Solvation Structure Dual‐Regulator Enabled Multidimensional Improvement for Low‐Temperature Potassium Ion Batteries

The graphite-based potassium ion batteries experience severe capacity degradation at low temperatures. Here, the solvation structure dual-regulator strategy is proposed, comprehensively considering freezing point, solvation energy, and solid electrolyte interface property. As a result, the graphite anode delivers a high capacity of 252 mAh g⁻¹ at −20 °C, which is over 85% of room-temperature capacity.

Abstract

The operation of graphite-based potassium ion batteries (Gr-PIBs) remains challenging at low temperatures, limited by slow dynamic behavior. Herein, the solvation structure dual-regulator strategy of electrolyte is proposed for multidimensional improvement of K⁺ transfer process including ion transfer at both bulk and interface. The designed electrolyte (an amide solvent, 2,2,2-Trifluoro-N, N-dimethylacetamide) with low freezing point and low viscosity as the primary regulator, and a fluorinated solvent (1,1,2,2-Tetrafluoroethyl-2,2,3,3-tetrafluoropropylether) as the secondary regulator provides a flowing environment and low resistive interface for fast ion transfer. As a result, the regulated electrolyte has a low freezing point of −51.9 °C and exhibits a high ionic conductivity of 3.2 mS cm⁻¹ at −20 °C. Based on the solvation structure dual-regulator, the graphite anode delivered a high capacity of 252 mAh g⁻¹ which is over 85% of room-temperature capacity, and the capacity retention rate of a full cell at −20 °C is over 80%. These results demonstrate that the solvation structure dual-regulator can improve the performances of Gr-PIBs, promoting the development of low-temperature PIBs and beyond.