Synthesis And Electrochemical Performance Of Graphene-based Composites

This paper constructed different graphene composites with graphene as matrix,explored the electrochemical performances of different crystal forms of silica and/or graphene based composites.The detailed research content and conclusions are as follows:?1?SiO₂@carbon/graphene?SiO₂@C/G?hybrid with superior electrochemical performance has been developed by self-assembly of colloidal silica,sucrose and graphene oxide in ultrasonic assisted hydrothermal process and subsequent heat treatment.The mass ratio of silica to sucrose is found crucial to the electrochemical performances of SiO₂@C/G hybrids.With increase ratio of silica to sucrose,the rising trendency of electrochemical performances are not increase always.SiO₂@C/G hybrid with 0.15 of the mass ratio of silica to sucrose shows the best reversible lithium storage performance,delivering 906 m Ah g-1 of initial discharge capacity and 542 m Ah g-1 even after 216 cycles at the current density of 100 m A g^-1.The synergetic effect of the good conductivity of SiO₂@C/G hybrids,the small particle size and the widespread of SiO₂ nanoparticles bring about the excellent cycling ability and high reversible capacity.?2?Crystalline SiO₂-graphene composite?named CS-G?has been successfully synthesized by employing diatomite as the silicon source and graphene as carbon matrix.Graphene presents conductive network,and diatomite nanoparticles are wrapped in the network.XRD results show that SiO₂ exists in the forms of quartz and cristobalite.At the current density of 100 m A g^-1,the specific capacity shows a trend of steady rise,and the lithium storage capacity stabilizes around 780 m Ah g^-1 after 110 cycles.Meanwhile,CS-G electrode shows a stable reversible specificcapacity and good rate performance.The unique network structure and good synergistic effect between SiO₂ and graphene has great contribution to the performance of the lithium storage,which can guarantee sufficient contact area with the electrolyte,effectively shorten the lithium ion diffusion path.?3?Disordered hard carbon/graphene?C@G?hybrid has been successfully designed and prepared for the first time through a facile route.SEM and TEM analyses show the uniform distribution of carbon microspheres and carbon layers on the surface of graphene.As an anode material of sodium-ion batteries,such a construction could ensure an effective contact area with the electrolyte and offer massive active sites.It displays a stable sodium storage capacity of ³00 m Ah g^-1 after 100 cycles at a current density of 50 m A g^-1 and exhibits an excellent rate performance.The unique structure and advantageous synergistic effect between disordered hard carbon and graphene make a significant contribution to the good Na+ insertion/extraction property.