Patent ID: 7442469

Claim:
A cathode active material comprising: a first composite oxide; and a second composite oxide mixed with said first composite oxide, wherein said first composite oxide is a zirconium-containing lithium cobalt composite oxide containing zirconium as a sub-component element in a first lithium cobalt composite oxide, and said first lithium cobalt composite oxide is Li t CoM s O 2 , where M denotes at least one kind of element selected from iron, vanadium, chromium, titanium, magnesium, aluminum, boron, and calcium, where s is a value within a range of 0≦s≦0.03, and where t is a value within a range of 0.05≦t≦1.15, wherein said second composite oxide is a second lithium cobalt composite oxide expressed by Li x Co l-y A y O 2 , where A denotes at least one kind of element selected from magnesium and aluminum, where x is a value within a range of 0.05≦x≦1.15, and where y is a value within a range of 0≦y≦0.03, wherein a content of said zirconium ranges from 0.0005 to 0.01 as a mole ratio Zr/Co to cobalt in the first lithium cobalt composite oxide, and wherein a content of the second lithium cobalt composite oxide ranges from 10 wt % to 40 wt %.