基于锂硫反应机制的全固态锂二次电池界面特性与电化学性能研究

All-solid-state lithium batteries are the next generation batteries with much higher energy density and excellent safety. Solid electrolytes as well as electrode/electrolyte interfacial properties are crucial to realize high performance all-solid-state lithium batteries. Generally, for oxide and sulfur electrodes with sulfide electrolytes, all-solid-state lithium batteries suffer from poor electrochemical performances due to high interface impedance and low electronic/ionic conductivities, respectively. In this project, high ionic conductivity sulfide electrolyte with excellent stability will be extensively investigated. And metal sulfides based on lithium-sulfur reaction mechanism, such as vanadium tetrasulfide and iron disulfide, will be employed as cathodes for all-solid-state lithium batteries using sulfide solid electrolyte. Carbonaceous materials will be used to improve the electronic conductivity of electrodes. The sulfide electrolytes will be in situ synthesized on the electrode surfaces in different solvents in order to improve the interfacial properties, especially the contact area between electrodes/electrolytes, forming both electronic and ionic conduction networks, which could improve the electrochemical properties of all-solid-state lithium batteries. The experiment parameters will be strictly adjusted and optimized. The dependences of the electrochemical performances of all-solid-state lithium batteries on microstructure and interfacial property will be studied in detail. Besides, the cause-effect relationship between structure and electrochemical performances will be investigated. Also the mechanism on lithium storage in all-solid-state lithium batteries using metal sulfide cathodes and sulfide solid electrolytes will be revealed. The achievement in this project will provide theory and practice basis for the new materials for all-solid-state batteries.

锂电池的固态化是解决其能量密度偏低和安全性差等问题的最佳途径之一，其中固体电解质体系及电极/电解质界面特性是实现电池高性能化的关键。本项目聚焦高锂离子电导率、高稳定性的硫化物固体电解质，针对氧化物电极与硫化物电解质界面阻抗高以及单质硫低的电子/离子传导性等问题，采用基于锂硫反应机制的硫的化合物作为正极，如四硫化钒、二硫化铁等，通过碳纳米结构复合改善电子电导，借助电极材料的尺寸及形貌调控其离子输运特性，液相条件下实现电极与电解质的原位复合以优化固固界面特性，同时构建电子/离子通道，实现固态锂电池电化学性能的有效提升。充分考察各种实验参数对电池性能的影响，系统分析材料的微观结构、界面特性与其电化学性能间的构效关系，阐明电极材料结构与性能之间的内在联系，并揭示基于金属硫化物电极的全固态锂电池的储锂机制，为实现其在新型锂电池中的应用以及研究新型全固态锂电池用电极材料奠定良好的科学基础。

全固态锂电池被认为是实现兼具高安全性与高能量密度电池器件的终极解决方案之一。本项目研制出系列室温电导率超过有机电解液的固体电解质材料，并发展了基于硫化物固体电解质的超薄膜；创制了多种结构硫基化合物正极，并基于不同反应机制，筛选出适用于高能量密度室温全固态锂硫电池的硫化物正极，彻底解决锂硫电池中多硫化物产生、溶解与穿梭的核心问题；提出解决基于硫化物固体电解质的全固态锂二次电池界面问题的普适性方法，通过构建纳米尺度下的硫化物固体电解质/活性物质/碳材料三相界面，有效解决了固固接触问题，提高了锂离子的传输动力学，为实现高性能全固态电池器件提供新的理论与技术支撑。