High-rate lithium-ion battery anodes based on silicon-coated vertically aligned carbon nanofibers

A multiscale hierarchical lithium-ion battery (LIB) anode composed of Si shells coaxially coated on vertically aligned carbon nanofibers has been explored. A high Li storage capacity of ~3,000-3,500 mAh (g^Si)^-1 and > 99% Coulombic efficiency have been obtained. Remarkable stability over 500 charge-discharge cycles have been demonstrated. Particularly, this electrode present a high-rate capability that the capacity remains within ~7% as the C-rate was increased from ~C/10 to ~8C. Electron microscopy, Raman spectroscopy and electrochemical impedance spectroscopy revealed that the electrode structure remains stable during long cycling. This high-rate property is likely associated with the unique nanocolumnar microstructure of Si in the shell. It reveals an exciting potential to develop high-performance LIBs.