A Metastable Oxygen Redox Cathode for Lithium‐Ion Batteries
Yanfang Wang, Cheng Li, Yingzhi Li, Raquel de Benito, J. B. WILLIAMS, Joshua M. Stratford, Zhiqiang Li, Chun Zeng, Ning Qin, Hongzhi Wang, Yulin Cao, Dominic Gardner, Wilgner Lima da Silva, Sahil Tippireddy, Qingmeng Gan, Fangchang Zhang, Fangchang Zhang, Wen Luo, Joshua W. Makepeace, Ke‐Jin Zhou, Kaili Zhang, Fucai Zhang, Fucai Zhang, Phoebe K. Allan, Zhouguang Lu
Abstract
Abstract Simultaneously harnessing cation and anion redox activities in the cathode is crucial for the development of high energy‐density lithium‐ion batteries. However, achieving long‐term stability for both mechanisms remains a significant challenge due to pronounced anisotropic volume changes at low lithium content, unfavorable cation migration, and oxygen loss. Here, we demonstrate exceptionally stable cation and anion redox behavior in a metastable, cobalt‐free layered oxide, Li 0.693 [Li 0.153 Ni 0.190 Mn 0.657 ]O 2 (LLNMO). After 50 cycles at 50 mA/g (~0.2 C), the cathode retains 97.4 % of its initial capacity (222.4 mAh/g) with negligible voltage decay. This remarkable stability is attributed to its metastable O6‐type structure (R‐3m symmetry) with unique local geometry. The face‐sharing connectivity between lithium layers and alternating transition metal (TM) layers effectively suppresses TM migration‐induced voltage decay during anion redox. Additionally, the structure balances interlayer cation/cation and anion/anion repulsions, resulting in minimal expansion and contraction during de‐/lithiation (<2.3 % along the c ‐axis) and excellent structural reversibility. These findings highlight that layered oxides with a metastable framework are promising cathode candidates for next‐generation ultra‐high‐energy lithium‐ion batteries.