Magnesium aluminate (MgAl2O4)-incorporated poly(ethylene oxide) (PEO)–lithium hexafluorophosphate (LiPF6) based composite polymer electrolyte (CPE) membranes were prepared by a hot press for the first time. The membranes were subjected to X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric (TG), differential scanning calorimetry (DSC), tensile, impedance spectroscopy, compatibility and transport number studies. The incorporation of MgAl2O4 greatly enhanced the ionic conductivity, compatibility and mechanical integrity of the polymeric membrane. Finally, an all solid state lithium cell composed of Li/CPE/LiFePO4 was assembled and its cycling profile was analyzed at 70°C. The cells delivered a discharge capacity of 127mAhg−1 at 1C-rate with very good capacity retention up to 100 cycles which is found to be better than those reported earlier.