Abstract: Provided is a lithium iron thiophosphate compound represented by a general formula: Li2xFe1-xPS3 wherein x is more than 0 and less than 1. This compound provides a lithium battery having high out put as well as high energy density when used as an electrode active material.

Abstract: A lamellar sodium-cobalt-manganese oxide represented by the general formula NaxCoyMn1−yO2 (where 0.6≦x≦0.8, 0.4≦y≦0.6) is disclosed, which is obtained by the steps of: mixing a sodium salt, a cobalt salt and a manganese salt in an aqueous solution state so as to be a molar ratio of sodium, cobalt and manganese of x: y: 1−y (where 0.6≦x≦0.8, 0.4≦y≦0.6) and drying the obtained mixture, sintering the obtained dried body in an oxygen-containing gas at 700 to 900° C., and quenching the sintered body from a temperature between 700° C. and 800° C. The lamellar sodium-cobalt manganese oxide of the present invention has a uniform composition and a single crystal structure, which is useful as an electrode active material for a lithium ion secondary battery.