Preparation And Electrochemical Properties Of Naphthalene Pitch Mesocarbon Microbeads

Mesocarbon microbeads(MCMB)is a new type of functional carbon material,which is characterized by unique spherical structure on micrometer scale,stable chemical properties and easy to graphitize.Therefore,MCMB has been well applied in carbon materials with high density and strength,activated carbon with high specific surface area,catalyst carrier,and electrocle material for lithium ion battery and so on.Especially in recent years,the rapid development of power batteries is promoting the research of mesocarbon microspheres.In this dissertation,the naphthalene pitches were prepared by self-rising pressure method of naphthalene as raw material with Al Cl3 as catalyst,and then its ash were removed by acid-washing,the sphere-containing pitch was obtained by mesophase thermal conversion.MCMB was sparated out from the corresponding mesophase thermal conversion products by solvent extraction.The carbon spheres were finally carbonized and activated by KOH.Respectively,its battery performance and capacitance performance were evaluated.At the same time,The microstructures of naphthalene pitches,its corresponding mesophase thermal conversion products and mesocarbon microbeads were studied by various characterization methods(including Industrial analysis,FTIR?GC/MS?GPC and TG/DTG?SEM?PLM?Raman?XRD),these results showed:(1)220°C was a suitable temperature for synthesizing naphthalene pitches.Its aromaticity was increased with the increase of the proportion of catalyst.The naphthalene pitches had higher solubility in toluene and quinoline.And the molecular weight distribution of naphthalene pitches were mainly in the range of 147?3940.Its mass average molecular weights were about 317 Da.The residual carbon yields at 750°C were about 30% and pickling can reduce the ash to less than 2%.The optical structures of naphthalene pitches after carbonization were mainly mosaic structures.(2)The sphere-containing mesophase thermal conversion products could be obtained by treating naphthene pitch at 390°C for 4h.And the addition of additives(Ca CO3 and Si O2)could promote the polycondensation of aromatic hydrocarbons,shorten the ball formation time,and increase the amount of spheres.The diameter of the sphere was mainly distributed at 3?10?m.The MCMB obtained by extraction without the additive had the best sphericity,its surface was smooth and the sphere had a uniform particle size.The addition of 10%Ca CO3 could obtain the highest extraction yield of 27.9%.(3)The surface of MCMB appeared cracks and no obvious hierarchical porous structure existed after KOH activation.At a current density of 1A/g,the corresponding specific capacity was only 106F/g.However,the addition of 5%Si O2 could significantly increase the specific capacity to 200F/g,which was attributed to the Si element uniformly distributed on the surface.The optimum ratio of carbon to alkali ratio was 1:3 at activation.(4)After carbonization at 1000°C,The MCMB surface was still very smooth,the particle size was slightly reduced and its shape looked like an ellipsoid.As anode materials in Li Bs,The first charge-discharge specific capacity was 362 m Ah/g and 859 m Ah/g,and the first coulombic efficiency was 42% at a current density of 15 m A/g.What's more,the coulombic efficiency was nearly 99% and keep a charge-discharge capacity of 150 m Ah/g after 50 cycles,proved that MCMB had an excellent charge-discharge reversibility.At a current density of 500 m A/g,the charge-discharge specific capacity was only 28 m Ah/g,its rate capability needed to be improved.