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 degrees 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.