| CPC H01M 4/364 (2013.01) [H01M 4/505 (2013.01); H01M 4/525 (2013.01); H01M 10/052 (2013.01)] | 20 Claims |

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1. An active material for a secondary battery,
the active material comprising aggregates, each including a plurality of single particles, or a mixture of the aggregates with non-aggregated single particles,
the active material comprising a first region having a relatively high content of an additional element (X) and a second region having a relatively low content of the additional element (X),
wherein the first region is at least one region of a grain boundary formed whereby the surfaces of the single particles constituting the aggregate contact one another and a void, pore or gap between the single particles, and/or a surface region of each single particle,
wherein the additional element (X) comprises at least one selected from the group consisting of Zr, Ti, Al, W, B, P, Mn, Ni, Mg, Cr, Ca, V, Sr, Y, F, Zn, Ga, Sn, Ru, Ce, La, and Si, and
the void is a crack-shaped gap, a hole-shaped pore, or both thereof.
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