Stable artificial solid electrolyte interphase with lithium selenide and lithium chloride for dendrite-free lithium metal anodes

Li dendrite growth and corresponding parasitic reactions are inherent vulnerability of lithium metal anodes, limiting practical adoption. Here, we report a stable artificial solid electrolyte interphase (SEI) layer consisting of Li2Se and LiCl with high Li ion conducting and insulating properties fabricated through a facile and low-cost approach. The designed artificial SEI layer on Li blocks direct contact with the electrolyte and enables dendrite-free Li plating through the artificial SEI layer. With these benefits, Li anodes modified with an artificial SEI show dendrite-free Li plating behaviors with a lower porosity of 30% compared to that of bare Li (43%) at a high current density of 5.0 mA cm−2 and a high capacity of 40 mAh cm−2. In addition, modified anodes exhibit stable cyclability with lower overpotentials in Li symmetric cells operated at 1.0 mA cm−2 with 1.0 mAh cm−2 for 400 cycles. The significant improvement in cycling performance over hundreds of cycles is achieved using LiCoO2 and LiFePO4 cathodes. Furthermore, higher average Coulombic efficiency of 96.4% is realized in a full cell consisting of a high-capacity Ni0.8Co0.1Mn0.1O2 (3.5 mAh cm−2) and thin (50 μm) modified Li anodes compared to that of bare Li anodes (94.3%).