Room-temperature liquid metal engineered iron current collector enables stable and dendrite-free sodium metal batteries in carbonate electrolytes

• A cheap Fe-based current collector is designed as the current collector. • Liquid metal is coated on the current collector to act as nucleation seeds. • The inherent mechanism of liquid metal in inhibiting Na dendrites is revealed. • Stable and dendrite-free Na metal anodes are achieved in carbonate electrolytes. • Better electrochemical performance is achieved under the regulation of liquid metal. Metallic sodium (Na) is believed to be a promising anode material for sodium-ion batteries (SIBs) due to its low electrochemical potential, high theoretical specific capacity, superior electrical conductivity, and so on. However, issues such as high chemical activity, the growth of Na dendrites, large volume change, and unstable interface impede its practical application. We design a cheap iron (Fe)-based substrate decorated by a thin liquid metal Ga layer for stable and dendrite-free Na metal anodes in low-cost carbonate electrolytes. The inherent mechanism of Ga-based liquid metal in inhibiting the growth of Na dendrites was revealed for the first time. Liquid metal Ga with sodiophilic property can act as nucleation seeds to decrease the nucleation barrier and induce homogeneous Na + flux, resulting in uniform and dendrite-free Na deposition. Full cells with Na 3 V 2 (PO 4 ) 3 cathode were also assembled to verify the practical application ability of the modified Na metal anode. Under the regulation of the liquid metal layer, the Coulombic efficiency, cycling life, and capacity of batteries are obviously enhanced. The strategy proposed here cannot only reduce the cost of batteries but also improve their electrochemical and safety performance.