Authors: Junliang Lu, Bo Cao, Bingwen Hu, Yuxin Liao, Rui Qi, Jiajie Liu, Changjian Zuo, Shenyang Xu, Zhibo Li, Cong Chen, Mingjian Zhang, Feng Pan
Published: 2021-12-01
Source: Full article
AbstractLithium‐excess manganese layered oxide Li2MnO3, attracts much attention as a cathode in Li‐ion batteries, due to the low cost and the ultrahigh theoretical capacity (≈460 mA h g−1). However, it delivers a low reversible practical capacity (<200 mA h g−1) due to the irreversible oxygen redox at high potentials (>4.5 V). Herein, heavy fluorination (9.5%) is successfully implemented in the layered anionic framework of a Li–Mn–O–F (LMOF) cathode through a unique ion‐exchange route. F substitution with O stabilizes the layered anionic framework, completely inhibits the O2 evolution during the first cycle, and greatly enhances the reversibility of oxygen redox, delivering an ultrahigh reversible capacity of 389 mA h g−1, which is 85% of the theoretical capacity of Li2MnO3. Moreover, it also induces a thin spinel shell coherently forming on the particle surface, which greatly improves the surface structure stability, making LMOF exhibit a superior cycling stability (a capacity retention of 91.8% after 120 cycles at 50 mA g−1) and excellent rate capability. These findings stress the importance of stabilizing the anionic framework in developing high‐performance low‐cost cathodes for next‐generation Li‐ion batteries.