具有三维导电网络和多尺度孔道的石墨烯/介孔碳复合材料的制备及其超级电容性能研究

Supercapacitors, with high power density and excellent security, are important energy storage devices. However, the low energy density of supercapacitors limits their application in many important areas. Graphene has very high theoretical specific surface area and excellent electrical conductive capacity, showing great potential as a high-performance supercapacitor electrode material. Unfortunately, wet-chemical route, current easy-to-scale-up method for preparing graphene, has drawbacks of low efficiency of graphite oxide stripping, and aggregation of graphene and/or re-stacking during the reduction and subsequent drying stages, which are unfavorable for graphene to retain the large specific surface area and hinders further improvement of the capacitance. Therefore, this project plans to fabricate graphene/mesoporous carbon composite with a three-dimensional conductive network and hierarchical pore structure. Graphene as the continuous conductive phase in as-prepared composite favors to acquire high conductivity, since its hierarchical pore structure is helpful to the diffusion/infiltration of the electrolyte and charge transfer in the composite, while its high specific surface area facilitates more area for charge storage. In the meantime, methods will be established to regulate the pore structure, pore size, surface wettability and conductivity of as-prepared composite; and a series of graphene/mesoporous carbon composites with different combinatory manners will be prepared. Moreover, the structure-activity relationship between the structure of as-prepared composites and their supercapacitor performance will be studied, and charge storage and transfer mechanisms in the composites will be revealed. This, hopefully, is to help to establish theoretical ground and provide experimental support for the preparation of electrode material with a high energy density and high power density.

超级电容器具有高的功率密度和优异的安全性，是重要的能量存储装置；但低的能量密度限制了它在许多重要领域的应用。石墨烯具有非常高的理论比表面积和优异的导电能力，是极具潜力的超级电容器用电极材料。但现有的能宏量制备石墨烯的化学方法，存在剥离效率低和石墨烯片层重新堆叠等问题，不利于制取高比表面积的石墨烯，并提高材料的比容量。鉴于此，本项目拟制备具有三维导电网络和多尺度孔道结构的石墨烯/介孔碳复合材料。其中石墨烯为连续导电相，将赋予材料高导电性；多尺度孔道结构有利于电解液的浸润和电荷的转移；高的比表面积有利于提供更多的电荷存储空间。设计、制备具有不同复合方式的石墨烯/介孔碳复合材料，并建立调控其孔隙结构、孔径尺寸、表面浸润性、材料导电性等结构与性质的方法；关联复合材料结构与其电容性能之间的构效关系；揭示电荷在其中的存储、转移机制，对制备高性能的电极材料具有重要的理论意义和应用价值。

石墨烯具有非常高的理论比表面积和优异的导电能力，是极具潜力的超级电容器用电极材料。但现有的能宏量制备石墨烯的化学方法，存在剥离效率低和石墨烯片层重新堆叠等问题，不利于制取高比表面积的石墨烯，并提高材料的比容量。基于上述研究背景，项目组开展了如下工作。. 1）氧化石墨烯（GO）和石墨烯制备：采用交变电磁场辅助的Hummers方法制备了GO，交变电场的引入能提高高锰酸钾的反应利用率，大幅减少原料消耗。臭氧或Fenton试剂能对GO进行二次氧化，增加其氧化程度。利用电化学方法剥离制备石墨烯的过程中，用石蜡、PVDF包裹石墨箔电极，能提高插层和剥离程度，获得具有大的横向尺寸的少层石墨烯。.2）石墨烯聚集结构的调控：建立了盐辅助水热路线制备RGO的方法，盐的加入改变了GO的聚集行为，产物中大尺寸的微孔比例显著增多。100A/g电流密度下，样品的比电容与对照样品相比较，能从151提高到194 F/g。当采用离子液（1.0M EMIMBF4/AN）作电解质时，1kW/kg功率密度下，样品的能量密度达到125.4 Wh/kg。利用盐辅助的喷雾干燥方法，制备了多孔RGO微球，盐的加入增加了产物回收率。样品经热还原处理后，在0.1A/g的电流密度下比容量达到325 F/g，同时其100A/g:1 A/g的容量保持率能达到72%，显示出优异的高倍率性能。.3) 石墨烯基复合碳材料的制备与性能：利用胆酸分子在盐诱导下的自组装行为，以酚醛树脂为碳源，构建了具有微孔-介孔-大孔的多级孔碳材料。提出了一种制备RGO/活性炭/碳纳米管三维复合凝胶的方法，重点研究了电极材料在高压致密化过程中孔结构的演变，碳纳米管的加入有利于介孔结构的保持，能显著提高材料的高倍率性能。.4）多孔碳结构对高容量锂电池负极材料体积变化的缓冲作用：构建了RGO/ATO，中空碳球@Fe3O4@碳两种多孔纳米复合材料，石墨烯或类石墨烯的多孔结构有助于缓冲高容量锂电池负极材料的体积变化，稳定其结构，进而提高材料的循环稳定性。.本项目建立了多种石墨烯基纳米材料的制备方法，以及调控石墨烯化学组成、孔隙结构、表面浸润性等的手段，获得了几种高性能的电极材料，部分阐明了复合材料结构与其电容性能之间的构效关系。该研究对制备高性能的电极材料具有重要的理论意义和应用价值。