The chemically cross-linked gel polymer electrolytes supported by the microporous polyethylene membrane were prepared for application in lithium-ion polymer cells. The chemical cross-linking by tris(2-(acryloyloxy)ethyl) phosphate enhanced the electrochemical stability of the electrolyte and also promoted strong interfacial adhesion between the electrodes and the membrane. Lithium-ion polymer cells composed of a carbon anode and a lithium–cobalt oxide cathode were assembled by in situ chemical cross-linking, and their charge/discharge cycling performances were evaluated. Effect of the cross-linking agent on cycling performances of the cells has been investigated.