Boosting the Structural Reversibility of Layered Oxide Cathode for Realizing Long‐Term Cycle Life Through Electronic Structure Regulation
Guohua Zhang, Yuheng Gao, Yuxin Fan, Yuheng Gao, Jianwei Wu, Jiwei Ma, Renyuan Zhang, Yunhui Huang
Abstract
Abstract O3‐type layered oxide cathode exhibits great application potential for practical sodium‐ion batteries, due to its cost‐effectiveness, abundant sodium and manganese resources, and high theoretical capacity. However, the irreversible phase transition, coupled with rapid capacity decay, which is primarily attributed to the Jahn‐Teller effect of Mn 3+ , remains a significant bottleneck for commercial application. Additionally, the sluggish kinetics during the (de)sodiation process require urgent improvement. Herein, an electronic structure regulation strategy is proposed by low‐valence Li/Cu co‐substitution to address these issues. The roles of Li/Cu on the electronic structure, structural evolution, and electrochemical properties in the Na 0.96 Ni 0.22 Fe 0.2 Mn 0.5 Li 0.04 Cu 0.04 O 2 (NFMLC) cathode are comprehensively explored through systematic in situ / ex situ characterization techniques and theoretical calculations. The results reveal that this strategy effectively activates more Ni 2+/3+ and Fe 3+/4+ redox reactions above 2.5 V, while suppressing Mn 3+/4+ redox activity below 2.5 V, thereby achieving highly structural reversibility. Therefore, the NFMLC electrode displays excellent long‐term cycling stability (81.5% capacity retention after 2000 cycles at 5 C), and significantly enhanced rate performance (from 45.5% to 80.4% under a ratio of 5 C to 0.5 C). This work provides a valuable perspective on the design of low‐cost, long‐life, and high‐performance layered oxide cathodes for practical sodium‐ion batteries.