Microwave-assisted Preparation Of Hollow Porous Carbon Spheres And Their Applications In The Field Of Energy Storage

Hollow porous carbon spheres are a kind of carbon materials with low density,large pore volume and high surface area.Because of those characteristics,it has a widespread applications in the field of gas storage,adsorption,drug delivery,catalysis and nanoreactors.Most of the conventional method for preparation hollow porous carbon spheres require a strict condition or a complex procedure.This report adopted microwave-assisted method through one-step to synthesis polymer-silica-surfactant?PSS?composites,which use RF as carbon precursor,TEOS as template,in the condition of ammonia as catalyst,CTAB as surfactant.Then the as-prepared PSS composite through carbonization and template-removed to obtain hollow carbon spheres.The method is simple,time-saving and under mild reaction condition?low temperature and atmospheric pressure?.The crystalline of the obtained products is determined by XRD.It is identified an amorphous carbon with low graphitization.Morphologies of hollow carbon materials and size of carbon spheres could be controlled by simply tuning the ratio of ethanol-water.It can be seen that with increasing ratios of water-ethanol,the diameters of carbon materials gradually decreases.Characterizations from SEM and TEM reveal that the as-prepared carbon spheres possess good dispersion,homogeneous size,high specific surface areas,large cavity volume and abundant micro/mesoporous shell.The results calculated by N₂ adsorption-desorption isotherm and the pore size distribution also demonstrate that the materials have high specific surface areas and large pore volume.When the hollow carbon spheres assembled as anode of lithium-ion batteries,they show good electrochemical performance.All the samples exhibit a higher reversible capacity than commercial graphite anode(theoretical capacity 372 mA h g^-1).The HPC-3exhibits the highest reversible capacity among the samples.The first discharge capacities of HPC-3 anode are 1750 mA h g^-1.After 100 cycles,the discharge-charge capacities still remained 97%compared to the second cycle with coulombic efficiency of 97.5%.Electrochemical impedance spectroscopy?EIS?results show that HPC-3 has the lowest Rct among the samples,which possess a fast charge-transfer speed.Hollow porous carbon spheres as cathode materials of lithium-sulfur batteries exhibit its structure advantages.The preparation process has a big influence for the performance of lithium-sulfur batteries.This paper discussed different morphologies of carbon materials,different types and proportions of binder how to effect the performance of the battery.It is found that battery using poly?vinylidene fluoride??PVDF?and polyethylene oxide?PEO?composite binder shows the best performance,also found that the proportion of the binder have little influence for the performance.