Preparation Of Composite Electrode Materials With MOF-derived Carbon Nanowall Arrays For Supercapacitors

Supercapacitors?SCs?are widely concerned owing to their high power density,long cycle life,fast charge/discharge ability and environment friendliness.However,the lower energy density of SCs limits their wide application compared to the rechargeable batteries.In order to solve this problem,the design of electrode materials with high power characteristics and high energy density has become a research hotspot to improve the electrochemical properties of SCs.Among them,pseudocapacitive materials can store more energy through Faradaic reaction than the double-layer capacitive materials.But the long-term cycle stability of pseudocapacitive materials is poorer than double-layer capacitive materials,which is the key issue to be solved urgently.This article focuses on the preparation of electrode materials with high energy density and power density.The major target of of this article is designing superior electrochemical performance composite electrode materials.Herein,we synthesis self-supporting composite nanostructure electrode materials with carbon fiber as the conductive substrate.Nickel cobalt sulfide?CoNi2S4?-based materials have attracted extensive attention as electrodes which arise from their high theoretical capacitance,but their wide application is limited by relatively low electrical conductivity and electrochemical stability.Herein,the metal-organic framework?MOF?derived carbon nanowall arrays?CNWAs?are successfully fabricated on carbon cloth?CC?as secondary substrate,which provides more sites for electrodeposition of CoNi2S4.Furthermore,the integration of Ni layer to bridge CoNi2S4 and CNWAs,which is favorable for fast charge transfer,as well as improved conductivity.Thus,the CC/CNWAs@Ni@CoNi2S4 electrode exhibits a remarkable specific capacitance(3163 F g^-1/2825 F g^-1 at 1 A g^-1/5 mV s^-1)and rate capability(1503 F g^-1/1500 F g^-1 at40 A g^-1/50 mV s^-1).The as-prepared CC/CNWAs@Ni@CoNi₂S₄//commercial activated carbon asymmetric supercapacitor?ASC?demonstrates superior electrochemical performance with maximum energy density of 53.8 W h kg^-1 at a power density of 801 W kg^-1 and long-term cycling stability with 90.1%retention after 10 000 cycles.In order to extend the cell potential of the asymmetric supercapacitor,the carbon cloth is used as conductive substrate,and the CNWAs are used as the secondary substrate to provide larger specific surface area.And the MnO2 and Fe2O3pseudocapacitive materials are used as positive and negative electrode respectively to prepare the asymmetric supercapacitor.Meanwhile,in order to reduces the interfacial contact resistance and the internal resistance of the entire electrode material,the highly conductive Ni layer is introduced between CNWAs and Fe2O3.Hence,the CC/CNWAs@MnO2 electrode exhibits a superior specific capacitance(303 F g^-1 at 1A g^-1)and rate capability(80 F g^-1 at 80 A g^-1).The CC/CNWAs@Ni@Fe₂O₃electrode delivers the specific capacitance of 167 F g^-1 at 1 A g^-1,and still retain 44 F g^-1 even at 50 A g^-1.The as-prepared CC/CNWAs@MnO2//CC/CNWAs@Ni@Fe2O3ASC demonstrates superior electrochemical performance.The operating voltage window of prepared ASC can achieve 2.3 V.The specific capacitance of the ASC is87 F g^-1 at 1 A g^-1 and maintain 22 F g^-1 at 30 A g^-1.