Lithium secondary battery

Details Lithium secondary battery Lithium secondary battery

1999-12-20

2001-10-09

Weiner, Laura (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Electrode

C429S231950, C429S220000, C429S221000, C429S223000, C429S224000, C429S225000, C429S231500, C429S231600

Reexamination Certificate

active

06300009

ABSTRACT:

BACKGROUND OF THE INVENTION
This application claims the priority of Japanese Patent Applications No. 10-376751/1998 filed on Dec. 25, 1998 and No. 11-279188/1999 filed on Sep. 30, 1999, which are incorporated herein by reference.
The present invention relates to a lithium secondary battery using a molybdenum sulfide as an active material of a positive electrode or a negative electrode and more particularly, it relates to improvement of the molybdenum sulfide for the purpose of improving the charge-discharge cycle performance of such a lithium secondary battery.
A lithium battery using a molybdenum sulfide, such as molybdenum disulfide (MoS
2
) and molybdenum trisulfide (MoS
3
), as a positive electrode active material is disadvantageously poor in the storage characteristic because sulfur eluted into the nonaqueous electrolyte reacts with lithium included in the negative electrode during the storage.
For the purpose of suppressing the reaction between sulfur and lithium, a positive electrode mixed material including a molybdenum sulfide and a powder of at least one metal reactive to sulfur selected from the group consisting of copper, silver, molybdenum, titanium, niobium and alloys of these metals has been proposed as a positive electrode material (Japanese Laid-Open Patent Publication No. 60-175371/1985).
When this positive electrode mixed material is used in a secondary battery, however, although the storage characteristic can be improved, the charge-discharged cycle performance cannot be sufficiently improved. This is because the unstable crystal structure of a molybdenum sulfide itself cannot be stabilized by adding the metal powder thereto (A. J. Jacobon, p. 2277, Journal of Electrochemical Society (1979)).
The present invention was devised in view of the aforementioned conventional problems, and the object is providing a lithium secondary battery using a molybdenum sulfide as an active material of a positive electrode or a negative electrode and exhibiting good charge-discharge cycle performance.
SUMMARY OF THE INVENTION
In order to achieve the object, in the lithium secondary battery of this invention (present battery) comprising a positive electrode, a negative electrode and a nonaqueous electrolyte, an active material of either the positive electrode or the negative electrode includes a composite sulfide having the same crystal structure as MoS
2
or Mo
2
S
3
, or the composite sulfide including lithium, which is represented by a composition formula, M
X
Mo
1−X
S
Y
, wherein M is at least one element selected from the group consisting of Cu, V, Cr, Mn, Fe, Co, Ni, Ti, Y, Cd, In, La, Ce, Pr, Nd, Sm, W, Pt, Pb, Ca, Sr and Ba; 0<X<0.46; and 1.5≦Y≦2.0.
By using the specific composite sulfide, the invention provides a lithium secondary battery using a molybdenum sulfide as an active material of a positive electrode or a negative electrode and exhibiting good charge-discharge cycle performance.


REFERENCES:
patent: 4139682 (1979-02-01), Jacobson et al.
patent: 4801441 (1989-01-01), Schleich
patent: 56-103872 A (1981-08-01), None
patent: 57-172661 A (1982-10-01), None
patent: 60-175371 A (1985-09-01), None
patent: 60-175374 A (1985-09-01), None

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