Study on cellulose/nylon 6 lithium battery separators modification by polyacrylonitrile in ionic liquid [Emim]Ac

In this study, a thermally stable and eco-friendly separator was prepared of polyacrylonitrile (PAN) modified cellulose/nylon 6 with PVP K30 used as the porogen, and using ionic liquid [Emim]Ac as the solvent. The effects of PAN concentration on the mechanical properties, liquid absorption, liquid retention, porosity and thermal stability of the separators were studied. The characteristics of modified separator were investigated through the methods of SEM, N2-adsorption isotherms, thermogravimetric analysis, contact angle measurements and electrochemical characterization. The results showed that the optimal composition of the casting solution in the ionic liquid was: 3wt% (PAN), 4wt% (cellulose), 3wt% (nylon 6), 4wt% (PVP K30). In this case, the tensile strength of the separator could reach 71.24MPa, and the elongation at break reached 33.7%. The electrolyte uptake, retention rate and porosity could reach 225.3%, 66.7% and 55.7%, respectively. The maximum thermal shrinkage stress and the thermal shrinkage rate reached 1.27N and 2.0%. The electrochemical window increased to 4.5V. The related characterization indicated that the mechanical properties, thermal stability, pore distribution, wettability and electrochemical properties of the modified separator were improved comparing with the unmodified separator. This work may provide a new method for preparing lithium-ion battery separators with high biocompatibility and good safety.