Secondary battery separator including porous film having fluorine-containing polymer of vinylidene fluoride, tetrafluoroethylene, and vinyl carboxylic acid or salt and secondary battery including the same

Abstract

A secondary battery separator including a porous substrate and a porous film firmly bonded to each other, the porous film being disposed on or above the porous substrate. The porous film contains a fluorine-containing polymer that contains a polymerized unit based on vinylidene fluoride, a polymerized unit based on tetrafluoroethylene, and a polymerized unit based on a monomer represented by the following formula (2-2):RRC═CRRCOY  (2-2)wherein R, R, and Rare each independently a hydrogen atom or a C1-C8 hydrocarbon group; Ris a C1-C8 hydrocarbon group; and Yis an inorganic cation and/or an organic cation. Also disclosed is a secondary battery including the secondary battery separator; a positive electrode; a negative electrode; and a non-aqueous electrolyte solution.