Boehmite-enhanced poly(vinylidene fluoride-co-hexafluoropropylene)/polyacrylonitrile (PVDF-HFP/PAN) coaxial electrospun nanofiber hybrid membrane: a superior separator for lithium-ion batteries

Polyethylene (PE) and polypropylene (PP) are widely employed in commercial lithium-ion battery (LIB) separators due to their superb mechanical strength and chemical stability. Nonetheless, inherent limitations such as inadequate high-temperature resilience, low porosity, and suboptimal wettability curtail their application in high-temperature settings and diminish their lifespan. Creating LIB separators with superior attributes is imperative to attain high electrochemical efficiency. Herein, we engineered a new hybrid membrane with boehmite (BM)-modified poly(vinylidene fluoride-co-hexafluoropropylene)/polyacrylonitrile (PVDF-HFP/PAN) coaxial nanofibers via electrospinning, subsequently integrating them into a LIB separator. Contrasted with prevailing commercial PP separators, the BM-doped PVDF-HFP/PAN (PAN@PVDF-HFP/BM) membrane showcased a commendable suite of properties, including a heightened shrinkage temperature of 160 °C, impressive porosity at 85.2%, remarkable electrolyte absorption capacity at 872.8%, and stellar ionic conductivity measuring 3.98 mS/cm. A LIB featuring the PAN@PVDF-HFP/BM separator was cycled 200 times at a current rate of 0.2 C, revealing minimal specific discharge capacity decay (from 164.9 to 153 mAhg⁻¹), and a capacity retention rate of 93.3%. Additionally, the enhancement mechanism of the coaxial nanofiber facilitated by boehmite has been elucidated using density functional theory (DFT) calculations. The PAN@PVDF-HFP/BM nanofiber membrane introduces a pioneering approach to fabricating LIB separators that boast prolonged longevity and high-temperature resilience.