Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1999-05-20
2001-02-20
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S231100, C429S231500, C423S406000, C423S608000, C501S103000, C501S134000
Reexamination Certificate
active
06190802
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to synthetic materials. More specifically, the invention relates to ceramic materials, and in particular to ceramic materials comprised of transition metal nitrides which incorporate a group I element, particularly lithium, therein, and which are doped with metals and/or metal oxides. The invention further relates to electrodes incorporating these materials, and in particular to cathodes for rechargeable lithium batteries.
BACKGROUND OF THE INVENTION
Rechargeable batteries are of ever increasing importance as power supplies for a variety of items. One important class of rechargeable batteries comprises rechargeable lithium batteries, and as used herein, the term is understood to include all types of rechargeable lithium and lithium ion batteries.
The cathode is an important component of a lithium battery. During discharging and charging of the battery, lithium ions are inserted into and removed from the bulk of the cathode material respectively. Battery performance in terms of capacity, charging rate, discharge rate and life time will depend, among other things, upon the material properties of the cathode material. Some important parameters for a cathode material are its electrical conductivity and lithium transport properties. Stability is also important, as is cost and ease of fabrication.
Prior art cathode materials for lithium batteries are primarily based on metallic oxides, and in particular on oxides of nickel, manganese and cobalt. Representative cathode materials widely employed in the prior art include LiMn
2
O
4
, LiCoO
2
and LiNiO
2
. In some instances, metal nitrides have been utilized in electrodes. U.S. Pat. Nos. 5,589,298 and 5,702,843 disclose the use of specific lithium metal nitrides as cathode materials for lithium batteries, and U.S. Pat. No. 5,754,394 discloses capacitor electrodes composed of metal nitrides.
As will be detailed hereinbelow, the present invention is directed to a unique class of ceramic materials. The base material thereof is generally a transition metal nitride, although it is to be understood that some proportion of oxygen may be present in the material, and in particular embodiments of the present invention, oxide or oxynitride materials are important dopants for the ceramics of the present invention. The materials of the present invention have very good electrical conductivity. Lithium is highly diffusive in the materials of the present invention, and they readily and reversibly allow for the insertion of lithium therein. The materials have a very stable lattice structure and this structure is preserved through repeated charge and discharge cycles. As will be further explained hereinbelow, the materials of the present invention include a dopant species which greatly enhances the beneficial properties thereof. These and other advantages of the invention will be apparent from the discussion, description and examples which follow.
BRIEF DESCRIPTION OF THE INVENTION
There is disclosed herein a transition metal based ceramic material of the general formula Li
&agr;
M
1−&bgr;
T
&bgr;
N
x
O
&dgr;
wherein M is a transition metal; T is a dopant metal, which may be present as a free metal or as one or more oxide or nitride compounds; and wherein x is less than or equal to 1; &dgr; is 0, or less than or equal to 4; &agr; is less than or equal to 3−x; and &bgr; is less than 0.2. In particular embodiments, M is vanadium. The dopant metal may comprise one or more transition metals, and group III and IV transition metals are particularly preferred. In some specific embodiments, the dopant is comprised of scandium, yttrium, lanthanum, zirconium, titanium and/or hafnium. The dopant metal may be present in the material as oxides of the foregoing metals, nitrides thereof and combinations thereof.
In one specific embodiment, the transition metal of the ceramic comprises vanadium, and the dopant is based upon zirconium, most particularly a mixture of zirconium and zirconium oxide.
Also disclosed herein are rechargeable lithium batteries incorporating the foregoing materials in their cathodes.
REFERENCES:
patent: 5286582 (1994-02-01), Tahara et al.
patent: 5589298 (1996-12-01), Takada et al.
patent: 5702843 (1997-12-01), Mitate et al.
patent: 5721070 (1998-02-01), Shackle
patent: 5754394 (1998-05-01), Evans et al.
patent: 5834139 (1998-11-01), Shodai et al.
patent: 5856043 (1999-01-01), Ohsaki et al.
patent: 5888669 (1999-03-01), Thompson, Jr. et al.
patent: 08078018 (1996-03-01), None
Clerc Daryl
Fay Matthew
Thompson Levi
Wixom Michael
Chaney Carol
Dove Tracy
Gifford, Krass, Groh Sprinkle, Anderson & Citkowski, P.C.
T/J Technologies Inc.
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