Design,Fabrication And Electrochemical Performance Study Of Cotton Fabrics-Based Flexible Electrodes

With the rapid development of society,the demand for efficient electrochemical energy storage and conversion devices is increasing,and the structural design of new electrode materials is also improving.Therefore,the electrode materials at present should not only show excellent electrochemical performance,but also have good cutability,mechanical stability and environmental friendliness.In this paper,cotton fabric is used as the substrate material of flexible electrode,and the electrochemical properties of the electrode are improved by electrochemical modification on its surface.The corresponding significant results as follows.(1)The composite electrode materials were successfully prepared by successively growing polypyrrole(PPy)and manganese bioxide(Mn O2)ultrathin nanosheets on the surface of cotton pads(CPs)through in situ polymerization and electrochemical deposition method.The PPy layer not only improves the conductivity of CPs,but also provides a large number of electrochemical active sites.Hence,wearable supercapacitors based on PCPs@Mn O2 materials show excellent electrochemical performance.At a current density of 1 m A cm-2,the area specific capacitance of the device is as high as 1.21 F cm-2,and the area specific capacitance can still be maintained at 88% after 5000 multi-rate cycles of charge and discharge.(2)The Zeolitic Imidazolate Framework-67(ZIF-67)array was further grown on the PCPs surface by solution method,and then the ZIF-67 array was transformed into hollow cobalt-nickel layered double hydroxides(Co Ni-LDH)array by ion exchange/etching method to obtain potato chips-like Co Ni-LDH@PCPs composites.Experimental and theoretical calculations show that Ni doping can modify the electronic structure and improve the reaction process of deprotonation/protonation in the electrochemical process.Therefore,the wearable supercapacitor based on Co Ni-LDH@PCPs electrode achieves a maximum energy density of 86.05 Wh kg-1at a power density of 0.8 k W kg-1.Moreover,the specific capacitance of the device can still be maintained at 93% after 5000 cycles of charge and discharge.More interestingly,the potato chips-like Co Ni-LDH@PCPs composites in this study can simultaneously act as electrocatalysts for oxygen evolution reaction(OER).At a current density of 10 m A cm-2,this electrocatalyst exhibits superior electrocatalytic activity with low overpotential(350 m V)and small tafel slope(58 m V dec-1).(3)To further improve the mechanical stability of the electrode,a tent-like MXene/Co Ni-LDH/MXene-CPs composite was obtained by using hollow Co Ni-LDH arrays grew on the MXene-coated CPs and then it was encapsulated again by MXene.The experimental results show that the addition of MXene not only shortens the diffusion distance of ions,but also buffers the volume change of Co Ni-LDH during charge/discharge.At a current density of 1 A g-1,the specific capacitance of the MXene/Co Ni-LDH/MXene-CPs electrode is as high as 1684 F g-1.Moreover,MXene/Co Ni-LDH/MXene-CPs electrodes as OER electrocatalyst can also exhibit superior electrocatalytic activity.At a current density of 10 m A cm-2,the overpotential of the electrocatalyst is only 297 mV.