Diaphragm used for lithium-ion storage battery and manufacturing method thereof

Secondary battery separator and a method for preparing a lithium ion, the membrane porosity of 50% to 70%, an average pore diameter in the range of 0.1 0.3um ~, maximum pore size and the average pore diameter ratio of 1.10 to 1.25. The method of the present invention is simple preparation process, the discharging process which synergistic crafts and a nucleating agent to control the plasma by porosity and pore size of the membrane, the solution to increase the pore size and porosity, a large proportion of the added inorganic separator fillers, for melt kneading, resulting in a uniform pore difficult.