rGO@TiO2-x Schottky heterojunction for enhanced bidirectional catalysis in polysulfide conversion

Few-layered N-doped rGO nanosheets covered with defective TiO2-x nanoparticles form an enriched 2D/0D Schottky heterojunction through interfacial N-Ti and C-Ti bonds, serving as a bipolar cathode host for lithium-sulfur batteries with enhanced electrochemical properties. [Display omitted] The shuttling and sluggish conversion kinetics of lithium polysulfides (LiPSs) lead to poor cycling performance and low energy efficiency in lithium-sulfur batteries (LSBs). In this work, a hierarchically structured nanocomposite, synthesized through a surfactant-directed hydrothermal growth following dopamine-protected pyrolysis, serves as a bidirectional catalyst for LSBs. This nanocomposite comprises N-doped reduced graphene oxide (rGO) nanosheets anchored with uniformly distributed TiO2-x nanoparticles via interfacial N-Ti and C-Ti bonding, resulting in the formation of abundant 2D/0D Schottky heterojunctions (rGO/TiO2-x). Density functional theory (DFT) calculations and in situ Raman characterizations demonstrate that rGO/TiO2-x effectively inhibits the shuttling of LiPSs with enhanced redox kinetics, achieving high utilization of the sulfur cathode and improving the overall reversibility. A high areal capacity is attained at a high sulfur loading and a low electrolyte/sulfur ratio. The initial specific capacity reaches 1010 mA h g−1 at a current density of 0.2C (1C = 1675 mA g−1), and a retention of 86.4 % is attained over 100 cycles. A light-emitting diode (LED) screen using two LSBs with rGO/TiO2-x demonstrates their high potential for practical applications.