Novel hydrothermal synthesis of Mn-TaS3@rGO nanocomposite as a superior multifunctional mediator for advanced Li-S batteries

Abstract

Because of its high theoretical capacity and energy density, the lithium-sulfur (Li–S) battery is a desirable next-generation energy storage technology. However, the shuttle effect of lithium polysulfide and the slow sulfur reaction kinetics remain significant barriers to Li–S battery application. In this work, tantalum trisulfide (TaS3) and selective manganese-doped tantalum trisulfide (Mn-TaS3) nanocomposites on reduced graphene oxide surface were developed via a one-step hydrothermal method for the first time and introduced as a novel multifunctional mediator in the Li-S battery. The surface engineering of Mn-TaS3@rGO with abundant defects not only exhibits the strong adsorption performance on lithium polysulfides (LiPSs) but also demonstrates the remarkable electrocatalytic effect on both the LiPSs conversion reaction in symmetric cell and the Li2S nucleation/dissolution processes in potentiostatic experiments, which would substantially promote the electrochemical performance of LSB. The cell assembled with Mn-TaS3@rGO/PP modified separator could significantly improve the cell conductivity and effectively accelerate the redox conversion of active sulfur during the charging/discharging process, which delivers exceptional long-term cycling with 683 mA h g−1 retention capacity after the 1000th cycle at 0.3C under the sulfur loading of 2.7 mg cm−2. Even at the E/S ratio as low as 5.0 µL mg−1, the reversible specific capacity of 692 mA h g−1 can be offered at 0.2C over 300 cycles. This research indicates that the novel Mn-TaS3@rGO multifunctional mediator is successfully fabricated and applied in Li-S batteries with extraordinary electrochemical performances and gives a strategy to explore the construction of a modified functional separator.