用于保护锂空气电池负极的离子液体聚合物隔膜的制备及性能研究

Lithium-air batteries are considered promising candidates for electric vehicles owing to their extremely high energy density. At present, much progress has been made in the research of air electrodes for lithium-air batteries. However, the study of lithium anodes in the open air is relatively slow, which has become a key factor restricting the application of lithium-air batteries. This project aims at releasing the problems of lithium dendrites and lithium corrosion in lithium-air batteries. By copolymerizing ionic liquid monomers with polymer monomers, an ionic liquid polymer is obtained. When used as the electrolyte and separator in lithium-air batteries, it is supposed to guide the uniform distribution of lithium ions, mechanically inhibit lithium dendrites, and protect the lithium anode from erosion. The research contents mainly include: (1) clarifying the relationship between the molecular structure of the ionic liquid polymer and the mechanical as well as electrochemical properties of the separator; (2) systematically studying the intrinsic relationship between the anion species and the composition as well as structure of SEI, revealing their effects on the formation process of SEI; (3) Investigating the electrochemical performance of lithium-air batteries, understanding the mechanism of lithium dendrite inhibition by SEI. On this basis, a separator for solid-state lithium-air batteries with long cycle life operating in the air is developed, which provides a new research idea and theoretical basis for the development of high-performance solid-state lithium-air batteries.

锂空气电池具有超高的比能量密度，最有望成为下一代电动汽车的动力能源。目前，对于锂空气电池正极材料的研究已经取得阶段性进展，但相对而言，敞开体系中负极的研究进展较为缓慢，成为制约锂空气电池应用的关键因素。本项目针对锂空气电池中锂枝晶和负极的腐蚀问题，拟将离子液体与聚合物分子共聚，制备离子液体聚合物作为电解质隔膜，用以引导锂离子均匀分布，同时机械抑制锂枝晶生长，隔绝空气对锂负极的侵蚀。具体研究问题包括：(1)阐明离子液体聚合物的分子结构与隔膜的机械、电化学等性能间的构效关系；（2）系统研究阴离子种类和SEI膜成分结构之间的内在联系，揭示其对SEI膜形成过程的作用效应；（3）开展锂空气电池中金属锂的稳定性、循环性能等电化学研究，深入理解SEI膜抑制锂枝晶生长的作用机制。在此基础上，研制出面向大气环境应用的、且具有长循环寿命的固态电解质隔膜，为高性能的固态锂空气电池的开发提供新的研究思路和理论依据

本项目针对锂金属电池中锂枝晶问题，将离子液体与聚合物分子共聚，制备离子液体聚合物作为电解质隔膜，既实现电解质从液态到固态的转变，同时还具有离子液体高离子电导率、“可设计”功能。在实施过程中，通过对比不同离子液体阳离子，完成对机械性能、离子电导率、锂离子迁移数等与电池性能密切相关因素的调控；通过实验和理论计算，阐明离子液体阴离子对SEI膜形成过程的作用效应，结合金属锂的演变情况，揭示其抑制锂枝晶生长的作用机制。所制备的固态电解质能够引导锂离子均匀分布，同时机械抑制锂枝晶生长，为实现高效固态锂金属电池的开发提供新的研究思路。相关成果已经发表SCI论文5篇，包括Nano Energy, Materials Horizons, ACS Sustainable Chemistry & Engineering, New Journal of Chemistry等期刊, 申请发明专利2项，培养硕士毕业生3名。