Syntheses of alternating copolymers based on PEO and fluorinated polymers are described. Introduction of fluorinated polymer chains reduces the Tm of PEO and also increases the affinity and miscibility with ionic liquids, which improves ionic conductivity even at room temperature. The disclosed polymers containing PFPE have superior safety and are more flame retardant as compared to traditional electrolytes. Such alternating copolymers can be used as solid or gel electrolytes in Li batteries.