Li Storage Behavior of C-Coated Si/SiOx Nanospheres As a High Capacity Anode Material for Lithium-Ion Battery

Wednesday, 8 October 2014
Expo Center, 1st Floor, Center and Right Foyers (Moon Palace Resort)
E. Park (Department of Energy Engineering, Hanyang University), M. Park, J. Lee, Y. J. Kim (Advanced Batteries Research Center, Korea Electronics Technology Institute, Korea.), and H. Kim (Department of Energy Engineering, Hanyang University)
Si has gained much attention as anode materials for lithium-ion battery due to its high theoretical capacity (3,580 mAhg-1) and low standard oxidation potential (0.4 V vs. Li/Li+). Despite these features, Si anode materials still have limits to commercial uses by poor cycle performance associated with their mechanical pulverization of Si due to severe volume change during alloying/dealloying with Li. To overcome this problem, various approaches have been suggested. In particular, the composites, which are composed of active Si and inactive buffer material, showed promising approaches for reducing the mechanical strain during cycles. On the other hand, nanostructuring of active materials would be helpful for further improvement of cycle performance. After heat treatment of Si/SiOx precursor at 1200 C under inert atmosphere, we obtained Si nanocrystals embedded SiOx nanospheres with a size of 200 nm, in which about 10 nm sized Si nanocrystals are embedded in amorphous SiOx matrix. In order to improve electrical conductivity of Si/SiOx nanocomposites, carbon layer was coated on the surface of Si/SiOx nanocomposites.

 The Si/SiOx nanospheres and C-coated Si/SiOx nanospheres were characterized by a field emission scanning electron microscope (FESEM), a high-resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) patterns, solid state 29Si magnetic angle spinning nuclear magnetic resonance (MAS NMR) and X-ray photoelectron spectroscopy (XPS) analyses.

 The C-coated Si/SiOx composites showed a reversible capacity of 950 mAh/g-1 at current density of 200 mAg-1 with stable cycle performance over 100 cycles and high rate capabilities. In this presentation, the electrochemical properties of the C-coated Si/SiOx nanocomposites will be discussed in more detail.