Low-cost amorphous-nanocrystalline magnesium halide solid electrolytes

All-solid-state magnesium batteries (ASSMBs) represent a highly promising next-generation energy storage technology. Their commercialization, however, hinges on the development of low-cost solid electrolytes with high Mg2+ conductivity. While substantial research has focused on lithium and sodium halide solid electrolytes, magnesium-based halide systems remain largely underexplored. Herein, we report a class of magnesium antimony halide solid electrolytes synthesized via mechanical milling of low-cost, readily available MgCl2 and SbF3 precursors. The raw materials for these electrolytes are 1–2 orders of magnitude cheaper than those required for state-of-the-art borohydride and chalcogenide systems. The optimized composition, 1.2MgCl2–SbF3, achieves a promising room-temperature Mg2+ conductivity of 3.64 × 10−5 S cm−1 after annealing. A symmetric Mg cell utilizing this electrolyte demonstrates stable cycling at 0.1 mA cm−2 at room temperature. Structural analysis reveals an amorphous–nanocrystalline composite morphology and confirms that a partial anion exchange reaction during processing creates mixed Sb–Cl–F bonding environments, which facilitate Mg2+ migration. This study underscores the significant potential of low-cost halide-based architectures as enablers for ASSMB technology.