Study On Preparation And Electrochemical Performance Of Nickel-cobail Graded Flexible Electrode Materials

Supercapacitors,due to their many advantages such as fast charge and discharge speed,long service life,aroused more ttention.Electrode materials,as the"heart"of supercapacitors,play a vital role in evaluating the performance of supercapacitors.With the in-depth study of transition metal electrodes,especially the development and use of nickel-cobalt-based materials,the development and popularization of supercapacitors has been greatly promoted.With the advent of the microelectronics era,various electronic devices are becoming smaller and more portable,which has also put forward new requirements for the development of supercapacitors electrode.?1?A flexible cathode with highly electrochemical performance for bendable supercapacitors have been achieved by electrochemical depositing hierarchical nanostructured Ni₃S₂/Ni?OH?₂ compounds on the surface of commercial conductive textile.A variety of physical structure characterizations are used to determine the material composition,surface valence,and nanostructures,and electrodes are made for electrochemical testing to evaluate their performance in electrochemical devices.Due to profuse exposed-edge planes,the obtained electrode exhibits remarkable hybrid properties with a highly specific capacity of 361?Ah cm^-2 at 2 mA cm^-2 in 3 M KOH medium,and excellent cycling stability?85%capacitance retention after 5000 cycles?.Further,the fabricated flexible and lightweight electrode is used to evaluate its performance in a solid-state flexible hybrid battery.The assembled flexible hybrid battery exhibits a high energy density of 10.97 Wh kg^-1 with a power density of 54.86mWh kg^-1.?2?In order to improve the stability of the substrate material,.nickel sulfide sheet-like nanoarray?NiS?with secondary nanoflakes vertically grown on primary nanosheets is fabricated via sulfurization of hierarchical structured Ni?OH?₂ supported on carbon cloth substrate.A carbon cloth with more corrosion resistance and more stable electrochemical properties is used as a support structure,and a secondary nanosheet modified NiS nanosheet array is grown by a hydrothermal method.A variety of physical structure characterizations are used to determine the material composition,surface valence,and nanostructures,and electrodes are made for electrochemical testing to evaluate their performance in specific electrochemical devices.Because of its unique open nanostructure,the prepared NiS nanosheet array has a high specific surface area,which undoubtedly provides more favorable conditions for ion transmission and electron transfer,and therefore exhibits excellent electrochemical performance.When the charge and discharge current density at 2 mA cm^-2,the NiS/CC composite electrode material shows a high specific capacitance of 430?Ah cm^-2.When the current density is increased to 20 mA cm^-2,the electrode material can still reach 45%.The capacity retention and AC impedance tests show that the NiS/CC electrode has a smaller and smaller series resistance?0.743??.?3?Hierarchical arrays of transition metal compounds directly grown on a current collector to fabricate the binder-free electrode are a promising strategy to achieve high-performance hybrid supercapacitors owing to its high surface area and low inner resistance.To engineer the microstructure of the hierarchical structure can further efficiently improve capacitive performance.In this work,a hierarchically structured Ni?OH?₂/NiS nano-sheet arrays,with the vertical growth of secondary nanosheets on their surface,are directly fabricated onto carbon cloth via an NH₄F-induced method.Besides,the Ni?OH?₂/NiS electrode also delivers excellent performance in a solid-state flexible supercapacitor.When the power density reach 4.72 W cm^-2,the obtained capacitor can provide an energy density of 0.58 mWh cm^-2.