Holey amorphous FeCoO-coated black phosphorus for robust polysulfide adsorption and catalytic conversion in lithium–sulfur batteries

Abstract

The application of lithium–sulfur (Li–S) batteries is hindered by the severe shuttle effect and sluggish redox conversion kinetics of lithium polysulfides (LiPSs). Herein, holey amorphous dual transition metal (cobalt and iron) oxide-coated black phosphorus nanosheets (BP@FeCoO) have been synthesized and utilized as a sulfur host in Li–S batteries. From the compositional outlook, compared with the individual counterparts, the hybrid material of BP and amorphous FeCoO containing rich oxygen vacancies has enhanced adsorption ability and catalytic activity toward LiPSs, as well as improved electrical conductivity and Li-ion diffusion rate. From the structural feature perspective, the 2D nanosheets decorated with abundant meso/microporous channels greatly enlarge the surface area of the BP@FeCoO electrode, which offers sufficient active sites for accommodating sulfur active species and provides buffer space to withstand the volume changes during the charge/discharge process. Due to these compositional and structural superiorities, the Li–S battery with BP@FeCoO/S electrode exhibited excellent electrochemical performance with high cycle stability (fading rate of 0.040% per cycle at 1C) and outstanding rate capability (644.3 mA h g⁻¹ at 5C). More impressively, with a high sulfur loading of 6.0 mg cm⁻², the BP@FeCoO/S electrode showed a high capacity of 903.9 mA h g⁻¹ at 0.2C.