Pyrazine induced synergetic amelioration of Li2Sx shuttling and improvement of lithium-sulfur battery performance

Abstract

Although lithium‑sulfur (LiS) batteries possess an exceptional theoretical specific capacity, their practical application has long been hindered by the severe shuttle effect of lithium polysulfides (LiPSs) and sluggish redox kinetics. To address these core challenges, this study proposes an electrolyte additive strategy based on nitrogen-containing heterocyclic molecules, systematically investigating the regulatory effects of pyridine, pyrazine, and 1,3,5-triazine on LiPS interfacial chemistry. All three additives are capable of anchoring LiPSs through LiN coordination and effectively modulating their frontier molecular orbital energy levels, thereby accelerating LiPS conversion and promoting the formation of three-dimensional (3D) Li2S deposition structures. Among them, pyrazine exhibits unique advantages due to its para-dinitrogen configuration: it not only achieves potent chemical anchoring but also reacts in situ with LiPSs to generate organosulfur intermediates, synergistically suppressing the shuttle effect and significantly enhancing sulfur utilization. Most importantly, this molecule achieves an optimal balance between coordination strength, orbital modulation capability, and interfacial stability. Consequently, the LiS cell utilizing the pyrazine additive delivers an initial discharge capacity of 709.48 mAh g−1 at 1C. Under practical conditions of high sulfur loading (3.0 mg cm−2) and lean electrolyte (E/S = 13.3 μL mg−1), the cell maintains a high reversible capacity of 527.06 mAh g−1 after 120 cycles at 0.2C, highlighting its superior cycling stability and potential for practical application.