| CPC H01M 4/62 (2013.01) [H01M 4/1391 (2013.01); H01M 4/364 (2013.01); H01M 4/38 (2013.01); H01M 4/525 (2013.01); H01M 10/0525 (2013.01); H01M 10/0562 (2013.01)] | 21 Claims |

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1. A positive active material for an all-solid secondary battery, the positive active material comprising:
a secondary particle including a plurality of primary particles; and
a buffer layer on a surface of the secondary particle;
wherein:
the secondary particle includes a nickel lithium transition metal oxide represented by Formula 1,
the buffer layer includes a copper compound represented by Formula 2,
LiaNibM1cO2-eAe <Formula 1>
in Formula 1,
M1 is an element of Groups 4 to 14,
A is F, S, Cl, Br, or a combination thereof; and
a, b, c, and e satisfy the following relations: 0.9≤a≤1.3, 0.5≤b<1, 0<c<1, b+c=1, and 0≤e<1,
LixCuyXz <Formula 2>
in Formula 2,
X is a halogen, and
x, y, and z satisfy the following relations: 1≤x≤3, 1≤y≤5, and 1≤z≤5.
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