An Ultralow-Concentration (0.05 M) Electrolyte for Advanced K-Ion Batteries

Abstract

Owing to the low viscosity, less corrosive risk, and low cost, the ultralow concentration electrolytes for the rechargeable alkali-metal-ion batteries have inspired numerous research interest. Herein, we reported 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 identified that KIBs with this ultralow concentration electrolytes could deliver considerable electrochemical performances in the wide range of temperature (0 ~ 60 ℃). The delivered specific capacities and cycling performances of the KIBs with 0.05 M and 1.0 M electrolytes were almost equivalent when tested at 25 ℃ and 60 ℃. Moreover, when tested at 0 ℃, the KIBs with 0.05 M electrolytes could even deliver higher specific capacity and initial coulombic efficiency than that with the 1.0 M electrolytes. The formation of the KF inorganic component in the solid electrolyte interphase layer for this ultralow concentration electrolyte could facilitate the transfer of K+ and favor the electrode stability. This work will shed light on the development of ultralow concentration electrolytes for rechargeable alkali-metal-ion batteries.