A cross-linked solid polymer electrolyte was prepared by copolymerizing photochemically acrylonitrile (AN), oligo(ethylene glycol ethyl ether) methacrylate, oligo(ethylene glycol) dimethacrylate in the presence of lithium perchlorate as a lithium salt, ethylene carbonate-propylene carbonate as a mixed plasticizer, and poly(ethylene oxide) as a polymer matrix. The maximum ionic conductivity of the polymer electrolyte was 2.35$ imes$10$^$-3/ S/cm. The interface resistance of the polymer electrolyte was very low compared to that of the polymer electrolyte without AN. The former electrolyte was stable up to 4.3 V and the Ah efficiency was nearly 100% during the charge-discharge cycle.