Layered Li(Ni_1−x−yCo_xMn_y)O₂ (NCM, with Ni ≥ 0.8) cathode materials are essential in achieving high energy densities in the next generation of lithium-ion batteries. To extend the materials' lifetime, it is necessary to understand the role played by crystal defects in the degradation during electrochemical cycling. In this study, NCM851005 (85% Ni) is investigated in the pristine state and after 100 and 200 cycles using scanning transmission electron microscopy, with the focus on the defects in the material. The formation of antiphase boundaries (APBs) from a dislocation in a pristine sample is proven. After 100 cycles, the APBs' length and width are enlarged compared with the pristine state. After 200 cycles, APBs further evolve into an intragranular rock-salt-like phase, distorting the nearby layered structure. It is suggested that the behavior of APBs plays a critical role in determining the performance of this cathode material with prolonged electrochemical cycling.

层状 Li(Ni _{1− x − y} Co _x Mn _y )O ₂（NCM，Ni≥0.8）正极材料对于实现下一代锂离子电池的高能量密度至关重要。为了延长材料的使用寿命，有必要了解晶体缺陷在电化学循环过程中的降解中所起的作用。在这项研究中，NCM851005（85% Ni）在原始状态下和 100 次和 200 次循环后使用扫描透射电子显微镜进行了研究，重点是材料中的缺陷。证明了原始样品中位错的反相边界 (APB) 的形成。100 次循环后，APB 的长度和宽度与原始状态相比有所扩大。200 次循环后，APBs 进一步演化为粒内岩盐状相，扭曲附近的层状结构。