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 rates tests, 1,8-OT has a high deposition capacity of 445.4 mAh g^-1 and a reversible capacity of 811 mAh ^-1 at 2 C, which still retained 94% of the initial capacity after recovery to 0.1 C. This study offers valuable insights into the chemistry of polysulfides, serving as a key reference for advancing their use in chemical catalysis.