TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The superfine filler is nano montmorillonite, nano calcium carbonate, clay, talc powder, wollastonite, kaolin, diatomite, montmorillonite, titanium dioxide, precipitated silica, fumed silica, graphite, carbon nanopowder, and/or carbon nanotube. The superfine filler particle diameter is less than 100 nm.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The cosolvent is phthalic acid esters, sebacic acid ester, adipate, phosphate esters, terephthalic acid ester, polyatomic alcohol, synthetic oil and paraffin, natural oils, polar solvents, and/or environment-friendly plasticizer. The extraction solvent is purified water, absolute ethyl alcohol, propyl alcohol, isopropyl alcohol, ethylene glycol, propylene glycol, glycerol, acetone, paraffin, and liquid paraffin. The extracting solution is hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, sodium hydroxide solution, or potassium hydroxide solution.    TECHNOLOGY FOCUS - POLYMERS - Preferred Method: The cast films liquor is prepared by melt mixing 30-69.3% pure polyphenylene sulfide resin, 20-58% cosolvent, 10-30% superfine filler, 0.2-0.5% thermal stabilizer, and 0.1-0.2% antioxidant. Rolling is controlled at 25-150 degrees C, and the stretching ratio is controlled at 1-1.5. Preferred Component: The insulation film comprises a two-layer composite structure AB, or a three-layer composite structure ABA, where A layer is polyphenyl thioether thin film and the B layer is a polyolefin microporous membrane. The thickness of the polyphenylene sulfide film is 10-15 mu m. The thickness of the polyolefin microporous film is 10-15 mu m. The modifier comprises modified polypropylene blended modification material and/or toughening agent. The polypropylene blended modification material comprises polyethylene, polypropylene, polybutene, propylene copolymer, acrylonitrile-butadiene-styrene copolymer, styrene-maleic anhydride copolymer, polymethyl methacrylate, acrylic resin, polystyrene, high impact polystyrene, polyamide-6, polyamide-66, polyamide-11, polyamide-12, polyamide 1010, polyamide 1212, aromatic polyamide, polybutylene terephthalate, polyethylene glycol terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, polytrimethylene terephthalate, 1,4-cyclohexanedimethanol, ethylene glycol esters and 1,4-cyclohexane dimethanol copolymer of polyethylene terephthalate, 1,4-cyclohexyl ester, liquid crystalline polyester, polycarbonate, polyphenylene oxide, polyurethane, or polysiloxane. The toughening agent is ethylene- alpha -olefin copolymer, ethylene-propylene copolymer elastomer, polypropylene thermoplastic elastomer, polypropylene copolymer elastomer, styrene-butadiene-styrene copolymer, styrene-hydrogenated butadiene-styrene copolymer, polyester elastomer, polyamide elastomer, polyurethane elastomer, acrylic impact modifier, silicon-containing acrylic impact modifier, ethylene-acrylic ester copolymer, or ethylene-acrylic ester-glycidyl ester of methacrylic acid.