A synergistic engineering layer with a versatile H2Ti3O7 electrocatalyst for a suppressed shuttle effect and enhanced catalytic conversion in lithium-sulfur batteries

Abstract

Lithium-sulfur batteries (Li-S batteries) are considered a promising technology for advanced energy storage devices, owing to their exceptionally high theoretical energy density and cost-effectiveness. However, the detrimental polysulfide shuttle effect and the sluggish redox kinetics of Li-S batteries are the major obstacles to the development of high-performance Li-S batteries. In this study, a synergistic engineering layer comprising a versatile H2Ti3O7 electrocatalyst and conductive supporting materials (HTO-sCNT-G) was developed for advanced Li-S batteries. In the ingenious three-dimensional internal hierarchical percolating microstructure of HTO-sCNT-G, the polar H2Ti3O7 nanowires acted as an effective mediator of polysulfide (PS) conversion and suppressed the shuttle effect due to their strong chemical interaction with PSs, while the carbon components (CNTs and graphene) provided a three-dimensional conductive network that increased the electronic conductivity of H2Ti3O7. Furthermore, the hierarchical porous structure without graphene overstacking increased the accessible surface area for rapid Li+ diffusion, thereby improving the ionic conductivity, and HTO-sCNT-G acted as an auxiliary sulfur host, providing an additional conductive network to reutilize the trapped PSs. Owing to the synergistic effect of HTO-sCNT-G, the resultant Li-S batteries exhibited an excellent electrochemical performance with a significantly high reversibility (1001 mA h g(-1) after 100 cycles at 0.2C and 794 mA h g(-1) after 500 cycles at 1C with an ultralow capacity decay of 0.057% per cycle) and improved rate capabilities at different current rates (792.1, 631.7, and 509.5 mA h g(-1) at 1, 2, and 3C). Thus, this study provides new insight for the development of synergistic engineering interlayers/modified separators for advanced Li-S batteries without elaborate electrocatalyst-conductive agent hybrid synthesis.