Layered lithium-rich transition metal oxides are promising cathode candidates for high-energy-density lithium batteries due to the redox contributions from transition metal cations and oxygen anions. However, their practical application is hindered by gradual capacity fading and voltage decay. Although oxygen loss and phase transformation are recognized as primary factors, the structural deterioration, chemical rearrangement, kinetic and thermodynamic effects remain unclear. Here we integrate analysis of morphological, structural and oxidation state evolution from individual atoms to secondary particles. By performing nanoscale to microscale characterizations, distinct structural change pathways associated with intraparticle heterogeneous reactions are identified. The high level of oxygen defects formed throughout the particle by slow electrochemical activation triggers progressive phase transformation and the formation of nanovoids. Ultrafast lithium (de)intercalation leads to oxygen-distortion-dominated lattice displacement, transition metal ion dissolution and lithium site variation. These inhomogeneous and irreversible structural changes are responsible for the low initial Coulombic efficiency, and ongoing particle cracking and expansion in the subsequent cycles.

由于过渡金属阳离子和氧阴离子的氧化还原贡献，层状富锂过渡金属氧化物是高能量密度锂电池的有前途的阴极候选者。然而，它们的实际应用受到容量逐渐衰减和电压衰减的阻碍。尽管氧损失和相变被认为是主要因素，但结构恶化、化学重排、动力学和热力学效应仍不清楚。在这里，我们整合了从单个原子到二次粒子的形态、结构和氧化态演变分析。通过进行纳米级到微米级表征，确定了与颗粒内非均相反应相关的不同结构变化途径。缓慢的电化学活化在整个颗粒中形成的高水平氧缺陷会触发进行相变和纳米空隙的形成。超快锂（脱层）导致氧畸变为主的晶格位移、过渡金属离子溶解和锂位点变化。这些不均匀和不可逆的结构变化是导致初始库仑效率低以及后续循环中持续颗粒开裂和膨胀的原因。