Straight-chain thiols as chemical kinetic transporters accelerate Li2S 3D nucleation

Abstract

The slow kinetics of intrinsic polysulfide conversion in lithium–sulfur batteries (LSBs) induce excessive build-up of polysulfides, potentially promoting the shuttling effect and higher active material loss. Here, we develop a class of straight-chain thiols as chemical power transmitters. The influence of chain length and the number of thiol molecules on lithium–sulfur batteries are analyzed and characterized. The results indicate that 1,8-octanedithiol (1,8-OT) exerted the best modification effect. In addition, 1,8-OT could chemically react with polysulfides, which promoted the conversion of long-chain polysulfides to short-chain, and enhanced the 3D nucleation kinetics of lithium sulfide (Li₂S), efficiently preventing the shuttle effect. This is ascribed to the strong thiophilicity of 1,8-OT, which binds to polysulfides via S–S bonding, a chemical process that enhances the conversion of polysulfides. These findings are confirmed by gas chromatography, mass spectrometry (GCMS), and Raman spectroscopy. Consequently, for constant potential and rate tests, 1,8-OT has a high deposition capacity of 445.4 mA h g⁻¹ and a reversible capacity of 811 mA h g⁻¹ at 2C, which still retained 94% of the initial capacity after recovery to 0.1C. This study offers valuable insights into the chemistry of polysulfides, serving as a key reference for advancing their use in chemical catalysis.