Anionic Redox Regulated via Metal-Ligand Combinations in Layered Sulfides

DOI number:10.1002/adma.202107353

Journal:Advanced Materials

Key Words:anionic redox；d-p covalent interactions；energy bands；layered cathodes；metal-ligand combination

Abstract:The increasing demand for energy storage is calling for improvements in cathode performance. In traditional layered cathodes, the higher energy of the metal 3d over the O 2p orbital results in one-band cationic redox; capacity solely from cations cannot meet the needs for higher energy density. Emerging anionic redox chemistry is promising to access higher capacity. In recent studies, the low-lying O nonbonding 2p orbital was designed to activate one-band oxygen redox, but they are still accompanied by reversibility problems like oxygen loss, irreversible cation migration, and voltage decay. Herein, by regulating the metal–ligand energy level, both extra capacities provided by anionic redox and highly reversible anionic redox process are realized in NaCr1−yVyS2 system. The simultaneous cationic and anionic redox of Cr/V and S is observed by in situ X-ray absorption near edge structure (XANES). Under high d–p hybridization, the strong covalent interaction stabilizes the holes on the anions, prevents irreversible dimerization and cation migration, and restrains voltage hysteresis and voltage decay. The work provides a fundamental understanding of highly reversible anionic redox in layered compounds, and demonstrates the feasibility of anionic redox chemistry based on hybridized bands with d–p covalence.

First Author:Tian Wang

Co-author:Guo-Xi Ren, He-Yi Xia, Zulipiya Shadike,Tao-Qing Huang, Xun-Lu Li, Si-Yu Yang, Ming-Wei Chen, Pan Liu

Correspondence Author:Shang-Peng Gao,Xiaosong Liu,Zheng-Wen Fu

Document Code:2107353

Volume:34

Issue:4

ISSN No.:0935-9648

Translation or Not:no

Date of Publication:2021-11-04

Links to published journals:https://onlinelibrary.wiley.com/doi/10.1002/adma.202107353