Challenges and approaches of single crystal Ni-rich layered cathodes in lithium batteries

High-energy density and high safety are incompatible with each other in lithium battery, which challenges today's energy storage and power applications. Ni-rich layered transition metal oxides (NMC) have been identified as the primary cathode candidate for powering next-generation electric vehicles and were extensively studied in the last two decades, leading to the fast promotion on its market share including both polycrystalline and single crystal NMC cathodes. Compared to polycrystalline NMC, single crystal NMC appears to be the superior one, especially at low Ni content (≤ 60%). However, the Ni-rich single crystal NMC cathodes experience even faster capacity decay than the polycrystalline one, rendering them unsuitable for practical applications. Accordingly, this work will systematically review the attenuation mechanism of single crystal NMC and generate fresh insights into the valuable research pathway. This perspective is desired to provide an accurate direction for the development of Ni-rich single crystal NMC cathodes.