锂离子电池中高安全系数固体电解质体系及其对锂枝晶生长的微观机理研究

High energy and high power lithium-based batteries are attractive to many today’s technological devices. However, lithium-based batteries suffer one major problem, the safety problem - dendrite induced short-circuit or explosion. Electrolyte configurations that improve uniformity of electrodeposition on battery charge are critical barriers to the safe use of these batteries. Regarding to the dendrite-induced short-circuit, we design a solid electrolyte system of ionic liquid-nanoparticle-macromolecule composites to solve the safety problem in batteries. Specifically, various kinds of ionic liquid chains are tethered to the surface of nanoparticles with different shapes and chemistry, and product is then blended with polymer binder to form ionic liquid-nanoparticle-macromolecule solid electrolyte. By tuning the structure, the physical and chemical properties, and the interactions with polymer component, we are able to simultaneously improve the mechanical strength and ionic conductivity, and thus reduce the space charge and suppress the lithium dendrites from puncturing the battery separator, and eventually increase the cell lifetime. Through systematic investigation of the effectiveness of ionic liquid-nanoparticle species and types, physical and chemical properties, and reaction conditions on lithium dendrite formation, the mechanism of solid electrolytes suppress dendrite is clarified, the factors that increase cell lifetime are determined, the relationship between electrolyte structure and dendrite suppression is illustrated. This work will provide a theoretical basis for the mechanism of lithium dendrite formation and propagation.

高能量大功率锂电池备受关注，但却面临重大安全问题：锂枝晶导致的短路或爆炸，而电解质结构对于锂沉积形貌和电池安全起着决定性的作用。因此，针对锂枝晶产生的电池短路这一关键科学问题，构建离子液体-纳米微粒-高分子三元固体电解质体系解决电池安全问题。通过调控离子液体纳米微粒的组成结构、物化性能以及与高分子组分的相互作用，将不同种类的离子液体接枝在不同形貌、成分的纳米微粒上，并与高分子粘合剂组合，制备离子液体-纳米微粒-高分子三元固体电解质，可达到同时实现提高机械强度和电导率的目的，从而减小空间电荷并防止锂枝晶刺穿隔膜，延长电池寿命。本项目除了通过系统研究离子液体-纳米微粒-高分子三元固体电解质的组成结构与物化性质及反应条件对锂枝晶生长的影响之外，还将进一步归纳出固体电解质抑制锂枝晶的基本原理，确定延长电池寿命的重要决定因素，阐明电解质结构与抑制锂枝晶之间的关系，为锂枝晶生长的微观机理提供理论依据。

高能量大功率锂电池备受关注，但却面临重大安全问题：锂枝晶导致的短路或爆炸，而电解质结构对于锂沉积形貌和电池安全起着决定性的作用。因此，针对锂枝晶产生的电池短路这一关键科学问题，本项目通过五个方面对其进行深入研究，包括：1.电解质电极界面锂离子迁移扩散调控；2.机械强度增强骨架抑制负极锂枝晶生长；3.高性能电解质设计与锂金属沉积形貌调节；4.固态电解质与全固态电极界面设计；5.离子液体杂化碳骨架实现高性能锂硫全电池。本项目所设计的软包电池在接近工业化条件下（50微米超薄锂，>4mah cm-2正极，贫量电解液）获得了稳定的循环性能，其能量密度可达300Wh kg-1，为固态锂金属电池的工业化做出了重要贡献；同时，所提出的抑制锂枝晶的方法受到同行的广泛关注，在国际上产生了重要影响。