An electrochemical separator film includes a polymer, and particles of a first inorganic material having a first particle size suspended in the polymer. An electrochemical cell structure, includes at least one electrode on a substrate, and a separator film residing on top of the electrode, wherein the separator film comprises a polymer, and particles of a first inorganic material having a first particle size suspended in the polymer. A method of manufacturing a separator film, includes combining a polymer with a solvent for the polymer to form a polymer solution, mixing particles of a first inorganic material with the polymer, the particles having a first particle size to produce a separator mixture, depositing the separator mixture onto a substrate, and drying the separator mixture until the solvent and non-solvent are no longer present forming the separator film.