Fig. 1: Fragmentation of solid Sb and resulting high capacity.

a Discharge potential of monolithic Sb electrodes in a three-electrode cell discharged to 160, 320, 480, 660, and 731 mAh g⁻¹ Sb, respectively, using constant current (25 mA) in CaCl₂-LiCl electrolyte at 520 °C. b Optical cross-section images of monolithic Sb electrodes at each state of discharge targeted in (a), and electron microscopy images at 160 and 660 mAh g⁻¹ Sb, showing the fragmentation of Sb with the formation of Ca-Sb compounds based on EDS point analysis. c SEM images of the desalted Sb positive electrode in a fully charged state after ~1100 discharge/charge cycles, primarily at a rate of C/5 between 0.6 and 1.3 V, showing a porous, networked structure consisting of micron-scale positive electrode particles. d Equilibrium potential of particulate Sb (square symbols) as a function of specific capacity via coulometric titration compared to the emf of binary Ca-Sb alloys (solid lines) using a liquid CaCl₂-LiCl electrolyte (red) in this work or a solid CaF₂ electrolyte (blue)¹⁶ in previous works. e Emf measurements of binary Ca-Sb alloys (54–65 at% Ca) in a liquid CaCl₂-LiCl electrolyte. These results were replicated in two additional and identical three-electrode cell assemblies.