Bifunctional Membrane for High Energy, Long Shelf Life Li-S Batteries

The adoption of high energy lithium sulfur batteries hinges on significant improvements in charge/recharge cycle life. Cycle life is limited by migration of dissolved polysulfide species which creates an electrochemical short circuit. In this NASA SBIR, Navitas Systems will demonstrate and scale up a bifunctional membrane separator that impedes polysulfide transport. Bifunctionality will combine pore structure engineered for high capacity and selectivity to polysulfides with metal-like electronic conductivity to support electrochemical regeneration. The proposed membranes will be fabricated using slurry cast methods that readily scale to continuous roll-to-roll production. The slurry will combine a nanoporous conductive ceramic powder with a binder and solvent. Slurries will be castable onto conventional porous polyolefin battery separators. In Phase I, membrane separators will be produced at bench scale and evaluated to assure good adhesion and uniform dispersion at the target weight loading, with minimal added impedance to lithium ion transport. Membrane separators will be incorporated into prototype lithium sulfur batteries and subjected to commercially relevant performance and life testing.