A battery includes an anode and a cathode. An electrolyte material is disposed between the anode and the cathode. A separator is disposed between the anode and the cathode. The separator comprises an anodized metal oxide layer haying substantially straight and parallel through-pores, wherein 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.