Multi-Functional and Conformal Na-Ion Conducting Membrane for Dendrite and Polysulfide Shuttle Suppression for Next Generation Room Temperature Sodium-Sulfur Batteries

To achieve adoption of large scale stationary electrical energy storage systems at economically and environmentally sustainable levels, cost and volumetric energy density are driving the choice of battery chemistry. Room temperature sodium-sulfur batteries are an ideal candidate for these applications as this chemistry is capable of achieving theoretical gravimetric and volumetric energy densities 2.5- to 3-fold higher than lithium ion at a fraction of the cost. Despite the advantages to energy density and cost, room temperature sodium-sulfur batteries have not reached commercial readiness, as they suffer from several key challenges including sodium dendrite formation, anode stability, and polysulfide shuttling, resulting in degradation on the anode, low efficiency, safety concerns, and shortened cycle life. This program will design a membrane to specifically address safety and cycle life for room temperature sodium-sulfur batteries. The resulting membrane will block polysulfide migration while conducting sodium ions between electrodes, and suppress uneven plating and dendrite formation during cycling. This will significantly reduce safety concerns and increase cycle life. In Phase I, each component of the membrane will be optimized and the final membrane design will be confirmed in full cells. Cycling and safety improvements over current separators will demonstrated, and the membrane will be characterized to demonstrate excellent ion conduction, dendrite suppression and ability to prevent anode corrosion. Stationary storage for grid applications is a major application for this technology, but improvements in safety and cycle life will widen the range of applications that can benefit from this next generation battery system to include electric vehicles along with a wide range of backup power applications.