Title of Invention

A PROCESS FOR PREPARATION OF LITHIUM COBALTATE BY A SOLID STATE THERMAL ONE STEP PROCESS

Abstract

The invention relates to a process for the preparation of lithium cobaltate by a solid state thermal one step process. The product is useful as a cathode material. The process is a single step and does not form any undesirable byproducts. In the process lithium oxide and cobalt nitrate are mixed uniformly in solid state in a ration of 1:2, adding heat generating agent, the mixture is grinded, heated to the temp of 650 to 700 deg C to obtain the product.

Full Text

SOLID STATE THERMAL SYNTHESIS OF LITHIUM COBALTATE Field of the invention The present invention relates to a novel solid state thermal process for the preparation of lithium cobaltate (LiCoOa) 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 (LiCo02) 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 LiNiO2 and LiMn2O4 electrodes. Methods reported in the art for the preparation of cathode lithium cobaltate (LiCoO2) 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 LiCoO2 spinel cathodes" - S. Choi and A. Manthiram, Journal of the Electrochemical Society, Vol. 149(2) (2002) A162-166. 2. "X-ray absorption spectroscopic study of LiAlyCoi-y02 cathode for lithium rechargeable batteries"- Won-Sub Yoon, Kyung-Keun Lee and Kwang-Bum Kim, Journal of the Electrochemical society, Vol. 149(2) (2002) A146-151. 3. "High temperature combustion synthesis and electrochemical characterization of LiNiO2, LiCoO2 and LiMn2O4 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 LiCoO2 thin films by sol gel method and characterization as positive electrodes for Li/ LiCo02 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 LiNi0.gCoO2 cathode material for lithium secondary batteries" - Jierong Ying, Chunrong Wan, Changyin Jiang and YangxingLi, J. of Power Sources, Vol. 99(2001) 78-84. 6. "Electrochemical characterization of layered LiCoO2 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. 1. "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 LiMmCU 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. "Electrochemical characterization of layered L1C0O2 films prepared by electrostatic deposition", Won-Sub Yoon, Sung-Ho Ban, Kyung-Keun Lee, KwangBum 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 spinal phase LiMn204 cathode materials prepared by the pechini process" W. Liu, G.C. Farrington, F. Kaput and B. Dunn, Journal of the Electrochemical society., Vol. 143 No.3 (1966) 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. An unreacted material is left behind which acts as impurity. 3. Partial reactions occur. 4. Several steps and long calcinations 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 (LiCo02) hitherto unattempted which obviates the drawbacks mentioned above. It is another object of the invention are achieved by the novel process of the invneiton 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 (L12O) and cobalt nitrate (Co(N03)2) in a ratio of 1:2 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 Li20 + Co(N03)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 Li20 is mixed with Co(N03)2 in the following ratios. Li20:Ni(N03)2=l: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. Brief description of the accompanying drawings Figure 1 is an X-ray diffraction pattern of lithium cobaltate obtained by the process of the invneiotn. Detailed description of the invention The present invention involves a solid state thermal one step process for the preparation of lithium cobaltate comprising mixing lithium oxide (Li20) and cobalt nitrate (Co(N03)2 in the following preferred ratio: Li20 : Ni(N03)2 = 1:2 Heating is carried out preferably in an electric furnace with all materials used being in the solid state. The following reaction occurs during the thermal process. Li20 + 2Co(N03)2 + 3(0) -> 2LiCo02 + 4N02 + 202 The reaction as can be seen proceeds in a single step and the product was confirmed as lithium cobaltate by X- ray diffraction. Li20 solid sate material is allowed to react with solid Co(N03)2 under controlled conditions at moderate temperatures which yields fairly very good sample of spinal structure useful as a very good intercalating cathode. Pure AR sample of Co(N03)2 is mixed with pure AR sample of Li2O in the molecular ratio of 2:1 such that a uniform mixture is formed with 3 times weight percentage of urea. In order to obtain a better homogeneous mixture, this mixture is ground well with double distilled water free DiEthylene Carbonate (DEC). This mixture is heated to 300°C and then further heated to 700°C for 5 hours continuously to yield lithium cobaltate (LiCoOa) which is evidenced by X-ray analysis (Figure la). The reaction can also be carried out by replacing urea with ammonium nitrate. LiaO solid state material is allowed to react with solid Co(NO3)2 under controlled conditions at moderate temperatures which yields fairly very good sample of spinel structure useful as a very good intercalating cathode. Pure AR sample of Co(NOs)2is mixed with pure AR sample of Li20 in the molecular ratio of 2:1 such that a uniform mixture is formed with 3 times weight percentage of ammonium nitrate. In order to obtain a better homogeneous mixture, this