LiBH4基空间约束电解质材料体系的构建及其在固态锂-硫电池中应用的性能与机理研究

Lithium-sulfur (Li-S) batteries are presently one of the most promising candidates for the next generation lithium batteries because of its relatively high theoretical specific capacity. However, the disadvantages of sulfur electrodes such as low conductivity, large volume change during cycling, the dissolution of high-order lithium polysulfide intermediates (Li2Sx, 4≤x≤8) in liquid electrolytes and the concomitant “shuttle effect”, hinder the commercialization of Li-S batteries. To promote high performance and alleviate safety concerns of Li-S batteries, one of the most attractive strategies is to configurate all-solid-state Li-S batteries. Complex hydride LiBH4 is considered as one of potential eletrolytes for all-solid-state batteries owing to fast Li-ion conductivity of the high–temperature phase LiBH4. For practical application, however, the LiBH4-based electrolytes are still plagued by low Li-ion conductivity at room termperature. Therefore, how to improve the Li-ion conductivity and decrease the operation temperature is crucial for the development of LiBH4-based solid electrolytes. On basis of our recent related studies, the present project starts from the construction of novel space-nanoconfined LiBH4 and LiI in the pores of the as-synthesized ordered mesoporous silica (LiBH4-LiI@SiO2) via a solution impregnation strategy. Firstly, the fabrication condition and ruler of the space-nanoconfined LiBH4-LiI@SiO2 composites, upon which the critical factors that affect the construction of the high Li-ion conductive LiBH4-LiI@SiO2 electrolytes for all-solid-state Li-S batteries will be revealed. Secondly, the efficacy of the LiBH4-LiI@SiO2 fabrication on the improvement of electrochemical properties in the Li-S batteries will be ascertained based on the systematical investigation of structural and Li-ion conductive performances of the LiBH4-LiI@SiO2 composites. The third task of this project is to explore the interaction and microstructure evolvement of components of the LiBH4-LiI@SiO2 composites during cycling, and to clarify the mechanism of electrochemical property improvement for the all-solid-state Li-S batteries. In one word, the implementation of this project will provide the relaible theoretical basis and technical guidance for the optimization design and electrochemical performance improvement of all-solid-state Li-ion batteries and other solid electrolytes.

锂-硫电池是极具潜力的新一代高能二次电池，但因硫导电性差、充放电过程体积变化大以及多硫化物物的溶解和伴随“穿梭效应”等问题，导致电池的循环性能差。构建全固态锂-硫电池是一重要的发展方向。LiBH4作为一种具潜在实用化的固体电解质材料，因其适用温度较高，需进一步改善。在前期工作的基础上，本项目拟以介孔SiO2为载体，通过溶液浸渍来构建新型的LiBH4基空间约束固体电解质材料体系——LiBH4-LiI@SiO2，研究LiBH4-LiI@SiO2材料体系的形成规律和条件，揭示影响高离子电导率电解质材料体系构建的关键因素；系统分析基于LiBH4-LiI@SiO2应用的全固态锂-硫电池的电化学性能；探索各组元在充/放电过程中的微观化学和物理性质，从根本上阐明固体电解质性能改善的微观机制。通过这些研究，为固态电池以及其它固体电解质材料的优化设计和综合性能的改善提理论依据和技术指导。

锂-硫电池为极具潜力的新一代高能二次电池，其中全固态锂-硫电池是一重要的发展方向，而作为固态电池核心的固体电解质开发尤为关键。LiBH4是一种具潜在实用化的固体电解质材料，但其适用温度和离子电导率尚无法满足实用化的要求，需要进一步研究得以改善。本项目开展LiBH4基空间约束电解质材料体系的构建及其在固态锂-硫电池中应用的性能与机理研究工作，主要围绕有序介孔SiO2载体材料的制备和LiBH4-LiI载入来构建复合固体电解质材料体系，系统研究制得的LiBH4-LiI@SiO2电解质应用于全固态锂-硫电池的电化学性能。研究结果表明：设计构建的LiBH4基电解质材料体系具有高离子电导率和高电极相容性，在全固态锂-硫电池中可实现在接近室温的可逆循环。基于本项目的研究，进一步开展了另一硼氢化物Li2B12H12固体电解质材料体系的工作，研究了该体系中成分、结构和形貌对锂离子传输性质的影响规律，以及拓展研究了络合氢化物LiAlH4作为负极材料在成分、结构和形貌对其储锂性能的影响规律；同时，针对锂-硫电池中金属锂枝晶生长的难题，项目组亦开展了稳定金属锂负极的相关研究。这些结果将为设计和开发高性能的储能电池材料奠定坚实的基础。受本项目资助，已在国内外期刊发表学术论文45篇，申请发明专利25项，含PCT国际专利2项和授权专利7项，并获得2018年度上海市自然科学一等奖；已培养毕业博士生2名，硕士生16名，项目负责人获得多项荣誉称号和项目资助。