Stable sodium metal anode enabled by interfacial room-temperature liquid metal engineering for high-performance sodium–sulfur batteries with carbonate-based electrolyte

Sodium (Na) metal is a competitive anode for next-generation energy storage applications in view of its low cost and high-energy density. However, the uncontrolled side reactions, unstable solid electrolyte interphase (SEI) and dendrite growth at the electrode/electrolyte interfaces impede the practical application of Na metal as anode. Herein, a heterogeneous Na-based alloys interfacial protective layer is constructed in situ on the surface of Na foil by self-diffusion of liquid metal at room temperature, named “HAIP Na.” The interfacial Na-based alloys layer with good electrolyte wettability and strong sodiophilicity, and assisted in the construction of NaF-rich SEI. By means of direct visualization and theoretical simulation, we verify that the interfacial Na-based alloys layer enabling uniform Na⁺ flux deposition and suppressing the dendrite growth. As a result, in the carbonate-based electrolyte, the HAIP Na||HAIP Na symmetric cells exhibit a remarkably enhanced cycling life for more than 650 h with a capacity of 1 mAh cm⁻² at a current density of 1 mA cm⁻². When the HAIP Na anode is paired with sulfurized polyacrylonitrile (SPAN) cathode, the SPAN||HAIP Na full cells demonstrate excellent rate performance and cycling stability.