Spontaneous Strain Buffer Enables Superior Cycling Stability in Single-Crystal Nickel-Rich NCM Cathode

The capacity degredation in layered Ni-rich LiNi x Co y Mn z O 2 ( x ≥ 0.8) cathode largely originated from drastic surface reactions and intergranular cracks in polycrystalline particles. Herein, we report a highly stable single-crystal LiNi 0.83 Co 0.12 Mn 0.05 O 2 cathode material, which can deliver a high specific capacity (∼209 mAh g –1 at 0.1 C, 2.8–4.3 V) and meanwhile display excellent cycling stability (>96% retention for 100 cycles and >93% for 200 cycles). By a combination of in situ X-ray diffraction and in situ pair distribution function analysis, an intermediate monoclinic distortion and irregular H3 stack are revealed in the single crystals upon charging–discharging processes. These structural changes might be driven by unique Li-intercalation kinetics in single crystals, which enables an additional strain buffer to reduce the cracks and thereby ensure the high cycling stability.