The cracking phenomenon of Ni-rich NMC (LiNi_xMn_yCo_1−x−yO₂, x ≥ 0.6) secondary particles is frequently discovered and believed to be one of critical reasons deteriorating the long-term cycling stability of NMC cathode in lithium ion batteries (LIBs). However, the initiation and evolution of those cracks is still controversial due to the limited quantification especially by in situ monitoring, leading to the challenge of identifying an efficient approach to inhibit the formation of the fractures during repeated cycling. Herein, the irreversible, anisotropic cycling lattice and mesoscale expansion/shrinkage of nano-grains during the first cycle, as revealed by in situ X-ray diffraction (XRD) and in situ atomic force microscopy (AFM), have been quantified and confirmed to be the dominant driving forces of microcracks initiation at the grain boundaries. These microcracks preferentially nucleate at the core region with random oriented nano-grains in early stage. The further growth and aggregation of microcracks into macrocrack eventually results in microfracture propagation radially outward to the periphery region with more uniform nano-grain orientation. This mesoscale nano-grain architecture controlled cracking process highlights the importance of predictive synthesis of cathode materials with controllable multiscale crystalline architecture for high-performance LIBs.

富含Ni的NMC（LiNi _x Mn _y Co _1−x-y O ₂，x≥0.6）二次粒子的开裂现象是经常发现的，并且被认为是降低NMC阴极长期循环稳定性的关键原因之一。锂离子电池（LIB）。然而，由于有限的量化，特别是通过现场监测，这些裂纹的产生和演化仍然存在争议，这导致了在重复循环期间确定抑制裂缝形成的有效方法的挑战。在这里，原位揭示了纳米颗粒在第一周期中不可逆的各向异性循环晶格和中尺度膨胀/收缩X射线衍射（XRD）和原位原子力显微镜（AFM）已被量化，并被证实是晶粒边界处微裂纹萌生的主要驱动力。这些微裂纹在早期以随机取向的纳米晶粒优先在核心区域成核。微裂纹的进一步生长和聚集最终成为大裂纹，最终导致微裂纹沿径向向外扩展到外围区域，纳米颗粒方向更均匀。这种中等规模的纳米颗粒结构受控的裂解过程突显了具有可控多尺度晶体结构的阴极材料的预测性合成对于高性能LIB的重要性。