the present invention relates to cobalt oxide particles useful as a precursor of a cathode active material for a non - aqueous electrolyte secondary cell which is capable of showing a stable crystal structure by insertion reaction therein , and producing a non - aqueous electrolyte secondary cell having a high safety and especially a high heat stability , a process for producing the cobalt oxide particles , a cathode active material for a non - aqueous electrolyte secondary cell using the cobalt oxide particles , a process for producing the cathode active material , and a non - aqueous electrolyte secondary cell using the cathode active material .