Redox electrolyte reactions under water-in-salt conditions: A mini review

Abstract

This review explores the electrochemical behavior of various redox electrolytes in water-in-salt electrolytes (WISEs), a class of highly concentrated salt electrolytes—mainly composed of LiTFSI—that significantly expand the electrochemical window in aqueous systems. In addition to the hydrogen evolution reaction and the oxygen evolution reaction, the review covers the electrochemical behavior in electrodeposition of metals, halides, ferri/ferrocyanide, and several organic redox electrolytes (TEMPO, Quinone, and Pyrazine) in WISEs. The influence of highly concentrated salt electrolytes on solvation structures and their impact on the stability, reversibility, and degradation mechanisms of these redox-active species are discussed, emphasizing the impact of solvation structure transitions on the electrochemical nature of various redox electrolytes.