The Research Of N-doping,Specific Surface Area Regulation And Electrochemical Properties Of Hard Carbon Nanotubes Derived From Conjugated Microporous Polymers

Conjugated microporous polymer?CMP?is a kind of three-dimensional framework polymer with conjugated structure.CMP has a great potential application prospect because of its good chemical stability and high specific surface area.Porous hard carbon material formed by high temperature pyrolysis CMP has a low crystallinity,the large spacing between carbon layers is beneficial to the diffusion of lithium ions.CMP is a very promising carbon material precursor,which can be used in lithium ion battery electrode material.The contents of this paper are as follows:?1?Conjugated microporous polymers were synthesized via sonogashira-hagihara cross-coupling reaction with the catalytic condition of Pd?0?/Cu?I?.Tubular CMP and nitrogen-containing tubular CMP?NCMP?were synthesized by using 1,3,5-triethynylbenzene and different monomers?1,5-dibromonaphthalene and 2-amino-3,5-dibromopyridine?,respectively.Then,HCNT and NHCNT were prepared by high-temperature pyrolysis CMP and NCMP,respectively.The structure and electrochemical performance of two different tubular carbon materials were studied.Through SEM and BET test,HCNT and NHCNT showed similar specific surface area and pore size distribution.Electrochemical performance tests showed that NHCNT sample exhibited a lower charge transfer resistance,relatively higher capacity and more stable cycle performance,which proved that the NHCNT material has good electrochemical performance.?2?Activated carbon materials were prepared by activating the NCMP material at a high temperature by using Zn Cl₂ and KOH as activator,respectively.The activator and NCMP materials were mixed with a mass ratio of 3:1,then pyrolysis at a high temperature.Intermediate products were washed by HNO₃ solution to obtain the final products Zn-NHCNT and K-NHCNT.Electrochemical tests showed that K-NHCNT has a high reversible capacity and stable cycle performance,showing a more excellent electrochemical performance,which proved that KOH is a better activator material.The TEM characterization shows that the NHCNT material maintains its morphology and structure during the high temperature activation of KOH,reflecting the structural stability of NHCNT.The BET result showed that the specific surface area of K-NHCNT is much larger than that of NHCNT.It can be seen that the KOH-activated KOH material has a more favorable morphology structure and thus ensures excellent electrochemical performance.?3?3%Ni-MnO,5%Ni-MnO and 10%Ni-MnO composites were prepared through a high temperature pyrolysis by controlling the ratio of Ni/Mn of the precursors.The results of XRD and SEM indicated that 5%Ni-MnO material has higher crystallinity.The addition of Ni reduces the particle size of the MnO sample,thereby shortening the diffusion path of Li⁺and electrons.Further through electrochemical tests,5%was determined as the optimal doping amount.Ni-MnO/NHCNT composites were prepared by doping NHCNT with 5%Ni-MnO.The electrochemical properties of Ni-MnO/NHCNT were analyzed by electrochemical tests,which proved that the doping of the metal oxide has improved the electrochemical performance of NHCNT.