Constructing Co/CoV2O6 tandem catalytic heterostructure to enhance lithium polysulfide conversion in lithium-sulfur batteries

The “shuttle effect” caused by polysulfide (LiPSs) dissolution and diffusion is a great challenge for sulfur (S) cathode in lithium-sulfur batteries (LSBs). Herein, we have successfully constructed Co/CoV ₂O ₆ tandem catalytic heterostructure anchored by N-doped carbon (Co/CoV ₂O ₆ /NC) via an impregnation-assisted pyriaolysis method. The “adsorption-transfer-conversion” tandem catalytic mechanism for LiPSs is realized by utilizing the three behaviors of the strong chemical adsorption of CoV ₂O ₆ to LiPSs, the strong conversion of Co to LiPSs, and the transport effect of CoV ₂O ₆ ←Co interfacial built-in electric field to polysulfide ions. This can effectively suppress the “shuttle effect” by separating the adsorption and conversion process of LiPSs at different active sites. The tandem catalytic characteristic coupled with the interfacial Co-N and V-N bonds among Co, CoV ₂O ₆ and NC, the high electrical conductivities of metal Co and NC conducting network, the hierarchical porous structure of polyhedral framework, collectively endow Co/CoV ₂O ₆ /NC@S cathode with strong structural stability, weak electrochemical polarization, good electrochemical reversibility and fast electrochemical kinetics. As a result, Co/CoV ₂O ₆ /NC@S cathode presents the significantly enhanced electrochemical performance with a high capacity of 558.4 mAh g ⁻¹ at 0.2 C after 100 cycles and a low-capacity decay rate of 0.123% per cycle during 300 cycles at 1 C.