基于溶剂化离子液体的新型锂离子电池固态电解质的研究

The replacement of conventional organic liquid electrolyte with solid electrolyte is a promising approach to improve the stability and energy density of the lithium ion batteries. However, solid electrolyte based on polymer and lithium salt shows low ionic conductivity at ambient temperatures. Although the addition of organic solvents help to improve the conductivity, stability and safety of the electrolyte will decrease due to the present of volatile and flammable solvents. Therefore the state-of-art solid electrolytes are far from practical implementation. In this project we are planning to invite solvate ionic liquid (SIL), a new class of ionic liquid, to take place of organic solvent and prepare a kind of novel solid polymer-SIL electrolytes. The content of this study includes: firstly systematic studying the interaction between various kinds of polymer and solvate ionic liquid, and revealing the influence rules of the composition and structure of the polymers on the stability of the SILs. Then, optimizing the SILs as well as investigating the microscopic interaction and transport mechanism of the electrolytes by the synergic effect, and achieving novel solid electrolyte with high stability and high lithium ion conductivity. This study will stimulate the improvement and implement application of solid electrolyte for lithium ion batteries.

使用固态电解质代替传统的有机液态电解质是提高锂离子电池稳定性和能量密度的重要手段。然而，由聚合物和锂盐组成的固态电解质在室温下的导电性差，虽然通过添加有机溶剂等方法可以提高导电性，但是易挥发和可燃溶剂分子的存在会降低电解质的稳定性和安全性；因此目前的固态电解质还难以实现应用。本项目拟引入溶剂化离子液体这种新型的离子液体材料，代替聚合物电解质中的有机小分子，制备一种新型的固态聚合物-溶剂化离子液体电解质。主要内容包括：首先较为系统地研究不同种类聚合物和溶剂化离子液体的相互作用，找出聚合物的组成、结构对溶剂化离子液体稳定性的影响规律；之后发挥二者的协调作用，通过优化溶剂化离子液体并研究电解质内部相互作用和传导机理，开发出具有高稳定性和锂离子传导的新型固态电解质。本项目将为实现固态电解质在锂离子电池上的实际应用奠定基础。

本课题制备了由聚丙烯腈(PAN)和溶剂化离子液体[Li(G4)][TFSA]构成的固态电解质，系统研究了电解质的物理化学性质。根据相关测试结果，改进了固态电解质的制备工艺和条件，获得了具有较高电化学性能的聚合物电解质，并实现了在由磷酸铁锂正极和金属锂负极组成的锂电池上的应用。针对锂电池中存在的电解质-电极界面问题，设计制备了一系列新型的锂离子电池电极材料，包括复合硫正极、碳包覆氧化硅负极、复合氧化钛/钛酸锂负极等新型电极，在获得了优异的电化学性能的基础上系统研究了电解质-电极界面对电池性能的影响。通过上述研究获得了高性能电极材料的制备方法和高稳定性电解质-电极界面的设计思路。利用离子液体高稳定性和良好的电化学性能，本课题进一步设计开发了基于碳纳米薄膜材料的电化学器件，实现了电场作用下的主动红外辐射调制功能，并系统研究了离子液体在碳纳米薄膜材料中的作用机制。