mixture is ground well with double distilled water free Di ethylene carbonate (DEC). This mixture was heated to 300°C and then heated to 700°C for 5 hours continuously to yield lithium cobaltate (LiCoCh) as is evidenced by X-ray analysis (Figure Ib). The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention. Example 1 Preparation ofLiCoOj: Li2O solid state material is allowed to react with solid Co(NOs)2 under controlled conditions at moderate temperatures which yields fairly very good sample of spinel structure useful as a very good intercalating cathode. Pure AR sample of Co(NC>3)2 is mixed with pure AR sample of Li2O in the molecular ratio of 2:1 such that a uniform mixture is formed with 3 times weight percentage of urea. In order to obtain a better homogeneous mixture, this mixture is ground well with double distilled water free Di Ethylene Carbonate (DEC). This mixture was heated to 300°C for 3 hours and then heated to 700°C for 5 hours continuously to yield lithium cobaltate (LiCoCh) which is evidenced by X-ray analysis (Figure la). Example 2 Preparation ofLiCoOz: LiaO solid state material is allowed to react with solid Co(N03)a under controlled conditions at moderate temperatures which yields fairly very good sample of spinel structure useful as a very good intercalating cathode. Pure AR sample of Co(NO3)2 is mixed with pure AR sample of Li2O in the molecular ratio of 2:1 such that a uniform mixture is formed with 3 times weight percentage of ammonium nitrate. In order to obtain a better homogeneous mixture, this mixture is ground well with double distilled water free Di ethylene carbonate (DEC). This mixture was heated to 300°C and then heated to 700°C for 5 hours continuously yields lithium cobaltate (LiCo02) formed which is evidenced by X-ray analysis (Figure Ib). Example 3 AR pure dry Li2O is mixed with pure dry AR Co(N03)2 in the molar ratio of 1:2 in a pestle and mortar arrangement and then the mix is further mixed with 3 times the weight of urea and then introduced in an electric furnace. This mixture was heated first for 3 hours at 300°C and then heated at 700°C for 5 hours. Components Li2O Co(N03)2 Urea Pre heating temperature Final temperature Time Compositions 0.333 g 0.667 g 3.00 g 300°C 500°C 8 hours Particle size of the product 10-20 um Nature of the product Black Efficiency of the process > 80% Example 4 Pure dry AR Li2O is mixed with pure dry AR Co(NO3)2 in the molar ratio of 1:2 in a pestle and mortar arrangement and then the mix is further mixed with 3 times the weight of ammonium nitrate. The final mixture was heated first for 3 hours at 300°C and then heated at 700°C for 5 hours. Components Li2O Co(N03)2 Ammonium nitrate Pre heating temperature Final temperature Time Particle size of the product Nature of the product Efficiency of the process Composition 0.333g 0.667 g 3.00 g 300°C 700°C 8 hours 10-20 um Black > 80% Conclusion 1. Lithium oxide reacts with Co(NC>3)2 in equimolar proportion of 1:2 to form 2. Urea, ammonium nitrate and similar heat generating materials can be used as a self-heat generating materials without much change in efficiency or product compositions and these materials are significant in the formation of spinel structure. 3. The temperature of formation is in the range of 650°C to 700°C 4. The heating time is only around 8 hours. The main advantages of the present invention are 1. It is a single step solid state thermal process 2. LizO can be used to react with Co(NC>3)2to form LiCoC>2 of high capacity cathode for intercalation. 3. Heating time is only around 8 hours, and hence considerable heating time can be saved. We Claim: 1. A process for the preparation of lithium cobaltate by a solid state thermal one step process comprising mixing lithium oxide (Li2O) and cobalt nitrate (Co(NO3)2) in a ratio of 1:2 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. 2. A process as claimed in claim 1 wherein the ratio of the Li2O + Co (N03)2 mixture and the heat generating materials is 1:3. 3. A process as claimed in claim 1 wherein the ground mixture is heated in a furnace for about 8 hours. 4. A process as claimed in claim 1 wherein the heat generating material is selected from urea and ammonium nitrate. 5. A process as claimed in claim 1 wherein an electric furnace is used for heating. 6. A process for preparation of lithium cobaltate by a solid state thermal one step process as substantially as herein described with reference to examples accompanying the specification.

Documents:

2759-DELNP-2004-Abstract-(11-06-2008).pdf

2759-delnp-2004-abstract.pdf

2759-DELNP-2004-Claims-(11-06-2008).pdf

2759-delnp-2004-claims.pdf

2759-DELNP-2004-Correspondence-Others-(10-09-2008).pdf

2759-DELNP-2004-Correspondence-Others-(11-06-2008).pdf

2759-delnp-2004-correspondence-others.pdf

2759-delnp-2004-description (complete)-11-06-2008.pdf

2759-delnp-2004-description (complete).pdf

2759-delnp-2004-drawings.pdf

2759-delnp-2004-form-1.pdf

2759-delnp-2004-form-18.pdf

2759-DELNP-2004-Form-2-(11-06-2008).pdf

2759-delnp-2004-form-2.pdf

2759-DELNP-2004-Form-3-(11-06-2008).pdf

2759-delnp-2004-form-3.pdf

2759-delnp-2004-form-5.pdf

2759-DELNP-2004-Petition-137-(10-09-2008).pdf

2759-DELNP-2004-Petition-137-(13-06-2008).pdf