Synchrotron X‐Ray Absorption Spectroscopy and Electrochemical Study of Bi2O2Se Electrode for Lithium‐/Potassium‐Ion Storage.

Elucidating the battery operating mechanism is important for designing better conversion‐type anodes as it determines the strategies used to improve electrochemical performances. Herein, the authors pioneered the electrochemical study of layered Bi2O2Se as anodes for lithium‐ion batteries (LIBs) and potassium‐ion batteries (PIBs). Surprisingly, the Bi2O2Se/graphite composite electrode shows even better cycle stability for PIBs. The electrochemical reaction mechanisms of the Bi2O2Se/graphite electrode for LIBs and PIBs are investigated by potential‐resolved in situ and ex situ X‐ray absorption spectroscopy based at the Bi LIII‐edge and Se K‐edge through characterizing the local atomic structure evolution, valence state change, and charge transfer. New insights are gained regarding the electrochemical process of Se2− anions in Bi2O2Se, where multiple Li–Se intermediates rather than the traditional single‐phase Li2Se are involved in this conversion‐type anode. The advanced understanding of anionic electrochemistry in conversion‐type anodes prompts one to find appropriate ways to suppress side‐reactions and improve the battery performances. [ABSTRACT FROM AUTHOR]