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

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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.