Challenges and Strategies towards Single‐Crystalline Ni‐Rich Layered Cathodes

The ever-increasing energy density requirements in electric vehicles (EVs) have boosted the development of Ni-rich layered oxide cathodes for state-of-the-art lithium-ion batteries. Nevertheless, the commercialization of polycrystalline Ni-rich cathodes (PCNCs) is hindered by the severe performance degradation and safety concerns that are tightly related to its particle cracking during cycling. Single-crystalline Ni-rich cathodes (SCNCs) with eliminated grain boundaries and high mechanical strength have recently attracted extensive attention owing to their superior structural and cycling stability, which present high crack resistance during electrochemical operation. Various articles have focused on the trial-and-error synthesis and modifications of SCNCs, as well as the comparison of performances and mechanisms with PCNCs. However, there has been much less effort in systematic analysis and summary to reveal their key challenges, controversies, and the corresponding primary causes. In this review, the advantages and debates in structural and electrochemical properties of SCNCs over PCNCs are summarized to provide fundamental understanding of SCNCs. Then the current practical issues and challenges are comprehensively discussed from the viewpoints of both academia and industry, as well as the proposed modification strategies and underlying mechanisms for SCNCs. The outlook and perspectives are further given to facilitate the commercial applications of SCNCs in high-performance EVs.