Positive electrode-active material and lithium cell...

Details Positive electrode-active material and lithium cell... Positive electrode-active material and lithium cell...

2000-10-12

2002-12-03

Weiner, Laura (Department: 1745)

Chemistry: electrical current producing apparatus, product, and

Current producing cell, elements, subcombinations and...

Electrode

C429S218100, C429S221000, C429S223000, C429S224000, C429S231500

Reexamination Certificate

active

06489057

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an active material for a positive electrode (positive electrode-active material) and a lithium cell comprising the same. In particular, the present invention relates to a positive electrode-active material with a high voltage and a high capacity and a lithium cell comprising the same.
2. Prior Art
Hitherto, a lithium cell comprising copper oxide (CuO) as a positive electrode-active material (hereinafter referred to as a “Li/CuO” cell) has been proposed as a lithium cell having a high capacity density (see Brounssely M., Jumel Y. and Cabano J. P., 152
nd
Electrochemical Society Meeting, Atlanta (1977)).
However, the Li/CuO cell has a low closed circuit voltage of about 1.2 to 1.5 V, and thus it cannot be used in applications which require a high voltage.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a positive electrode-active material which can achieve a high voltage without decreasing the capacity, and a lithium cell comprising such a positive electrode-active material.
Accordingly, the present invention provides a positive electrode-active material consisting of at least one compound selected from the group consisting of a copper-boron double oxide of the formula:
Cu
j
M
k
B
m
O
n
  (I)
wherein M is a metal atom, and j, k, m and n are each a positive integer, a copper-molybdenum double oxide of the formula:
Cu
x
Mo
y
O
z
  (II)
wherein x, y and z are each a positive integer, and a copper double oxide of the formula:
CuM′
2
O
4
  (III)
wherein M′ is at least one element selected from the group consisting of B, Al, Ga, Mn, Co, Ni and a rare earth element Ln (for example, Y, La, etc.)
Furthermore, the present invention provides a lithium cell comprising a positive electrode comprising the above active material of the present invention, a lithium negative electrode, and an electrolyte solution.
In the lithium cell of the present invention, for example, a Li/Cu
2
FeBO
5
cell, unlike the conventional Li/CuO cell, the circumstance around the reducing copper atom of Cu
2
FeBO
5
is different from that of CuO, and thus the distance of the Cu-O bond varies. In addition, the Cu atom is bonded with Fe and B. Therefore, the lattice energy is increased. It is known that the increase of a lattice energy and the variation of the distance between a reducing atom and the nearest atom increase a discharge voltage (Masayuki Yoshio and Akiya Ozawa Ed., “Lithium Ion Secondary Cells”, page 8 (published by Nikkan Kogyo Shinbunsha), 1996).
In the synthesis of the positive electrode-active material such as Cu
2
FeBO
5
, CuB
2
O
4
, Cu
3
Mo
2
O
9
, etc., since B
2
O
3
, H
3
BO
3
or MoO
3
having a low melting point is used, Cu
2
FeBO
5
, CuB
2
O
4
or Cu
3
Mo
2
O
9
of a single phase can be synthesized at a relatively low temperature, and the particles of Cu
2
FeBO
5
, CuB
2
O
4
or Cu
3
Mo
2
O
9
having a small particle size can be produced by the synthesis at such a low temperature. The use of such Cu
2
FeBO
5
, CuB
2
O
4
or Cu
3
Mo
2
O
9
having a small particle size as a positive electrode-active material can increase the conductivity of the positive electrode and, in turn, the discharge voltage. In the course of discharging, the Cu
2
FeBO
5
or CuB
2
O
4
particles may generate B
2
O
3
or boron compounds and Fe2O3, and Cu
3
Mo
2
O
9
may generate MoO
3
, and such generated materials discharge in the range between 1 V and 3 V. Thus, the capacity of the cell further increases. Therefore, in cooperation with the above-described increase of the discharge voltage, a lithium cell having a high voltage and a high capacity can be obtained.
FIGS. 3 and 4
show the discharge characteristics of the cell of Reference Example 1 comprising B
2
O
3
as a positive electrode-active material, and that of the cell of Reference Example 2 comprising MoO
3
as a positive electrode-active material, respectively. From
FIGS. 3 and 4
, it can be understood that the cells of Reference Examples 1 and 2 discharge at a higher voltage than a cell comprising CuO as a positive electrode-active material, the discharge characteristics of which are shown in FIG.
2
.


REFERENCES:
patent: 4292382 (1981-09-01), Lecerf et al.
patent: 4444857 (1984-04-01), Duchange et al.
patent: 5001023 (1991-03-01), Cheshire et al.
patent: 5547785 (1996-08-01), Yumiba et al.
patent: 2-267861 (1990-11-01), None
patent: 3-271365 (1991-12-01), None

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