Stabilized cellulose separator based on NaCl and glycerol with uniform structure

Abstract

A membranes used as battery separators must be thermally stable because they have to withstand extreme environments such as high temperatures. However, the membrane also must have a uniformly porous structure for the movement of Li ion, which reduces the thermal stability of the membrane. Thus, to solve this problem, thermally stable membrane was developed. Here in, for the first time, we succeeded that nano-sized porous composite membrane with thermally stable was fabricated from high molecular weight cellulose acetate (CA) and additives, Glycerol and NaCl, using a hydraulic force. The mol ratio of CA and glycerol was fixed at 1 and 0.1, respectively. With various mol ratio of NaCl, The optimal ratio for the additives to be well dispersed in the composite was investigated through water flux. At 0.07 mol ratio NaCl, it was measured that average water flux was 9.431 L/m2h and the coefficient of determination (R2) was 0.9802, which meaning it has a reproducible and largest water flux than other NaCl mol ratios. Thus, the optimal ratio was glycerol:NaCl = 0.1:0.07 mol ratio. In the optimal ratio, average porosity of the composite was measured to 10.20 ± 0.08%. It was confirmed by SEM that the pore sizes of the surfaces were similar. The thermodynamic properties of the CA/glycerol/NaCl composites was measured using TGA and DTG. It was shown that the thermal stability of the CA/glycerol/NaCl composite had a thermal behavior similar to neat CA film even though pore was formed. This was demonstrated that thermal stability was improved by stabling coordination bonding between the carbonyl group of CA and remaining additives. In addition, the degree of coordination bonding with the carbonyl group of CA according to the amount of NaCl was investigated using XPS.