锂硫电池具有理论能量密度高、成本低等优点，是当前电池领域的研究热点。高电解液用量、穿梭效应、低载硫量是阻碍锂硫电池实用化的主要挑战，其根源是充放电中间产物多硫化物在醚类电解液的超高溶解度(~8 M)，当前仅有少量文献从电解液角度解决上述问题。本项目将设计完全不溶多硫化物的高浓度锂盐碳酸酯电解液，利用配位的碳酸酯分子与多硫化物间可控的亲核反应，在正极表面生成具有自修复功能的界面层，进一步结合高浓度电解液对多硫化物微溶的特性，从根本上解决穿梭效应，实现锂硫电池在低电解液用量条件下的稳定循环。通过研究活性物质氧化还原路径、硫化物成核、生长和分解的动态演变过程，探明锂硫电池在高浓度锂盐碳酸酯电解液中独特的反应机制；通过构建具有离子、电子复合高电导的高载量硫正极，改善电化学反应的传质传荷问题；研究电解液用量、正极复合导电性、界面与电化学性能的构效关系，为显著提升锂硫电池的能量密度和循环性能奠定基础。

Lithium sulfur batteries have become attractive candidates due to their high theoretical energy density, low cost and environmental friendless. However, the state-of-the art Li-S batteries is plagued by the polysulfide shutting phenomenon with rapid capacity fading over cycling in the conventional ether-based electrolyte, which requires a large amount of electrolyte that considerably comprise the overall energy density. All of these issues are correlated to the catholyte operational mode with fully dissolved polysulfide in ether-based electrolyte (the solubility is as high as 8 M). This proposal intends to decrease the electrolyte volume by tuning the electrolyte structure - by driving a fundamental shift of the electrolyte from fully solvating polysulfides to non-solvating with fully coordinated solvent molecules. The electrolyte solvent we choose here is the widely used carbonate which was proved to be unstable towards polysulfide species. We will start by studying the chemical stability of the highly coordinated carbonate with polysulfides, followed by analysis of the surface changes with the tunable coordination electrolyte structure. The minimum dissolved polysulfide is predicted to react with the limited accessible carbonate at the beginning of the first cycle, forming a robust self-healing SEI layer on the sulfur electrode that impedes polysulfide dissolution. We will study the impacts to the sulfur redox chemistry, from a fully solvated polysulfide in the conventional ether electrolyte to a non-solvating system in our proposed carbonate electrolyte. Integrating the cathode with continuous electron/ion pathway upon lithiation is essentially important to the electrochemical reaction in this concentrated carbonate electrolyte; strategies will be established in this proposal as well. The structure-activity relationship of the electrolyte structure, the electrode structure and the performance of lithium sulfur battery with low E/S ratios will be studied. This project will enrich the research of interface chemistry, electrolyte chemistry and electrode structure development, which will definitely beneficial to the development of practical lithium sulfur batteries with high energy density and long cycling life.