Surface-modified electrospun polyacrylonitrile nano-membrane for a lithium-ion battery separator based on phase separation mechanism

A separator is an indispensable part of a lithium-ion battery and can seriously affect the battery performance. This study demonstrates the feasibility of a non-solvent-induced phase-separation mechanism for the preparation of lithium-ion battery separators. Based on the mechanism, polyacrylonitrile (PAN) solutions were prepared with different proportions of dimethylformamide (DMF) and tetrahydrofuran (THF) for electrospinning to prepare separators. The surface and interior of the fibers of the electrospun membranes show different morphologies, which make a difference in the performance of batteries based on these separators. The property mixing of DMF and THF can cause microporous structures on the surface and inside of the electrospun fibers, and some pores are internal and external interconnected. This improves the porosity (67.7%), ionic conductivity (1.96 mS·cm−1), electrochemical stability (4.2 V), and battery performance compared to commercial Celgard separators.