Preparation method of separator with high tensile strength for lithium secondary battery and The lithium secondary battery thereby

摘要

A method for preparing a separator for a lithium secondary battery, a separator prepared by the method, and a lithium secondary battery containing the separator are provided to improve ion conductivity and mechanical properties by introducing a symmetric structure to a separator. A method for preparing a separator for a lithium secondary battery comprises the steps of dissolving a vinylidene fluoride-based polymer in a solvent to prepare a polymer solution and adding a nonsolvent to the polymer solution to prepare an oversaturated polymer solution; casting the polymer solution on a substrate and evaporating the solvent to obtain a film-shaped polymer membrane; and adding the polymer membrane to a nonsolvent to form a pore by phase transition method. Preferably the nonsolvent is at least one selected from methanol, ethanol, propanol, water, acetone, THF, dimethylformamide, N-methylpyrrolidone and methylisobutylketone.