Slurry Of Carbon Nanotubes As Conductive Additive For Lithium Batteries

Carbon Nanotubes(CNTs)have unique geometry property,remarkable electronic conductivity,great chemical stability and extraordinary thermal and mechanical stability.It has been the hot spot of the research since it has been discovery,and been considered to be one of the most application prospect of nanometer materials.It has been demonstrated that the reversible capacity can be improved significantly by adding CNTs into LiFePO4(LFP)cathode as conductive additive because of forming a continuous conductive network on the bulk of electrode,which significantly reduces the electrical resistance of the cathode.However,CNTs are not able to be dispersed homogeneously in water due to the hydrophobicity of CNTs side wall.Carbon nanotubes have many aspects to be improved as conductive additive.In this thesis,S-doped carbon nanotubes(SCNTs)obtained by a post treatment approach are used as conductive additive for Li FePO4(LFP)cathodes in Lithium ion batteries(LIBs).The SCNTs exhibit better hydrophily as compared to the pristine CNTs because of S doping.Thus the SCNTs can be stably dispersed in water,forming an aqueous conductive slurry.The LFP cathode using the aqueous SCNTs slurry as conductive additive.The cells were galvanostatically charged and discharged in the voltage range on a charge and discharge tester.The main research results are shown as follows:CNTs obtained by a chemical vapor deposition process were used as the starting material.SCNTs were synthesized by the S doping reaction between CNTs and MgSO4.EDS mapping and XPS analysis reveal that S atoms have been homogeneously incorporated into the sp2 carbon frameworks via covalent bonds.The SCNTs exhibit higher specific surface area,higher conductivity and better hydrophily as compared to the pristine CNTs because of S doping.Thus the SCNTs can be stably dispersed in water,forming an aqueous conductive slurry.The LFP cathode using the aqueous SCNTs slurry as conductive additive exhibits excellent electrochemical performances in terms of capacity,rate capability and cycling stability due to the uniform dispersibility of SCNTs in the bulk of electrodes forming a continuous conductive network.Carbon nanotube and graphene composite conductive was prepared by using colloid mill.In order to investigate the influence of CNTs on the electrochemical performance of LIBs,different mass ratios between CNTs and graphene in the conductive additives were used.The mass ratio between SCNTs and carbon black was 8 to 2 in the conductive additive was optimized.The as-prepared LFP cathodes exhibited excellent electrode performance.