具有三维离子/电子快速传输通道的高负载量石墨烯基柔性非对称超级电容器研究

The increase of areal mass loading, capacitance and device operation-voltage window can directly improve the areal energy density of graphene-based flexible energy storage device. However, the increase of mass loading often leads to lengthen ion/electron transport paths in graphene films, which limits ion/electron transport in graphene films and results in materials with low capacitance and poor rate capacity. To solve the problem, this project makes use of functional groups or electrochemically active organic molecules modified graphene ribbons and carbon nanotubes as basic unit, preparing high mass loading graphene-based films by three-dimensional (3D) space assembly with the integration of 3D ion diffusion channels, integrated conductive network, high pseudocapacitance and flexible. Flexible asymmetric supercapacitors with high area energy/power density are assembled according to the working voltage of different functional groups or small molecules. The design of the graphene ribbon ensures that the fast diffusion of electrolyte ions on the direction of perpendicular to the graphene films, and the carbon nanotubes can construct ion diffusion channel between the layers in the graphene films, resulting the graphene-based film to form 3D ion diffusion channels. This research focuses on the effect of ribbons structure, chemical modification and carbon nanotubes on the electrochemical properties of the graphene-based films. Therefore, our results would provide theoretical and experimental basis for the design of high areal energy/power density flexible energy storage device.

针对石墨烯基柔性储能器件面积能量密度低的问题，通过提高电极材料质量负载量、电化学容量以及器件工作电压能够改善上述难题。然而如何解决高质量负载下石墨烯基膜内部离子传输阻力大、比容量低和倍率特性差的问题则显得尤为关键。本项目拟采用官能团或有机小分子修饰的条带状石墨烯和碳纳米管为构筑单元，制备出具有三维离子快速扩散通道、整体导电网络、高赝电容、优良力学性能等功能集成的高负载量石墨烯基膜。利用不同官能团、有机小分子工作电压的不同，分别作为正、负赝电容电极，组装出具有高面积能量/功率密度的柔性非对称超级电容器。条带状结构设计确保了电解液离子在垂直石墨烯膜方向上的快速扩散；碳纳米管在石墨烯层间搭建离子扩散通道，同时弥补导电性的不足。阐明高负载量石墨烯基膜条带状结构设计、化学修饰、碳纳米管引入与电化学储能特性间的本质联系，为推动高面积能量/功率密度石墨烯基柔性储能器件的应用提供理论基础和实验依据。

储能器件正受限于面积能量密度低的问题，通过提高电极材料质量负载量、电化学比容量以及器件工作电压能够改善上述难题。然而，随着单位面积负载量增加电极内部电解液离子/电子传输阻力也随之增大，导致其电化学性能显著降低。因此如何使工作电极在高负载量下实现内部快速的离子/电子传输，使其具备高比容量和高倍率特性，是目前国内外研究的热点和难点。针对该研究的热点和难点问题，在国家自然科学青年基金的资助下，本项目执行人分别以官能团修饰的条带状石墨烯、多孔石墨烯、杂原子掺杂碳材料、赝电容材料为构筑单元，通过多种结构调控制备出具有三维离子快速扩散通道、整体导电网络、高赝电容等功能集成的一系列电极材料。该系列电极材料在活性物质负载量超过10 mg cm-2的条件下表现出良好电化学性能。相应的一些电极材料组装成器件后也表现出较高的能量密度。通过该项目研究：（1）解决电极材料高质量负载下材料内部电解液离子、电子传输阻力大的难题，制备出在高负载量下保持良好电化学性能的电极；（2）同时解决了超级电容器面积能量/功率密度低的问题。该工作阐明了化学修饰、结构设计与电化学储能特性间的本质联系，为推动高面积能量/功率密度储能器件的应用提供了理论基础和实验依据。