高容量锂离子电池核壳型硅/碳复合电极材料的制备与性能

Preparation and Properties of the High Capacity Si@PVP-GCB Core-shell Composite Anode Material Used in Li-ion Batteries

通过自组装方式采用一步法制备了锂离子电池硅碳复合电极材料.使用X射线衍射仪(XRD)、透射电子显微镜(TEM)和扫描电子显微镜(SEM)等对样品结构进行表征.结果表明,聚乙烯吡咯烷酮(PVP)包覆的纳米硅颗粒(Si@PVP)均匀嵌入到具有三维网络纳米孔结构的导电石墨化炭黑(GCB)骨架中,形成核壳复合型(Si@PVP-GCB)纳米颗粒,既提高了该复合电极材料的导电性能,又改善了材料的机械强度.在纳米级GCB颗粒内部存在的中空石墨环结构和包覆在纳米Si颗粒外面的PVP包覆层都有效缓冲了纳米Si颗粒在充放电过程中较大的体积变化,从而使纳米Si颗粒更加稳定.电化学测试结果表明,Si@PVP-GCB电极材料在电流密度为50 m A/g时,经过100次循环后其可逆容量仍达到545 m A·h/g时,远高于商品化的石墨微球(GMs)电极材料的容量(理论容量为372 m A·h/g).

Si/C composite electrode material, Si@PVP-GCB [ GCB=graphitized carbon black, PVP=poly （ N-vinyl-2-pyrrolidone] was prepared at room temperature by one step-assembly technique. The samples were characterized by X-ray diffraction（ XRD） , transmission electron microscopy（ TEM） , scanning electron micros-copy（SEM）, thermogravimetric analysis（TG） and Raman spectroscopy. It is found that a well-connected three dimensional（3D） nanoporous GCB network uniformly embedded with core-shell nanoparticles of the sili-con nanoparticles（SiNPs） core and the PVP shell was formed. The GCB 3D network not only contributes to the high electrical conductivity of Si@PVP-GCB, but also strengthens the mechanical properties of the elec-trode material. Apart from that, the special hollow structure of GCB nanoparticles and PVP coating shell can buffer the volume variation of SiNPs much more effectively. The electrochemical results show that the Si@PVP-GCB delivered a reversible capacity of 545 mA·h/g at the current density of 50 mA/g after 100 cy-cles, much higher than that of the commercial graphite microspheres（ GMs, 372 mA·h/g） .