高性能、超微结构硫-碳电极的设计及其在碱金属-硫电池中的应用

With a theoretical capacity of 1675 mAh/g, natural abundance and low cost, element sulfur has been considered as one of the most promising alternative cathode materials for green transportation. However, due to the insulativity of sulfur, it can not be used as cathode directly. In terms of high corrosion resistance, high temperature tolerance, low thermal expansion coefficient and high conductivity performance, carbon materials have already been extensively applied as electrical auxiliary materials on alkalis - sulfur batteries. Meanwhile, there are still some persistent problems on sulfur/carbon (S/C) composite, such as, low sulfur loading ability and utilization capability; high resistivity; poor interface compatibility between electrolyte and S/C composite; deposition of corrosion products between sulfur/polysulfide and metal/electrode materials. To overcome these problems, in this research, many attempts will be made. 1) In view of the different carbon materials with superfine microstructure, such as carbon fibers, carbon nano-tubes, carbon spheres, porous carbon, as well as graphene, the sulfur loading ability and the conductivity of them will be improved by optimizing their surface state, active specific surface area, and the functional group numbers. 2) In terms of the math module established between the perfomance of battery and the parameters of different types of S/C composite, the critical factors that influenced the performance of battery will be elaborated. 3) On account of "the weakest link theory", the highly conductive and stress released S/C composite that have good interface compatibility with electrolyte，electrode and current collctor will be designed and fabricated to reduce the polarization and control the decay rate of battery. 4) Based on the relationship between the corrosion and the performance of battery, the surface coating and spraying process that inhibite the corrossion between sulfur/polysulfide and metal/electrode materials will be made to improve the service life of the battery.

硫的理论比容量达1675 mAh/g，储量丰富、价格低廉，是理想的正极材料。但因电导率低，不能用作电池电极材料。碳是一种好的导电辅助材料，与硫复合可用作碱金属-硫电池的正极。但存在1）固硫能力差；2）硫的利用率低；3）高电阻率；4）与电解质等接触界面相容性性差，应力大；5）硫及多硫化物对电极、金属的腐蚀产物沉积导致阻抗增加等问题。本项目将1）基于各种超微结构碳材料如碳纤维、碳管、碳球、石墨烯等，通过表面状态、活性比表面积、官能团数量等的优化控制提升其活性、强度和电导率。2）制作不同形式的硫碳电极，建立电池性能与其相关参数的数学模型，对影响电池充放电性能的关键因素进行阐明。3）基于最弱连接理论，设计制备与电极等界面兼容、应力可释放的硫碳复合电极，控制或消除电池劣化趋势和衰减速率。4）建立腐蚀速率与时间、电池性能等关系图，通过包覆、喷涂等工艺抑制硫及多硫化物对电极等的腐蚀，提高电池使用寿命。

硫的理论比容量达1675 mAh/g，储量丰富、价格低廉，是理想的正极材料。但因电导率低，不能用作电池电极材料。碳是一种好的导电辅助材料，与硫复合可用作碱金.属-硫电池的正极。但存在1）固硫能力差；2）硫的利用率低；3）高电阻率；4）与电解质等接触界面相容性性差，应力大；5）硫及多硫化物对电极、金属的腐蚀产物沉积导致阻抗增加等问题。本项目通过1）基于碳纤维/硅基材料等，通过表面状态、活性比表面积、官能团数量等的优化控制提升其活性、强度和电导率。2）制作不同形式的电极，建立电池性能与其相关参数的数学模型，对影响电池充放电性能的关键因素进行阐明。3）基于最弱连接理论，设计制备与电极等界面兼容、应力可释放的碳复合电极，控制或消除电池劣化趋势和衰减速率。4）建立腐蚀速率与时间、电池性能等关系图，通过包覆、喷涂等工艺抑制硫及多硫化物对电极等的腐蚀，提高电池使用寿命。同时，我们开展了5）无机氧化物作为硫正极添加剂和具有核壳结构的导电高分子基复合硫正极的相关研究，有效提高了硫正极的导电能力，抑制了多硫化锂在电解液中的溶解，缓冲了充放电过程中体积效应对电池性能的冲击，进而提高锂硫电池活性物质利用率、循环稳定性和库伦效率。6）通过导电高分子基功能性中间层的添加，一方面提高了电极和电解液的润湿性，降低电池极化；第二方面，阻挡放电中间产物多硫化锂在电解液中的溶解和迁移，降低穿梭效应对电池性能的影响；第三，功能性中间层的的添加也可以保护硫正极的结构稳定性，提高电池的循环稳定性。.