High-Performance Sodium Metal Batteries with Sodium–Bismuth Alloy Anode

For the application of sodium batteries, one challenge is the irregular deposition and dendrite growth during the cycling process. Herein, we report that spontaneous alloying reactions can occur by the mechanical mixing and pressing processes of the sodium metal and semimetal bismuth powder, which can regulate the deposition of sodium ions. The improvement of the surface tension and affinity to sodium ions of the metal electrode can inhibit the dendrite growth. The alloy anode can be used not only in carbonate-based electrolytes but also in the flame-retardant electrolyte. We demonstrate that the Na–Bi alloy electrode in a carbonate electrolyte keeps stable cyclability with a much lower overpotential of 20 mV for more than 1200 h. The voltage hysteresis can be effectively reduced by using the Na–Bi alloy anode. The Na3V2(PO4)3 electrode with a flame-retardant electrolyte shows a Coulombic efficiency of 99.9% at 585 mA g–1 during long cycles. It still shows an impressive capacity retention of 95%.