Interface Chemistry Engineering toward Layer-Structured Oxide for Potassium-Ion Batteries

An unstable cathode–electrolyte interface leads to a continuous decomposition of the electrolyte and low Coulombic efficiency, resulting in rapid capacity degradation. A stable cathode–electrolyte interface chemistry engineering was thus employed to achieve the highly stable K0.5MnO2 as a cathode for potassium-ion batteries (PIBs). Theoretical calculations and experimental results show that carbonate electrolyte of potassium bis(fluorosulfonyl)imide (KFSI) in ethyl methyl carbonate (EMC) can facilitate the realization of anion-dominated interfacial behavior and the construction of a stable cathode electrolyte interphase (CEI) film with uniform inorganic/organic compositions. It can accelerate the K+ solvation–desolvation process and induce the formation of a stable CEI with more inorganic components, contributing to the stable and fast charge/ions transfer kinetics. The designed electrolyte provides new insights for enhancing the stability of a layered oxide cathode, which is of great significance for promoting the development of cathodes for PIBs.