Positive electrode material for lithium secondary battery

Details Positive electrode material for lithium secondary battery Positive electrode material for lithium secondary battery

2000-12-07

2004-09-14

Ryan, Patrick (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Electrode

C429S231900, C429S231100, C429S224000, C429S223000, C429S231500, C429S231600

Reexamination Certificate

active

06790560

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to material technology for lithium secondary batteries which can be used as power source for various devices such as computer, portable or cellular telephone, and portable audio device, and more specifically to positive electrode material for lithium secondary batteries and lithium secondary batteries having such positive electrode material.
As positive electrode material for lithium secondary batteries, there are known composite oxides, such as LiCoO
2
and LiNiO
2
, including Li and transition metal such as cobalt, nickel and manganese.
Published Japanese Patent Specifications, Kokai Nos. H10(1998)-116614 and H11(1999)-71115 disclose spinel type lithium manganese oxides as positive electrode material.
SUMMARY OF THE INVENTION
The positive electrode material as disclosed in the above-mentioned Japanese Published Specifications has a structure to improve the durability by the substitution, for lithium or manganese in lithium manganese oxide, of another metal. Though such a structure is advantageous in durability, it is not competent enough to prevent undesired decrease in charge-discharge capacity of a battery, especially in initial charge-discharge capacity.
It is therefore an object of the present invention to provide positive electrode material for a lithium secondary battery and a lithium secondary battery having such positive electrode material capable of improving the lifetime of a lithium secondary battery without decreasing the charge-discharge capacity.
According to the present invention, a positive electrode material for a lithium secondary battery comprises: a lithium manganese oxide having a spinel structure, expressed by one of the general formulae;
LixMnyO
4
(where 1≦x≦1.33 and 3−x<y≦3.1−x); and
LixMnyMzO
4
(where M is a metallic element other than Li and Mn, 1≦x≦1.33, 3−x−z<y≦3.1−x−z, and O<z≦1.0).
The metallic element M may be at least one selected from the group consisting of Mg, Al, Cr and Ni.
A lithium secondary battery according to the present invention comprises: a negative electrode comprising a negative electrode active material capable of retaining and releasing lithium ions; a nonaqueous electrolyte having ionic conductivity of lithium ions; and a positive electrode comprising a positive electrode active material comprising a composite oxide which comprises Li and which is capable of retaining and releasing lithium ions. The composite oxide is a lithium manganese oxide having a spinel structure expressed, by one of the above-mentioned general formulae.


REFERENCES:
patent: 5700597 (1997-12-01), Zhong et al.
patent: 5759717 (1998-06-01), Amine et al.
patent: 5869208 (1999-02-01), Miyasaka
patent: 0 762 521 (1997-03-01), None
patent: 3-285262 (1991-12-01), None
patent: 10-116614 (1998-05-01), None
patent: 11-071115 (1999-03-01), None
M. Hosoya et al., “The Defect Structure Model in Nonstoichiometric LiMn2O4-&dgr;”,J. Electrochem. Soc., vol. 144, No. 4, pp. 52-53, The Electrochemical Society, Inc., (Apr. 1997).
N. Hayashi et al., “Cathode, of LiMg2-yO4and LiMg2-yO4-&dgr;Spinel Phases for Lithium Secondary Batteries”,J. Electrochem. Soc., 146 (4), pp. 1351-1354, The Electrochemical Society, Inc. (1999).

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