Designing principle for Ni-rich cathode materials with high energy density for practical applications

Nickel(Ni)-rich lithium transition metal oxides (e.g. LiNi0.8Co0.15Al0.05O2 (NCA), LiNi1-x-yMnxCoyO2 (x + y < 1) (NMC)) with layered structure are regarded as promising cathode candidates for constructing high energy density lithium ion batteries, so as to promote the market penetration of zero-emission electric vehicles. However, the poor structural and interfacial stability of Ni-rich NMC or NCA still hamper their large-scale applications. This review article mainly summarizes the recent progress achieved in the development of Ni-rich cathode materials, with an aim to provide important clues for future design Ni-rich cathodes and eventually enable their practical applications. Firstly, we introduce the improved method for the synthesis of Ni-rich cathode materials and discuss the relationships between the synthesis method, physicochemical properties, and the electrochemical performances of the cathode materials. Secondly, the insightful understandings on the capacity and voltage fading mechanism as well as the reasons of poor structure stability are comprehensively overviewed. Then, we summarize the main progress regarding to the novel approaches and attempts to prolong the cycling lifetime of Ni-rich materials and safety. Finally, we end up this review by proposing new perspectives and insights to stimulate more revolutionary strategies to boost the practical applications of Ni-rich cathodes.