高体积容量混合超级电容器的石墨烯/超微Co3O4正极研究

The volumetric capacitance of hybrid supercapacitors based on graphene/ultrafine Co3O4 particles cathode is still lower due to the lower activity and the larger dead volume in the composite materials or the electrodes. In this project, the laser irradiation method and the electrostatic spinning technology are proposed to prepare the graphene/ultrafine Co3O4 particles cathode with controllable microstructures. The performance, especially volumetric capacitance, was improved in the hybrid supercapacitors based on the graphene/ultrafine Co3O4 particles cathode, in which the functions and electrochemical activities of each component were fully utilized. In the preparation process of the liquid phase laser irradiation, the highly conductive graphene and the ultrafine Co3O4 particles (~10 nm) can be obtained through a laser fragmentation and photothermal reduction effects, which leads to the in-situ preparation of the highly active graphene/ultrafine Co3O4 particles. The graphene/ultrafine Co3O4 particles fiber-thin-film electrodes with high-porosity, high-loading mass, and self-standing property can been constructed by the electrostatic spinning technology with fiber-film forming property. The graphene/ultrafine Co3O4 particles were uniformly dispersed in the fiber in the thin-film electrodes, which further reduces the dead volume in the electrodes. By a careful investigation on the electron/ion transport abilities and dynamic characteristics in the graphene/ultrafine Co3O4 cathode, the relationship between the microstructure of the cathode and its electrochemical properties is explored, providing theoretical guidance and material foundation for the development of the high volumetric performance hybrid supercapacitors.

由于石墨烯/Co3O4正极复合材料的活性较低且死体积较大，其混合超级电容器体积容量仍较低。本项目拟通过激光辐照法和静电纺丝技术制备微观结构可调的石墨烯/超微Co3O4复合材料，用作混合超级电容器电极每个组元的功能和电化学活性可被充分利用，进而提高其性能，尤其是体积容量。利用液相激光辐照的光热还原和碎裂效应，可生长高导电石墨烯和超微Co3O4粒子（~10nm），进而原位合成高活性的石墨烯/超微Co3O4复合材料。随后，利用静电纺丝技术的纤维成膜特性，将石墨烯/超微Co3O4均匀分散到薄膜中的每根纤维中，直接构筑多孔隙、高负载量自支撑石墨烯/Co3O4纤维薄膜电极，进一步减小电极死体积。通过系统研究电子和离子在电极中的传输动力学特性，探索石墨烯/超微Co3O4材料及电极薄膜的微结构与其电化学性能之间的关系，为发展高体积混合超级电容器的提供理论依据和材料基础。

体积比容量是电化学储能器件的重要指标之一。为了改善石墨烯/Co3O4复合材料作为混合超级电容器正极活性较低且死体积较大的问题，提升其体积比容量，本项目主要通过激光辐照法和静电纺丝技术制备了微观结构可调的Co3O4基复合材料，并对其电化学性能进行了研究，主要研究内容、重要结果、关键数据及其科学意义如下：. （1）采用新颖的激光辐照方法，同步实现氧化石墨烯的还原和Co3O4的复合，最终获得了具有高性能的Co3O4/石墨烯复合材料。研究发现，激光辐照后Co3O4被破碎成细小的纳米颗粒（5~20 nm），均匀地锚定在石墨烯上，且与石墨烯紧密地结合在一起。在三电极体系下，最优Co3O4/石墨烯复合材料比电容可达978.1 F g−1；. （2）采用静电纺丝技术获得了具有良好稳定性的Co3O4/石墨烯/碳纳米纤维复合材料。微结构表征显示，Co3O4/石墨烯复合材料均匀地分散在碳纳米纤维上，碳纤维骨架有效抑制了Co3O4颗粒的团聚和在电化学反应过程中的溶解，因此有效提高了Co3O4/石墨烯/碳纳米纤维复合材料的倍率性能（51.3%）和循环稳定性。. （3）将上述静电纺丝制备的自支撑Co3O4/石墨烯/碳纳米纤维薄膜电极作为混合超级电容器的正极，对其电化学性能进行了系统研究。Co3O4/石墨烯/碳纳米纤维单电极的体积比容量超过1200 F cm-3，基于该电极材料构建的混合超级电容器能量密度突破1mWh cm-3。. （4）通过系统研究电子和离子在电极中的传输动力学特性，探索石墨烯/超微Co3O4材料及电极薄膜的微结构与其电化学性能之间的关系，为发展高体积混合超级电容器的提供理论依据和材料基础。