A new solid polymer electrolyte, composed of a polymeric matrix of biodegradable polymer, poly-ɛ-caprolactone (PCL) and 10% LiClO4 was used in a rechargeable lithium polymer battery. A LiNiCoO2 film prepared by the combination of sol–gel synthesis and a template concept was used as the cathode. Cyclic voltammetry, charge/discharge cycle and electrochemical impedance spectroscopy, were used to characterize the Li|PCL, 10% LiClO4|LiNiCoO2 device. The specific charge/discharge capacity was determined to be 182mAhg−1 in the first cycles and 120mAhg−1 after 50 cycles. High lithium chemical diffusion coefficients values were obtained by electrochemical impedance spectroscopy.