Detailed analysis of the microstructural changes during lithiation of a full‐concentration‐gradient (FCG) cathode with an average composition of Li[Ni_0.75Co_0.10Mn_0.15]O₂ is performed starting from its hydroxide precursor, FCG [Ni_0.75Co_0.10Mn_0.15](OH)₂ prior to lithiation. Transmission electron microscopy (TEM) reveals that a unique rod‐shaped primary particle morphology and radial crystallographic texture are present in the prelithiation stage. In addition, TEM detected a two‐phase structure consisting of MnOOH and Ni(OH)₂, and crystallographic twins of MnOOH on the Mn‐rich precursor surface. The formation of numerous twins is driven by the lattice mismatch between MnOOH and Ni(OH)₂. Furthermore, the twins persist in the lithiated cathode; however, their density decrease with increasing lithiation temperature. Cation disordering, which influences cathode performance, is observed to continuously decrease with increasing lithiation temperature with a minimum observed at 790 °C. Consequently, lithiation at 790 °C (for 10 h) produced optimal discharge capacity and cycling stability. Above 790 °C, an increase in cation disordering and excessive coarsening of the primary particles lead to the deterioration of electrochemical properties. The twins in the FCG cathode precursor may promote the optimal primary particle morphology by retarding the random coalescence of primary particles during lithiation, effectively preserving both the morphology and crystallographic texture of the precursor.

中文翻译：

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锂离子电池浓度梯度Li [Ni0.75Co0.10Mn0.15] O2正极的微观结构演变

从其氢氧化物前体FCG [Ni _0.75 Co _0.10 Mn ]开始，对平均浓度为Li [Ni _0.75 Co _0.10 Mn _0.15 ] O ₂的全浓度梯度（FCG）阴极锂化过程中的微观结构变化进行详细分析。锂化之前为_0.15 ]（OH）₂。透射电子显微镜（TEM）显示，在预锂化阶段存在独特的棒状初级粒子形态和放射状晶体学织构。此外，TEM检测到由MnOOH和Ni（OH）₂组成的两相结构，以及富锰前体表面上的MnOOH晶体双晶。MnOOH和Ni（OH）₂之间的晶格失配驱动了许多孪晶的形成。此外，双胞胎仍留在锂化阴极中。但是，它们的密度随着锂化温度的升高而降低。观察到影响阴极性能的阳离子无序度随着锂化温度的升高而持续降低，在790°C时观察到的最小值。因此，在790°C（持续10 h）的锂化产生了最佳的放电容量和循环稳定性。高于790°C，阳离子无序度的增加和初级粒子的过度粗化会导致电化学性能下降。FCG阴极前体中的孪晶可通过延迟锂化过程中初级粒子的随机聚结来促进最佳的初级粒子形态，从而有效地保留前体的形态和晶体织构。