Stabilizing sodium metal anode by in-situ formed Ag metal layer

Abstract

The key to practical applications of sodium (Na) metal batteries is to develop high-performance Na metal anode. However, the unstable electrode/electrolyte interface induced by the Na dendrite growth severely shortens the working life of Na metal anode. In this work, we have developed a facile method based on a replacement reaction to construct an Ag metal layer for Na metal electrodes. The presence of robust and sodiophilic Ag metal layer can guide the uniform plating and stripping of Na ions on the surface of Na metal anode and effectively suppress the Na dendrite growth. Benefiting from a stable electrode/electrolyte interface, the increase of interfacial resistance of the Ag-protected Na metal (Na@Ag) electrode is significantly lower than that of the bare Na electrode after repeated plating/stripping. As a result, the symmetric cell with two identical Na@Ag electrodes exhibits superior cycling stability with stable over-potentials for more than 1100 h at a current density of 1 mA cm−2 and good rate performance with an over-potential of 210 mV at a current density of 5 mA cm−2 compared to the symmetric cell with two identical bare Na electrodes. Moreover, the full cell with an NaTi2(PO4)3 (NTP) cathode and an Na@Ag anode maintains good cycling stability with a capacity retention of 93.8% after 600 cycles, while the Na||NTP full cell breaks down in the 243th cycle.