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Abstract

A positive electrode active material for a lithium secondary battery containing a lithium-cobalt composite oxide, which has a large volume capacity density, has a high safety and is excellent in charge and discharge cyclic durability, and its production process, are provided. A lithium-cobalt composite oxide represented by the formula Li.sub.pCo.sub.xM.sub.yO.sub.zF.sub.a (wherein M is a transition metal element other than Co or an alkaline earth metal element, 0.9.ltoreq.p.ltoreq.1.1, 0.980.ltoreq.x.ltoreq.1.000, 0.ltoreq.y.ltoreq.0.02, 1.9.ltoreq.z.ltoreq.2.1, x+y=1 and 0.ltoreq.a.ltoreq.0.02) and comprising a mixture containing substantially spherical hard first particles of lithium-cobalt composite oxide having such a sharp particle size distribution that the volume basis cumulative size D10 is at least 50% of the average particle size D50, and the volume basis cumulative size D90 is at most 150% of the average particle size D50, and second particles of lithium-cobalt composite oxide filling the space among the first particles, in a mass ratio of first particles/second particles of from 1/2 to 9/1, and process for producing the same.

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First Claim