<p>The incompatibility of conventional electrolytes with both graphite anodes and high-voltage cathodes remains a critical bottleneck in potassium-ion battery (KIB) development. Herein, we propose a monofluorination strategy for electrolyte solvent design, wherein the terminal methyl (-CH₃) groups in standard linear carbonates (diethyl carbonate) are replaced by fluoromethyl (-CH₂F) groups. The introduced fluorine atoms attenuate the solvating power of the carbonyl oxygen while enabling a distinctive K-F and K–O tridentate coordination geometry. This tailored potassium-ion solvation structure promotes the synergistic decomposition of the fluorinated solvent and anions, fostering the formation of favorable fluorine-rich inorganic species in both the solid-electrolyte interphase (SEI) on the anode and the cathode-electrolyte interphase (CEI). As a result, the graphite anode achieves significantly enhanced cycling durability, retaining 90.74% of its capacity after 500 cycles at 0.5 C. Concurrently, the KFeHCF cathode demonstrates stable operation up to 4.5&#xa0;V (vs. K⁺/K) with 75.44% capacity retention over 1000 cycles at 200&#xa0;mA/g. This work establishes terminal monofluorination of linear carbonates as an effective approach to couple optimized K⁺ solvation with fluorine-enriched interphase engineering, providing a practical molecular design strategy for durable, high-voltage KIB electrolytes.</p>