Nanosized core/shell silicon@carbon anode material for lithium ion batteries with polyvinylidene fluoride as carbon source

A nanosized anode material for lithium ion batteries with silicon as core and amorphous carbon as shell was synthesized by dispersing nanosized silicon in polyvinylidene fluoride solution and a subsequent pyrolysis process. The amorphous nature of the carbon in the composite was detected by X-ray diffraction and Raman spectroscopy. The core/shell structure was further identified by transmission electron microscopy. High reversible capacity and acceptable rate capability were exhibited compared with pristine silicon. The reversible capacity of the silicon@carbon nanocomposite at 50 mA g(-1) after 30 cycles is 1290 mAh g(-1) with a capacity retention of 97%. A stable reversible capacity of 450 mAh g(-1) was delivered even at 1000 mA g(-1). These improvements are attributed to the amorphous carbon shell, which suppresses the agglomeration of nanosized silicon, reduces the cell impedance, buffers the volume changes and stabilizes the electrode structure during charge/discharge cycles.