Utilizing Methacrylated Lignin as a Sustainable Macro-Crosslinker for Synthesizing Innovative PVA/AMPS Composites Crosslinked Hydrogel Nanofibers: A Potential Application for Lithium-Ion Battery Separators

There are significant issues with commercial separators that must be resolved before they can be used in high-energy-density batteries. These problems include low porosity, poor electrolyte wetting, and low mechanical properties. This study presents a facile method for preparing composite crosslinked hydrogel nanofibers of polyvinyl alcohol (PVA) with 2-acrylamide-2-methylpropanesulfonic acid (AMPS) for lithium-ion battery separators by utilizing methacrylated lignin (LMA) as a bio-based crosslinker. Initially, LMA was synthesized by grafting glycidyl methacrylate (GMA) onto lignin via esterification. Subsequently, a crosslinked hydrogel nanofiber membrane (PVA/AMPS-LMA) was electrospun with varying LMA fractions, which were polymerized by combining free radical copolymerization and esterification reactions. The effectiveness of LMA as a crosslinker was assessed against the N, N'-methylene bisacrylamide (MBA). The study showed that using LMA as a crosslinker significantly improved the membrane's properties. The PVA/AMPS-LMA separator displayed superior features such as mechanical strength, thermal stability, porosity, electrolyte uptake, ionic conductivity, and lithium-ion transference number, when compared with PVA/AMPS, PVA, and Celgard separators. Specifically, the PVA/AMPS-LMA separator demonstrated a high mechanical strength of 24.9 MPa, strong thermal stability at 170 °C with no shrinkage, high porosity (84.3%), and electrolyte uptake (661.4%). It also exhibited exceptional ionic conductivity (2.75 mS/cm) and a notable lithium-ion transference number (tLi+ = 0.717). In coin batteries, the PVA/AMPS-LMA separator retained over 96% capacity (142.4 mAh/g) after 200 cycles at 1C. This performance exceeded that of PVA/AMPS, PVA, and Celgard separators, suggesting that PVA/AMPS-LMA separators have the potential to replace their commercial counterparts.