锂硫电池中硫/碳复合材料退化机理的质谱学研究

Lithium sulfur battery is a kind of green battery with highest specific-energy density, low cost and environment friendliness. But poor cycling performance caused by degradation or dissolution reactions has restrained the development and application. In the present project, many kinds of sulfur/carbon composite materials will be prepared and used for the systematic studies of degradation mechanism. The project details include: (1) Many mixtures of sulfur/carbon composite materials, and adhesive, electric agents, electrolyte and so on will be prepared and optimized previously; (2) In different conditions, on-line GD-MS, GC-MS and ESI-MS will be applied to study the thermal behavior, decomposition, oxidation reactions, then the possible reactive intermediates and mechanism can be predicted according to the results and typical theory; (3) The on-line analysis and coupled mass spectrometry technique will be deeply used to monitor the gas phase and liquid compounds, and isolate, capture and characterize the reactive intermediates, which can help to clarify the predicted mechanism; (4) Finally, the degeneration mechanism and regularity of sulfur/carbon composite materials will be proposed, and the main factors caused the degradation of sulfur/carbon composite materials will be probed. Moreover, the feasible pathway will be proposed to improve or inhibit the degradation of sulfur/carbon composite as cathode for lithium sulfur batteries. The present studies will be hoped to provide the important information for the improvement of sulfur/carbon composite materials and cycling performance of lithium sulfur batteries.

锂硫电池是一种具有高比能量、成本低廉、环境友好等优点的"绿色电池"，但其电极材料退化、容量衰减等因素导致循环性能差进而制约了大规模推广使用。本项目拟以锂硫二次电池中硫/碳复合材料为研究对象，系统研究硫/碳复合材料在多种气氛条件下的退化机理。研究计划包括：(1)制备并优化硫/碳复合材料，以及与导电剂、粘结剂、电解液、负极等多种组合体系；(2)在多种气氛下，运用GD-MS、在线(on-line)GC-MS方法、ESI-MS初步研究不同体系中硫/碳复合材料退化过程中可能的热力学行为、分解、氧化等反应，依据经典理论推测可能的反应中间体及历程；(3)在线分析与联用质谱技术全面、深入监控气相及液相组分，分离、捕捉并表征活泼中间体及产物，验证、阐释反应机理；(4)揭示材料退化机理及规律，探讨引起退化的主导因素，提出抑制退化的有效途径，为硫/碳复合材料的改进以及锂硫电池的容量及循环性能提高提供科学依据。

锂硫电池的电极退化是导致其容量快速衰减、制约其广泛应用的一个重要因素。本项目中以锂硫二次电池中硫/碳复合材料为研究对象，系统研究并阐明硫/碳复合材料在液相、气相等条件下的退化机理，同时揭示电极的退化与电解质有着较大关联，通过对电解质的持续优化，提高电池的循环性能。具体内容包括：(1) 制备并优化硫/碳复合材料，以及与导电剂、粘结剂、电解液、负极等多种组合电池体系；(2) 运用液相色谱质谱 (ESI-MS) 捕捉并表征了不同体系中硫/碳复合材料退化过程中多硫化合物以及多硫与电解质的络合物, 验证、阐释退化过程与反应机理；(3) 发展在线萃取衍生化的方法，结合气相色谱质谱 (GC-MS) 表征不同体系中硫/碳复合材料退化过程中多硫化合物以及多硫与固态电解质的络合物；(4) 揭示电极的退化与电解质有着较大关联，通过单一电解质、复合共溶电解质以及半固态电解质的优化设计，来降低电解质对电极退化的影响，MS方法连续监控结果表明复合共溶电解质以及半固态电解质在可以解决穿梭问题、降低甚至抑制电极的退化，有效提高电池的循环性能。研究工作为硫/碳复合材料的改进以及锂硫电池的容量及循环性能提高提供科学依据。