A Novel TiO₂-Wrapped Activated Carbon Fiber/Sulfur Hybrid Cathode for High Performance Lithium Sulfur Batteries

Traditional Li-ion batteries are encountering a technical hurdle in further increasing their energy density. Li-S batteries have been attracted increasing attention owing to the high theoretical capacity of element sulfur (S, 1672 mAh g^-1). Nevertheless, the insulation nature of the S element and polysulfide shuttle effect, resulting in low S utilization and poor cycling stability, are the main obstacles to widespread practical utilization of Li-S batteries. To tackle these issues, a well-designed hybrid cathode, consisted of S-infused activated carbon fiber (ACF) cloth and a thin TiO₂ wrapping layer (TiO₂-ACF/S), is developed in this work with the TiO₂ wrapping layer as a polysulfide chemisorption layer, while the ACF cloth being a conductive network. Compared to the pure S and ACF/S cathodes, the TiO₂-ACF/S hybrid cathode, with a high S loading of about 3.0 mg cm^-2, displays an improved initial specific capacity (915 mAh g^-1 at 0.2C), cycle stability (capacity retention of 77% after 100 cycles, 702 mAh g^-1), and rate ability (438 mAh g^-1 at 5C). The enhanced electrochemical performances of TiO₂-ACF/S hybrid cathode are attributed to the synergistic effects from TiO₂ (polysulfide chemisorption material), ACF (electronically conductive material) and S (high hosting capacity of Li ions).