Microstructures and electrochemical performances of nano-sized SiOx (1.18 <= x <= 1.83) as an anode material for a lithium(Li)-ion battery

Abstract

Nano-sized SiOx is synthesized by an evaporation and condensation process using induction melting with the injection of various mixed gases. In particular, the effects of O-2 gas on their microstructures and electrochemical properties are investigated. The x-values of the synthesized SiOx can be controlled from 1.18 to 1.83 by varying the O-2/Ar ratios in the injected gas. A micro-structural analysis reveals that mixture of nanoparticles and nanowires is formed and that the relative amount of nanowire decreases with an increase of the oxygen contents in the injected gas. When x is low, crystalline Si is formed, but this phase disappears when x exceeds 1.28. From the electrochemical analysis of the various SiOx powders, the Initial Columbic Efficiency (ICE) decreases with the increase in the x-values - largely due to the oxidation of Li-ions such as Li2O and Li4SiO4. Cycle stability, however, is improved with the increase of the x-values, indicating that strain and stress during insertion and extraction of Li-ions are properly released due to the oxide buffer around the Si as well as the nano-sized structure. When x = 1.18, a specific capacity of 660 mAh g(-1) with a columbic efficiency of 99.8% at the 50th cycle is obtained. (C) 2013 Elsevier B.V. All rights reserved.