LITHIUM-ION BATTERY SEPARATOR WITH HIGH-TEMPERATURE RESISTANCE PROPERTY, PREPARATION METHOD THEREFOR, AND LITHIUM-ION BATTERY PREPARED THEREWITH

A lithium-ion battery separator with high-temperature resistance, a preparation method thereof and a lithium-ion battery prepared therefrom fall within the field of lithium-ion battery separators. The separator has a thickness of 3.5-30 µm, a porosity of 30-80%, an adjustable pore size of 20-2000 nm, a biaxial tensile strength of ≥ 50 MPa, an air permeability of ≤ 400 s/100cc, and a breaking temperature of ≥ 160°C. The preparation method comprises the following steps: mixing, melting, and plasticizing 20%-60% of a polypropylene main material, 2%-10% of a solubilizer, 30%-80% of a solvent, 0.1%-5% of a nucleating aid and/or 0.1%-1% of an antioxidant, carrying out twin-screw extrusion, carrying out thermally induced phase separation to obtain a cast sheet, and carrying out cast sheet stretching, extraction, and post-treatment or directly carrying out extraction and post-treatment. The separator has the characteristics of high-temperature resistance, biaxial high strength, uniform pore size, high specific resistance.