锂硫电池用微孔聚合物电解质的交联网络结构设计、原位合成及性能研究

Lithium-sulfur (Li-S) battery has been recognized as one of most promising next generation energy storage device. However, the commercial success and development of Li-S battery is mainly limited by the solution and shuttle effect of formed lithium polysulfides during discharging in liquid electrolyte. The use of solid polymer electrolyte can fundamentally address the shuttle effect issue of polysulfides but its limited ionic conductivity and the large electrode/electrolyte interfacial resistance restrict the practical uses. This project proposes to synthesize a compact gel polymer electrolyte with microporous structure, which contains good mechanical strength and highly cross-linked three-dimensional(3D) polymer network, to synchronously achieve the high mechanical strength and high ionic conductivity of gel polymer electrolyte. In-situ preparation method will be developed to achieve the closely bonding of 3D cross-linked microporous polymer elastic skeleton with sulfur electrode surface for the assembling of Li-S battery with high rate and cycle performance, and the suppression mechanism of such electrolyte for the solution and shuttle effect of lithium polysulfides will be investigated. At last, the above polymer electrolyte matrix will be composited with hollow silica filler to obtain the multi-level lithium ion conductive channels and thin layer organic/inorganic composite solid electrolyte, and a new solid state Li-S batteries system will be establish to promote the development of all solid state Li-S batteries. This project will study new type of electrolyte systems and their structure design and preparation method to develop a common method to solve the shuttle effect of lithium polysulfides, which have great importance to the theoretical development and practical use of Li-S batteries.

锂硫电池是极具发展前景的下一代高能量密度储能器件，然而硫的放电中间产物多硫化锂在电解液中的溶解和穿梭效应制约了其实际应用。固态聚合物电解质可从根本上解决上述问题，但是存在室温离子电导率低、与电极界面阻抗大等问题。本项目提出合成具有致密结构的微孔凝胶聚合物电解质，在其内部设计和构建高度交联的三维网络，同时实现其高机械强度和高离子电导率；通过原位制备方法在纯硫电极表面构建稳定有效的电极/聚合物电解质界面，组装高倍率和长循环寿命锂硫电池，并揭示该电解质对多硫离子溶解及穿梭效应的抑制机理；在上述基础上，将聚合物电解质基体与空心二氧化硅填料复合，获得具有多层次锂离子输运通道的薄层有机/无机复合固态电解质，为锂硫电池提供新型固态电解质体系，推动全固态锂硫电池的发展。本项目通过研究新型锂硫电池电解质体系及其结构设计和制备方法，发展一种解决多硫化锂穿梭效应的普适性方法，具有重要的实际应用价值和科学意义。

锂硫电池是极具发展前景的下一代储能器件，然而放电产物多硫化锂在电解液中的溶解和穿梭效应导致循环性能严重衰减，固态锂硫电池及其电解质材料是重要发展方向。项目基于双酚A二缩水甘油醚、聚醚胺和聚乙二醇二缩水甘油醚，通过开环聚合反应合成了致密结构三维交联网络微孔凝胶聚合物电解质；以聚碳酸酯二醇、六亚甲基二异氰酸酯和三乙醇胺为单体，通过在锂硫正极中原位聚合形成新型锂硫电池双功能正极粘结剂和凝胶电解质；通过热聚合反应制备了具有超高离子电导率的季戊四醇四丙烯酸酯基新型凝胶聚合物电解质；聚合物电解质丰富的官能团能够有效吸附多硫化物，弹性的聚合物骨架完整地覆盖于硫电极表面，构建了强健而稳定的碳硫电极/聚合物电解质界面，抑制了多硫化物的溶解和穿梭效应。项目进一步开发了新型聚合物/陶瓷纳米线复合全固态电解质，提出了低阻抗全固态电池一体化结构的设计思想，制备了电子离子双导体碳包覆Li1.4Al0.4Ti1.6(PO4)3陶瓷电解质，不但对多硫化锂具有较强的吸附作用，同时为多硫化锂向Li2S快速转化提供了高效的离子和电子输运通道，从而显著提高了锂硫电池的比容量和循环稳定性；开发了LiNi0.8Co0.15Al0.05O2/石墨烯、VS2/CNT、Li4Ti5O12/碳纤维等锂硫电池中间层，实现了多硫化锂的高效转化，并抑制了自放电，获得了良好性能的凝胶态和固态锂硫电池。项目最后发明了无机陶瓷电解质/锂金属多功能复合导电界面层，实现了陶瓷电解质和锂金属负极界面良好相容性和高效离子输运，为全固态电池产业化提供了解决方案。项目在Nature Commun.、Adv. Mater、Angew. Chem. Int. Ed.、Adv. Energy Mater.等期刊共发表论文20篇，申请发明专利6项；培养教育部长江学者奖励计划青年学者1名（2018）、博士后3名、博士生2名、硕士生8名。