Figure 2. (a) ATR-FTIR spectroscopy and (b) XRD patterns of cellulose and cellulose/CaCO3 membranes.
In order to study the effect of CaCO3 nanoparticles on the thermal stability of cellulose porous membranes, thermogravimetric tests were carried out on porous membranes, and the corresponding results are listed in Figure 3 and Table 1 . As shown in Figure 3a , the initial decomposition temperature did not change regularly after the addition of CaCO3, probably due to the absorption of water by cellulose with a large number of hydroxyl groups. The maximum decomposition temperature increased with the addition of CaCO3, from 351.3 °C to 355.7 °C and 356.7 °C respectively, indicating that CaCO3 increases the thermal stability of the cellulose membrane. Moreover, the residual mass increased from 7.2% to 12.1% due to the decomposition temperature of CaCO3 being greater than 700 °C.
As shown in Figure 3b , the commercial PP separator and the cellulose-based membranes prepared in this work were subjected to 150 °C and 180 °C for half an hour to evaluate the dimensional stability at high temperature. The commercial PP separator shrank significantly and can not maintain the initial round shape, and the shrinkage was severe at 180 °C. In contrast, the cellulose and cellulose/CaCO3 membranes can remain the original shape even at high temperatures of 150 °C and 180 °C. Notably, excellent dimensional stability is important to effectively prevent short-circuiting when the battery is overheated. It can be predicted that LIBs with cellulose/CaCO3 membranes would manifest improved safety performance than that with commercial PP separator.[38]