| 摘要 |
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>p</SUB>Co<SUB>x</SUB>M<SUB>y</SUB>O<SUB>z</SUB>F<SUB>a </SUB>(wherein M is a transition metal element other than Co or an alkaline earth metal element, 0.9<=p<=1.1, 0.980<=x<=1.000, 0<=y<=0.02, 1.9<=z<=2.1, x+y=1 and 0<=a<=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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