A Garnet‐Type Solid‐Electrolyte‐Based Molten Lithium−Molybdenum−Iron(II) Chloride Battery with Advanced Reaction Mechanism

Solid-electrolyte-based molten-metal batteries have attracted considerable attention for grid-scale energy storage. Although ZEBRA batteries are considered one of the promising candidates, they still have the potential concern of metal particle growth and ion exchange with the β"-Al2 O3 electrolyte. Herein, a Li6.4 La3 Zr1.4 Ta0.6 O12 solid-electrolyte-based molten lithium-molybdenum-iron(II) chloride battery (denoted as Li-Mo-FeCl2 ) operated at temperature of 250 °C, comprising a mixture of Fe and LiCl cathode materials, a Li anode, a garnet-type Li-ion ceramic electrolyte, and Mo additive, is designed to overcome these obstacles. Different from conventional battery reaction mechanisms, this battery revolutionarily synchronizes the reversible Fe-Mo alloying-dealloying reactions with the delithiation-lithiation processes, meaning that the porous Mo framework derived from Fe-Mo alloy simultaneously suppresses the growth of pure Fe particles. By adopting a Li anode and a Li-ion ceramic electrolyte, the corrosion problem between the cathode and the solid electrolyte is overcome. With similar battery cost ($12 kWh-1 ), the theoretical energy density of Li-Mo-FeCl2 battery surpasses that of a Na-FeCl2 ZEBRA battery over 25%, to 576 Wh kg-1 and 2216 Wh L-1 , respectively. Experimental results further prove this cell has excellent cycling performance (472 mAh gLiCl-1 after 300 cycles, 50 mg active material) and strong tolerance against the overcharge-overdischarge (3-1.6 V) and freezing-thawing (25-250 °C) incidents.