Assessment of Mixed-Cation Molten Salt Electrolytes for Li-based Liquid Metal Batteries

The implementation of Li-based liquid metal batteries (LMBs) for grid-scale energy storage has been limited by the high cost of materials, especially for fabrication of Li-halide based molten salt electrolytes (e.g., LiCl, LiBr, LiF, LiI). This study aims to determine the impact of incorporating lower cost alkali/alkaline earth halide salts with foreign cations (e.g., Sr2+, 2+ , K+) + ) into a Li-based molten salt electrolyte to build a foundation for continued LMB electrolyte design and development. The widely reported LiF-LiCl-LiBr (22-31-47 mol%, T m = 430-443 degrees C) electrolyte is used within the Li || Sb-Sn LMB system as a baseline from which to compare the performance of similar systems with eutectic salts of LiCl-SrCl2 2 (64.3-35.7 mol%, T m = 489 degrees C) and LiCl-KCl (59.2-40.8 mol%, T m = 352 degrees C) with a specific focus on the positive Sb-Sn electrode in a 3-electrode cell. While good chemical reversibility was maintained for the Li || Sb-Sn systems with mixed-cation molten salts, a shift in the electroactive species from Li + to Sr2+ 2+ limited the capacity of the LMB system with a LiCl-SrCl2 2 electrolyte and reduced rate capability was observed for the LiCl-KCl containing system.