Embodiments of the present disclosure generally relate to methods for preparing porous separators used in battery technology, such as within an electrochemical cell. In one or more embodiments, a method of preparing a porous separator for an electrochemical cell is provided and includes placing a mixture containing a polymer precursor composition and a porogen onto a surface and forming a polymeric film on the surface from the mixture by a polymerization process. The polymeric film contains pores distributed throughout a polymeric material. The pores are formed during the polymerization process and the porogen is disposed within the pores. In one or more examples, the polymeric film is formed by a polymerization-induced phase separation (PIPS) process and contains about 20 wt% to about 70 wt% of the porogen.