NOVELTY - A lithium-ion secondary battery comprises an electrode component containing a positive electrode, a negative electrode and a separator interposed between the positive electrode and negative electrode, and a battery case which accommodated the electrode component. The electrode component comprises film derived from lithium bis(oxalato)borate and sodium. The separator comprises base material (76) containing plastic porous membrane, and heat-resistant layer (78) which is formed on the surface of the base material, and containing filler (F) and binder.    USE - Lithium-ion secondary battery is used as power supply for electric motor of electric vehicle, motor vehicle, and hybrid vehicle e.g. plug-in hybrid car.    ADVANTAGE - The safe lithium-ion secondary battery has stable battery characteristics.    DETAILED DESCRIPTION - A lithium-ion secondary battery comprises an electrode component containing a positive electrode, a negative electrode and a separator interposed between positive electrode and negative electrode, and a battery case which accommodated the electrode component. The electrode component comprises film derived from lithium bis(oxalato)borate and sodium. The separator comprises base material containing plastics porous membrane, and heat-resistant layer which is formed on the surface of the base material, and containing filler (F) and binder. The binder of the heat-resistant layer comprises a binder group (A) containing binder having softening temperature of 175 degrees C or more, and a binder group (B) containing binder having softening temperature of 175 degrees C or less. The mean molecular weight of the binder of the binder group (B) is 10000-500000. The content of the binder group (B) is 5-50 wt.% with respect to 100 wt.% binder group (A).    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of heat-resistant layer of separator. (Drawing includes non-English language text)    Base material (76)    Heat-resistant layer (78)    Binder groups (A,B)    Filler (F)    Pores of separator base material (H)