Lithium ion secondary battery, cathode active material therefor and production thereof

A non-aqueous electrolyte lithium ion secondary battery comprising a cathode, an anode comprising lithium, a lithium alloy or carbonaceous material which can intercalate or deintercalate lithium ions, a separator interposed between the cathode and the anode, and a lithium ion-conductive non-aqueous electrolyte, in which the cathode comprises as a cathode active material a substituted lithium cobalt composite oxide which has the general formula:

• LixMyCo1−yO2
• in which M represents at least one metallic element selected from the group consisting of Ti and Mo;
• x is in the range of 0.8 to 1.2;
• and y is in the range of 0.001 to 0.10, an electrically conductive material and a binder, wherein the substituted lithium cobalt composite oxide is such that it is prepared by mixing powders of a lithium compound, a cobalt compound and a compound of the substitution element M in methanol in such a molar ratio of the elements, Li, Co and M as to meet the general formula, to prepare a mixture in the form of paste, drying the resulting mixture and firing the dried mixture at a temperature in the range of 600° C. to 1100° C. under an oxidative atmosphere.