Salt-concentrated electrolytes for graphite anode in potassium ion battery

Abstract Potassium ion batteries have emerged as promising energy storage devices. Searching for proper electrode materials is still a challenge. Graphite as an anode has been demonstrated a good potassium storage capability. Here, in this work, we study the effect of electrolytes (KFSI-DME) with different salt concentrations on the electrochemical performance of graphite. Electrolyte with a high salt concentration (7 mol kg−1) provides a de-solvated K+ intercalation behavior, giving a high K storage capacity of ~232 mAh g−1, a low insertion voltage at ~0.2 V K+/K, a high Coulombic efficiency, and a better cycling performance. In a dilute concentration electrolyte (3 mol kg−1), [K-DMEx]+ complexes co-insert into the graphite at an operational voltage above 0.5 V vs. K+/K with a specific discharge capacity of 187 mAh g−1. Optimizing the electrolyte composition provides an effective way to improve the energy density including capacity and operational voltage as well as enhance cycling life of the graphite electrode.