A bifunctional VS2-Ti3C2 heterostructure electrocatalyst for boosting polysulfide redox in high performance lithium-sulfur batteries

The commercial development of lithium-sulfur batteries (LSBs) is extremely hindered due to the shortcomings of sluggish reaction kinetics and the lithium polysulfide (LiPS) shuttling effect. For overcoming these limitations, a bifunctional VS2-Ti3C2 heterostructure electrocatalyst is designed as a sulfur host material in LSBs, combining suitable adsorption capacity, enhanced catalytic activity, and layer-by-layer interstitial channels to achieve a balanced and efficient "capture-diffusion-catalysis" process. Density functional theory (DFT) calculations indicate that the intrinsically conductive VS2-Ti3C2 possesses an elevated d-band center, improving interaction with LiPSs and accelerating interfacial electron transfer. In addition, the layer interstitial spaces of the 3D lamellar interspersed network facilitate lithium ion diffusion. As a result, LSBs assembled with VS2-Ti3C2/S exhibit a high reversible discharge capacity (1237 mA h g(-1) at 0.2C), excellent rate performance (559 mA h g(-1) at 10C), and robust cycle stability (0.024% decay rate after 500 cycles at 1C). Moreover, even at a high sulfur loading of 4.0 mg cm(-2), a favorable capacity of 852 mA h g(-1) with a capacity retention of 90.5% is still maintained after 150 cycles. This work provides inspiring insights into heterostructure materials with a high rate and sulfur loading in mediating conversions and migrations of matter toward LSBs with promising performance.