Preparation Of Flexible Composite Electrode Materials Based On Carbon Cloth And Their Application In Supercapacitors

As a relatively new type of energy storage equipment,supercapacitors have greater energy density and power density than traditional capacitors,and have higher power density,faster charging and discharging rate and longer cycle life than lithium-ion batteries which have been widely used.In particular,the research and development of flexible supercapacitors is of great significance to meet people’s demand for wearable electronic devices.Flexible supercapacitors need to be light,thin and have good electrochemical performance,which requires the development of flexible electrode materials with special structure.Compared with other flexible substrate materials,carbon cloth（CC）flexible electrode materials have the characteristics of large specific surface area,strong corrosion resistance and good flexibility,which have been widely studied.However,due to the poor hydrophilicity and lack of abundant pore structure,commercial carbon cloth has a small area specific capacity when it is directly used as electrode material of supercapacitor.As a result,the energy density is low when it is assembled into supercapacitor devices,which has no practical application value.According to many studies,loading other active substances on carbon cloth surface is the most effective strategy to improve the area specific capacity of carbon cloth electrode.In this paper,other active substances are grown on the surface of carbon cloth by in-situ method,avoiding the use of binder in the process of electrode preparation.The prepared carbon cloth composite electrode has good electrochemical performance.Specific research results are as follows:（1）CC/N-CNT composites were obtained by in situ growth of nitrogen-doped carbon nanotubes（N-CNT）on carbon cloth substrates using melamine as the carbon and nitrogen sources and Co as the catalyst.The material has been used as a flexible working electrode for supercapacitors and electrochemical tests have been carried out in a three-electrode system.When the current density is 2 m A/cm²,the area specific capacity of CC/N-CNT can reach 4081.6 m F/cm².When the current density is increased from 2 m A/cm² to 20 m A/cm²,the area specific capacity of CC/N-CNT can be maintained at 72.8%.At a current density of 10 m A/cm²,the specific capacity can be maintained at 90.3%of the first cycle capacitance after 5000 cycles.In addition,the working electrode has good mechanical flexibility,and its area specific capacity can still maintain 97.6%of that before bending after 50 times.Two CC/N-CNT electrodes with the same area were assembled into symmetrical supercapacitors for electrochemical performance test.When the current density is 2 m A/cm²,the area specific capacity is 572.6 m F/cm²,and when the power density is 1000μW/cm² and10000μW/cm²,the energy densities can reach 79.53μWh/cm² and 40.28μWh/cm²,respectively.（2）By using ionic liquid containing N,B and F as heteroatom dopant,the composite materials of carbon cloth and N,B and F doped carbon nanotubes（CC/NBF-CNT）were prepared successfully,and the electrochemical performance of the composites was compared with that of CC/N-CNT.The CC/NBF-CNT can reach the maximum specific area capacity of 4303.2 m F/cm² at the current density of 2m A/cm².When the current density increases from 2 m A/cm² to 20 m A/cm²,the capacity retention rate can reach 77.4%.CC/N-CNT has higher area specific capacity and capacity retention rate than CC/N-CNT tested under the same conditions.The sample can still maintain 97.1%of the initial capacity after 6700 consecutive charge-discharge cycles,and has better cyclic stability than CC/N-CNT.which proves that multi-heteroatom doping has a good optimization effect on the electrode.Two CC/NBF-CNT electrodes with the same area were assembled into a symmetrical supercapacitor for electrochemical performance testing,and the area specific capacity was 750.8 m F/cm² at a current density of 2 m A/cm²,and the energy density could reach 104.3μWh/cm² and 61.4μWh/cm² at power densities of 1000μW/cm² and10000μW/cm²,respectively,which has higher energy density than the symmetric electrode assembled by CC/N-CNT,proving that the multi-heteroatom doping has a good optimization effect on the electrode.（3）The carbon cloth of growing nitrogen-doped carbon nanotubes was used as the substrate,the CC/N-CNT/Co（OH）₂ electrodes were obtained by growing Co（OH）₂nanosheets on them by electrochemical deposition.The electrode can reach a mass specific capacity of 550.2 F/g at a current density of 0.5 A/g.When the current density is increased from 0.5 A/g to 10 A/g,its capacity retention rate can reach70.2%,which has good multiplicative performance.The carbon cloth of growing nitrogen-doped carbon nanotubes was used as the substrate,the CC/N-CNT/Co₃O₄ electrode was obtained by growing Co₃O₄ on it using hydrothermal method.The electrode can achieve a maximum mass specific capacity of 528.4 F/g at a current density of 1 A/g,which has a higher mass specific capacity than CC/Co₃O₄ prepared by growing Co₃O₄ directly on carbon cloth,and has a capacity retention rate of 91%after 3000 consecutive charge/discharge cycles.