Coating processes – Electrical product produced – Electron emissive or suppressive
Reexamination Certificate
1999-11-18
2002-03-26
Barr, Michael (Department: 1762)
Coating processes
Electrical product produced
Electron emissive or suppressive
C427S126300, C427S126400, C427S126600, C427S376200, C429S218100, C429S223000, C429S231950
Reexamination Certificate
active
06361822
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing an electrode for a non-aqueous electrolyte battery, and more particularly, to a method for producing a non-aqueous electrolyte battery electrode which includes an electrode active material layer containing at least an active material having a composition of Li
x
Ni
y
M
z
O
2
(where x satisfies 0.8<x<1.5, y+z satisfies 0.8<y+z<1.2, z satisfies O≦z<0.35, and M is at least one element selected from Co, Mg, Ca, Sr, Al, Mn and Fe) and has excellent battery characteristics and preservation properties.
TECHNICAL BACKGROUND OF THE INVENTION
Recent development of devices in the electronic field is remarkable, and various devices such as video cameras, liquid crystal cameras, portable telephones, laptop computers, and word processors are now being developed. In accordance therewith, there are increasing needs for reduction in size and weight and achievement of high energy density in batteries that are to be used as power sources for these electronic devices.
Conventionally, lead batteries or nickel-cadmium batteries have been used for these electronic devices. These conventional batteries cannot sufficiently meet the needs for reduction in size and weight and achievement of high energy density.
Accordingly, there are proposed non-aqueous electrolyte batteries using a non-aqueous electrolytic solution containing a lithium salt dissolved in a non-aqueous solvent. As these non-aqueous electrolyte batteries, batteries in which a metal lithium, a lithium alloy, or a carbon material capable of being doped and undoped with lithium ions is used as a negative electrode material and a lithium cobalt composite oxide is used as a positive electrode material are already in practical use.
Having a high operation voltage of 3 to 4V, the non-aqueous electrolyte batteries of this type can be made to have a high energy density and excellent cycle characteristics with only a small amount of self-discharge.
Also, in order to attain further reduction in size and weight and achievement of high energy density in these non-aqueous electrolyte batteries, eager researches for development of active materials and the like are now being carried out. As positive electrode active materials, Ni-containing lithium composite oxides such as lithium-nickel composite oxides and lithium-nickel-cobalt composite oxides are also proposed.
For example, Japanese Laid-open Patent Publication No. 9-213,330/1997 discloses a method for producing an electrode active material for a non-aqueous electrolyte battery. Namely, the publication discloses a method of calcining a mixture of a lithium compound, a nickel compound, and an N compound (where N is an element other than Li, Ni, or O) in a calcining furnace to obtain a lithium-nickel composite oxide represented by the general formula : Li
x
Ni
y
N
z
O
2
(0.8<x<1.2, 0.8<y+z<1.2, and O≦z<0.2), wherein a gas containing 0.01 vol % or less of carbonic acid gas and having a moisture dew point of −20° C. or less is supplied into the calcining furnace at a gas supply rate in which an amount of at least five times the inner volume of the calcining furnace is supplied within one hour.
Thus, although the publication discloses an atmosphere in producing an electrode active material, it fails to provide a disclosure on an environment for preserving the electrode active material or a special treatment before preparation of a mixture-coating material.
DISCLOSURE OF THE INVENTION
Objects of the Invention
The present inventors have made researches on the properties of nickel-containing lithium composite oxides and found that nickel-containing lithium composite oxides tend to absorb moisture in air more than lithium-cobalt composite oxides. Use of an active material in a state with a lot of absorbed moisture in battery causes problems such as decrease in a charge/discharge capacity of the battery, increase in internal resistance, and deterioration of the preservation property.
Accordingly, the purpose of the present invention is to provide a method for producing an electrode for a non-aqueous electrolyte battery which can solve the above-mentioned problems of the prior art as well as giving a large capacity to the battery and controlling the internal resistance of the battery to a low level.
SUMMARY OF THE INVENTION
The present inventors have made an eager research and found out that a nickel-containing lithium composite oxide with low water content can be used for preparation of a mixture-coating material by adjustment of a preservation environment after production of the nickel-containing lithium composite oxide or by a special treatment before the preparation of the mixture-coating material, thus completing the present invention.
Namely, the present invention provides a method for producing an electrode for a non-aqueous electrolyte battery by preparing an electrode active material mixture-coating material containing at least an active material having a composition of Li
x
Ni
y
M
z
O
2
(where x satisfies 0.8<x<1.5, y+z satisfies 0.8<y+z<1.2, z satisfies O≦z<0.35, and M is at least one element selected from Co, Mg, Ca, Sr, Al, Mn and Fe) and by applying said active material mixture-coating material onto a collector, said method comprising the step of preserving said active material in a gas having a moisture dew point of −20° C. or less from immediately after production of said active material till preparation of said active material mixture-coating material.
Also, the present invention provides a method for producing an electrode for a non-aqueous electrolyte battery by preparing an electrode active material mixture-coating material containing at least an active material having a composition of Li
x
Ni
y
M
z
O
2
(where x satisfies 0.8<x<1.5, y+z satisfies 0.8<y+z<1.2, z satisfies O≦z<0.35, and M is at least one element selected from Co, Mg, Ca, Sr, Al, Mn and Fe) and by applying said active material mixture-coating material onto a collector, said method comprising the step of subjecting said active material to vacuum drying immediately before preparation of said active material mixture-coating material.
Further, the present invention provides a method for producing an electrode for a non-aqueous electrolyte battery by preparing an electrode active material mixture-coating material containing at least an active material having a composition of Li
x
Ni
y
M
z
O
2
(where x satisfies 0.8<x<1.5, y+z satisfies 0.8<y+z<1.2, z satisfies O≦z<0.35, and M is at least one element selected from Co, Mg, Ca, Sr, Al, Mn and Fe) and by applying said active material mixture-coating material on a collector, said method comprising the steps of preserving said active material in a gas having a moisture dew point of −20° C. or less from immediately after production of said active material till preparation of said active material mixture-coating material and subjecting said active material to vacuum drying immediately before preparation of said active material mixture-coating material.
In the present invention, said gas having a moisture dew point of −20° C. or less is preferably air, nitrogen gas, or a rare gas.
According to the present invention, an active material having a composition of Li
x
Ni
y
M
z
O
2
with low water content can be supplied for an electrode. Therefore, use of a non-aqueous electrolyte battery electrode produced by the method of the present invention can give a large capacity to a battery and can control the internal resistance of the battery to a low level.
DETAILED DESCRIPTION OF THE INVENTION
The lithium composite oxide to be used in the present invention is represented by the general formula: Li
x
Ni
y
M
z
O
2
(where x satisfies 0.8<x<1.5, y+z satisfies 0.8<y+z<1.2, z satisfies O≦z<O. 35, and M is at least one element selected from Co, Mg, Ca, Sr, Al, Mn and Fe).
An example of a method for producing such a lithium comp
Iijima Tadayoshi
Kurose Shigeo
Takahashi Tetsuya
Barr Michael
Rader & Fishman & Grauer, PLLC
TDK Corporation
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