesized by the method of the present invention as the negative electrode active material were 1. Li metal deposition did not occur even after cycling, and safety was high 2. Compared to the carbonaceous material of Comparative Example 1. Clearly, the charge / discharge capacity per volume is superior 3. Comparative Example 2 From the comparison with Comparative Example 3, the negative electrode active material synthesis according to the present invention significantly improved the charge / discharge capacity and cycleability. Is clear. It is well known in the art that the battery performance of the active material for a lithium secondary battery varies depending on the raw material for synthesizing the active material, and the starting material is the same in the present invention. Even after forming the oxide represented by the general formula (1), the general formula (2)
It is surprising that such a large performance improvement was observed by reacting with the compound of. Further, the effect of the present invention is particularly remarkable by firing at 600 ° C. or lower.

[0073]

As described above, the negative electrode active material composed of the oxide represented by the following general formula (1) and the Li-containing metal oxide synthesized by firing the compound represented by the following general formula (2), With the lithium secondary battery characterized by comprising a positive electrode active material and an organic electrolyte containing a lithium salt, a lithium secondary battery having excellent safety, high charge / discharge capacity and excellent cycleability could be obtained. General formula (1) MxRyOz General formula (2) LivL

[Brief description of drawings]

FIG. 1 shows an X-ray diffraction pattern of Compound A.

FIG. 2 shows an X-ray diffraction pattern of Comparative Compound A.

FIG. 3 shows a cross-sectional view of a coin battery used in Examples.

[Explanation of symbols]

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

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Maekawa 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Fuji Photo Film Co., Ltd.

Claims (2)

[Claims] 1. A lithium secondary battery comprising an organic electrolyte containing a positive electrode active material, a negative electrode active material, and a lithium salt, and a composite comprising at least two kinds of metals represented by the following general formula (1) as the negative electrode active material. A lithium secondary battery comprising an oxide and a Li-containing metal oxide obtained by firing a Li-containing compound represented by the following general formula (2). General formula (1) MxRyOz (In the formula, M and R are each a divalent to hexavalent metal, and M is Mg, Mn, Fe, Co, Ni, Cu, Zn, M.
At least one selected from o and R represents a Va group metal element. x, y, z are 0 <x / y ≦ 3, 2 ≦ z / y ≦
The range is 7. ) General formula (2) LivL (wherein L represents a mono-, di- or trivalent group, and OH, CO3,
NO3, SO3, SO4, PO4, B4O7, ClO3, Cl
O4, SCN, HCO2, CH3CO2, C2O4, C4H4O
6, at least one of CF3SO3, PF6, F, Cl, Br, I and the like. v represents 1, 2, and 3. ) 2. The firing temperature of the Li-containing metal oxide obtained by firing the compound of the general formula (1) and the compound of the general formula (2) is 150 ° C. or higher and 600 ° C. or lower. The lithium secondary battery described.