高能量密度纤维电极材料的构筑及其柔性与电容性能的优化平衡

For the flexible fiber-based supercapacitors, the challenges existing are how to achieve high energy density without compromising their rate stability and how to balance optimization between flexibility and specific capacitance. In this project, the holey graphene nanosheets with large size and carbon nanotubes are selected to optimize the flexibility and conductivity of the assembled materials, the holey MnO2 nanosheets (or nanowires) are selected to optimize the specific capacitance, and the graphene/manganese dioxide/carbon nanotube flexible composite fiber electrodes with both ion-fast transfer channel and controllable aspect ratio are expected to be prepared by counter-drop-casting technology. By investigating the holey ratio of nanosheets (or nanowires), the size of nanosheets, the component content, the assembled rate, and the entanglement method, the regularity between porous structure and the specific capacitance of the assembled fiber-based electrodes will be clarified. By testing the electrochemical parameters of the assembled materials and device such as electrochemical impedance spectroscopy, the variation of the ion transport and the specific capacitance is studied. By using the prepared fiber-based electrodes with good flexible and excellent capacitance, the symmetrical and asymmetric flexible solid-state fiber supercapacitors are assembled. By investigating the bending degree, tensile strength and folding degree of the prepared electrodes and device, the relationship between the flexibility and specific capacity is investigated, which can provide the basis for optimizing the flexibility and electrical performance of the assembled fiber-based electrodes and the device. The research is expected to overcome the outstanding problems such as the low specific capacity, the slow reaction dynamics and the low coulomb efficiency of the solid fiber electrode, and the flexible fiber supercapacitor with high energy density is expected to be developed.

针对柔性纤维超级电容器能量密度低及柔性和比容量优化平衡矛盾的瓶颈问题，项目拟以大尺寸孔洞石墨烯纳米层与碳纳米管优化材料柔性和导电性，以孔洞二氧化锰纳米层（线）优化材料比电容，采用对向滴铸组装技术制备具有离子快速传输通道，纵横比可控的石墨烯/二氧化锰/碳纳米管柔性复合纤维电极材料；通过研究组装纳米层（线）孔洞化率、纳米层大小、组分含量、组装速率及缠绕方法与电化学电容关系，阐明组装材料结构改善柔性复合纤维比电容的规律；通过对组装材料及器件电化学阻抗谱等测定，研究组装材料离子传输与材料比能量的变化规律；以制备的纤维电极组装对称及不对称柔性全固态纤维超级电容器，研究电极及器件弯曲程度、抗拉伸量及折叠程度等柔性参数下的比容量，为优化平衡材料与器件柔性和电性能提供依据，达到克服实心纤维电极比容量低、反应动力学迟缓和库仑效率低等突出问题，开发高能量密度下倍率性能优异的柔性纤维超级电容器。

柔性纤维超级电容器作为可穿戴柔性电子器件电源显示了巨大应用前景，而能量密度低和柔性与电容优化平衡是该类器件面临的挑战。四年来课题组在三个方面进行了系统性研究工作。一是纤维电极设计、制备及宽温全固态纤维电容器电容与柔性优化平衡，发现不同电性剥离纳米片层液晶相是组装纤维电容器电极材料最佳悬浮液，湿法纺丝技术是将固化液晶相纺丝液组装柔性纤维有效方法，高导电性石墨烯和高柔性有机芳纶纤维类材料是改善纺丝纤维导电性能和柔韧性的良好柱撑剂。采用具有低温抗冻、高温耐热、轻量、柔性和高离子导电性等特征有机水凝胶电解质，可实现组装纤维器件宽温条件下的正常工作，为极端条件下全固态柔性纤维电容器应用提供了新策略。以T/A-5复合纤维电极材料和F-MMT/PVA有机水凝胶电解质组装的全固态对称柔性纤维电容器具有26.2 mWh cm-3高体积能量密度及-40~80 C宽温工作范围。二是柔性超级电容器用高容量薄膜电极制备及组装器件性能与柔性优化平衡。开发了大尺寸少层硼烯溶剂热辅助剥离新技术，以制备的硼量子点（BQDs）作为柱撑剂组装的Ti3C2Tx/BQDs复合薄膜电极展现出显著倍率增强效应，为发展高功率密度柔性薄膜超级电容器提供了新方法。以拓扑化学剥离法制备的超大尺寸少层硅氧烯纳米片为Li-O2电池双功能光催化剂，光辅助Li-O2电池的电能转换效率达185%，为实现太阳能与电能的高性能转换和存储提供了新机遇。三是钠离子电容器新型电极材料制备及其器件性能研究。采用溶剂热随后高温处理、静电纺丝结合高温热处理和静电纺丝结合硫化处理等方法，开发了系列高倍率性能Nb2O5和Ti2Nb2O9基复合电极材料；以制备的系列复合电极材料为负极和AC为正极，组装了兼具高能量/功率密度和长循环寿命钠离子电容器，解决了钠离子电容器电池型负极与电容型正极间动力学匹配性差瓶颈问题，为提高组装器件能量密度和功率密度提供了新策略。