A multifunctional ex-situ artificial hybrid interphase layer to stabilize sodium metal anode

The construction of an ex-situ artificial solid electrolyte interphase (SEI) layer has been recognized as a viable solution to address the limitation of sodium metal anode (SMA). However, most artificial SEI layers are generated by a single element (i.e. Na-halides, Na-phosphides, or Na-chalcogenides) limiting the lifespans of SMA. To further enhance the cyclic stability and mechanical strength, a multicomponent interphase layer composed of Na₂Se, Mn metal, and Zn metal (i.e. Na₂Se/MZ) on the surface of Na is proposed. This unique hybrid interphase layer is spontaneously produced via chemical reaction during the rolling/folding of binary metal selenides (MnSe/ZnSe@C) with Na metal. In the Na₂Se/MZ protective layer, Na₂Se enables fast Na transport, Mn atoms further enhance mechanical strength. Specifically, the Zn atoms make an alloy with Na (NaZn₁₃) during the initial deposition of Na which further provides sodiophilic nucleation sites. Compared with artificial interphase layers (Na₂Se/M or Na₂Se/Z) generated by single metal selenides, the Na||Na symmetric cells with multicomponent protected layers demonstrate exceptional extended cycling life of 8000 h and 1200 h at 1 mA cm⁻² and 4 mA cm⁻², respectively. Na@Na₂Se/MZ=|NVP full cells also demonstrate an extended cycling life of 2300 cycles at 15 C with 78 % capacity retention and a high-rate capacity of >60 mAh g⁻¹ at 30 C. Our findings open the path for realizing high capacity and fast-charging SMBs.