Monolayer FeGeX (X = S, Se, and Te) as Highly Efficient Electrocatalysts for Lithium-Sulfur Batteries.

The high energy density, low cost, and environmental friendliness of lithium-sulfur (Li-S) batteries enable them to be promising next-generation energy storage systems. However, the commercialization of Li-S batteries is presently hindered by the bottlenecks, such as the low conductivity of sulfur species, shuttle effect of polysulfides, and poor conversion efficiency in discharging/charging processes. Here, on the basis of first-principles calculations, we predicted that the two-dimensional magnetic FeGeX (X = S, Se, and Te) monolayers are quite promising to overcome the aforesaid problems. The FeGeX monolayer has metallic electronic structures and moderate binding strength to the soluble lithium polysulfides, which are expected to improve the overall electric conductivity of sulfur species and anchor the soluble lithium polysulfides to suppress the shuttle effect. Remarkably, FeGeX monolayers show bifunctional electrocatalytic activity to the S reduction reaction and the LiS decomposition reaction, which improves the conversion efficiency in discharging and charging processes. This finding may open up an avenue for the development of high-performance Li-S batteries.