The Preparation And Electrochemical Performance Of Si/Graphene Nanometer Lithium Ion Battery Anode Material

Silicon-based anode materials for lithium ion batteries have attracted much attention due to the highest theoretical specific capacity(4200mAh/g vs.Li14Si5),relatively low working potential(<0.5 V vs.Li/Li+)and abundant resources.However,silicon experiences a dramatic volume change(>300%)during lithiation/delithiation processes,leading to structural failure of electrode,electric disconnection between active materials and current collector and the unstable formation of solid-electrolyte interface film.Besides,silicon has low electric conductivity.Both drawback mentioned above result in short cycling life and poor rate capability of silicon-based materials,sequentially limit the practical application of them.To solve the issues,we synthesis Si/RGO composites by combining reduced graphene oxide(RGO)and different forms of silicon.RGO can provide a solid electrically conductive system and buffer system,prolong the cycling life and improve the rate capability of Si/C composites.X-ray diffraction,scanning electron microscopy,transmission electron microscopy,Raman spectroscopy,and nitrogen adsorption are used to characterize the phase constitution and structure of the samples.The main contents are listed as below:A sandwich-like Si/RGO@PANI nanocomposite as anode for lithium ion batteries was successfully in-situ prepared under condition of ultrasonication by using RGO and silicon nano particles as precursors,aniline as monomers,phytic acid as a dopant and ammonium persulfate as an oxidizer(initiator).The sandwich structure composed of graphene sheets,conductive polyaniline,and nano silicon particles create an efficient conductive network which can endure the great volume change of silicon and retain structural stability during Li-ion insertion/extraction.The electrodes consisting of this sandwich-like Si/RGO@PANI nanocomposite reveal excellent cyclability and rate capability,and can be considered as an ideal anode material for lithium ion battery.The progress made in this work provides a facile route for preparing Si-based anode materials with high electrochemical performance for advanced lithium ion batteries.OMSi@C/RGO Mesoporous composites for lithium ion batteries is successfully synthesized by evaporating the solvent/dispersant by using SBA-15(SiO2,mesoporous structure)and RGO as material sources,poly(vinylidene fluoride)(PVDF)as carbon sources and N-Methyl pyrrolidone(NMP)as solvent and dispersant.The huge volume change of silicon is accommodated by the highly ordered mesoporous structure of OMSi and pyrolytic carbon cladding,and the electric system built by pyrolytic carbon and RGO provides good electic conductivity of active materials.Used as anode for lithium ion batteries,it showed good cycling stability and rate capability,and the successful synthese process provided a choice for the commercialization of Si-based anode materials.OMSi@SiOx@C/RGO Mesoporous composites for lithium ion batteries is successfully synthesized by evaporating the solvent/dispersant using Triethoxysilane(TES)as the precursor of SiOx,SBA-15(SiO2,mesoporous structure)and RGO as material sources,poly(vinylidene fluoride)(PVDF)as carbon sources and N-Methyl pyrrolidone(NMP)as solvent and dispersant.The huge volume change of silicon is accommodated by the highly ordered mesoporous structure of OMSi pyrolytic carbon cladding and SiOx cladding,and the electric system built by pyrolytic carbon and RGO provides good electic conductivity of active materials.Used as anode for lithium ion batteries,it showed good electrochemical performance,and the slow activation phenomenon is discovered.