Title of Invention | "A PROCESS FOR THE SYNTHESIS OF LI CO0.5 MN0.5O2 USEFUL AS CATHODE MATERIAL FOR REVERSIBLE LITHIUM ION CELLS" |
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Abstract | The present invention provides a process for the synthesis of LiCoo.s Mno.5O2 cathode material for reversible lithium ion cells. The composite is very useful for high voltage lithium reversible cells and can be prepared by mixing oxides of cobalt, manganese with lithium hydroxide by heating together all in solid state condition. A novel method of preparing LI LiCoo.5Mno.5O2 was carried out by uniform mixing of oxides of Co and Mn with LiOH and this mixture was made into a paste by adding necessary quantity of glycerol an the paste was calcined at 750°C. continuously for 12 hrs in a furnace. The prepared product was subjected to x-ray analysis. The product was found to be in single phase. |
Full Text | This invention relates to a process for the synthesis of LiCo0.5 Mn0.5O2 useful s cathode material for reversible lithium ion cells. This invention relates to the preparation of lithium cobalt manganite (LiCo0.5 Mn0.5O2) a composite, which is very useful for high voltage lithium reversible cells and can be prepared be prepared by mixing oxides of cobalt, manganese with lithium hydroxide by heating together all in solid state condition. LiCo0.5 Mn0.5O2 is a reversible cathode material useful for high voltage cells of lithium in nonaqueous media. LiCo0.5 Mn0.5O2 compound is hexagonal material is well known from 1995 as a good battery cathode for reversibility in nonaqueous solutions. This compound can be prepared from LiOH / Li2Co3 Ni(OH) and MnCO3. They were mixed together and heated at 700-850°C in O2 atmosphere [Y. Nitta, K.Okamura, K.Haraguchi, S.Kobayashi and A. Ohta, J. Power Sources, 54 (1995) 511. In the above procedure available in the literature, some disadvantages were observed. They are as follows Phase impurity Longer duration of thermal preparation Several steps of preparation The object of this invention is to synthesis LiCo0.5 Mn0.5O2under suitable solid state reaction method which obviates the defects and draw backs hither to known in other method of preparation of related compound from already known procedure in literatures. But in the literature, no information is available about LiCoo.5 Mno.5 O2. Another object of the invention is to provide a process for the synthesis of LiCo0.5 Mn0.5O2 cathode material for reversible lithium ion cells. Accordingly the present invention provides a process for the synthesis of LiCoo.s Mno.sO2 useful as cathode material for reversible lithium ion cells which comprises: preparing a paste of LiOH, Co3O4 and Mn2O3 in a molar ratio of 1: 1/2 : 1/2 respectively in glycerol and optionally in presence of binding agent, heating the paste so obtained slowly up to 250°C to get dried mass and followed by heating at 600-800 °C for 10-12 hrs to obtain lithium cobalt manganite LiCo0.5 Mn0.5O2 In an embodiment of this invention the molar ratios of LiOH, Co3O4 and Mn2O3 may be 1: 1/2 :1/2 In another embodiment of this invention the temperature of preparation of LiCoi/2 Mni/2 O2 is in between 600-800°C for 12 hours. In yet another embodiment of this invention glycerol used as a binding agent for uniform product formation this prevents nay side reaction or partial reaction. A novel method of preparing LI Co0.5 Mn0.5O2 was carried out by uniform mixing of oxides of Co and Mn with LiOH and this mixture was made into a paste by adding necessary quantity of glycerol an the paste was calcined at 750°CcontinuousIy for 12 hrs in a furnace. The prepared product was subjected to x-ray analysis. The product was found to be in single phase. The present invention, describes the method of synthesis of cathode material for a secondary battery, by heating a paste prepared by mixing fine particles of LiOH, Mn2O3 and Co3O4 in glycerol. This paste was initially heated slowly in a furnace to evaporate off glycerol in order to get a dried mass at 250°C. This dried mass was then continuously heated to 750°C for 12 hrs. The compound formed was slowly cooled to room temperature and was ground well and then examined for its particles size, colour and XRD exposure. It was found that the prepared sample was brownish black in colour and was homogenous. X-rays analysis confirmed the formation of LiCo05 Mn05O2 according to Fig. I. The paste of Li, Co and Mn salt may be prepared by adding glycerol optionally in presence of citric acid or urea as binding agent. The novelty of this method is that the carbonates of Li and Mn are avoided. Therefore the reduction of oxides CO2 is considerably decreased during the complex spinal compound formation followed by better yield and purer product. The novelty of this process is highlighted as follows: This process gives pure product and leaves behind no unreacted components. This has been identified by x-ray analysis. This process does not produce any side reactions or partial reaction. The time takes for the thermal preparations of the product is less then other methods due to the addition glycerol as binding agent. It is simple process and needs one step only. The following examples are given by the way of illustration and should not construed the scope of this invention. Hydroxides