The positive electrode active material and a method of manufacturing the same for lithium secondary battery

It is to provide a cathode active material for a lithium ion secondary battery, which has high safety, a high discharge voltage, a large capacity and excellent cyclic durability, and a process for producing it. A cathode active material for a lithium secondary battery, characterized by comprising a particulate lithium cobalt composite oxide represented by the formula Li a Co b Al c Mg d A e O f F g (1) (wherein A is Ti, Nb or Ta, O.90<=a<=1.10, 0.97<=b<=1.00, 0.000l<=c<=0.02, 0.000l<=d<=0.02, 0.000l<=e<=0.01, 1.98<=f<=2.02, 0<=g<=0.02, and 0.0003<=c+d+e<=0.03).