Simultaneous Formation of Artificial SEI Film and 3D Host for Stable Metallic Sodium Anodes.

Metallic sodium is a promising anode for sodium-based batteries, owing to its high theoretical capacity (1165 mAh g) and low potential (-2.714 V vs standard hydrogen electrode). However, the growth of sodium dendrites and the infinite volume change of metallic sodium during sodium striping/plating result in a low Coulombic efficiency and poor cycling stability, generating a safety hazard of sodium-based batteries. Here, an efficient approach was proposed to simultaneously generate an artificial SEI film and 3D host for metallic sodium based on a conversion reaction (CR) between sodium and MoS (4Na + MoS = 2NaS + Mo) at room temperature. In the resultant sodium-MoS hybrid after the conversion reaction (Na-MoS (CR)), the production NaS is homogeneously dispersed on the surface of metallic sodium, which can act as an artificial SEI film, efficiently preventing the growth of sodium dendrites; the residual MoS nanosheets can construct a 3D host to confine metallic sodium, accommodating largely the volume change of sodium. Consequently, the Na-MoS (CR) hybrid exhibits very low overpotential of 25 mV and a very long cycle stability more than 1000 cycles. This novel strategy is promising to promote the development of metal (lithium, sodium, zinc)-based electrodes.