Synthesis Of Microporous And Meso-microporous Carbon Derived From Carbonized Porous Polymer For Lithium Batteries

With the development of technology and improvement of living standards,the demand for energy storage has increased rapidly with time.Lithium batteries have received widespread attention for its excellent comprehensive performance as compared to other rechargeable systems.In the development of lithium batteries,electrode material still as a key factor for restricting the performance and market promotion so that development of a new generation of lithium battery electrode materials is imminent.Due to the excellent stability,porosity,high surface area and electric conductivity,porous material especially porous carbon materials play an important role in electrode carrier.In the previous reports,porous carbon derived from metal organic frameworks(MOFs)due to their high surface area and varies heteroatom doping have attracted great attention,however,the low yield is limit their practice progress.In recent years,the porous polymer such as porous aromatic frameworks(PAFs),covalent-organic frameworks(COFs)and polymers of intrinsic microporosity(PIMs)due to the strong covalent linkages in frameworks,the high stability,surface area and concentrations of carbon species make them very promising for energy storage as precursors for preparation of carbon.The thesis devoted to prepare varies structures porous carbon derived from porous polymer and investigate their applications for lithium batteries and improvement the electrochemical performance.We investigate the main affect factors for the performance for lithium batteries,the thesis mainly including four sections as follows:In chapter ?,a series of composites with ultrasmall SnO2 and Sn nanoparticles uniformly embedded in the KOH-activated carbonized PAF-1 matrix,the excellent electrochemical performance due to the electrical conductivity and porosity for host material could allows the charge transfer,the unique structure can capably alleviate the expansion and contraction stress,accommodate the large volume changes all along the insertion/extraction processes and prevent the pulverization and aggregation of nanoparticles upon prolonged cycling.Consequently,a synergy between host and guest material which markedly improves the capacity of the material.This technique can likewise be extended to other pairs of microporous materials and nanoparticles for improvement electrochemical performance.Base on the research has shown the competitive advantages for microporous materials as electrodes carrier in chapter ?,the study expand to a higher energy density for lithium-sulfur(Li-S)battery system.In chapter ?,we developed a carbonized 2-D porous organic frameworks(JUC-Z2)as host material and compare the effects of sulfur contents and melt-diffusion strategy for electrochemical performance.The confinement of small sulfur molecules(S2-4)in the micropores(0.5 nm)plays an important role in retarding the dissolution of polysulfide and maintain the integrity of electrode.The appropriate sulfur content in the microporous of host material act as physical barriers which hinder the penetration of ether-base molecules in the electrolyte and essential to improve the cycling performance.The much-improved electrochemical performance suggests that carbonized 2-D porous polymer could be a promising host material for Li-S batteries.In order to further investigate the universality of carbonized porous polymer as host material for lithium batteries,the microporous carbon was derived from a 3-D porous polymer(COF-300)which was carbonization at different temperatures to adjust microporous distribution to investigate the electrochemical performance in chapter ?.The factors for improvement the electrochemical performance as follows: first,the confinement effect of micropores(0.5 nm);second,the larger pore volume of host material which calculate less than 0.5 nm,the more small sulfur molecules in the micropore that result in the stability of electrode.Last,nitrogen-dopping in composites could adsorb sulfur to improve the electrochemical activity of sulfur cathodes.Thus,the much improved electrochemical performance due to the confinement of small sulfur molecules suggest that carbonized nitrogen-containing porous polymer no matter 2-D or 3-D polymer could be a promising host material for Li-S batteries.In chapter ?,we design and synthesis a core-shell ordered mesopore-micropore carbon which derived from porous polymer(PIM-1)as microporous source.The material is a combination of the advantages of mesoporous and microporous material,offset the inadequacy of each other.The melt-diffusion strategy used to impregnate sulfur in the material and exhibits the improvement electrochemical performance.As compare with ordered mesoporous carbon and microporous carbon which derived from carbonization PIM-1,the core-shell structure carbon material exhibits some advantages as follows: first,the excellent cycling performance.The confinement of small sulfur molecules(S2-4)in the micropores plays an important role in retarding the dissolution of polysulfide.Second,the high sulfur content(71.3 wt%)in composite which improve the areal capacity efficiency.Thus,the design and synthesis a core-shell ordered mesopore-micropore carbon which derived from porous polymer(PIM-1)as microporous source is a new way for improve electrochemical performance for Li-S batteries.In conclusion,the thesis based on the electrode carrier for lithium batteries,by using of porous polymer as starting material were developed and the affect factors of electrochemical performance for lithium batteries were discussed.The thesis and the results provide a theoretical support for prepare porous carbon materials derived from porous polymer and their application in lithium batteries system.