Abstract
Si/C/TiO2 composite nanofibers were fabricated using an electrospinning method, followed by a carbonization in helium gas at 800 oC for 4 hrs. Sulfur was employed as a template to facilitate the formation of void structure, thus providing space to the large volume expansion of silicon during lithiation process and mitigate pulverization of silicon particles. Carbonized nanofibers containing TiO2 and Si nanoparticles were also prepared for comparison. The structure, morphology, phase and composition of these nanofibers were characterized using Raman spectroscopy, scanning electron microscopy, energy dispersive spectroscopy, powder X-ray diffraction, and thermogravimetric analyzer. Carbonized nanofibers containing TiO2 showed a low but stable specific capacity of 105 mAh g-1 after 100 cycles at a current density of 0.09 A g-1. Carbonized nanofibers containing silicon nanoparticles demonstrated an initially high but fast degrading capacity, which is only 73 mAh g-1 after 100 cycles. In contrast, the capacity of silicon in SiNP/C/TiO2 nanofibers prepared using a sulfur-templating method is ~ 3459 mAh g-1 at the fourth cycle, 52 % of which can be maintained after 80 cycles. It is believed that sulfur is functioning as a template to help the formation of void between silicon nanoparticles and TiO2, thus allowing for the ~300% volume change during Si lithiation and delithiation process.
