NOVELTY - A lithium-ion secondary battery comprises electrolyte solution, and separator. The electrolyte solution contains solvent and supporting electrolyte. The solvent is propylene carbonate, ethylene carbonate, butylene carbonate, fluoroethylene carbonate, and ionic liquid. The supporting electrolyte is lithium tetrafluoroborate, lithium perchlorate or lithium bis(oxalate)borate. The separator is microporous film or nonwoven fabric chosen from aramid, polyimide, polyamidoimide, polyester, polyethylene terephthalate, ethylene-vinyl alcohol copolymer, or glass fiber.    USE - Lithium-ion secondary battery. Uses include but are not limited to mobile communication apparatus, portable electronic device, electric power-assisted bicycle, electrically-driven two-wheeled bicycle and electric vehicle.    ADVANTAGE - The lithium-ion secondary battery has excellent charge-discharge characteristics at high temperature.    DETAILED DESCRIPTION - A lithium-ion secondary battery comprises positive electrode active material, negative electrode active material, binder, collector, electrolyte solution, separator, and cladding material. The positive electrode active material comprises polyanion-type material, and transition-metal compound containing lithium-titanium phosphate, iron sulfate, iron molybdate, ferrous sulfate, lithium-iron phosphate, lithium-vanadium phosphate, lithium-iron arsenate, titanium-niobium phosphate, lithium-iron-niobium phosphate, lithium-iron-titanium phosphate, iron pyrophosphate, lithium pyrophosphate, titanium pyrophosphate, lithium-vanadium pyrophosphate, molybdenum pyrophosphate, phosphomolybdate, phosphovanadate, lithium vanadyl phosphate, sulfovanadate, arsenovanadate, lithium vanadyl silicate, lithium vanadyl molybdate, vanadium borate, ferrotungstate, lithium-vanadium fluorophosphate, lithium-cobalt fluorophosphate, lithium-iron sulfophosphate, or dilithium-iron sulfophosphate. The polyanion-type material is lithium phosphate compound (LiMPO4, where M is nickel, cobalt, manganese or iron, LiM2(SO4)3, where M is vanadium, titanium, and iron LiM2(XO4)3, where M is iron, manganese, titanium, vanadium and niobium, and X is sulfur, phosphorus, molybdenum, tungsten, arsenic, and silicon, LiMVO4, where M is manganese, nickel and cobalt, Li2MSiO4, where M is nickel, cobalt, manganese and iron and LiMBO3, where M is nickel, cobalt, manganese and iron). The negative electrode active material comprises lithium-titanate (Li4Ti5O12), silicate (SiOx, where x is 0-1.6) and tin oxide. The binder consists of polyimide precursor. The electrolyte solution contains solvent and supporting electrolyte. The solvent is propylene carbonate, ethylene carbonate, butylene carbonate, fluoroethylene carbonate, glyme-type material, lactone-type material, nitrile-type material, and ionic liquid. The supporting electrolyte is lithium tetrafluoroborate, lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(oxalate)borate. The separator is microporous film or nonwoven fabric chosen from aramid, polyimide, polyamidoimide, polyester, polyethylene terephthalate, ethylene-vinyl alcohol copolymer, or glass fiber. The cladding material comprises metallic sheath containing aluminum, stainless steel, or nickel plating steel plate, and sealing material containing fluororesin (A), polyethylene terephthalate, epoxy resin, polyphenylene sulfide, polyacrylate, polysulfone, polyether-sulfone, polyether imide, polyetheretherketone, liquid crystalline polyester, polyimide, and polyamidoimide. The fluororesin (A) is polytetrafluoroethylene, polychloro trifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, perfluoro alkoxy fluororesin, tetrafluoroethylene and hexafluoropropylene copolymer, ethylene and tetrafluoroethylene copolymer, or ethylenechlorotrifluoroethylene copolymer.