Preparation And Properties Of Flexible Electrodes For Graphene-based Modified Cotton Fabric

The booming development of flexible wearable devices has benefited mankind a lot,its applications in sensing,monitoring,communication,etc.,had provided people with a lot of convenience in daily life.Meanwhile,the demand for flexible energy storage devices corresponding to flexible wearable devices is also increasing.Flexible supercapacitors retain the characteristics like high power density,long cycle life and excellent charge-discharge ability,while perfectly adapting to wearable devices.The core of supercapacitor is the flexible electrode with excellent performance.In recent years,the research and development of flexible electrodes have been reported continuously,and quite a few of them have excellent electrochemical properties.However,these reports almost contain the following problems,such as the high cost of raw materials,high energy consumption or harsh conditions in the preparation process,chemical contamination during preparation and use,difficulty in large quantities of preparation,and only suitable for laboratory experiments,etc.,which hinder the commercialization and application of these electrodes in human society.On the premise of ensuring stable performance,finding universal electrode materials,simplifying the preparation process,reducing pollution,and being able to be prepared on a large scale are the key to realize commercial application of flexible electrodes.In this paper,the cotton fabric is used as the base,and graphene is used as the electrode material to modify the cotton fabric,so as to prepare the double-layer flexible fabric electrode.Copper nanoparticles（Cu NPs）and polypyrrole（PPy）were used as electrode reinforcing materials to add pseudocapacitors to the fabric electrode,and two multilayer hybrid electrodes were constructed.The electrochemical performance of three electrodes and three all-solid-state symmetric supercapacitors composed of electrodes was tested to explore the effects of different electrode materials on the performance of fabric electrodes,and seeking a general process for the preparation of flexible fabric electrodes,so as to provide method for the large-scale production and application of flexible electrodes.The main research contents are as follows:（1）Graphene oxide（GO）was prepared by the modified Hummers process.Coating GO on cotton fabric by screen printing process to modify it,the GO/cotton（GCF）was reduced by chemical reduction method to obtain RGO/cotton fabric（RCF）as the fabric electrode sample.The electrochemical performance of RCF electrode and all solid state supercapacitor assembled by RCF was tested.At the sweep speed of 5m V s^-1,the specific capacitance of RCF is 55.4 F g^-1,with good reversibility.The maximum specific capacitance of RCF supercapacitor is 50.5 F g^-1,which has good cycle stability.After 1000 times of charge and discharge test,the capacitor retention rate is 82.6%.The highest energy density is 3.03 Wh Kg^-1,and the highest power density is 92.8 W Kg^-1.（2）Copper/RGO/cotton fabric electrode（CRCF）was obtained by polymerization of Cu NPs on the surface of RCF with a simple in situ polymerization method,and CRCF all-solid state supercapacitors were assembled.Electrochemical performance of CRCF electrode and CRCF supercapacitor was tested.Cu NPs provide pseudo capacitance components for the fabric electrode.At a sweep speed of 5 m V s^-1,the specific capacitance of CRCF is 197.4 F g^-1,but the reversibility is relatively modest.The maximum specific capacitance of CRCF supercapacitor is 179.4 F g^-1,which has good magnification performance.After 200 charge-discharge tests,the capacitance retention rate is 59.8%,and the cycle stability is low.The maximum energy density of supercapacitors is 8.52 Wh Kg^-1 and the maximum power density is 100.05 W Kg^-1.（3）Pyrrole was polymerized on the surface of RCF with aqueous ferric chloride as oxidant,and PPy/RGO/cotton fabric electrode（PRCF）was obtained by in-situ polymerization method.Based on PRCF,all-solid-state supercapacitors were assembled.The load of PPy improves the conductivity of the electrode,and it provides a pseudocapacitor by itself.Moreover,the stacking of PPy creates nanoscale pores,allowing the electrode to obtain more storage space.At a sweep speed of 5 m V s^-1,the specific capacitance of PRCF reaches 310.3 F g^-1.After 1000 times of charge and discharge test,the capacitance retention rate is 95.5%,with excellent cycle stability.The maximum energy density of the supercapacitor is 16.23 Wh Kg^-1,and the maximum power density is 92.8 W Kg^-1.