Porous silicon-graphene-carbon composite as high performance anode material for lithium ion batteries

摘要

The porous silicon-graphene-carbon (SGC) composite is prepared by freeze-drying and chemical vapor deposition (CVD) process with commercially available nano-silicon, phenolic resin and graphene oxide as raw materials. The self-assembly process makes the nano-silicon into a porous structure and uniform recombination with the graphene oxide, and finally a nano-carbon layer is coated on the surface of the SGC composite by a CVD process. The composition, morphology and pore properties of SGC composite are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and pore size analysis. The nano-carbon layer on the surface of the SGC is examined by transmission electron microscopy (TEM) and Raman spectrometer. The contents of C, Si and O in precursor and SGC are analyzed by X-Ray Fluorescence (XRF), and the electrochemical performances of composite material are analyzed by half-cell and full-cell experiments. The results show that the SGC composite is porous structure with the average pore size of 20-30 nm, and the surface of the porous silicon-graphene is coated by a thickness of 5 nm carbon layers. The reversible capacity and initial coulombic efficiency (ICE) of the SGC are 2180 mAh g(-1) and 79.3%. The capacity retention is higher than 70.1% after 100 charge/discharge cycles by the half-cell experiment; and the capacity of the composite anode is still as high as 550 m Ah g(-1) after 820 charge/discharge cycles by full-cell experiment. Therefore, the structure design strategy of the composite is beneficial to buffer the volume effect of nano-silicon, prevent iterative growth of the SEI film and boost the electrochemical performances.