Si protected by metal-organic segments as anodes in Si-air batteries

Abstract

Silicon-air batteries have attracted attention because of their high theoretical energy densities. However, the practical application of Si-air batteries is limited by the corrosion of silicon anodes. In this work, metal-organic segments (MOSs) coating was used for the first time to protect anodes in silicon-air batteries and the effects of MOS coating on the electrochemical performance of silicon-air batteries have been systematically investigated. The surface morphology of Si@MOS composites can be well-controlled by changing solution concentrations. The potentiodynamic polarization curves and the theoretical calculation prove that the corrosion rate of the silicon anodes can be effectively inhibited by the MOS coating. The critical KOH solution concentration can be reduced from 1.9 M for bare silicon to 1.3 M for Si@MOS composite anode. The Si@MOS composite anode also exhibits a longer discharge time of about 430 h at 0.9 V with a specific capacity 114 mAh g−1, which is much higher than that of bare Si (250 h with a specific capacity of 71 mAh g−1). This work not only demonstrates a surface modification method to protect the Si anode, but also provides a novel idea to improve the performance of Si-air batteries.