Electrospun of polyvinyl alcohol composite hydrogel nanofibers prepared by in-situ polymerization: A novel approach to fabricate hydrogel nanofiber membrane for lithium-ion batteries

The increasing demand for high-performance lithium-ion batteries has propelled the exploration of advanced materials to overcome limitations associated with commercially available polyolefin-based separators. This study introduces a pioneering approach involving the synthesis of a crosslinked hydrogel nanofiber membrane (PDs) composed of polyvinyl alcohol (PVA) and N, N-dimethylacrylamide (DMAAm) through the combination of the photo-polymerization with electrospinning process. To address key drawbacks observed in existing separators—namely, low porosity, inadequate thermal stability, and insufficient electrolyte wettability—the porosity of the PDs hydrogel nanofibers was systematically controlled through both heating drying (PD12-HD) and freeze-drying (PD12-FD) methods. The separator's properties and performance were thoroughly examined, focusing on its chemical, mechanical, thermal, swelling, morphological, conductivity, and electrochemical properties. Comprehensive characterization of the PD12-FD separator revealed remarkable attributes surpassing those of a commercial counterpart (Celgard). The PD12-FD separator demonstrated exceptional mechanical strength (16.3 MPa), robust thermal stability (no shrinkage or deformation at 170 °C), high porosity (84.66 %), substantial electrolyte uptake capacity (672.86 %), superior ionic conductivity (3.405 mS/cm), and high lithium-ion transfer number (tLi+ = 0.678). The improvement is attributed to the cross-linked structure formed between PVA and DMAAm. Importantly, coin cells assembled with the PD12-FD separator exhibited outstanding electrochemical performance. Even after 150 cycles at 1C, the PD12-FD separator maintained a capacity above 95 % (145.48 mAh/g), surpassing both PVA and Celgard separators. This study proposes a novel methodology for fabricating hydrogel nanofiber separators and introduces a customizable synthesis approach for producing separators with enhanced performance and controlled characteristics.