Solvation engineering decouples bulk and interfacial chemistry for robust potassium-ion batteries

solvation structure that is regulated by anion-solvent interactions, while maintaining adequate anion participation in the solvation sheath. This configuration exhibits interface stabilization and low desolvation barriers, with a kinetic compensation mechanism yielding a higher K⁺ transference number. When assembled in potassium batteries, it achieves highly reversible K plating/stripping with a Coulombic efficiency of 98.9% in K||Cu cells, 85% capacity retention over 1600 cycles in a graphite electrode, and stable, fast-cycling performance in both K||Prussian blue analogue half-cells and graphite||Prussian blue analogue full-cells over a wide working temperature range of -20 to +45 °C. This work establishes a viable approach for tailoring specific electrolyte properties by precisely tuning microscopic solvation structures through anion-solvent interaction.