基于镍泡沫支撑的Co_3O_4纳米多孔结构的高性能超级电容器电极

在众多能量存储和转化器件中,超级电容器由于具有功率密度高、充放电迅速和优异的循环性能的优点而被广泛研究.然而,较低的比容量和能量密度,限制了超级电容作为大尺度能量存储和转化器件的广泛应用.为了提高超级电容器的比容量,需要增大电极材料和电解质的接触面积,进而促进电极材料俘获/释放电解质中的粒子(例如电子、离子或者小分子).在此,我们通过简单的水热法联合高温退火实验方案能够大规模制备出镍泡沫支撑的Co_3O_4多孔纳米结构.无需借助导电胶和粘合剂,在集流器镍泡沫上"生长"Co_3O_4多孔纳米结构直接作为超级电容的电极材料.这种多孔纳米结构和一体化设计思路不仅能够有效提高电极的导电性,而且能够有效缩短离子和电子的迁移路径.由于多孔的结构特征和优异的导电性能,Co_3O_4电极表现出超高比容量(在电流密度为2.5 m A·cm~(-2)和5.5 m A·cm~(-2)时,比容量分别为1.87 F·cm(-2)(936 F·g-1)和1.80 F·cm~(-2)(907 F·g-1))、较好的倍率性能(电流密度从2.5 m A·cm~(-2)增大到100 m A·cm~(-2)时,保留其48.37%的初始电容)和超高的循环稳定性(经历4000次电流密度为10 m A·cm~(-2)的循环充放电过程,保留其92.3%的比容量).这种多孔纳米结构和一体化设计思路对设计其他高性能储能器件具有重要的指导意义.

Co3O4 mesoporous nanostructure supported by Ni foam as high-performance supercapacitor electrodes

In various energy conversion and storage devices, supercapacitors have been extensively used due to their high power densities, fast delivery rates, and exceptionally long cycle lives. However, the low specific capacitances and low energy densities of supercapacitors largely hinder widespread applications in large-scale energy conversion and storage systems. To improve the specific capacitances of the supercapacitors, the surface areas of the electrode materials should be made as large as possible to allow the capturing and releasing of “particles” (such as ions, molecules, or electric charges). Here in this work, we demonstrate an efficient approach to the large-scale production of Co₃O₄ mesoporous nanostructure supported by Ni foam via a simple hydrothermal synthesis followed by ambient annealing at 300 ℃ for 4 h. The designed and fabricated Co₃O₄ mesoporous nanostructures directly serve as binder- and conductive-agent-free electrodes for supercapacitors, which thus provide more chemical reaction sites, shorten the migration paths for electrons and ions, and improve the electrical conductivity. By taking advantage of the structural features and excellent electronic conductivity, the Co₃O₄ exhibits the ultrahigh specific capacitances (1.87 F·cm^-2 (936 F·g^-1) and 1.80 F·cm^-2 (907 F·g^-1) at current densities of 2.5 mA·cm^-2 and 5.5 mA·cm^-2, respectively), high rate capacitances (48.37% of the capacitance can be retained when the current density increases from 2.5 mA·cm^-2 to 100 mA·cm^-2) and excellent cycling stability (92.3% of the capacitance can be retained after 4000 charge/discharge cycles at a current density of 10 mA·cm^-2). The nanostructuring approach and utilizing a binder- and conductive-agent-free electrode can be readily extended to other electrochromic compounds of high-performance energy storage devices.