1. An oxide-based positive electrode active material for all-solid-state lithium ion batteries, the oxide-based positive electrode active material having a compositional formula represented by:LiaNixCoyMn1-x-yO2, with 0.98 ≤ a ≤ 1.05; 0.8 ≤ x ≤ 1.0; and 0 ≤ y ≤ 0.20,wherein the oxide-based positive electrode active material has an average particle diameter D50 of from 1.0 to 5.0 µm, a tap density of from 1.6 to 2.5 g/cc, and a circularity of from 0.85 to 0.95.
positive electrode active material
D50
1.0 to 5.0 µm
µm
positive electrode active material
tap density
1.6 to 2.5 g/cc
g/cc