锂硫电池用多功能集成式纤维束载硫体的皮胶原纤维模板设计、可控制备与构效关系

Lithium-sulfur (Li-S) battery system possesses high capacity and high energy density in theory, but it also faces a number of problems including low sulfur utilization, poor rate capability, and short cycle life，which is leaded by the intrinsic insulating property of sulfur cathode and the “shuttle effect” owing to high dissolubility of intermediate polysulfides in the electrolytes. An “initiative” solution, which is mainly based on polar chemical adsorption and fast redox transformation towards polysulfides, has been recently developed as new strategy to succeed in addressing the above issues facing sulfur cathode. Hence, this project intends to use skin collagen fiber as starting material, and study its potential application in Li-S battery field. By taking advantages of chemistry and structure characteristics of collagen fiber, a series of novel multi-functional sulfur-hosting fiber bundle matrix, which holds an integrated functions of electronic conductivity, catalytic effect and shuttle inhibition, as well as corresponding composite cathodes of Li-S batteries are designed and fabricated with applied comprehensive knowledge in leather, tannin, and materials chemistry. Based on the structural analysis, electrochemical performance test and theoretical calculation, the structure-activity relationship between the structure, composition, ion/electron transport, sulfur immobilization, and lithium storage performances of the composite cathodes materials would be revealed. More importantly, it would be also realized to achieve an effective synergy on high sulfur loading, high sulfur utilization, long cycle life and high energy density of Li-S batteries. This project potentially provides a solid theoretic and experimental foundation to develop the low-cost and efficient synthetic approach for advanced sulfur cathode materials in Li-S batteries.

锂硫（Li-S）电池体系理论上具有高容量和高能量密度特点，但硫正极材料本身的绝缘性和因中间体多硫化物溶解引起的“穿梭效应”，使Li-S电池存在硫利用率低、倍率性能差、循环寿命短等问题。基于极性化学吸附和快速转化多硫化物的“主动出击”方案，已逐渐成为目前解决硫正极系列问题新的研究策略。为此，本项目以皮胶原纤维为模板，利用其特殊的化学与结构特性，综合运用制革化学、单宁化学、材料化学学科知识，设计构建集电子导电、催化效应、抑制穿梭等功能于一体的新型多功能纤维束载硫基体，以及一系列具有重要应用前景的Li-S电池复合正极材料。结合材料的结构分析、电性能测试和理论计算，揭示该复合材料的结构-组成-离子/电子输运-固硫特性-储锂性能之间的构效关系，实现Li-S电池高载硫率、高硫利用率、长循环寿命与高能量密度的有效协同。本项目的开展有望为低成本、高性能Li-S电池正极材料的研究提供重要的理论与实践基础。

高能量密度锂硫（Li-S）电池被认为是下一代有前途的能量存储系统之一。然而，硫正极中缓慢的氧化还原动力学和严重的多硫化物穿梭效应以及锂金属负极枝晶生长等问题不可避免地降低了Li-S的电化学性能，并阻碍了它们的实际应用。针对上述问题，本项目利用具有独特几何构型和特殊化学组成的可再生皮胶原纤维为基质材料，并基于极性化学吸附与多硫化物快速转化相结合的“主动出击”解决方案，确定了一套可多样化设计制备胶原纤维衍生的集电子导电、催化效应、抑制穿梭等功能于一体的新型多功能纤维束载体材料，以及一系列具有重要应用前景的Li-S电池电极材料的研究方法，具体包括：1）皮胶原纤维-金属盐直接反应法制备金属单质Ni/石墨化碳笼共嵌的多孔碳基载硫纤维材料；2）合理设计具有亲硫-亲锂特性的金属单质Co/NbC共修饰的多功能集成纤维宿主载体；3）局部化学自氮化构筑TiN/TiO2异质结内置的多腔室碳纳米纤维宿主材料；4）选择性氮化策略制备非碳基、高密度TiO2/VN异质结构纳米纤维复合载硫体，上述所制备的多功能载体材料实现了活性物质硫在碳纤维孔道内部的高效负载，有效应对了硫正极和锂金属负极所面临的挑站，同时还探索出一条可通过精确的制备工艺和调控机制来改善相关活性材料的电化学性能的有效途径，研究成果将为皮胶原纤维在Li-S电池技术领域的应用奠定重要的理论和研究基础。