Extensive comparison of doping and coating strategies for Ni-rich positive electrode materials

Nickel-rich NMC (LiNi_xMn_yCo_1−x−yO₂, x ⩾ 0.8) electrode materials are known for their great potential as lithium battery cathode active materials due to their high capacities, low cost, and environment friendliness. However, these materials confront some technical challenges such as structural, surface, and electrochemical instability while different synthesis methods have large influences on NMC morphology, structure, and electrochemical performance. This review summarizes the most common synthesis techniques which have been employed to prepare high-quality Ni-rich positive electrode materials. Besides, recently reported and widely recognized studies on the degradation and mitigation mechanisms of Ni-rich electrodes are outlined in this paper. This review summarizes different studies on doping of Ni-rich materials which are useful for enhancing the capacity and performance and mitigating structural decay of the electrodes. Moreover, surface modifications by thin coatings with metal oxides and Li containing metal oxide layers are also reviewed as those overlayers can enhance stability of NMCs during the long-term cycling. Therefore, the focus of this paper is on fabrication of Ni rich NMC material, as well as reviewing the effect of doping, surface coating and synergistic effect of both for enhancing Ni-rich electrode material performance.