An Exploratory Research Of Oxidized Carbon Nanotube Based Lithium Batteries

The accelerated development of mobile electronic devices and electric vehicles motivate the design of novel rechargeable batteries.The emerged 5G phones required high-energy-density flexible batteries with short charging time.Unmanned aerial vehicles need to climb rapidly during the take-off phase,requiring high-power-density energy storage equipment.Developing electrochemical energy storage systems with high energy an d power densities is attractive for practical use,and it could be achieved by the well dispersion property of the active materials and conductive agents.In this work,we utilize the structural advantages of carbon nanotubes?CNTs?to fabricate well-dispersed composite electrodes.In order to prepare CNT-based composites with good dispersion behavior,the dispersion of CNTs should be improved first.By building a mathematical model of carbon nanotubes as charged cylindrical surfaces,we verified that negatively charged carbon nanotubes are more easily dispersed than uncharged carbon nanotubes due to the electrostatic repulsive forces.It is also found that the presence of uniformly distributed negative charges could provide the most effective dispersion stabilities of CNTs in an ethanol/water solvent.This study introduce oxygen-containing functional groups led to negative charges on the external surface of CNTs by using oxidation modification methods.Lithium sulfur battery,with high theoretical specific capacity and natural abundance,has aroused much attention in recent years.It is an essential issue to improve sulfur content without sacrificing sulfur utilization.This study prepares well-dispersed CNTs to load sulfur.CO₂ modified carbon nanotubes?CO₂-CNTs?is fabricated by heating CNT arrays to 900?in CO₂ atmosphere,leading to uniformly distributed negative charges on the surface of CNTs.This study develops stable dispersion of CO₂-CNTs:The CO₂-CNTs with uniformly distributed negative charges on surface result superior CNT dispersion properties than air-CNTs with concentrated ones,which contain sufficient active sites to enhance sulfur content.A flexible binder-free CNT&S electrodes is fabricated via a low-power sonication assisted method.The well-dispersed CO₂-CNT&S electrodes results in low polarization,fast charge transport and superior electrochemical performance.A flexible MnO₂ nanoparticle anchored oxidized CNT?MnO ₂/a CNT?electrode is prepared for ultrafast lithium storage.The fabricati on process is based on the redox reaction of KMnO₄ and CNTs.MnO₂ nanoparticles is ultrathin??10 nm?,which can combine rapid surface redox processes and solid-state lithium diffusion to exhibit high specific capacities under high current densities.A unique Mn-O-C linkage enable MnO₂ nanoparticles tightly attached to CNTs,preventing MnO₂ aggregation or detachment from CNTs during rapid charge/discharge processes.MnO₂/a CNT electrode exhibited best high-current performance to date among the reported MnO ₂/C electrodes,which can be attributed to two aspects:The capacitive lithium storage behavior contributed to the high capacity and the strong Mn-O-C bonding interaction lead to cycling stability.This work paves the way for the practical application of hyb rid supercapacitor-battery energy storage devices.