Membranes and Materials for Energy Efficiency - Subtopic d) Other. Title: Polysulfide-Blocking Polymer Membrane Separators for Rechargeable Lithium-Sulfur Batteries

Renewable sources of energy including solar and wind are fast gaining ground on fossil fuels, in part because of their sustainability and environmental benefits. A major issue, however, has been finding efficient ways to store the energy that renewables generate for use when the demand for energy is high. Lithium-­‐sulfur batteries, which store electrical energy by transferring electrons to or from a sulfur electrode, are well poised to provide high-­‐density, long-­‐term and low-­‐cost electrochemical energy storage. The potential of lithium-­‐sulfur batteries has yet to be fully realized, however, due to the uncontrolled migration of soluble sulfur species through the membrane. This crossover of polysulfides through the membrane reduces battery efficiency and lifetime. Novel polysulfide-­‐blocking membranes have shown promise in laboratory-­‐scale demonstrations; however, a low-­‐cost manufacturing process for these membranes has yet to emerge. Therefore, in Phase I of this project, the viability of translating these seminal discoveries into large-­‐area ion-­‐selective membranes suitable for developing lithium-­‐sulfur battery prototypes will be assessed. To do so, a batch process for the large-­‐scale synthesis of leading-­‐edge polysulfide-­‐blocking membrane materials will be established. Thereafter, a roll-­‐to-­‐roll coating process will be developed, whereby inks of these polysulfide-­‐blocking membrane materials are deposited in a continuous manner onto large-­‐area porous polymer supports. The influence of coating strategy on membrane performance metrics, including overall membrane resistance and sustained polysulfide-­‐blocking ability, will be carefully evaluated in order to advance a process to a pilot coater in Phase II and beyond. The economic benefits of wide-­‐spread adoption lithium-­‐sulfur batteries that incorporate polysulfide-­‐ blocking membranes are clear: lithium-­‐sulfur batteries reduce the cost of electrochemical energy storage five-­‐fold. The environmental benefits are likewise clear: sulfur is a recycled material, essentially a by-­‐product of the oil industry; its use obviates the need for toxic and expensive heavy metals. From a technical perspective, the volumetric energy density of the lithium-­‐sulfur battery is twice that of today’s lithium-­‐ion battery technology. From the consumer perspective, it follows that vehicles powered by light-­‐weight lithium-­‐sulfur batteries would double their present range. Lithium-­‐sulfur batteries offer safety advantages over lithium-­‐ion batteries and are therefore also attractive for behind-­‐the-­‐meter storage in commercial buildings and homes. On that point, in 2020 at least 400 MW of annual installed capacity is projected for these distributed energy resources, which comes at a cost of $400 million using today’s lithium-­‐ion pricing. Lithium-­‐sulfur batteries would provide cost savings of >$80M annually, presuming a conservative market penetration (initially) of at least 25%. Notably, these markets are growing significantly, greater than 45% annually. Rechargeable lithium-­‐sulfur battery technology is critical to our nation’s energy security. Their integration in electric vehicles and in homes allows consumers expanded choice to productively integrate renewables to serve their daily energy needs. This award supports the development of new membranes that ensure these batteries enjoy a long life.