Fabrication Of Continuous Carbon Nanotube Fibers And Composites For Electrochemical Properties

As a new kind of high performance fiber,carbon nanotube?CNT?fibers have great potential in applications.Based on the floating chemical vapor deposition?CVD?system,continuous preparation of CNT fibers can be achieved with new catalyst system.Following the preparation technology,continuous flexible composite electrode materials are fabricated using in situ method or online post-processing method respectively,showing a good application prospect in energy field.Based on floating catalytic reaction,ferrocene,cobaltocene,nickelocene and their composites are used as catalyst to fabricate continuous CNT fibers.Three kinds of catalysts exhibit different catalytic properties and spinning state.thiophene,being as sulfur source,can control the growth and structure of CNTs.Sulphur parcel catalyst particles,inhibiting the carbon dissolution,promoting the carbon diffusion in catalyst surface and the formation of CNTs.Large scale diameter collapsed CNT is achieved with high amount of thiophene using FeNi alloy as catalyst,the width of the collapsed CNT can reach 25 nm through TEM images,CNTs are complete collapsed.Nano carbon fibers are achieved when the hydrogen flow is low,while CNT are achieved when the flow is high.Hydrogen can restrict carbon deposit into catalyst,keeping the activity of catalyst,which is conducive to the formation of pure CNT fibers.Through real-time observation of the CNT aggregation changes in the gas flow,the CNT growth and assembly behavior is studied systematically,which indicates that there are three important reasons for CNT assembling into CNT sock in the reaction zone:stable flow,Van der Waals force to assemble and bundles intertexture.The applications of CNT fibers in magnetism and fiber-shaped supercapacitor are explored.3D hierarchical carbon nanotube/reduced graphene oxide?CNT/rGO?hybrid films of enhanced electrochemical capacitive performance are obtained,by dispersing graphene oxide?GO?sheets into ethanol carbon source,ferrocene as catalyst and thiophene as promoter,the hybrid films are fabricated in novel direct injection floating catalyst chemical vapor deposition?CVD?method.With the addition of the rGO sheets,the hybrid films with enhanced surface area still retain the connecting structures of CNT networks.The resulting CNT/rGO films exhibit a high specific capacitances in aqueous,acid,neutral and solid electrolyte,which is 151 F/g in 2 M KOH aqueous solution.The hybrid films with low content of rGO sheets receive more than triple specific capacitances as compensation for the pure CNT films.In addition,the capacitance retention of 97%after 5000 cycles demonstrates an excellent cycling property.These results indicate a promising material for scalable products to capacitive applications.Continuous composite fiber electrodes are achieved using online post-processing method and twisting method with lithium iron phosphate?LFP?and carbon coated titanium phosphate lithium?LTP?as active materials,following the fabrication of CNT fibers.The active materials and CNTs contact closely.Composite fibers exhibit good specific capacity and rate performance in 1 M Li₂SO₄ solution.Flexible fiber-shaped aqueous lithium ion batteries are fabricated by LFP/CNT composite fibers as cathode,LTP/CNT composite fibers as anode,CMC/Li₂SO₄ gel as solid electrolyte.A high specific capacity is 29.1 mAh/g at a current density of 0.25 A/g.The battery has high energy density with 30.12 Wh/kg.