Electrochemical characterizations on Si and C-coated Si particle electrodes for lithium-ion batteries

The understanding of cycling and electrochemical characteristics of Si particle anodes for Li-ion batteries has previously been hindered by very fast capacity fading. Optimizing the electrode architecture to significantly improve its stability up to the 1000 mAh/g charge-discharge level has made it possible to investigate these properties to a greater depth than before. The capacity fading and lithiation mechanisms of Si and C-coated Si particles have been studied in this paper by cycling test and electrochemical impedance spectroscopy (EIS) analysis. The capacity vs cycle number plot exhibits two regions of different fading rates, including an initial region of slow fading followed by accelerated decay. The latter may be associated with large-scale failure of the electrode structure. EIS revealed a core-shell lithiation mechanism of Si. C-coating not only exerts remarkable favorable effects against capacity fading, but also serves as a conduit for Li ions to the reaction with Si particles. (c) 2005 The Electrochemical Society.