Positive active material for rechargeable lithium battery...

Details Positive active material for rechargeable lithium battery... Positive active material for rechargeable lithium battery...

1999-10-29

2001-02-06

Weiner, Laura (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Electrode

C429S221000, C429S231100, C429S231200, C429S231600

Reexamination Certificate

active

06183911

ABSTRACT:

BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a positive active material for rechargeable lithium batteries and a method of preparing the same and, more particularly, to a manganese-based positive active material for rechargeable lithium batteries which has a good cycle life characteristic.
(b) Description of the Related Art
Generally, manganese-based compounds such as LiMn
2
O
4
and LiMnO
2
are the positive active material of choice for rechargeable lithium batteries because of their low cost, abundance and environmentally friendly characteristics. Among such manganese-based compounds, LiMn
2
O
4
is particularly stable for the battery use and thus attractive for the electric vehicle application.
However, as compared to other lithiated transition metal oxides such as LiCoO
2
and LiNiO
2
, LiMn
2
O
4
has a relatively low discharge capacity. Furthermore, when high rate of charge and discharge operations are cycled, the discharge capacity is excessively reduced. In particular, when the charge and discharge operations are continuously performed at high temperatures, manganese distributed in the surface of LiMn
2
O
4
readily elutes to the electrolyte, causing a disproportionation reaction. This reaction seriously deteriorates the cycle life characteristic of the battery.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a manganese-based positive active material for rechargeable lithium batteries which exhibits a good cycle life characteristic at high temperatures.
This and other objects may be achieved by a positive active material for rechargeable lithium batteries including an active material component processed from a manganese-based compound. The manganese-based compound is selected from Li
x
MnO
2
, Li
x
MnF
2
, Li
x
MnS
2
, Li
x
MnO
2-z
F
z
, Li
x
MnO
2-z
S
z
, Li
x
Mn
1-y
M
y
O
2
, Li
x
Mn
1-y
M
y
F
2
, Li
x
Mn
1-y
M
y
S
2
, Li
x
Mn
1-y
M
y
O
2-z
F
z
, Li
x
Mn
1-y
M
y
O
2-z
S
z
, Li
x
Mn
2
O
4
, Li
x
Mn
2
F
4
, Li
x
Mn
2
S
4
, Li
x
Mn
2
O
4-z
F
z
, Li
x
Mn
2
O
4-z
S
z
, Li
x
Mn
2-y
M
y
O
4
, Li
x
Mn
2-y
M
y
F
4
, Li
x
Mn
2-y
M
y
S
4
, Li
x
Mn
2-y
M
y
O
4-z
F
z
, or Li
x
Mn
2-y
M
y
O
4-z
S
z
where 0<x≦1.5, 0.05≦y≦0.3, z≦1.0 and M is selected from Al, Co, Cr, Mg, Fe, La, Sr or Ce. A vanadium pentoxide is coated on the active material component.
A method of preparing the positive active material is performed by obtaining a powder from a source material. The source material is selected from Li
x
MnO
2
, Li
x
MnF
2
, Li
x
MnS
2
, Li
x
MnO
2-z
F
z
, Li
x
MnO
2-z
S
z
, Li
x
Mn
1-y
M
y
O
2
, Li
x
Mn
1-y
M
y
F
2
, Li
x
Mn
1-y
M
y
S
2
, Li
x
Mn
1-y
M
y
O
2-z
F
z
, Li
x
Mn
1-y
M
y
O
2-z
S
z
, Li
x
Mn
2
O
4
, Li
x
Mn
2
F
4
, Li
x
Mn
2
S
4
, Li
x
Mn
2
O
4-z
F
z
, Li
x
Mn
2
O
4-z
Sz, Li
x
Mn
2-y
M
y
O
4
, Li
x
Mn
2-y
M
y
F
4
, Li
x
Mn
2-y
M
y
S
4
, Li
x
Mn
2-y
M
y
O
4-z
F
z
, or Li
x
Mn
2-y
M
y
O
4-z
S
z
, where 0<x≦1.5, 0.05≦y≦0.3, z≦1.0 and M is selected from Al, Co, Cr, Mg, Fe, La, Sr or Ce. The powder is then coated with a vanadium pentoxide (V
2
O
5
) aqueous solution or a V
2
O
5
alcoholic solution to make a V
2
O
5
solution-coated powder. Thereafter, the V
2
O
5
solution-coated powder is heat-treated to thereby prepare a V
2
O
5
-coated active material.


REFERENCES:
patent: 6037095 (2000-03-01), Miyasaka
patent: 6040087 (2000-03-01), Kawakami
patent: 52-137640 (1977-11-01), None
patent: 53-91333 (1978-08-01), None
patent: 53-107625 (1978-09-01), None

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