Role of Substitution Elements in Enhancing the Structural Stability of Li-Rich Layered Cathodes
Baodan Zhang, Yiming Zhang, Xiaotong Wang, Hui Liu, Yawen Yan, Shiyuan Zhou, Yonglin Tang, Guifan Zeng, Xiaohong Wu, Hong‐Gang Liao, Yongfu Qiu, Huan Huang, Lirong Zheng, Juping Xu, Wen Yin, Zhongyuan Huang, Yinguo Xiao, Qingshui Xie, Dong‐Liang Peng, Chao Li, Yu Qiao, Shi‐Gang Sun
Abstract
Element doping/substitution has been recognized as an effective strategy to enhance the structural stability of layered cathodes. However, abundant substitution studies not only lack a clear identification of the substitution sites in the material lattice, but the rigid interpretation of the transition metal (TM)–O covalent theory is also not sufficiently convincing, resulting in the doping/substitution proposals being dragged into design blindness. In this work, taking Li 1.2 Ni 0.2 Mn 0.6 O 2 as a prototype, the intense correlation between the “disordered degree” (Li/Ni mixing) and interface-structure stability (e.g., TM–O environment, slab/lattice, and Li + reversibility) is revealed. Specifically, the degree of disorder induced by the Mg/Ti substitution extends in the opposite direction, conducive to sharp differences in the stability of TM–O, Li + diffusion, and anion redox reversibility, delivering fairly distinct electrochemical performance. Based on the established paradigm of systematic characterization/analysis, the “degree of disorder” has been shown to be a powerful indicator of material modification by element substitution/doping.