| CPC H01M 4/505 (2013.01) [C01G 53/50 (2013.01); H01M 4/525 (2013.01); H01M 10/0525 (2013.01); C01P 2006/32 (2013.01); C01P 2006/40 (2013.01); H01M 2004/028 (2013.01)] | 12 Claims |

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1. A lithium secondary battery comprising:
a positive electrode;
a negative electrode;
a separator interposed between the positive electrode and the negative electrode; and
an electrolyte,
wherein the positive electrode includes, as a positive electrode active material, a lithium composite transition metal oxide powder having a layered structure and a nickel content accounting for 50 atm % or more of total transition metals, wherein the lithium composite transition metal oxide is represented by Chemical Formula 1:
Lix[NiaCobMncMd]O2 [Chemical Formula 1]
wherein, in Chemical Formula 1,
M is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, Mo and Co, and the M essentially includes Zr, and 0.9<x<1.2, 0.80<a<0.99, 0<b<0.4, 0<c<0.4, and 0<d<0.2,
wherein the lithium composite transition metal oxide powder is prepared such that the lithium composite transition metal oxide powder has an amount of change in lithium-oxygen (Li—O) interlayer spacing (ΔT1), as represented by Equation (1), of 0 or more:
ΔT1=Tf−T0 Equation (1):
wherein, in Equation (1), Tf is a Li—O interlayer spacing in the lithium composite transition metal oxide in a fully charged state, and T0 is a Li—O interlayer spacing in the lithium composite transition metal oxide before charging.
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