Activation of rice hull char with steam to improve lithium storage performance of SiO2/C

Abstract

Rice hull-derived SiO2/C composites are promising anode materials for Li-ion battery, but it is a challenge to improve their lithium storage performance by a simple method. In this research, SiO2/C composites were prepared by heating rice hull char in steam flow for different time to study effects of steam activation on lithium storage performance of SiO2/C. As the activation time increased, the composites’ reversible capacity rose, because of the increase in silica content and micropore volume and the decrease in graphitization degree. Besides, when the activation time rose, the composites’ predominant electrochemical impedance (Rct &Zw) decreased whereas the initial coulombic efficiency firstly decreased and then increased. By activation of rice hull char with steam for 2 h, the reversible capacity of SiO2/C at 0.2 A/g increased by 170 %–691 mAh/g. This value exceeded the corresponding values for most reported SiO2/C composites. The research revealed that steam activation was an effective strategy for improving lithium storage performance of SiO2/C and value-added conversion of rice hull char.