In-Situ Alloy-Modified Sodiophilic Current Collectors for Anode-Less Sodium Metal Batteries

Anode-less sodium metal batteries have drawn dramatica attention owing to their high specific energy and low cost. However, the growth of sodium dendrites and the resulting loss of active materials and serious safety concerns hinder their practical applications. In this work, a bismuth-based modification layer with good sodiophilicity is constructed on the surface of Cu foil (denoted as Cu@Bi) to control the deposition of Na metal. The activation-derived porous Na-rich alloy phase can provide abundant nucleation sites and reduce the nucleation overpotential to induce the uniform and dense deposition of Na metal. When evaluated in half cell, the Cu@Bi current collectors can operate for 750 h at 1 mA cm−2 and 1 mAh cm−2, with an average coulombic efficiency (CE) of 99.5%. When the current density is improved to 2 mA cm−2, the Cu@Bi can also stably maintain for 750 cycles, demonstrating the remarkable effect of the modification layer. When coupled with the Na3V2(PO4)3 cathode, the full cell exhibits stable cycle performance over 80 cycles. The modification strategy of alloy modification can provide fresh ideas for the research and application of anode-less and even anode-free metal batteries.