Gel polymer electrolytes containing a mixture of organic solvent and ionic liquid were prepared and their electrochemical properties were investigated. The gel polymer electrolytes exhibited good electrochemical stability and stable interfacial properties toward lithium metal. Using these gel polymer electrolytes, lithium metal polymer cells composed of a lithium anode and a LiFePO 4 cathode were assembled, and their cycling performances were evaluated. The cells showed good cycling performance comparable to that of a cell assembled with gel polymer electrolyte containing only organic liquid electrolyte. The Li/LiFePO 4 cells assembled with a gel polymer electrolyte containing ionic liquid are expected to be one of the promising candidates for high energy density lithium batteries with improved safety.