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Comparative Study on the Electrochemical Performances of SiO Anode Materials with Carbon-Coating and Boron-Doping for Lithium-Ion Batteries

Thursday, 23 June 2016
Riverside Center (Hyatt Regency)
S. H. Baek, J. Woo, and J. H. Kim (DGIST)
Recently, Silicon monoxide (SiO) has been received much attention as an alternative choice instead of pure Si anode materials. When SiO anode undergoes lithiation processes, Li oxide (Li2O) and Li silicates (Li4SiO4) are mainly formed and that act as a more stable phase than the Li-Si alloys during long cycles. Moreover SiO is thermodynamically unstable at all temperatures, it can be easily transformed into nano-crystalline Si (nc-Si) and SiOx during heat treatment, triggering a disproportionation reaction. The nc-Si acts to increase the reversible capacity and the SiOx matrix plays an important role in accommodating the volume expansion of embedded nc-Si during alloying/de-alloying processes. However, the electrical conductivity of heat-treated SiO remains low because of this material’s intrinsic semiconductor nature and inactive phases. Carbon coating has been regarded as one of the most effective and typical ways to improve the electrochemical properties of SiOx. Dispersed carbon particles provide pathways for electron transfer and decrease the resistance of the electrode, thus resulting in improved conductivity and electrochemical properties of the SiO negative electrode. However, the local capacity fading caused by electrical loss between the active materials and the carbon coating is unavoidable during long cycle test. Moreover, carbon coating requires additional processing with carbon sources. In this study, we introduce a comparative study that consists of boron-doped SiO (HB-SiO) and carbon-coated SiO (HC-SiO) to verify the effective way for improving the electrochemical performances of SiO anode materials. From the electrochemical results, HB-SiO electrode exhibits about 1.6 times higher than that of HC-SiO electrode, having 611 mAh g-1 at 0.5 C rate after 500 cycles. Electrochemical impedance spectroscopy (EIS) measurement reveals that the internal resistance of the HB-SiO electrode is superior to that of HC-SiO electrode.