Single-crystal nickel-rich cathode materials: fundamentals, challenges and prospects

Single-crystal nickel-rich materials are considered promising cathode materials for high-energy lithium-ion batteries. The reduction in grain boundaries reduces the initiation and propagation of microcracks, thereby improving cycling stability and thermal resistance. However, the dense structure of single-crystal particles restricts lithium-ion diffusion and weakens interfacial stability, leading to poor rate performance. Therefore, further advancements are necessary to meet the performance requirements of next-generation lithium-ion batteries. This review summarizes current synthesis strategies-including co-precipitation combined with solid-state sintering, molten salt flux, sol-gel, spray pyrolysis, and solid-state methods-with an emphasis on their influence on particle morphology and crystallinity. Various modification techniques, such as element doping, surface coating, and interfacial engineering, are also discussed for their roles in enhancing lithium-ion transport and mitigating structural degradation. Comparative electrochemical analysis shows that single-crystal nickel-rich materials exhibit higher capacity retention and slower capacity fading than polycrystalline counterparts under high-rate and elevated-temperature conditions. However, issues such as sluggish lithium-ion diffusion kinetics, cation mixing, and intragranular cracking remain to be addressed. Future research should integrate a deeper understanding of failure mechanisms with scalable synthesis techniques and cost-effective processing to facilitate the commercial application of single-crystal nickel-rich cathodes.