Alginate-Based Electrospun Nanofiber for Sustainable High Ionic Conductivity Lithium–Ion Battery Separator

Commercial Li–ion battery separators made from polypropylene (PP) and polyethylene (PE) present sustainability issues with limited ionic conductivity. Alginate (Alg), a biobased polymer, offers sustainability by its natural abundance and biodegradability. It also offers ionic conductivity improvement through the presence of hydroxyl and carboxylate functional groups. In this study, we fabricate an Alg-based nanofiber separator using electrospinning to enhance the specific surface area of the separator, exposing more functional groups on the surface. The presence of Alg on the electrospun separator resulted in superior ionic conductivity of 2.65 and 5.97 mS cm^–1 for poly(vinyl alcohol) (PVA)-Alg20 and PVA-Alg40, respectively. Even further, PVA-Alg40 demonstrated excellent electrochemical stability and consistent Li plating/stripping performance for up to 1000 h. Additionally, in LFP/Li cells, the PVA-Alg40 separator maintained stable capacity (charging and discharging capacities stabilizing around 150 and 140 mAh g^–1) and high Coulombic efficiency (95–100%) over 140 cycles of charge–discharge test. This study highlights the potential of Alg-based separators as a sustainable and effective alternative to conventional separators in Li–ion batteries.