| 摘要 |
A positive-electrode active material for a lithium-ion secondary battery has an average composition expressed by the following formula (1): <?in-line-formulae description="In-line Formulae" end="lead"?>LixCo1-y-zMyCezOb-aXa (1)<?in-line-formulae description="In-line Formulae" end="tail"?> wherein M represents at least one element selected from the group consisting of boron B, magnesium Mg, aluminum Al, silicon Si, phosphorous P, sulfur S, titanium Ti, chromium Cr, manganese Mn, iron Fe, cobalt Co, nickel Ni, copper Cu, zinc Zn, gallium Ga, yttrium Y, zirconium Zr, molybdenum Mo, silver Ag, tungsten W, indium In, tin Sn, lead Pb, and antimony Sb, X represents a halogen element, and x, y, z, a, and b satisfy 0.2<x<=1.2, 0<=y<=0.1, 0.5<z<=5.0, 1.8<=b<=2.2, and 0<=a<=1.0, respectively, and the concentration of cerium Ce is higher in the vicinity of the surface than in the inside.
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