Operando Br K-edge dispersive X-ray absorption fine structure analysis for Br/Br redox mediator for Li-Air batteries

伊藤 仁彦*; 松村 大樹; Song, C.*; 久保 佳美*

ACS Energy Letters (Internet), 7(6), p.2024 - 2028, 2022/06

https://doi.org/10.1021/acsenergylett.2c00912

The behavior of Br/Br redox mediator (RM), which has been shown to suppress charging overpotential in lithium-air batteries, has been detected for the first time using operando Br K-edge dispersive X-ray absorption fine structure. Br ions in the electrolyte increase monotonically after 30% charging, which indicates that a part of Br formed via the oxidation of Br during charging does not oxidize LiO as RM but gets accumulated in the cell. Consistent with this result, the O evolution efficiency gradually decreases from the initial 100% as the charging progresses, and CO is emitted at the end of the charging. All these results clearly show that the Br/Br RM functions effectively at the beginning of charging but gradually loses its function as charging proceeds.