• Fluorine-grafted quasi-solid-state composite electrolyte (F-QSCE)@30 exhibits high ionic conductivity of 1.21 mS cm–1 at 25 °C.
• The inductive effect weakens the coordination between Li+ and TFSI‒, enhancing Li+ transport.
• LiF in the solid electrolyte interphase of F-QSCE@30 comes from decomposed F segments, not TFSI‒.
• F-QSCE@30 maintains stability with Li metal for over 4000 h and inhibits dendrite growth.