A review of nickel-rich layered oxide cathodes: synthetic strategies, structural characteristics, failure mechanism, improvement approaches and prospects

Nickel-rich layered oxide cathode materials have high specific capacity and are environmentally-benign, hence they are considered as the most relevant next-generation positive-electrode materials for lithium-ion batteries, particularly for powering plug-in hybrid electric vehicles and battery electric vehicles. The rich nickel content in layered oxides is highly beneficial in improving the energy density, but the cycle ability, rate capability and thermal stability inevitably decrease with the increase of nickel percentage, leading to the gradual failure of lithium-ion batteries. Therefore, it is an essential requisite to give a thorough review of previous research, thereby providing a clear understanding of the relationships between the material structure and their electrochemical activities, and improving the electrochemical performances of nickel-rich layered oxide cathode materials through reasonable modifications. In this article, the structural characteristics and synthetic methods are systematically reviewed. Particularly, the capacity failure mechanism and the corresponding improvement strategies of nickel-rich layered oxides are emphasized and discussed from atomic scale to macro-scale along with the latest literature review. A brief analysis of the perspectives is also presented with several possible research directions for technical and commercial success of nickel-rich layered oxide cathodes.