An ultralow-concentration (0.05 M) electrolyte for advanced K-ion batteries

Abstract

Owing to their low viscosity, low corrosion risk, and low cost, ultralow-concentration electrolytes for rechargeable alkali-metal-ion batteries have received much research interest. Herein, we report an ultralow-concentration electrolyte (<0.1 M) for K-ion batteries (KIBs). Using the electrolyte with only 0.05 M potassium bis(fluorosulfonyl)imide (KFSI) in ethylene carbonate (EC) and ethyl methyl carbonate (EMC) as an example, we found that KIBs with this ultralow-concentration electrolyte could deliver considerable electrochemical performance over a wide range of temperature (0–60 °C). The delivered specific capacities and cycling performances of KIBs with 0.05 M and 1.0 M electrolytes were almost equivalent when tested at 25 °C and 60 °C. Moreover, when tested at 0 °C, KIBs with 0.05 M electrolyte could even deliver a higher specific capacity and initial coulombic efficiency than those with 1.0 M electrolyte. The formation of a KF inorganic component in the solid electrolyte interphase layer for this ultralow-concentration electrolyte could facilitate the transfer of K⁺ ions and favor electrode stability. This work sheds light on the development of ultralow-concentration electrolytes for rechargeable alkali-metal-ion batteries.