Accelerated Li–S Chemistry at A Cooperative Interface Built In Situ
The performances of lithium–sulfur (Li–S) batteries have been markedly handicapped by the intricate multi-electron sulfur chemistry involving reversible conversion of polysulfides (LiPSs) to Li2S upon discharge and back to S8 upon charge. Herein, graphene in-situ coated TiO2 nanotube is realized via direct chemical vapor deposition (CVD) techinique, leading to the design of graphene-TiO2 (G-TiO2) promotor for Li–S chemistry. With the aid of detailed experimental and theoretical characterizations, we reveal that the direct CVD-derived G-TiO2 realizes not only the coupling of Li+-ion diffusion and electron transfer but also efficient regulation of LiPSs, thereby producing synergistic catalyzing effect on both LiPS conversion and Li2S decomposition. As a result, S/graphene-TiO2 (S/G-TiO2) presents a remarkable rate capability and an ultralow capacity decay rate of 0.052% over 1000 cycles at 2.0 C. Even at a high sulfur loading of 9.4 mg cm–2, such cathode still delivers superior areal capacity of 8.7 mAh cm–2. This work would motivate the deep-seated revisiting of sulfur reaction mechanism and offer a rational strategy to construct high-energy and long-life Li–S batteries.