Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
2000-02-16
2003-12-02
Ryan, Patrick (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S224000, C429S231100, C429S231800, C429S188000, C429S322000
Reexamination Certificate
active
06656638
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a non-aqueous electrolyte battery having a positive electrode, a negative electrode and a non-aqueous electrolyte interposed between the positive and negative electrodes.
2. Description of the Prior Art
Recently, in keeping pace with rapid progress in a variety of electronic equipments, investigations are going on in the field of a re-chargeable secondary battery as a battery that can be used conveniently for long and economically. Typical of the secondary batteries are lead storage batteries, alkali storage batteries and lithium secondary batteries. Of these, lithium secondary batteries are superior secondary batteries having such advantages as high output or high energy density.
These lithium secondary batteries are made up of reversibly introducing and desorbing lithium ions, a separator arranged between the positive and negative electrodes and a non-aqueous electrolyte. In general, lainar electrically conductive high molecular materials, carbon materials or metal oxides, doped with metal lithium, lithium alloys or lithium, are used as negative electrode active materials.
On the other hand, metal oxides, metal sulfides or polymers are used as the positive electrode active material. For example, non-lithium compounds, such as TiS
2
, MoS
2
, NbSe
2
or V
2
O
5
, or lithium-containing complex materials, such as LiMO
2
, where M=Co, Ni, Mn or Fe, have been proposed. These compounds may also be used in combination.
As the non-aqueous electrolytes, a solution obtained on dissolving lithium salts in non-protonic organic solvents, such as propylene carbonate, is used.
As a separator, a high-molecular film, such as a polypropylene film, is used. The separator needs to be as thin as possible in view of lithium ion conductivity and energy density. The separator thickness is usually not larger than approximately 50 &mgr;m in view of practical utility.
Although the tendency is towards a higher capacity of the lithium secondary battery, the battery material selection in search for the best material is underway for cost reduction. Although a spinel structure manganese oxide is well-known as a manganese oxide used for the positive electrode, the theoretical capacity of the spinel manganese oxide is of the order of 150 mAh/g which is below 274 mAh/g as the theoretical capacity of LiCoO
2
. For this reason, researches for a complex oxides represented by LiMnO
2
, having the theoretical capacity of the same order of magnitude as LiCoO
2
, are going on briskly.
Depending on the temperature at the the of synthesis, high temperature type LiMnO
2
is reported (R. Hoppe, G. Brachtel and M. Jansen in Z. Anorg. Allg. Chemie, 417, 1 (1975)), and low temperature type LiMnO
2
is also reported (T. Ohzuku, A. Ueda and T. Hirai (Chem. Express. 7,193 (1992), as the complex oxides represented by LiMnO
2
.
Whilst the theoretical capacity is of the order of 300 mAh/g for both high temperature type LiMnO
2
and low temperature type LiMnO
2
, if these LiMnO
2
compounds are used in an actual non-aqueous electrolyte battery, the actual capacity is smaller than the theoretical capacity, because of limitations as to the potential region in which the electrolyte may remain in stability.
For example, the charging capacity in an actual non-aqueous electrolyte battery is said to be of the order of 150 mAh/g and 200 mAh/g for the high temperature type LiMnO
2
and for the low temperature type LiMnO
2
, respectively. As for the discharging capacity, it is as low as 50 mAh/g or less, for the potential area not lower than 1.5 V, because the LiMnO
2
compound is unavoidably modified in structure during the charging/discharging process.
Although the high temperature type LiMnO
2
and the low temperature type LiMnO
2
differ in the charging capacity, if the compounds are oxidized to a potential in the vicinity of 4.5 V, the discharging capacity becomes extremely small. Under these circumstances, it is desired to increase the discharging capacity of the LiMnO
2
compound.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a non-aqueous electrolyte battery having an improved capacity of the lithium manganese oxide used for the positive electrode.
The present invention provides a non-aqueous electrolyte battery including a positive electrode containing a complex oxide of a transition metal, a negative electrode arranged facing the positive electrode and containing metal lithium, lithium alloy, or a carbon material capable of doping and undoping lithium, and a non-aqueous electrolyte interposed between the positive electrode and the negative electrode. The complex oxide of a transition metal is a complex oxide of lithium and manganese represented by the general formula LiMn
1−y
B
y
O
2
, with 0<y<1.
In the present non-aqueous electrolyte battery, according to the present invention, in which LiMn
1−y
B
y
O
2
obtained on adding B to LiMnO
2
is used as a positive electrode, LiMnO
2
is stabilized to realize a large capacity.
That is, according to the present invention, in which a lithium manganese oxide, part of Mn of which is replaced by B (LiMn
1−y
B
y
O
2
), is used as an active material for the positive electrode, it is possible to realize a non-aqueous electrolyte battery having a large capacity.
REFERENCES:
patent: 5556721 (1996-09-01), Sasaki et al.
patent: 5578395 (1996-11-01), Yoshimura et al.
patent: 5686138 (1997-11-01), Fujimoto et al.
patent: 6413678 (2002-07-01), Hamamoto et al.
patent: 19615800 (1996-12-01), None
patent: 0630064 (1994-12-01), None
patent: 08227709 (1996-09-01), None
patent: 09129228 (1997-05-01), None
patent: 98/38648 (1998-09-01), None
Martin Angela J
Ryan Patrick
Sonnenschein Nath & Rosenthal LLP
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