Synthesis And Electrochemical Investigation Of Silica-based And Silicon-based Spherical Composite Anode Materials

As anode materials for lithium ion batterires,silicon oxide and silicon have low lithiation potential and higher theoretical capacity,which make them potential anode candidates for the new-generation lithium ion batteries.However,the low electric conductivity and large volume variation during lithiation/delithiation of the two candidates may result in low rate capability and poor cyclic performance.To eliminate these shortbackes,SiO2-based and Si-based spherical composite anode materials have been synthesized through suspension nebulization and spray pyrolysis methods followed by carbonization.Their microstructure and electrochemical performance have been characterized and evaluated,which indicate that:1.SiO2/C and SiO2/C/Graphene spherical composites have been successfully synthesized through nebulization and spray pyrolysis methods.The sphere sizes are in a range of 200-500 nm.Three-dimentional conductive networks have been established by amorphous carbon and graphene,in which SiO2 nanoparticles have been embedded in the SiO2/C/Graphene spheres.In addition,mesopores have been formed in the SiO2/C/Graphene spheres.2.SiO2/C/Graphene spheres exhibit much improved cyclic capacity and stability than SiO2/C.Its reversible capacity can reach 741 mAh g-1,with capacity retention of 97%after 100 discharge/charge cycles.The addition of graphene can decrease the charge transfer resistance and enhance structural stability of the spheres.3.Si/C/Graphene spheres synthesized through magnesiothermal reduction of SiO2/C/Graphene display low cyclic capacity.SiC has been formed in Si/C/Graphene spheres.4.Si/C,Si/C/Graphene and Si/C/Graphene/CNT spherical composites have been successfully synthesized using Si nanoparticles as starling materials through nebulization and spray pyrolysis methods.The sphere sizes are in a range of 500 nm-2 ?m.5.Si/C/Graphene/CNT exhibits much improved cyclic stability compared with other Si-based spherical composites.The charge/discharge capacities of Si/C/Graphene/CNT are 784.2/831.2 mAh g-1 after 15 cycles.The reversible capacity retention is 94%.The charge transfer resistance of Si/C/Graphene/CNT spheres is 2 ?,which is lower than those of Si/C and Si/C/Graphene.