The effect of carbon coatings on the electrochemical performance of composite electrodes

摘要

The present work focuses on the large-scale production of Fe_2O_3/C, TiO_2/C and Fe_2O_3/TiO_2/C composite fibers by centrifugal spinning (CF). Fe_2O_3/PVP, TiO_2/PVP, and Fe_2O_3/TiO_2/PVP precursor solutions were prepared and centrifugally spun at 7200 RPM to obtain precursor micro fibrous mats. The precursor fibers were then stabilized in air at 200 °C for 3 hours followed by calcination in Argon atmosphere at 500 °C for 4 hours to obtain composite carbon fibers. In addition, TiO_2-slurry based electrode was prepared from mixing 70% of TiO_2 active material with 20 % carbon black and PAN binder. The TiO_2 electrode delivered a good electrochemical performance and cyclability. The Fe_2O_3/C, TiO_2/C and Fe_2O_3 /TiO_2/C composite-fiber anodes demonstrated a stable cycling performance with a discharge capacity of 200, 144, and 235 mAh g~(-1) respectively after 100 cycles at 100 mAh g~(-1) with the exception of the first cycle which was tested at 50 mAh g~(-1). The high surface area of the centrifugally spun composite fibers resulted in high irreversible capacity at the first cycle compared the slurry-based electrode. Although these composite electrodes exhibited stable capacity and a decent cyclability, further work is required to improve the Coulombic efficiency of composite-fiber electrodes and enhance their overall electrochemical performance and rate capability.