A porous membrane may be manufactured with a high content of filler material and a polymer binder. After forming the membrane, the membrane may be post processed to reform the polymer binder into a stronger yet still porous membrane. The post processing may include bringing the membrane above the melt temperature of the polymer or by immersing the membrane in a solvent. Photomicrographs show that the structure may change, yet the performance of the material in batteries and other electrochemical cells may remain the same or even improve.