基于相变微胶囊的温度自调节柔性超级电容器制备及其控温机理研究

To overcome the effect of different ambient temperatures and heat release during the charge-discharge process on electrochemical properties and use security of flexible supercapacitors, the applicant proposes the project of designing a novel passive thermal management system for flexible supercapacitors by incorporating phase-change microcapsules. First of all, the carbon nanotube-reinforced mechanism in the core-shell structure of microcapsules using the mixture of alkylated carbon nanotubes and organic phase-change material as the core material, will be built up from inside to outside by combining in-situ polymerization method and layer-by-layer self-assembly technique, so as to improving their mechanical and thermal conductive properties, and decreasing the supercooling degree. Second, three-dimensional porous graphene and conductive polymer are deposited in turn onto the free-standing carbon nanotube film/fiber surface using the electrochemical method so that the phase-change microcapsules are fixed firmly at the same time of realizing the enhancement of capacitance. Thereafter, the modified fiber electrode is coated with gel electrolyte and then used as the axis to wrap the modified film electrode to fabricate a coaxial fiber-shaped flexible supercapacitor. The internal relationship between the structure of microcapsules and electrodes and the performances of supercapacitors, and and the corresponding physical mechanism will be studied. The temperature-controlling mechanism will be explored. The research of this project will provide a new approach and theoretical foundation for the design and development of high-performance flexible supercapacitors.

为克服不同的环境温度和充放电时放热对柔性超级电容器电化学性能和使用安全性的影响，本项目设计在柔性超级电容器中复合相变微胶囊以构建结构新颖的被动式热管理机制。首先以烷基化碳纳米管和有机相变材料的复合物为核，联合原位聚合法和层层自组装技术在相变微胶囊的核壳结构中构筑自内而外的碳纳米管强化机制，以提高其力学强度和导热性能，并减小过冷度；利用电化学方法在自支撑碳纳米管薄膜和纤维表面先后沉积三维多孔石墨烯和导电聚合物，在实现电容增强的同时完成相变微胶囊的稳定负载；然后用凝胶电解质涂覆改性的纤维电极，并以此为轴缠绕改性薄膜电极制备同轴型柔性超级电容器，研究微胶囊和电极结构与电容器性能之间的内在关联和物理机制，揭示控温机理，为高性能柔性超级电容器设计和开发提供新的方法和理论基础。

温度是影响超级电容器电化学性能、可靠性和使用安全性的重要因素。本项目创新性地将相变调温与电化学储能有机结合起来，在柔性超级电容器中构建被动式热管理机制。研究内容包括新型相变微胶囊合成、有机-无机杂化改性，揭示合成工艺、核壳结构和微胶囊性能之间的关系；采用电化学沉积的方法在碳纳米管薄膜/纤维表面沉积三维多孔石墨烯和导电聚合物制成自支撑相变调温电极，探讨相变微胶囊在电极中的负载技术、导电聚合物修饰与构效关系，继而使用聚合物凝胶电解质组装柔性超级电容器，研究超级电容器的温度效应和相变控温机理。主要结果如下：. （1）对微胶囊进行碳纳米管修饰可以有效降低过冷度，改善相变微胶囊的力学强度、热稳定性和导热性能。芯材中引入长链烷基碳纳米管增强了芯材与碳纳米管之间的相容性，减少沉降，利于碳纳米管的均匀分散。 . （2）电化学沉积的还原氧化石墨烯和导电聚合物形成三维网状结构，不仅实现了对相变微胶囊的稳定负载，而且增加了电极比表面积和活性位点，提高超级电容器的电容。. （3）柔性电极中引入相变微胶囊减小了超级电容器电化学性能受温度变化的波动幅度。例如，掺杂密胺树脂相变微胶囊使超级电容器的比电容随温度上升速率从0.47 mF cm-2 ℃-1下降到0.31 mF cm-2 ℃-1。. （4）将相变微胶囊表面用导电聚合物修饰后应用于超级电容器中，不仅实现了对柔性超级电容器的原位热管理，而且使微胶囊表面由电化学惰性转变成电化学活性，对超级电容器的电容性能有明显的增益作用。. 该项目研究形成了比较成熟的高性能相变微胶囊合成和柔性超级电容器原位热管理系列技术，揭示了相变调温机制，对高性能柔性超级电容器设计和开发有很好的参考价值。