Solvation geometry engineering for stable high-voltage potassium-ion batteries

Abstract

To advance the practical application of potassium-ion batteries (PIBs), the lack of robust electrolytes must be addressed, as the prevailing fluorinated solvents present a cost-prohibitive and environmentally unsustainable solution. Here, we propose an asymmetric alkylation strategy to overcome this limitation, engineering a fluorine-free, high-flash-point, and green ether-based electrolyte. This design reconstitutes the solvent coordination geometry through dual steric hindrance, which concurrently weakens cation–solvent binding and modulates the electronic structure of the solvation cluster. Consequently, the designed electrolyte demonstrates exceptional interfacial compatibility, enabling the high-voltage K₂Mn[Fe(CN)₆]‖graphite and K₂Mn[Fe(CN)₆]‖hard carbon full-cells to achieve capacity retention rates of 75.75% after 1400 cycles at 0.33C and 80.09% after 1500 cycles at 0.5C, respectively. Moreover, this stability is preserved at elevated temperatures, with both full-cells exhibiting stable operation over hundreds of cycles. This work establishes an effective electrolyte design strategy for realizing high-performance, cost-effective, and environmentally friendly PIBs.