A combination of nonsolvent and thermally induced phase separation (N-TIPS) technique for the preparation of highly porous cellulose acetate membrane as lithium-ion battery separators

Polyolefin-based lithium-ion battery separators generally exhibit poor wettability and low porosity, which hamper their ability to preserve electrolyte solution, thus adversely impacting battery performance because it correlates with ionic transport. Therefore, developing a separator with better wettability and porosity has received significant interest in improving battery performance due to its contribution to ionic transport. Herein, porous cellulose acetate (CA) separators were prepared via nonsolvent and thermally induced phase separation (N-TIPS) technique using N-methyl-2-pyrrolidone (NMP) as the polymer solvent and water as the nonsolvent. A glass plate was casted with cellulose acetate dissolved in NMP. Following this, the polymer solution was evaporated at 75 degrees C, then was immersed in a water coagulation bath as the nonsolvent, resulting in a flexible membrane. An evaporation time at 55, 65, or 75 min was performed to determine how evaporation affected the structures of membrane pore. CA-based separator that treated with 55 min of evaporation generates the highest ionic conductivity of 3.07 x 10-2 mS.cm-1, which can be attributed to their uniform microporous structure, porosity of 62%, and electrolyte uptake of 331%. In comparison to Celgard, a commercial polyolefin-based separator that just able to generate an ionic conductivity of 9.41 x 10-4 mS.cm-1, the CA 55 membrane exhibits far superior electrochemical performance. Based on these results, the CA 55 membrane is considered a feasible alternative for utilization in lithium-ion battery separators.