Thermal stability andflame retardant property are significant
parameters to evaluate the safety characteristic of separators. In
order to investigate the thermal stability of the SiO2/PEI-PU
membranes, thermal shrinkage behavior is observed by measuring
the area-based dimensional change after storing the membranes at
the temperature range from 90 to 180
C for 0.5 h respectively. As
can be seen inFig. 6a, the Celgard membrane thermally shrinks
seriously with increasing temperature, whereas, the dimensional
changes of PEI-PU and SiO2/PEI-PU membranes are negligible over
wide temperature ranges (90–130
C), and become more pronounced as the temperature increased (140–180
C). The photographs of relevant membranes before and after exposure to 180
C
for 0.5 h are presented in Fig. 6b and c. The Celgard membrane
shrinks severely (92%) with the color change from white to
transparent, whereas the relevant PEI-PU and SiO2/PEI-PU
membranes shrink by 9% and 5%, respectively. Based on these,
we can conclude that the SiO2/PEI-PU membranes exhibit better
thermal stability than PEI-PU and Celgard membranes. Accordingly, we can deduce that the significantly improved thermal stability