基于三维石墨烯/有序氮掺杂碳材料的高体积比容量柔性超级电容器

Flexible supercapacitor with high volumetric capacitance has been revealed critical to the new generation of portable energy storage system with high efficiency. As a typical flexible electrode with high stability, graphene film usually suffers with a very low volumetric capacitance. Focusing on this problem, this project will build order-structured nitrogen doped carbon material on three dimensional graphene flexible electrode, aiming to get novel flexible electrode with high volumetric capacitance, good rate performance and long cycle life. Through controlling the pyrolysis process of nitrogen contained conjugated polymers with ordered nano-array structure, we aim to build nitrogen doped carbon material with high nitrogen content and ordered structure in porous flexible electrode, thus getting high specific capacitance. Based on this, the volumetric capacitance will be improved through optimizing the loading amount of active material on graphene skeleton and the packing density of the whole electrode. Furthermore, the channel structure of the composite electrode and morphology of the nitrogen-doped carbon material array will be regulated to obtain high electron and ion transport properties, thus improving rate performance of the electrode. By this way, the problem of the low volumetric energy density of graphene based flexible electrode will be synthetically solved. Finally, the relationship between material structure and energy-storage performance will be investigated. This project will provide theoretical and practical basis for the design and development of high performance supercapacitor in the future.

兼具良好稳定性和高体积比容量的柔性电极是柔性超级电容器用于新一代高效便携储能系统的关键。针对石墨烯柔性电极体积比容量低的基本科学问题，本项目拟将具有良好导电性、电化学稳定性以及高容量的有序氮掺杂碳材料引入三维石墨烯柔性膜，构筑具有高体积比容量，同时具有良好倍率性和稳定性的柔性超级电容器器件。首先，借助模板保护和分段热解等方法，对含氮共轭聚合物有序阵列的热处理过程进行优化，在多孔柔性电极中可控构筑具有高氮掺杂量和有序纳米结构的氮掺杂碳材料；其次，优化柔性复合电极中活性材料负载量和电极堆积密度，提高柔性电极的体积比容量；再次，调控复合电极孔道及氮掺杂碳材料阵列的形貌与结构，以获得高效的电子和离子传输性能，提高电极倍率性能。通过以上研究综合解决三维石墨烯密度低引起的体积能量密度差的问题，揭示复合电极中的材料结构与器件性能的关系规律，为高性能柔性超级电容器的开发提供理论和应用依据。

开发具有高比容量、高稳定性、耐弯折性能好的柔性电极是获得可靠的柔性储能器件的关键环节。碳材料柔性电极性能稳定，已得到广泛研究，然而石墨烯柔性电极通常体积比容量较低。氮掺杂碳材料将杂原子氮掺杂进入碳结构中，其与碳材料相比具有更高比容量，而且具有良好稳定性，是获得高性能柔性电极的理想材料。虽然基于氮杂碳材料电极制备已有较多研究，但是关于柔性电极的研发较少，而对材料中氮掺碳材料的形貌、氮元素的种类以及碳材料中的氮含量有效调控的研究更为缺乏。本项目采用了三维石墨烯柔性基底和有序阵列结构的以及自身柔性的氮掺杂纳米碳材料相结合的策略，通过复合电极的构筑和结构优化，制备了具有良好稳定性的和耐弯折性能的柔性电极。首先在三维石墨烯柔性骨架上复合聚苯胺纳米线阵列作为前驱体，通过分步升温控制热解条件，得到具有不同疏密长短的氮掺碳材料阵列的自支撑电极，所得到的复合材料显示了增强的电化学比容量、倍率性能，在5A g-1的电流密度下循环20000圈后，容量没有衰减，并且耐弯折性能良好；其次我们利用凝胶和柔性衬底相结合的策略，获得了一系列具有相互连通大孔结构的柔性自支撑氮掺杂碳材料膜电极，一方面其相互连通的大孔结构有利于离子的传输和吸脱附，另一方面其均匀的氮掺杂和石墨烯网络结构提供了稳定的电子快速转移通道，该膜电极获得了455.4 F g-1的质量比容量和34.5 Wh kg-1的能量密度。