LiFSA-KFSA Binary Molten Salt Enables Durable Lithium-antimony Batteries at 80-100 °C

Abstract

The transition to decarbonized energy systems necessitates large-scale, cost-effective grid storage solutions. While lithium-antimony (Li||Sb) molten-salt batteries offer high power density and long cycle life, their traditional operation above 400 ℃ presents major engineering and cost hurdles. Here, we report a transformative Li||Sb molten-salt battery that operates at 80-100 ℃ using a lithium bis(fluorosulfonyl)imide and potassium bis(fluorosulfonyl)imide (LiFSA-KFSA) binary molten salt electrolyte. This system achieves high energy density and high-power density (~308.78 Wh kg−1, ~8958.12 W kg−1) and remarkable long-term cyclability, retaining 48.68% capacity over 2000 cycles. In-situ synchrotron X-ray characterization elucidates a highly reversible phase evolution in micron-sized Sb during (de)lithiation, facilitated by a stabilizing anion-derived inorganic solid-electrolyte interphase. This work redefines Li||Sb batteries as a practical mid-temperature technology, offering a durable and potentially low-cost candidate for grid-scale energy storage.