Facilitating Sodium Nucleation in Anode-Free Sodium Batteries

Sodium metal batteries (NMBs) have attracted significant attention as next-generation, high energy density battery technologies. However, NMBs are disadvantaged by the excessive Na metal used as the anode, which decreases energy density and safety. So-called anode-free NMBs, where the anode is electrochemically generated during charging, are a promising solution. However, such batteries are still prone to dendrite growth and capacity fade. In this work, we computationally and experimentally screen a range of metals, including Zn, Cu, and alpha-brass, as current collectors for anode-free NMBs. Our results show that Zn was the best performing current collector material, inducing small nucleation overpotentials of -16.5 mV and increasing cycling stability up to 200 cycles with an average Coulombic efficiency of 98.9%. We propose this high performance is due to high lattice compatibility between Na and Zn as well as the formation of a favorable ZnF2-rich interphase. This study offers valuable insight into selecting current collectors and engineering the interfacial chemistry to improve the performance of anode-free NMBs.