This book addresses the comprehensive understanding of Ni-rich layered oxide of lithium-ion batteries cathodes materials, especially focusing on the effect of dopant on the intrinsic and extrinsic effect to its host materials. This book can be divided into three parts, that is, 1. overall understanding of layered oxide system, 2. intrinsic effect of dopant on layered oxides, and 3. extrinsic effect of dopant on layered oxides. To truly understand and discover the fundamental solution (e.g. doping) to improve the Ni-rich layered oxides cathodic performance, understanding the foundation of layered oxide degradation mechanism is the key, thus, the first chapter focuses on discovering the true degradation mechanisms of layered oxides systems. Then, the second and third chapter deals with the effect of dopant on alleviating the fundamental degradation mechanism of Ni-rich layered oxides, which we believe is the first insight ever been provided. The content described in this book will provide research insight to develop high-performance Ni-rich layered oxide cathode materials and serve as a guide for those who study energy storage systems.