A lithium ion secondary battery comprising: a positive electrode, a negative electrode, a separator interposed between the positive and negative electrodes, and an electrolyte prepared by dissolving a lithium salt in a non-aqueous solvent, wherein the separator comprises a porous film layer containing basic solid particles and a composite binder, the porous film layer is adhered to at least one surface of at least one of the positive and negative electrodes, the composite binder comprises a primary binder and a secondary binder, the primary binder comprises polyether sulfone and the secondary binder comprises polyvinylpyrrolidone.