of lithium & oxides of Mn and Co were taken as a mixture and mixture was ground together in a pestle and mortar arrangement to get a fine powder. To these powder small quantities of glycerol was added and again ground well till a fine paste was formed. The paste was transferred to a crucible (silica or porcelain). The content was initially heated slowly to 200°C & then finally strongly to 800°C for 12 hours. The product formed was cooled & ground well to a nice powder & was subjected to x-ray analysis for confirmly & purity. The following examples are given by way of synthesizing LiCo0.5 Mn0.5O2 Example -1 Components LiOH 0.839 gm Co3O4 0.802 gm Mn2O3 0.788 gm Flux (urea) 2.402 gm Binder (Glycerol) 3 ml Temperature 750°C Duration of heating 12 hrs Colour of the product brownish black Efficiency of the product 92% Phase Single Single electrode potential of LiCo0.5 Mn0.5O2 w.r.t in 1M LiClO4 3.01v In propylene carbonate A standard procedure to measure the single electrode potential of the cathode. LiOH, Co3O4 and Mn2O3 compounds are taken is 1 :1/2: 1/2 molar proportion a mortar. Glycerol was added small quantity and the mixture was ground well with a pestle. Addition of glycerol was continued till an uniform paste was formed. The sample is the form of paste was transferred in to silica vessel & was kept in a muffle furnace. Example - 2 Components LiOH 0.839 gm Co3O4 0.802 gm Mn2O3 0.788 gm Flux (urea) 2.402 gm Binder (Glycerol) 3 ml Temperature 750°C Duration of heating 12hrs Colour of the product brownish black Efficiency of the product 92% Phase Single Single electrode potential of LiCo0.5 Mn0.5O2w.r.t in 1M LiClO4 3.01V In propylene carbonate A co-pending application no. 395 del 2001 relates to 'A novel wet grinding procedure for the synthesis of LiCOMnO4 battery cathode material for rocking chair lithium ion cells'. Hydroxides of lithium & oxides of Mn and Co were taken as a mixture and mixture was ground together in a pestle and mortar arrangement to get a fine powder. To this powder small quantities of glycerol was added and again ground well till a fine paste was formed. The paste was transferred to a crucible (silica or porcelain). The content was initially heated slowly to 200°C & then finally strongly to 75°C for 12 hours. The product formed was cooled & ground well to a nice powder & was subjected to x-Cray analysis for confirmly & purity. A standard procedure to measure the single electrode potential of the cathode. The advantages for the preparation of LiCo0.5 Mn0.5O2 are follows: 1. Fine particles of the reactants viz LiOH, Mn2O3 and Co3O4 were bound by glycerol and made the mixture into a paste for uniform reaction during heating. 2. Glycerol is used as a binder for the inorganic solid state reactants 3. The process of present invention provides a single phase component LiCo0.5 Mn0.5O2 free from impurities as evidenced by x-ray analysis. 4. All the reactants react uniformly leaving no un-reacted initial reactant components. 5. Addition of glycerol as a binder has no influence in the formation of the final product. 6. An uniform homogeneous mixture of the ground compounds viz, oxides of manganese and Cobalt with LiOH were made into a paste to get a product of high purity. 7. Glycerol was used as a solvent for biding the oxides viz, manganese and cobalt with LiOH for making a paste of required consistency. The addition of glycerol enhanced the product of fine particles. 8. The addition of flux (urea) / excess addition of glycerol (solvent) as a binding material for oxides does not change the colour or quality of the end product. We Claim: 1. A process for the synthesis of LiCoo.5 Mno 5O2 useful as cathode material for reversible lithium ion cells which comprises: preparing a paste of LiOH, CO3O4 and Mn2O3 in a molar ratio of 1:1/2 :1/2respectively in glycerol and optionally in presence of binding agent, heating the paste so obtained slowly up to 250°C to get dried mass and followed by heating at 600-800 °C for 10-12 hrs to obtain lithium cobalt manganite (LiCoos Mn0 502). 2. A process as claimed in claim 1 wherein the binding agent are selected from citric acid or urea. 3. A process for the synthesis of LiCoo.5 Mno 5O2 useful as cathode material for reversible lithium ion cells substantially as herein described with reference to the examples and drawing accompanying the specification. |
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396-del-2001-correspondence-others.pdf
396-del-2001-correspondence-po.pdf
396-del-2001-description (complete).pdf
Patent Number | 231656 | |||||||||||||||
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Indian Patent Application Number | 396/DEL/2001 | |||||||||||||||
PG Journal Number | 13/2009 | |||||||||||||||
Publication Date | 27-Mar-2009 | |||||||||||||||
Grant Date | 07-Mar-2009 | |||||||||||||||
Date of Filing | 29-Mar-2001 | |||||||||||||||
Name of Patentee | COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH | |||||||||||||||
Applicant Address | RAFI MARG, NEW DELHI-110 001, INDIA. | |||||||||||||||
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PCT International Classification Number | H01M 4/50 | |||||||||||||||
PCT International Application Number | N/A | |||||||||||||||
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