Electrochemical Properties Of Carbon Cloth-based Metal Sulfide Composites And Their Flexible Supercapacitors

As a new type of energy storage device,flexible supercapacitor has potential application value in the field of portable and wearable devices,and the electrode material is one of the key factors to determine the performance of supercapacitor.Carbon cloth（CC）,as a typical flexible substrate material,has been widely concerned because of its high flexibility and high conductivity,but it has the disadvantage of low specific capacitance.To solve this problem,the electrochemical performance of the material can be effectively improved by directly loading high-performance metal sulfide on the carbon cloth.In this work,carbon cloth is used as the research object,which is composited with Sn S₂,CuS and VS₂respectively.By taking full use of the synergistic effect between carbon materials and metal sulfides,high-performance flexible electrode material is obtained,and its feasibility in practical application is verified by assembling asymmetric flexible supercapacitors.Two-dimensional SnS₂ nanosheets grow on the surface of acidified carbon cloth by a simple one-step hydrothermal method.Comparison of surface morphology and analysis of electrochemical properties of Sn S₂/CC composites by controlling hydrothermal reaction temperature.When the reaction temperature was 180℃,the Sn S₂nanosheets on the surface of carbon cloth had the most uniform distribution,showing the best electrochemical performance(194.4 m F cm^-2),and the capacitance retention rate is 86.5%after 10000 cycles.When the scan rate increases from 10 m V s^-1to 50 m V s^-1,the contribution rate of capacitance increases from 75.6%to 87.7%.The performance of the asymmetric flexible supercapacitor assembled with Sn S₂/CC-180 as electrode has no obvious degradation after multiple bending at different bending angles.After 5000 cycles,the capacitance retention rate is 75%,and it has high energy density and power density.In order to improve the capacitive performance of electrode materials,high performance CuS nanosheets were loaded on the surface of carbon cloth by a one-step solvothermal method.These nanosheets grow alternately,and expose more active sites,which is good for the transport of electrolyte ions.The results show that the capacitance of CuS/CC-4 composites is significantly improved,and the highest specific capacitance is obtained when the reaction time is 4 h,reaching 436.5 m F cm^-2at 1 m A cm^-2.The specific capacitance can still maintain 75.1%after 5000 cycles.An asymmetric flexible supercapacitor based on CuS/CC-4 electrode can increase the voltage window to 1.6 V and the specific capacitance retention can reach 86.4%after5000 charge-discharge cycles.The maximum energy density of the device can reach0.027 m Wh cm^-2.A 2 V LED lamp can be turned on for 60 seconds by connecting two devices in series.In order to further improve the energy density and power density of the device,VS₂/CC-6,VS₂/CC-12,VS₂/CC-18 and VS₂/CC-24 samples were prepared under different hydrothermal conditions.The results show that the morphology and electrochemical performance of VS₂/CC-12 are the best(972.5 m F cm^-2at 1 m A cm^-2),and the specific capacitance retention is 77.5%after 10000 times of charge and discharge tests at 10 m A cm^-2.When the scanning rate is expanded from 10 m V s^-1to50 m V s^-1,the contribution rate of pseudocapacitor decreases from 71.1%to 53.1%,indicating that the contribution of pseudocapacitor occupies the leading position.An asymmetric flexible supercapacitor assembled by the composite can work stably in a wide voltage window of 1.7 V,and the specific capacitance can reach 550.6 m F cm^-2at 5 m A cm^-2.After 5000 charge discharge tests,the specific capacitance retention of the device is 81.2%.The maximum energy density and power density are 0.22 m Wh cm^-2and 8.26 m W cm^-2,respectively.In this work,carbon cloth as the substrate,using the high conductivity of carbon cloth and high capacitance performance of metal sulfide to give full play to the advantages of different components.Sn S₂nanosheets can improve the agglomeration and cycling properties of nanomaterials.CuS nanosheets further promote the transmission and transfer of electrons,which improve the specific capacitance of electrode.VS₂nanosheets can comprehensively improve the specific capacitance of electrode materials and energy density of devices.The results show that the performance of asymmetric flexible supercapacitor has no obvious decline under different bending angles,and it can provide energy for LED lamps stably,which has excellent mechanical stability and practical application value.Carbon cloth-based metal sulfide electrode materials and their flexible supercapacitors have excellent flexibility and electrochemical performance,which show great potential in the field of flexible energy storage.