A bifunctional double-layer Fe3O4-Polyvinylidene fluoride(PVDF)/PVDF separator with enhanced thermal stability for Li-S batteries

Li-S batteries, utilizing sulfur as the active material, have garnered significant attention due to their impressive theoretical specific capacity of 1675 mA h g-1. However, the commercialization of these batteries faces challenges primarily stemming from the volume expansion of sulfur and the shuttling effect caused by soluble polysulfides. In this study, we present a novel solution through the development of a bifunctional double-layer Fe3O4-PVDF/PVDF separator via electrospinning. The mesh structure of PVDF facilitates rapid lithium ion transport and effectively accommodates the volume expansion of sulfur during discharge/charge, leveraging its high thermal stability and mechanical properties. The incorporation of Fe3O4 within the PVDF matrix serves to trap polysulfides, mitigating the shuttle effect. Experimental results demonstrate that Li-S batteries employing the Fe3O4-PVDF/PVDF separator exhibit an initial discharge capacity of 1052.7mAh g-1 at a current density of 0.5C, with a commendably low capacity decay rate of 0.08% per cycle after 250 cycles. This innovative separator design showcases promising advancements in addressing critical issues hindering the commercial viability of Li-S batteries.