A novel nanoporous polymer membrane comprised of poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) co-polymer was prepared by phase inversion techniques using two different non-solvents. The films were subjected to scanning electron microscope (SEM) and nitrogen adsorption/desorption analysis. The morphology and porosity of the membranes are correlated with the chemical structure of the non-solvents used. Also, nanoparticle LiCr0.01Mn1.99O4 cathode material was prepared by solid-state reaction followed by ball milling. The prepared samples were analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM). The charge–discharge behavior of lithium cells made from the coupling of the nanoporous polymer membrane with the LiCr0.01Mn1.99O4 nanoparticle cathode was studied. The cathode nanoparticles resulting from ball milling were found to be more important in enhanced cell performance than the nanostructure of the nanoporous polymer membranes.