A process of manufacturing a lithium ion battery that includes an anode and a cathode. In the process, a cathodic electrode layer and a composite structure are assembled to form a stack. The stack includes the cathodic electrode layer, an anodic electrode layer and a separator layer between the cathodic electrode layer and the anodic electrode layer. The composite structure includes the anodic electrode layer and the separator layer. The separator layer includes a porous anodized metal oxide layer containing substantially straight and parallel nanometer scale through-pores haying a diameter of less than 100 nm. The anodized metal oxide of the porous anodized metal oxide layer is selected from the group consisting of aluminum oxide, titanium oxide, zirconium oxide, niobium oxide, tungsten oxide, tantalum oxide, and hafnium oxide.