Cathode active material for non-aqueous electrolyte secondary cell and process for producing the same

Abstract

A cathode active material for a non-aqueous electrolyte secondary cell having a c-axis length of lattice constant of 14.080 to 14.160 Å, an average particle size of 0.1 to 5.0 μm, and a composition represented by the formula: LiCo (1-x-y) Mn x Mg y O 2 where x is a number of 0.008 to 0.18; and y is a number of 0 to 0.18. This cathode active material is capable of maintaining an initial discharge capacity required for secondary cells and shows improved charge/discharge cycle characteristics under high temperature conditions.

1 .- 4 . Canceled.  
     
     
         5 . A process for producing the cathode active material for a non-aqueous electrolyte secondary cell, comprising: 
 adding an aqueous alkali solution to a solution containing a cobalt salt and a manganese salt with or without a magnesium salt to conduct a neutralization reaction therebetween;    oxidizing a resultant mixed solution by passing an oxygen-containing gas therethrough to obtain a cobalt oxide containing manganese or both manganese and magnesium;    mixing the cobalt oxide with a lithium compound; and    heat-treating a resultant mixture of the cobalt oxide and the lithium compound.    
     
     
         6 . A process according to  claim 5 , wherein the manganese salt is added in an amount of 0.1 to 20 mol %, calculated as manganese, based on cobalt; the magnesium salt is added in an amount of not more than 20 mol %, calculated as magnesium, based on cobalt; the equivalent ratio of alkali contained in the aqueous alkali solution added for the neutralization reaction to a neutralized component of the whole metal salts is 1.0 to 1.2; the oxidation reaction temperature is not less than 30° C.; the mixing molar ratio of lithium to a sum of cobalt and manganese is 0.95 to 1.05; and the heat-treating temperature is 600 to 950° C.  
     
     
         7 .- 10 . Canceled.  
     
     
         11 . The process of  claim 5  wherein cathode active material has a c-axis length of lattice constant of 14.080 to 14.160 Å, an average particle size of 0.1 to 5.0 μm, and a composition represented by the formula:  
       LiCo (1-x-y) Mn x Mg y O 2    
       wherein x is a number of 0.008 to 0.18; and y is a number of 0 to 0.18.  
     
     
         12 . The process according to  claim 11  wherein the cathode active material has an a-axis length of lattice constant of 2.81 to 2.83 Å.  
     
     
         13 . The process according to  claim 11  wherein the cathode active material has a BET specific surface area of 0.1 to 2.5 m 2 /g and a crystallite size of 400 to 1,200 Å.  
     
     
         14 . The process according to  claim 11  wherein the cathode active material in which y is 0.01 to 0.15.