Disclosed, as a particle for cathode active materials, is a novel one-body particle for cathode active materials, including a core of lithium transition metal oxide containing Ni and a surface-layer portion formed on at least a part of the core, wherein the surface-layer portion contains both Co and a structure-stabilizing element, the core is present as a non-aggregated primary particle, and the structure-stabilizing element has a bond dissociation energy (BDE) with oxygen (O) greater than a bond dissociation energy (BDE) of Co and oxygen (O).