Polyethylene separator is irradiated by gamma ray to investigate the effect on electrochemical and thermal properties of polyethylene separators. Applied irradiation dose was 50, 100, 150 and 200 kGy. Iris observed that the melt integrity temperature is increased as the higher close of irradiation is applied. In case of non-irradiated PE separator, shut-down temperature is about 133 degrees C and melt integrity temperature is 146 degrees C. On the other hand, the separator with irradiation dose of 200 kGy, shut-down temperature is about 136 degrees C and melt integrity temperature is about 166 degrees C. Thermal shrinkage test is performed at 150 and 120 degrees C for 1 beach. It is observed that the irradiated separator has better thermal shrinkage resistance than the non-irradiated one because of the cross-link of polyethylene formed by gamma ray irradiation. Therefore, it can be concluded that the cross-link of polyethylene formed by gamma ray irradiation is strongly effective against thermal shrinkage. The electrochemical test is performed at high rate using the irradiated separator and the non-irradiated one to investigate any trade-off. The high rate discharge characteristic of the irradiated separator is better than that of the non-irradiated one. FTIR spectral analysis of the irradiated and non-irradiated separators is performed and ionic conductivity was measured to understand the reason. (C) 2009 Elsevier B.V. All rights reserved.