改性金属锂负极和超支化聚合物固体电解质在锂硫电池中的应用

Lithium sulfur secondary battery is a two-electron reaction electrochemical system based on elemental sulfur cathode and lithium anode with a high theoretical energy density of 2600 Wh/kg. It is recently the research hotspot in the field of high specific power cells and needs to be further improved immediately. However, the uncontrolled growth of lithium dendrites during the battery operation would cause poor stability and serious safety problems, thus restricting the practical application of lithium sulfur battery. This project will innovatively build a new type of interface modification layer with high lithium ion conductivity on the surface of lithium anode through spontaneous reaction between the diblock alcohol ethoxylate molecular and lithium metal. The uniform deposition of lithium ion can be thus realized to inhibit the growth of lithium dendrites and obtain ideal lithium anode with high Coulombic efficiency and long cycle life. At the same time, in order to develop solid-state electrolyte with high ionic conductivity, it is proposed to in-situ polymerize the hyperbranched polymer solid-state electrolyte on the electrode surface to increase its lithium ion conductivity and mechanical strength, so as to effectively reduce the interfacial contact resistance and improve the specific capacity and cycling stability of solid lithium sulfur battery. By using in-situ electrochemical method, the formation of the electrolyte interface and its dynamic evolution mechanism will be systematically investigated. This research project emphasizes the importance for solving the low Coulombic efficiency and poor cycle performance of lithium metal anode, improving battery safety and promoting the fundamental and application development of lithium sulfur battery.

锂硫二次电池是基于单质硫正极和金属锂负极的两电子反应电化学体系，理论能量密度高达2600Wh/kg，是近年来高比能动力电池领域中的研究热点和亟待突破的重点体系。然而，无法控制的锂枝晶生长引起低的循环效率和严重的安全隐患，制约了锂硫电池的实际应用。本项目将创新性地通过双嵌段分子高碳脂肪醇聚氧乙烯醚与金属锂的表面反应构筑新型高导锂性锂金属界面修饰层，实现锂离子的均匀沉积，抑制锂枝晶的生长，获得高库伦效率和长寿命金属锂负极。同时，为研制高离子电导率固体电解质，拟在电极表面原位聚合超支化聚合物固体电解质，提高固体电解质锂离子的传导能力和机械强度，减少界面接触电阻，提升锂硫电池的比容量和循环稳定性。通过原位电化学手段，阐明固体电解质界面的形成和动态演化机制。该研究项目对解决当前金属锂负极存在库伦效率低和循环性能差的问题、对提高电池的安全性和促进锂硫电池的基础与应用发展具有重要的实践意义和科学意义。

锂硫二次电池是基于单质硫正极和金属锂负极的两电子反应电化学体系，理论能量密度高达2600Wh/kg，是近年来高比能动力电池领域中的研究热点和亟待突破的重点体系。然而，无法控制的锂枝晶生长、多硫离子的穿梭效应引起低的循环效率和严重的安全隐患，制约了锂硫电池的实际应用。本项目为解决锂硫电池循环过程中无法控制的锂枝晶生长引起的库伦效率低和安全性问题，创新性地通过双嵌段分子高碳脂肪醇聚氧乙烯醚与金属锂的表面反应构筑新型高导锂性锂金属界面修饰层，实现锂离子的均匀沉积，抑制锂枝晶的生长，获得高库伦效率和长寿命金属锂负极。同时，在电极表面原位聚合超支化聚合物固体电解质，提高了固体电解质锂离子的传导能力和机械强度，减少界面接触电阻，提升了固态锂硫电池的比容量和循环稳定性。同时，通过原位电化学手段，阐明了固体电解质界面的形成和动态演化机制。设计并建立了一系列原位表征测试系统，包括原位紫外分析技术、原位X射线衍射分析技术等，以所获得的主要实验结果和基本电化学理论为基础，结合理论计算等方法研究了电极界面固体电解质界面膜（SEI）元素组成和深度分布、表面成膜等反应，在对固态锂硫电池中电极材料输运行为和界面特性等问题上形成了清晰系统性的理解和认识，开发出了高容量和高能量密度的固态锂硫电池。该研究项目对解决当前金属锂负极存在的库伦效率低和循环性能差问题、提高电池的安全性和促进锂硫电池的基础与应用发展具有重要的科学意义。