Electro-mechanical degradation is commonly observed in various battery electrode materials, which are often prepared as polycrystalline particles consisting of nanoscale primary grains. The anisotropic volume change during lithium extraction/insertion makes these materials intrinsically vulnerable to grain-boundary (inter-granular) fracture that leads to rapid impedance growth and capacity decay. Here, guided by fracture mechanics analysis, we synthesize microsized single-crystal Ni-rich layered-oxide (NMC) cathode materials via an industrially-applicable molten-salt approach. Using single-crystal LiNi_0.6Mn_0.2Co_0.2O₂ as a model material, we show that the cycle performance of the Ni-rich NMC can be significantly improved by eliminating the internal grain boundaries and inter-granular fracture. The single-crystal LiNi_0.6Mn_0.2Co_0.2O₂ cathodes show high specific capacity (183 mAh g⁻¹ at 0.1 C rate, 4.3−2.8 V) and excellent capacity retention (94% after 300 cycles at 1C/1C cycling). Further, it is confirmed for the first time that the single-crystal LiNi_0.6Mn_0.2Co_0.2O₂ particles are stable against intra-granular fracture as well under normal operating conditions but do crack if severely overcharged. Electrochemical-shock resistant single-crystal NMC reveals an alternative path towards developing better battery cathode materials, beyond the traditional one built upon polycrystalline NMC.

通常在各种电池电极材料中观察到机电降解，所述电池电极材料通常被制备为由纳米级一次晶粒组成的多晶颗粒。锂提取/插入过程中的各向异性体积变化使这些材料本质上易受晶界（晶间）断裂的影响，从而导致阻抗快速增长和电容衰减。在这里，在断裂力学分析的指导下，我们通过工业上可应用的熔融盐法合成了微米尺寸的单晶富镍层状氧化物（NMC）阴极材料。使用单晶LiNi _0.6 Mn _0.2 Co _0.2 O ₂作为模型材料，我们表明，通过消除内部晶界和晶间断裂，可以显着改善富镍NMC的循环性能。单晶LiNi _0.6 Mn _0.2 Co _0.2 O ₂阴极显示出高的比容量（0.1 C速率，4.3-2.8 V时为183 mAh g ^-1）和出色的容量保持率（在1C / 1C循环300次循环后为94％）。此外，首次确认了单晶LiNi _0.6 Mn _0.2 Co _0.2 O ₂颗粒在正常工作条件下也能抵抗颗粒内破裂，但如果过度充电，则会破裂。耐电化学冲击的单晶NMC揭示了开发更好的电池阴极材料的另一条途径，这超越了基于多晶NMC的传统阴极材料。