Synergistic Control of Pore Architecture and Electrochemical Properties in HEC/PEO-Based Blends through Drying Time Adjustment

Porous polymer membranes serve as essential components in lithium-ion batteries, particularly as separators, due to their superior mechanical robustness, electrolyte compatibility, and capacity for facilitating high ionic conductivity. In this study, a composite membrane was fabricated by blending hydroxyethyl cellulose (HEC), a biodegradable and highly hydrophilic polymer, with poly(ethylene oxide) (PEO), known for its exceptional chain flexibility. The polymer blend was coated onto a thermally and chemically stable, cost-effective nonwoven fabric (NWF), followed by a vacuum-assisted nonsolvent-induced phase separation (NIPS) process. By systematically varying the drying time prior to phase separation, the structural characteristics of the resulting membranes were effectively tailored. Membranes subjected to 30 and 90 min of drying exhibited high gas permeabilities of 627 ± 223 and 515 ± 68 L/m²·h, respectively. Gurley measurements and contact angle assessments indicated that shorter drying times favored the development of straight, interconnected pore networks, enhancing fluid transport properties. Fourier-transform infrared (FTIR) spectroscopy further revealed increased polymer–polymer interactions and the emergence of new hydrogen-bonding networks following phase separation. These molecular rearrangements contributed to an expanded surface area and improved porosity within the membrane structure.