(Invited) Stabilizing the Electrodes and Interfaces in Lithium-Sulfur Batteries

As the electrification of transportation sector and grid storage of electricity produced from renewable sources like solar and wind are rapidly evolving, cost, sustainability, and supply chain challenges will become the dominant issue. Lithium-sulfur batteries offer significant sustainability and cost advantages compared to the currently used lithium-ion batteries as sulfur is abundant and inexpensive and offers an order of magnitude higher capacity than the oxide cathodes. However, the commercialization of lithium-sulfur batteries is met with a few challenges, such as poor cycle life in practical cells. These challenges originate from the poor electronic and ionic conduction in sulfur and its discharged products, polysulfide shuttle, and poor cyclability of lithium-metal anode. To overcome some of these difficulties, generally a large amount of conductive carbon and liquid electrolyte are added to the cell; they enhance the cycle life, but drastically lower the practical energy density and make the lithium-sulfur batteries uncompetitive with lithium-ion batteries. To overcome the above challenges, this presentation will focus on optimizing sulfur and lithium sulfide cathodes, incorporation of electrocatalysts into the cathode to enhance sulfur redox, development of advanced electrolytes, incorporation of additives into the cathode and electrolyte to stabilize the cathode-electrolyte and anode-electrolyte interfaces, anode-free cells that eliminate the handling of thin lithium-metal foils, while keeping the sulfur loading and electrolyte/sulfur ratio at a practically accepted level. The improvements achieved and the mechanisms involved in the performance improvement will be discussed based on in-depth characterization data obtained with time-of-flight secondary ion spectrometry (TOF-SIMS), x-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR) spectroscopy, etc .