(Digital Presentation) Higher Surface Area Lithium Anode for Mediated Lithium-Sulfur Flow Batteries

Abstract

There is a need for safe, reliable, high capacity storage for long duration energy storage. The low cost and high capacity of sulfur make Li-S batteries ideal for this purpose. However, sulfur has poor electrical conductivity and Li-S batteries are prone to polysulfide shuttling that decreases the battery life. Additionally, lithium metal cannot be cycled at high rates or dendritic growth is produced. We have previously addressed the issues with the S by combining aspects of a static Li-S battery with aspects of a redox targeting system and flow battery. With this system we demonstrated that fundamental Li-S chemistry and novel SEI engineering strategies can be adapted to the hybrid redox flow battery architecture, obviating the need for ion-selective membranes or flowing carbon additives, and offering a potential pathway for inexpensive, scalable, safe MWh scale Li-S energy storage.However, with a planar Li anode the current density was limited to 0.5 mA cm-2, severely limiting the flow battery power output. In this study we present recent progress developing higher surface area anodes to enhance the rate performance of Li metal anodes in flow batteries. The high effective surface area of these structures decreases the local current density while maintaining a high device-level current and thus charge rate. The low local current density and seeded nucleation points on the scaffold promote uniform Li deposition during charging. Candidate electrode materials are evaluated in a mediated Li-S flow battery and cycling rate and capacity retention are compared against a traditional planar Li anode.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.