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 °C presents major engineering and cost hurdles. Here, we report a transformative Li‖Sb molten-salt battery that operates at 80–100 °C 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.