Abstract: A cathode active material contains a secondary particle containing or consisting of a group of a plurality of primary particles. At least some of the primary particles disposed on the surface of the secondary particle include first primary particle in the form of flakes having a pair of first crystal faces facing toward each other. The first crystal faces are arranged in a radial direction, ends of the first crystal faces pair are provided with a plurality of crystal faces different from the first crystal faces to connect the ends of the first crystal faces pair. Longitudinal cross-sections of the first primary particle contain a pair of first crystal faces spaced apart from each other. Second and third crystal faces are disposed in the outermost surface of the secondary particle to be connected to each other at an angle.