| 摘要 |
Provided are a cathode active material and a secondary battery both having a higher capacity and superior cycle characteristics and capable of obtaining a sufficient discharge capacity during large current discharge. A cathode ( 21 ) and an anode ( 22 ) with a separator ( 23 ) in between are spirally wound. The cathode ( 21 ) comprises a highly stable complex oxide Li<SUB>x</SUB>Ni<SUB>1-y-z</SUB>Mn<SUB>y</SUB>MI<SUB>z</SUB>O<SUB>2 </SUB>and a highly conductive complex oxide Li<SUB>8</SUB>MII<SUB>1-t-u</SUB>Mn<SUB>t</SUB>MIII<SUB>u</SUB>O<SUB>2</SUB>. Each of MI and MIII includes at least one kind selected from the group consisting of elements in Group 2 through Group 14, and MII includes at least one kind selected from the group consisting of Ni and Co, and the values of x, y, z, s, t and u are within a range of 0.9<=x<1.1, 0.25<=y<=0.45, 0.01<=z<=0.30, 0.9<=s<1.1, 0.05<=t<=0.20, and 0.01<=u<=0.10, respectively. The highly stable complex oxide in which an amount of substitution of a different element is larger and the highly conductive complex oxide in which an amount of substitution of a different element is smaller are mixed, so superior cycle characteristics and a sufficient discharge capacity during large current discharge can be achieved.
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