A thermodynamically stable quasi-liquid interface for dendrite-free sodium metal anodes

Dendrite-associated cell degradation is a key challenge to the practical application of sodium metal anodes. Here, we present that incorporation of a tiny amount of mercury into sodium generates a unique quasi-liquid interface that affords long-term cycling stability. This amalgam layer allows fast electron transfer and sodium migration at the electrolyte-electrode interphase, which significantly promote the cycling performance over 5000 h with a practically desired capacity of 2 mA h cm(-2) and a current density of 8 mA cm(-2). In situ optical microscopy analyses confirm that dendrite nucleation and growth can be remarkably suppressed with the amalgam-protected anodes. Prototype full cells also demonstrate a much improved rate and long-term cycling stability. These promising results provide new perspectives on the regulation of sodium electrodeposition by introducing low-melting metals and hence the elimination of the dendritic morphology for the practical development of sodium metal batteries.