MXene Gel Separators for Lithium-Sulfur Batteries

Abstract

Energy storage, not just generation, is vitally important in solving the energy crisis. Lithium-sulfur batteries hold the potential to dramatically expand our available energy storage capacity beyond that of current batteries. However, a phenomenon called lithium polysulfide shuttling limits the cycle life of lithium-sulfur batteries. Developing advanced separators is one promising approach to mitigate lithium polysulfide shuttling. In this work, MXene gel separators are explored, taking advantage of MXenes' polysulfide adsorption properties. Gel separators for lithium-sulfur batteries were made from PVA with 1 wt%, 5 wt%, or 10 wt% Ti₃C₂ or PVDF-HFP with a PEGDME-based electrolyte and 0.5 wt%, 1.0 wt% or 1.5 wt% Ti₃C₂. Polysulfide diffusion testing showed a general trend of higher Ti₃C₂ concentrations resulting in slower diffusion, i.e., reduced shuttling. MXene incorporation in the separators changed the color of the shuttled lithium polysulfides, indicating a change in their chain lengths. SEM and EDS showed significant differences in surface morphology and composition before and after the testing. Further research possibilities are also outlined.