Positive Electrode Active Material for All-Solid-State Lithium Secondary Batteries

A positive electrode active material for an all-solid-state lithium secondary battery, which is capable of improving the rate characteristics, the cycle characteristics, and the initial charge and discharge efficiency even in the case where a sulfide-based solid electrolyte is used, wherein the surface of a lithium-containing composite oxide, referred to as present core particles, is coated with a compound, referred to as, LiAO compound, containing Li, A, where A represents one or more elements selected from the group consisting of Ti, Zr, Ta, Nb, Zn, W, and Al, and O; and a halogen is present on the surface of the present core particles.