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 0.33 C and 80.09% after 1500 cycles at 0.5 C, respectively. Moreover, this stability is preserved under 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.