POSITIVE ELECTRODE ACTIVE MATERIAL, POSITIVE ELECTRODE PLATE, LITHIUM ION SECONDARY BATTERY, AND APPARATUS

The present application discloses a positive electrode active material, a positive electrode plate, a lithium-ion secondary battery (5), and an apparatus. The positive electrode active material satisfies a chemical formula Li1+x(NiaCobMnc)1-dMdO2-yAy, wherein M is one or more selected from Zr, Sr, B, Ti, Mg, Sn and Al, A is one or more selected from S, N, F, Cl, Br and I, -0.01 ≤ x ≤ 0.2, a ≥ 0.5, 0.12 ≤ b/c ≤ 0.9, 0.002 ≤ b × c/a2 ≤ 0.23, a + b + c = 1, 0 ≤ d ≤ 0.1, and 0 ≤ y < 0.2; and an interval particle size distribution curve of the positive electrode active material has a full width at half maximum DFW of from 4 µm to 8 µm. The positive electrode active material provided in the present application has relatively low cobalt content and relatively high cycle life and capacity performance. The lithium-ion secondary battery (5) adopting the positive electrode active material can have both good cycle performance and relatively high energy density.