基于有机聚硫化合物构筑高性能SEI膜及其对锂枝晶生长的抑制机理研究

The drawbacks of which have seriously retarded the industrial production of lithium sulfur batteries are the serious safety problem caused by lithium anode. Constructing the solid electrolyte interface layer (SEI layer) on the surface of the lithium anode is one of the most effective strategies to solve the safety problem of the lithium sulfur batteries. Generally, the flexibility, toughness and stability of these SEI layers on the surface of the lithium anode could not withstand the depth utilization of the lithium during Li plating/stripping processes, and the SEI layers still break after cycling. Hence, it is urgent to develop a kind of flexible, robust, stable, homogeneous and even SEI layers. In this project, a series of functional organosulfides would be designed and prepared because the flexible and robust of the SEI layer could be highly improved when utilizing the organosulfides. And so, the high performance SEI layers would be constructed utilizing the above organosulfides through the in-situ-constructed and artificially-constructed methods. On this basis, the ion/electron conduction mechanism and the inhibiting mechanism of lithium dendrite growth of SEI layer are investigated, which provide theoretical direction and technical support for solving the safety problem of the lithium anode in lithium sulfur batteries.

目前制约锂硫电池实用化进程的主要障碍是锂负极所存在的安全隐患问题。在锂负极表面构筑高性能固态电解质膜（SEI膜）是解决锂硫电池安全问题的有效途径之一。由于通常构筑的SEI膜的柔韧性、机械性能、稳定性能差，难以满足锂负极的深度利用，因此急需开发具有高柔韧性、高机械性、高稳定性和高一致性的锂负极SEI膜。由于有机聚硫化合物可大幅度提升SEI膜的柔韧性和机械性能，因此本项目拟设计并制备一系列有机聚硫化合物，然后以有机聚硫化合物为基础采用原位构筑SEI膜和人工构筑SEI膜两种方法制备高性能锂负极SEI膜，并在此基础上探究锂负极SEI膜的离子/电子传导机理和有机聚硫化合物对锂枝晶生长的抑制机理，为解决锂负极安全问题提供理论依据和技术支撑。

为了解决锂硫电池中锂负极存在的安全隐患问题，研究基于有机聚硫化合物采用原位构筑SEI膜、人工构筑SEI膜和聚合物电解质的方法制备了高性能锂负极SEI膜并探究了锂枝晶生长的抑制机理。主要成果包括：1）设计制备一种主链多硫侧链PEG的具有导离子功能的有机聚硫聚合物（PSPEG），探讨该PSPEG为电解液添加剂时其浓度对原位构筑的SEI膜性能及对锂枝晶生长的影响；2）以聚甲基硅氧烷为基础设计制备一系列含硫硅氧烷聚合物，并通过人工构筑SEI膜的方法稳定锂负极，探讨有机含硫硅氧烷聚合物的结构、硫链长度、含量等与人工构筑的SEI膜性能以及锂枝晶生长的抑制机制之间的关系；3）采用浇铸-成膜和原位聚合的方法制备了两种有机聚硫凝胶聚合物电解质(PVDF/PSPEG和PDS/PDOL/DME)，两种有机聚硫凝胶聚合物电解质均具有较高的离子电导率和宽的电化学窗口，而且二者均能稳定金属锂负极界面，提高金属锂的界面稳定性；4）组装锂硫软包装电池，验证使用有机聚硫聚合物改性的金属锂负极的商业化应用潜力。研究中分别了探究锂负极SEI膜的离子/电子传导机理和有机聚硫化合物对锂枝晶生长的抑制机理，为解决锂硫电池中锂负极安全问题提供理论依据和技术支撑。