Leveraging doping strategies and interface engineering to enhance catalytic transformation of lithium polysulfides for high-performance lithium-sulfur batteries.

The commercialization of lithium-sulfur (Li-S) batteries has faced challenges due to the shuttle effect of soluble intermediate polysulfides and the sluggish kinetics of sulfur redox reactions. In this study, a synergistic catalyst medium was developed as a high-performance sulfur cathode material for Li-S batteries. Termed A/R-TiO@ Ni-N-MXene, this sulfur cathode material features an in-situ derived anatase-rutile homojunction of TiO nanoparticles on Ni-N dual-atom-doped MXene nanosheets. Using in-situ transmission electron microscopy (TEM) technique, we observed the growth process of the homojunction for the first time confirming that homojunctions facilitated charge transfer, while dual-atom doping offered abundant active sites for anchoring and converting soluble polysulfides. Theoretical calculations and experiments showed that these synergistic effects effectively mitigated the shuttle effect, leading to improved cycling performance of Li-S batteries. After 500 cycles at a 1C rate, Li-S batteries using A/R-TiO@Ni-N-MXene as cathode materials exhibited stable and highly reversible capacity with a capacity decay of only 0.056 % per cycle. Even after 150 cycles at a 0.1C rate, a high-capacity retention rate of 62.8 % was achieved. Additionally, efficient sulfur utilization was observed, with 1280.76 mA h/g at 0.1C, 694.24 mA h/g at 1C, alongside a sulfur loading of 1.5-2 mg/cm. The effective strategy based on homojunctions showcases promise for designing high-performance Li-S batteries.