Abstract:

In this paper， the effects of stretch behavior on the micropore structure， strength and thermal shrinkage of lithium battery separator were investigated. The design of experiment verification and effect analysis indicated that the stretch temperature had the strongest positive effect on the porosity of separator， followed by its stretch rate. The effect weakened at stretch rates between 8.5 and 10 times. Meanwhile， the stretch rate and stretch temperature had a strong interaction effect. In addition， the correlation coefficient between the stretch factor and regression model established by the pore size was 98.6 %. The negative effect of stretch temperature on the strength of the diaphragm was the strongest， followed by the positive effect of stretch magnification. When the stretch rate of the separator was 8.5~10 times， its efficacy was weakened. The separator obtained the best strength response value at a stretch rate of 37.5 %/s. In addition， the effects of pore formation and strength were explained through topography analysis. The negative effect of stretch temperature on the thermal shrinkage of the diaphragm was the strongest， followed by the positive effect of the stretch rate. The hedging of the effect weakened at a stretch rate of 7~8.5 times， and the stretch temperature and stretch rate had a strong interaction. The regression coefficient between separator crystallinity and thermal shrinkage was 81.1 %. The larger the separator crystallinity， the smaller was the thermal shrinkage.

Key words: lithium battery separator, stretch orientation, pore size, strength, heat shrinkage