| CPC H01M 4/525 (2013.01) [H01M 4/0404 (2013.01); H01M 4/505 (2013.01); H01M 10/052 (2013.01)] | 8 Claims |

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1. A cathode material for a secondary battery, comprising:
a cathode active material and an irreversible additive,
the irreversible additive being an oxide represented by the following Chemical Formula 1,
wherein the oxide has a monoclinic crystal structure prior to an initial charge of the secondary battery,
Li2+aCu1−bMbO2+c (1)
in Formula 1, −0.2≤a≤0.2, 0≤b<0.5, 0≤c≤0.2, and
M is one or more elements selected from the group consisting of Ni, Mg, Pt, Al, Co, P, and B
wherein the cathode active material comprises an oxide represented by the following Chemical Formula 2,
Li(NiaCobMnc)O2 (2)
in Formula 2, 0<a<1, 0<b<1, 0<c<1, a+b+c=1.
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