Modification Of The Anode Materials In Li-ion Batteries

Carbon spheres are widely applied in catalyst supports,lubricants,additives for reinforced plastics and rubbers,electrode materials in fuel cells and supercapacitors,]as well as anodes in Li-ion batteries.This is mainly because of their high packing density,strong acid and alkali resistance,good thermal stability,proper electronic properties,low surface-to-volume ratio,and high structural stability.Methods employed to synthesize carbon spheres include chemical vapor deposition,[13]carbonization of polymer spheres,soft or hard templating method,high pressure carbonization,and hydrothermal synthesis.However,these methods suffer from the use of harsh reaction conditions,toxic reactants,tedious process,and high cost,limiting their industrial application.Therefore,a facile method for the synthesis of carbon spheres is highly desired.Li-ion batteries have attracted widespread attention and their anode materials are mainly made of commercially available carbons.To further improve their electrochemical performance,various nanostructured carbon materials have been developed,including carbon films,carbon nanotubes,grapheme,porous carbon,carbon spheres,carbon nanosheets,and Tin-encapsulated spherical hollow carbon Significant improvement in the capacity and cycling performance at high charge/discharge rates has been obtained for some of these carbon materials,mainly due to the structural and composition variation,e.g.,by introduction of nanoporous structures,which are able to shorten the solid-state diffusion length of the lithium ion and enhance the lithium storage capability.However,the large scale production of these carbon materials is still a great challenge due to their complex synthesis processes and high cost.Nowadays,the commercial anode materials are still the graphite microspheres(GMs)and mesophase carbon microbeads(MCMBs)with a high graphitization degree.However,these GMs and MCMBs have relatively low rate performance and capacity(only 372 mAh·g-1),which are not available for future Li-batteries with high energy density and large power output.In addition,hard carbon(HC)materials generated from sucrose have been investigated as anode materials for Li-ion batteries due to their high lithium storage capacity(above 600 mAhg-1),although they have a relatively low conductivity compared with graphitized carbon(GC).Therefore,by integrating GC with high conductivity and HC with a high capacity,as well as porous structure,it is possible to create new carbon anodes.In this work,we report the simple preparation of graphitized porous carbon microspheres(GPCMs)via spray drying process(SDP),followed by graphitization,in which,carbon black(CB)nanoparticles were employed as GC source and sucrose as both HC source and binder to connect GC.The prepared GPCMs are composed of core-shell nanoparticles with the GC core derived from graphitized CB(GCB)and HC shell generated from sucrose.The interstitial space among these core-shell nanoparticles and the hollow core of GCB nanoparticles created after graphitization provides the nanoporous structure.These characteristics endow GPCMs with much improved electrochemical properties compared with GMs.Particularly,as promising optional carbon anode materials for future Li-ion batteries,the manufacture of GPCMs comparable to the cost and scalability of commercial GMs is possible by this approach.The contents are generally included as follows:1?We report the large scale synthesis of porous carbon microspheres(PCMs)by spray drying technique using commercial carbon black(CB)nanoparticles as the primary carbon resource and sucrose HC as binder under different temperatures(900 and 2800 ?).2?We report the large scale synthesis of porous carbon/silicon(C/Si)microspheres by spray drying technique using CB nanoparticles as primary carbon resource,Si nanoparticles as the additive,and sucrose as the binder,and followed with heat treatment at 900 ?.Meanwhile,different influences from the different silicon contents were alao tested.