Hosted by: Ignace Jarrige

The utilization of anion redox reaction is opening a new approach to increase rechargeable capacities in alkaline ion batteries recently. It is important to understand the oxidation state and electronic structure of anion in the electrodes at different state of charge. Herein, we designed and synthesized the O3-NaCr2/3Ti1/3S2 (NCTS) material, which is delivering a high capacity of 190 mAh g-1 (0.95 Na+) as a cathode for sodium battery based on the cation and anion redox processes. To study the underlying nature of anionic redox chemistry in this layered chalcogenide, we investigated the charge compensation mechanism and structure evolution of NCTS electrode using multi-model synchrotron x-ray techniques and scanning transmission electron microscopy. Our experimental results provided core evidence to reveal various charge compensation mechanisms, involving the formation of electron holes, anionic dimers, and disulfide-like species. These results provide a new insight to clarify the nature of anionic redox process of layered chalcogenides, which is important for the development of novel cathode materials with high energy density.