Preparation And Properties Of High Performance Si-based Composites As Anode Materials For Lithium-ion Batteries

Sillion based anode has captured much attention due to its high theoretical capacity(4200 mAh g-1)and rich reserve.However,huge volumetric change(>300%)occurs during the lithiation/delithiation process,leading to the serious pulverization and cracking of the electrode,thus resulting in a poor cycling stability.Preparing Si/carbon composites by dispersing some components with excellent electrical conductivity such as carbon materials or graphene with good mechanical properties.In this study,we synthesized three kinds of novel and adaptable Si-based composites in a safer and more economical method.(1)Preparation and study of silicon/porous carbon nanofibers.We developed a silicon/porous carbon nanofibers wrapped by reduced graphene oxide(Si/PCNFs@rGO)structure via a facial preparation process consisting of a simple electrospinning method followed by a carbonization process and a sequent electrodeposition.The rGO protective layer acting as a dual-functional enhancer could not only accommodate the volume expansion of Si but also enhance the electrical conductivity,leading to an improved electrochemical performance.The as-obtained Si/P-CNFs@rGO electrode exhibits an excellent performance,with a high reversible capacity of 1851.3 mAh g-1 at a current density of 0.2 A g-1 with almost no capacity fading up to 50th cycle,a high reversible capacity of 1217.8 mAh g-1 with an excellent coulombic efficiency(CE)of 99.0%at 0.53 A g-1 after 300 cycles.(2)Preparation and study of protective layer coated silicon/carbon composites.A novel Si@carbon@polyaniline-based carbon(Si@C@PC)and a novel Si@carbon@polyaniline-based carbon-Ni@reduced graphene oxide(Si@C@PC-Ni@rGO)were designed.Furfuralcohol is firstly used as carbon precursor to be coated on the surface of Si nanoparticles via impregnation and then converted into carbon layer.And then Si@C structure was transferred into a solution of aniline,hydrochloric acid and ammonium peroxydisulfate with the condition of ice bath and agitation.Lastly,the product was pyrolyzed as carbon layer coated on Si@C during subsequent annealing treatment.At the same time of polymerization of aniline,a piece of nickel foam was immersed into the solution,severed as the support of Si@C@PANI adsorption.The as-obtained Si@C@PC and Si@C@PC-Ni@rGO electrodes exhibit excellent performances,which can be attributed to the dual protection of carbon layer and graphene sheets.