Regulating the Anion Redox and Suppressing the Structural Distortion of Cation-Disordered Rock-Salt Cathode Materials to Improve Cycling Durability through Chlorine Substitution
Weijian Tang, Guojun Zhou, Chengzhi Hu, Afei Li, Zhangxian Chen, Zeheng Yang, Jianhui Su, Weixin Zhang
Abstract
Owing to the capacity boost from anion redox activities, cation-disordered rock-salt oxides are considered as potential candidates for the next-generation of high energy density Li-ion cathode materials. Unfortunately, the anion redox process that affords ultra-high specific capacity often triggers irreversible O 2 release, which brings about structural degradation and rapid capacity decay. In this study, we present a partial chlorine (Cl) substitution strategy to synthesize a new cation-disordered rock-salt compound of Li 1.225 Ti 0.45 Mn 0.325 O 1.9 Cl 0.1 and investigate the impact of Cl substitution on the oxygen redox process and the structural stability of cation-disordered rock-salt cathodes. We find that partial replacement of O 2– by Cl – expands the cell volume and promotes anion redox reaction reversibility, thus increasing the Li + ion diffusion rate and suppressing irreversible lattice oxygen loss. As a result, the Li 1.225 Ti 0.45 Mn 0.325 O 1.9 Cl 0.1 cathode exhibits significantly improved cycling durability at high current densities, compared with the pristine Li 1.225 Ti 0.45 Mn 0.325 O 2 cathode. This work demonstrates the promising feasibility of the Cl substitution process for advanced cation-disordered rock-salt cathode materials.