Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
2001-03-27
2003-05-13
Weiner, Laura (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S245000
Reexamination Certificate
active
06562518
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates generally to the field of lithium cobalt oxide (LiCoO
2
) films. More particularly, the invention relates to fabrication of highly textured LiCoO
2
films by rapid thermal annealing.
2. Discussion of the Related Art
Thin films of LiCoO
2
are used as the cathode in thin film lithium and lithium ion batteries. The films are deposited by rf magnetron sputtering of LiCoO
2
.
FIG. 1
shows an x-ray diffraction pattern of an LiCoO
2
film annealed for two hours at 700° C. according to the prior art. In order to crystallize the films and achieve the high degree of preferred orientation that optimizes battery performance, they are heated at 700° C. in flowing O
2
for 2 hours. In order to lower the cost of manufacturing, it is desirable to shorten the annealing time as much as possible without compromising battery performance.
Heretofore, the requirements of low cost manufacturing and short annealing times referred to above have not been fully met. What is needed is a solution that addresses each of these requirements independently or concurrently. The invention is directed to meeting these requirements, among others.
SUMMARY OF THE INVENTION
A goal of the invention is to reduce the costs associated with LiCoO
2
thin films. Another goal is to reduce the annealing times associated with the manufacture of LiCoO
2
thin films.
One embodiment of the invention is related to a method for manufacturing LiCoO
2
films. The method includes depositing the LiCoO
2
film, rapidly heating the LiCoO
2
film to a target temperature and holding the temperature of the LiCoO
2
film at the target temperature for a target annealing time.
The method can also include rapid cooling of the LiCoO
2
film after holding the LiCoO
2
film within the target temperature range for the target annealing time. The target temperature is preferably greater than approximately 700° C., more preferably at least approximately 800° C. and most preferably at least approximately 850° C. Further, the target temperature range is preferably approximately 700-1000° C., more preferably approximately 750-950° C. and most preferably approximately 850-950° C. The target annealing time is preferably at most approximately an hour, more preferably at most approximately 30 minutes and most preferably at most approximately 15 minutes. Further, the target annealing time is preferably approximately 5-60 minutes, more preferably approximately 10-20 minutes and most preferably about 12-17 minutes.
The invention includes cathodes made according to the above methods. The invention also includes batteries which include these cathodes.
These, and other, goals and embodiments of the invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following description, while indicating preferred embodiments of the invention and numerous specific details thereof, is given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the invention without departing from the spirit thereof, and the invention includes all such modifications.
REFERENCES:
patent: 5110696 (1992-05-01), Shokoohi et al.
patent: 6344366 (2002-02-01), Bates
Bates et al., “Preferred orientation of polycrystalline licoo2 films,”J. of The Electrochem. Soc., 147:59-70, 2000.
Fragnaud et al., “Characterization of sprayed and sputter deposited LiCoO2 thin films for rechargeable microbatteries,”J Power Sources, 63:187-191, 1996.
Lee et al., “Substrate effect on the microstructure and electrochemical properties in the deposition of a thin film LiCoO2 electrode,”Electrochem. Solid-State Ltrs., 2:512-515, 1999.
Wang et al., “Characterization of thin-film rechargeable ithium batteries with lithium cobalt oxide cathodes,”J of The Electrochem. Soc, 143:3203-3213, 1996.
Gray Cary Ware & Freidenrich LLP
Lockheed Martin Energy Research Corporation
Weiner Laura
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