Metal-organic framework-derived porous carbon for the advanced aqueous zinc-ion hybrid capacitor

锌离子水系混合电容器的金属有机框架衍生多孔碳材料

Aqueous zinc ion hybrid capacitors(ZIHCs)are considered one of the most promising electrochemical energy storage systems due to their high safety,environmental friendliness,low cost,and high power density.However,the low energy density and the lack of sustainable design strategies for the cathodes hinder the practical application of ZIHCs.Herein,we design the N and O co-doped porous carbon cathode by annealing metal-organic framework(ZIF-8).ZIF-8 retains the original dodecahedral structure with a high specific surface(2814.67 m^(2)/g)and I_(G)/I_(D) ratio of 1.0 during carbonization and achieves self-doping of N and O heteroatoms.Abundant defect sites are introduced into the porous carbon to provide additional active sites for ion adsorption after the activation of carbonized ZIF-8 by KOH treatment.The ZIHCs assembled with modified ZIF-8 as the cathode and commercial zinc foil as the anode show an energy density of 125 W∙h/kg and a power density of 79 W/kg.In addition,this ZIHCs device achieves capacity retention of 77.8%after 9000 electrochemical cycles,which is attributed to the diverse pore structure and plentiful defect sites of ZIF-8-800(KOH).The proposed strategy may be useful in developing high-performance metal-ion hybrid capacitors for large-scale energy storage.

锌离子水系混合电容器(ZIHCs)因其安全性高、环保、成本低和功率密度大而被认为是一类有前途的电化学储能系统。然而,低能量密度和缺乏可持续的正极设计策略阻碍了其实际应用。我们通过退火金属有机框架(ZIF-8)的方法设计N、O共掺杂的多孔碳正极材料。ZIF-8在碳化过程中可以保留原始的十二面体结构,具有极高的比表面积(2814.67 m^(2)/g),I_(G)/I_(D)比为1.0。通过KOH对碳化ZIF-8进行活化处理后,多孔碳中引入了大量缺陷位点,为离子吸附提供了额外的活性位点。以改性ZIF-8为正极、商用锌箔为负极组装而成的ZIHC表现出125 W·h/kg的能量密度和79 W/kg的功率密度。此外,这种ZIHCs器件在9000次电化学循环后的容量保持率达到了77.8%。这种高效的正极制备策略有助于开发用于大规模储能的高性能金属离子混合电容器。