Self-assembly of silicon/carbon hybrids and natural graphite as anode materials for lithium-ion batteries

Silicon/carbon/natural graphite (Si-C-NG) composites have been successfully prepared by the granulation of natural graphite (NG) and silicon/poly(acrylonitrile-co-divinylbenzene) [Si/poly(AN-co-DVB)] hybrid microspheres via spray drying and subsequent pyrolysis. The poly(AN-co-DVB) microspheres containing silicon nano-flakes are synthesized by microsuspension polymerization using benzoyl peroxide (BPO) as initiator and polyvinyl alcohol (PVA) as dispersant in aqueous phase. The morphology and microstructure of Si-C-NG composites are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Raman spectroscopy. It is found that the Si nanoparticles are uniformly enwrapped by pyrolytic carbon derived from poly(AN-co-DVB) to form Si-C core/shell structures, which are subsequently decorated on the surface of NG, resulting in a spherical Si-C-NG structure. When used as anode materials for lithium-ion batteries, the Si-C-NG composites exhibit a high specific capacity of 471.5 mA h g^-1, a high initial coulombic efficiency of 78.4%, and a good cycling stability with capacity retention of 87.9% after 100 cycles at a current density of 100 mA g^-1.