Rechargeable sodium-metal batteries (RSMBs) with high energy density and low cost are attracting extensive attention as promising energy-storage technologies. However, the poor cyclability and safety issues caused by unstable solid electrolyte interphase (SEI) structure and dendrite issues limit their practical application. Herein, it is theoretically predicted that constructing the Ni3 S2 /Ni3 P heterostructure with high work function can lower the Fermi energy level, and therefore effectively suppressing continuous electrolyte decomposition derived from the electron-tunneling effect after long-term sodiation process. Furthermore, the Ni3 S2 /Ni3 P heterostructure on 3D porous nickel foam (Ni3 S2 /Ni3 P@NF) is experimentally fabricated as an advanced Na-anode current collector. The seamless Ni3 S2 /Ni3 P heterostructure not only offers abundant active sites to induce uniform Na+ deposition and enhance ion-transport kinetics, but also facilitates the formation of stable SEI for dendrite-free sodium anode, which are confirmed by cryogenic components transmission electron microscopy tests and in situ spectroscopy characterization. As a result, the Na-composite anode (Ni3 S2 /Ni3 P@NF@Na) delivers stable plating/stripping process of 5000 h and high average Coulombic efficiency of 99.7% over 2500 cycles. More impressively, the assembled sodium-ion full cell displays ultralong cycle life of 10 000 cycles at 20 C. The strategy of stabilizing the sodium-metal anode gives fundamental insight into the potential construction of advanced RSMBs.
Keywords: Fermi level; current collectors; heterostructures; sodium-metal batteries; solid electrolyte interphase.
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