变价金属离子对氮杂石墨烯基锂硫电池的性能调控研究

The lithium-sulfur battery has attracted much attention due to its high theoretical energy density (2600 Wh/kg). Besides, the cathode material sulfur is also low cost and environmental friendly. However, the difficulties in increasing sulfur utilization, coulombic efficiency as well as cyclic stability have posed obstacles towards its commercialization. Among them, the most critical point lies in the “shuttle effect” caused by the dissolution and migration of lithium polysulfides. In this proposal, carbon-sulfur composites would be constructed based on nitrogen-doped graphene and modify the redox interface. Furthermore, the lithium sulfides would be anchored and converted by metal/metal ions with variable valence states. The redox kinetic characteristics for both electrodes would get improved. Through various analytical approaches, the changes in the metal ions and lithium polysulfides under different states will be investigated. Theoretically, the reaction mechanisms between metals ions, nitrogen doping, functional grops and lithium polysulfides could be further explored. Specifically, to mitigate rate capacity decay, increase the power density and improve cyclability and shelf life, the transport characteristics of electron/lithium ions, the diffusion and migration behaviors of lithium sulfides have to be investigated synergistically, coupled with the manipulation of electrode/electrolyte interfaces. Therefore, a deep understanding of lithium-sulfur battery with high performance can be achieved.

锂硫二次电池因具有高理论能量密度(2600 Wh/kg)，且单质硫价格低廉、环境友好的优点，受到广泛关注。目前存在的主要问题是如何提高活性物质硫的利用率和库仑效率并改善循环稳定性。其中，抑制多硫化锂的溶解、扩散迁移所导致的“穿梭效应”最为关键。在本研究中，首先依托氮杂石墨烯材料构筑碳硫复合物以有效改善碳硫反应界面。进一步引入变价金属离子去“锚定”与转化多硫化锂并改善电极动力学过程。通过多种测试手段，分析在充放电的不同阶段，金属离子与多硫化锂变化规律。理论分析在金属离子、氮掺杂和官能团的共同作用下，多硫化锂固定与转化的化学机理。通过有效调控基础性的电极/电解液界面，并协同研究电子、锂离子输运和多硫化锂扩散迁移等性质，才能在高倍率充放电过程中减小容量衰减、增加功率密度、提高电极循环性能和使用寿命并深入理解高性能锂硫电池的运行规律。

锂硫二次电池因具有高理论能量密度(2600 Wh/kg)，且单质硫价格低廉、环境友好的优点，受到广泛关注。目前存在的主要问题是如何提高活性物质硫的利用率和库仑效率并改善循环稳定性。其中，锂多硫化合物的溶解、扩散迁移所导致的“穿梭效应”最为关键。在本研究中，首先依托氮杂石墨烯材料构筑碳硫复合物，并有效改善碳硫反应界面。进一步通过引入变价金属离子去“锚定”锂多硫化合物，改变硫的放电步骤并改善电极动力学过程。可以从理论上研究金属与锂多硫化合物的结合能力并探索反应机理。通过多种原位和离位测试手段，分析在充放电的不同阶段，金属离子的价态变化规律。特别需要指出，通过有效调控基础性的电极/电解液界面，并协同研究电子、锂离子输运和锂多硫化合物扩散迁移等性质，才能在高倍率充放电过程中减小容量衰减、增加功率密度、提高电极的循环性能和使用寿命并深入理解高性能锂硫电池的运行规律。.在国家自然科学基金青年项目（51702012）的资助下，目前发表SCI文章3篇。中国专利授权1项 (专利号：ZL201810893168.8；公开号：CN108987721B)，另有一项专利第一次审查意见通知书已下达（专利申请号： 201811179423.9）。已毕业硕士研究生四名。项目负责人获得国家留学基金委支持(201802180015)，参与清洁能源项目，分别在瑞典和美国从事访问学者和博士后研究，共计18个月。