Synthesis And Electrochemical Properties Of Carbon Cloth-based Nanocomposites

Supercapacitors have broad application prospects in electric vehicles,aerospace and information communication,because of high power density,fast charge and discharge speed,high energy conversion efficiency,no memory effect and environmental friendliness.In recent years,in order to meet the demand for miniaturization and thinning of highly integrated electronic devices,researchers try their best to create flexible wearable electronic instruments by transform supercapacitors with more thin and flexible.Carbon cloth is widely used as a base material for flexible supercapacitor electrodes,because of stable electrochemical properties,3D porous structure,excellent electrical conductivity and mechanical properties.However,pure carbon fibers have lower specific capacitance and energy density.Therefore,flexible electrode materials with high electrochemical activity has become a hot spot of current research.In this paper,carbon cloth is used as the base material,and the composite materials are made by supporting manganese-based oxide（MnO₂,LiMn₂O₄,Mn₂O₃）or carbon material（nitrogen-doped carbon,NC）,and the synergistic effect improve the electrochemical performance of the supercapacitor.The morphology,phase and electrochemical properties of the composites were tested and analyzed.The main research contents and results are as follows:（1）CC/MnO₂ intermediate was prepared by in-situ oxidation-reduction reaction with carbon cloth as the substrate,then acetone was used as reducing agent,LiOH·H₂O provided lithium source,and CC/MnO₂/LiMn₂O₄ composite was synthesized by hydrothermal reaction.The phase,morphology and specific surface area of the composite were characterized by XRD,SEM and BET,and the electrochemical properties of this material were tested by electrochemical workstation.The results showed that the nanostructure of MnO₂ was uniformly coated on carbon fiber,and LiMn₂O₄ was distributed on the surface of MnO₂ in a hexahedron shape.At a current density of 0.5 A g^-1,the specific capacity of CC/MnO₂/LiMn₂O₄ was 292.91 F g^-1.The capacity retention was 86.81%after 1000 times.（2）The CC/MnO₂ intermediate was prepared by redox reaction,and then the formed MnO₂ was used as a manganese source to react with trimesic acid at room temperature to form Mn-MOF,and finally calcined in an air atmosphere at 400℃to form CC/MnO₂/Mn₂O₃.A series of phase and morphology characterizations of the composites were carried out and electrochemical performance tests were carried out by electrochemical workstations.The results showed that the specific surface area of CC/MnO₂/Mn₂O₃ was as high as 99.77 m² g^-1,and this material exhibited the specific capacitance of 473.33 F g^-11 at a current density of 0.5A g^-1.The capacity retention rate is 88.04%after 3000 cycles.An asymmetric supercapacitors were assembled using CC/MnO₂/Mn₂O₃ as positive electrode and activated carbon（AC）as negative electrode,When the power density was 1.1 kW kg^-1,the highest energy density was88 W h kg^-1.（3）CC/MnO₂ intermediate was prepared by in-situ oxidation-reduction reaction,and then the as-prepared MnO₂ as manganese source reacted with 1,3,5-benzenetricarboxylic acid at room temperature to form CC/MnO₂/Mn-MOF.Finally,the CC/MnO₂/NC composites were synthesized by annealing in a nitrogen atmosphere.The morphology and electrochemical properties of this composites were characterized and analyzed.The results showed that the MnO₂/NC material was uniformly coated on the carbon fiber in a honeycomb structure.At a current density of 0.5 A g^-1,the specific capacitance of CC/MnO₂/NC was 640 F g^-1,which was better than the specific capacitance of CC/MnO₂(233.52 F g^-1).The capacity retention rate of CC/MnO₂/NC was as high as 94.64%after 3000 cycles of cycling test.An asymmetric supercapacitors were assembled using CC/MnO₂/Mn₂O₃ as positive electrode and activated carbon（AC）as negative electrode,When the power density was 1 kW kg^-1,the highest energy density was 69.44 W h kg^-1;And when the energy density was 7.2 W h kg^-1,the maximum power density was 10 kW kg^-1.