Solid state thermal synthesis of lithium cobaltate

Details Solid state thermal synthesis of lithium cobaltate Solid state thermal synthesis of lithium cobaltate

2002-03-28

2004-05-18

Silverman, Stanley S. (Department: 1754)

Chemistry of inorganic compounds

Oxygen or compound thereof

Metal containing

C429S231300

Reexamination Certificate

active

06737037

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a novel solid state thermal process for the preparation of lithium cobaltate (LiCoO
2
) useful as a cathode material in nonaqueous, solid state and polymer electrolyte for secondary rock in chair or intercalated batteries.
BACKGROUND OF THE INVENTION
Lithium cobaltate (LiCoO
2
) is widely used as a cathode in lithium secondary cells in the view of its high reversibility to lithium ions and less fading capacity over LiNiO
2
and LiMn
2
O
4
electrodes.
Methods reported in the art for the preparation of cathode lithium cobaltate (LiCoO
2
) disclose the reaction of lithium nitrate, or lithium hydroxide, lithium acetate or any other lithium salts with cobalt nitrates, oxides, acetates, hydroxides, sulphates by soft chemistry method like sol-gel process between temperature ranges of 350-500° C. for long duration of time and multistep preparation procedures. Normally, in solid state thermal methods in the synthesis of these oxide materials, the duration of preparation is long heating, intermittent cooling and grinding process. Other preparation methods are also available in literature for synthesizing lithium cobaltate like pulsed laser deposition, sputtering and electrostatic spray deposition.
REFERENCES
1. “Synthesis and electrochemical properties of LiCoO
2
spinel cathodes”—S. Chol and A. Manthiram,
Journal of the Electrochemical Society
, Vol. 149(2) (2002) A162-166.
2. “X-ray absorption spectroscopic study of LiAl
y
CO
1-y
O
2
cathode for lithium rechargeable batteries”—Won-Sub Yoon, Kyung-Keun Lee and Kwang-Bum Kim,
Journal of the Electrochemical society, Vol.
149(?) (2002) A146-151.
3. “High temperature combustion synthesis and electrochemical characterization of LiNiO
2
, LiCoO
2
and LiMn
2
O
4
for lithium ion secondary batteries”—M. M. Rao, C. Liebenow, M. Jayalakshmi, M. Wulff, U. Guth and F. Scholz,
J. of Solid State Electrochemistry, Vol.
5
, Issue
5 (2001) 348-354.
4. “Fabrication of LiCoO
2
thin films by sol gel method and characterization as positive electrodes for Li/LiCoO
2
cells”—M. N. Kim, H. Chung, Y. Park, J. Kim, J. Son, K. Park and H. Kim,
Journal of Power Sources, Vol.
99(2001) 34-40.
5. “Preparation and characterization of high-density sperical LiNi
0.8
CoO
2
cathode material for lithium secondary batteries”—Jierong Ying, Chunrong Wan, Changyin Jiang and Yangxing Li,
J. of Power Sources, Vol.
99 (2001) 78-84.
6. “Electrochemical characterization of layered LiCoO
2
films prepared by electrostatic deposition”, Won-Sub Yoon, Sung-Ho Ban, Kyung-Keun Lee, Kwang-Bum Kim, Min Dyu Kim and Jay Min Lee,
J. of Power Sources, Vol.
97-98 (2001) 282-286.
7. “Emulsion-derived lithium manganese oxide powder for positive electrodes in lithium ion batteries” Chung-Hsin Lu & Shang-Wei Lin.
J. of Power Sources, Vol.
93(2001) 14-19.
8. “Cobalt doped chromium oxides as cathode materials for secondary batteries for secondary lithium batteries” Dong Zhang, Branko N. Popov, Yury M. Poddrahansky, Pankaj Arora and Ralph E. White,
J. of Power Sources, Vol.
83 (1999) 121-127.
9. “Synthesis and electrochemical studies of spinel phase LiMn
2
O
4
cathode materials prepared by the pechini process” W. Liu, G. C. Farrington, F. Chaput and B. Dunn,
Journal of the Electrochemical society, Vol.
143
, No.
3(1996) 879-884.
The above reported conventional processes show several disadvantages. Generally any one or all of the following are seen:
1. Side reactions occur, i.e., formation of unexpected and unwanted byproducts.
2. Unreacted material is left behind which acts as impurity.
3. Partial reactions occur.
4. Several steps and long calcination time are needed for preparation.
5. Controlled conditions required.
6. Undesirable phases formed.
It is therefore important to develop processes which overcome the disadvantages enumerated above.
OBJECTS OF THE INVENTION
The main object of this present invention is to provide a novel method for the preparation of Lithium cobaltate (LiCoO
2
) hitherto unattempted which obviates the drawbacks mentioned above.
It is another object of the invention to avoid multi-step processes, formation of undesirable and unexpected byproducts and undesirable phases reported in prior art.
SUMMARY OF THE INVENTION
These and other objects of the invention are achieved by the novel process of the invention comprising solid state thermal one step reaction of lithium oxide and cobalt nitrate
Accordingly, the present invention relates to a process for the preparation of lithium cobaltate by a solid state thermal one step process comprising mixing lithium oxide (Li
2
O) and cobalt nitrate (Co(NO
3
)
2
) in solid state uniformly, adding a heat generating material to the mixture and grinding the mixture, heating the ground mixture at a temperature in the range of 650 to 700° C. to obtain the desired lithium cobaltate.
In one embodiment of the invention, the ratio of the Li
2
O+Co(NO
3
)
2
mixture and the heat generating material is 1:3.
In another embodiment of the invention the ground mixture is heated in a furnace for about 8 hours.
In one embodiment of the invention, the Li
2
O is mixed with Co(NO
3
)
2
in the following ratios.
Li
2
O:Ni(NO
3
)
2
1:2
In another embodiment of the invention, the heat generating material is selected from urea and ammonium nitrate.
In yet another embodiment of the invention electric furnace is used for heating.
In still another embodiment of the invention, the materials used are all in solid state.


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patent: 1327951 (2001-12-01), None
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patent: 2001357846 (2001-12-01), None
Kiyoshi Kanamura et al.,Electrochem. and Solid State Ltrs,2000, 3(6):256-258.
PCT Search Report.
S. Choi et al.,J. Electrochem. So.,2002, 149(2), 162-166.
Won Sub Yoon et al,J. Electrochem So.,2002, 149(2) 146-151.
Mun-Kyu Kim et al,J of Power Sources.,2001, vol. 99, 34-40.
Jierong Ying et al,J of Power Sources,2001, vol. 99, 78-84.
Won-Sub Yoon et al.,J. of Power Sources,2001, vol. 97-98, 282-286.
Dong Zhang et al,J of power sources,1999, vol. 83, 121-127.
W. Liu et al,J of Electrochem Soc.,1996, 143:3, 879-884.

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