Positive electrode active material and lithium ion secondary battery

Abstract

The positive electrode active material includes single crystal particles and polycrystalline particles, the polycrystalline particles are formed by associating a plurality of the single crystal particles, each of the single crystal particles and the polycrystalline particles includes a lithium nickel composite oxide having a layered structure, and the single crystal particles satisfy all relationships of the following formulas (1) to (3). In the formulas (1) to (3), D10, D50 and D90 each represent a particle diameter having an integrated value of 10%, a particle diameter having an integrated value of 50%, and a particle diameter having an integrated value of 90% in a volume-based particle size distribution of the single crystal particles, and D10, D50 and D90 each have units of micrometers. D ⁢ 10 ≤ 2.5 ( 1 ) D ⁢ 50 ≤ 5. ( 2 ) ( D ⁢ 90 - D ⁢ 1 ⁢ 0 ) / D ⁢ 5 ⁢ 0 ≥ 3. ( 3 )

Dependencies are inferred from the claim text.