Ni-rich cathode materials have emerged as a class of low-cost and high-energy-density Li ions batteries cathodes. However, the bulk and surface degradation of Ni-rich cathode remains controversial. By transmission electron microscopy (TEM), the bulk and surface degradation of nickel-rich cathode are distinguished by the causes and development time. Structure deterioration with rock-salt phase is observed in the bulk and surface region. The triggered phase transition by defect chain reaction (DCR) mechanism is unveiled by the first-principle-calculation simulations. The critical factor in DCR mechanism is the migration barrier of Ni. The decrease in migration barrier of Ni due to the oxygen vacancy and the lowering of the system energy by the Li ion compensation causes extra cation mixing and lattice distortion. Hence, Ni ion migration introduces strain perpendicular to the Ni layers with oxygen defects and Li vacancies, which leads to dislocations and defects with lattice distortion. Based on the model, a manganese oxide coating method was proposed to adjust the valence state of nickel and avoid the oxygen defects. The treated cathode presented an excellent long-term cycling performance, about 80.6% of the initial capacity after 200 cycles.

富镍阴极材料已成为一类低成本，高能量密度的锂离子电池阴极。然而，富镍阴极的整体和表面降解仍存在争议。通过透射电子显微镜（TEM），富镍阴极的体积和表面降解可以通过原因和显影时间来区分。在大块和表层区域观察到盐岩相引起的结构恶化。通过第一原理计算仿真揭示了缺陷链反应（DCR）机制触发的相变。DCR机制的关键因素是Ni的迁移势垒。由于氧空位而导致的Ni迁移势垒的降低以及通过Li离子补偿引起的系统能量的降低导致额外的阳离子混合和晶格畸变。因此，Ni离子迁移引入垂直于具有氧缺陷和Li空位的Ni层的应变，这导致具有晶格畸变的位错和缺陷。在此模型的基础上，提出了一种锰氧化物涂层方法，以调节镍的价态并避免氧缺陷。处理后的阴极具有出色的长期循环性能，约200次循环后的初始容量的80.6％。