Transformation of Polysulfide Catholyte Chemistry through Lithium-Arene Complexes for Superior Solubility and Cyclability in Li–S Batteries

The development of high-performance lithium–sulfur batteries (LSBs) has been focused on overcoming the limitations associated with traditional polysulfide catholyte synthesis. We report an innovative catholyte synthesis method using lithium-arene complexes, offering significant advancements in terms of solubility, stability, and scalability. By leveraging the interaction of metallic lithium with biphenyl (BP) and sulfur, we developed a Li+BP+S catholyte formulation that outperforms conventional Li₂S+S systems. The Li+BP+S catholyte demonstrates superior solubility, achieving up to 12 M active sulfur and faster dissolution rates at lower temperatures, reducing preparation times by 66%. Electrochemical evaluations revealed enhanced capacity retention, with the catholyte maintaining 83.2% of its initial capacity after 500 cycles and exhibiting minimal capacity fading of 0.03% per cycle. Material characterization confirmed a uniform sulfur distribution, improved charge transfer capability, and reduced polysulfide clustering, as evidenced by nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) analyses. The Li+BP+S system also demonstrated high-rate capability and long-term stability, retaining significant capacity under lean electrolyte conditions. The mechanism by which the addition of arenes aids Li dissolution is also proposed on the basis of theoretical calculations. These findings highlight the potential of lithium–arene complexes to revolutionize LSB technology, paving the way for safer, more efficient, and scalable LSB systems.