Battery separator is a porous sheet placed between the positive and negative electrodes in a liquid electrolyte, a gel electrolyte or a molten salt battery. Its function is to prevent physical contact of the positive and negative electrodes while serving as an electrolyte reservoir to enable free ionic transport. According to the structure, the separator can be divided as micro porous and non-woven. An ideal battery separator should have the properties of high porosity, small mean pore diameter, oxidation resistance, puncture resistance, thermal dimensional stability and freedom from harmful chemical contaminants, favourable voltage characteristics, retardation of antimony transfer, electrochemical compatibility and prevention of dendrite growth.