Abstract: To improve the thermal stability and electrolyte wettability of polyolefin-based separators, a high performance organic-inorganic composite separator was prepared by a phase inversion process using microporous zeolite nano-particles and polyvinylidene fluoride (PVDF). The results show that compared with the polyolefin-based separator(PE), the zeolite/PVDF composite separator exhibits well-developed microstructure, superior thermal resistance and excellent liquid electrolyte wettability, for example the porosity of the present separator is over 70% which is about one time higher than that of PE separator, and the zeolite/PVDF composite separator exhibits exce-llent thermal stabilitywith area shrinkage of 5% after the heat treatment at 160℃ for 0.5 h, while PE separator and PVDF separator show 100% and 50% thermal shrinkage under the same condition respectively. Moreover, the electrolyte contact angle of zeolite/PVDF composite separator is about 7.4°, while those of PE separator and PVDF separator are about 42.5° and 31.7°. Based on the above advantages, zeolite/PVDF composite separator exhibits better electrochemical performances, such as the C-rate discharge capability and cycling performance, as compared to the commercialized PE separator.