Investigation of the discharging behaviors of different doped silicon nanowires in alkaline Si-air batteries

Abstract

Compared with metal-air batteries, Si-air batteries have advantages on gravimetric/volumetric capacity and safety. This novel battery using flat Si wafer as anode has been preliminarily researched in recent ten years. In this work, Si nanowires (NWs) have been fabricated on p < 100 > and n < 100 > Si wafers and their discharging behaviors under various operating conditions have been systematically analyzed compared with flat Si wafer anodes. Si NWs anodes universally exhibit longer discharge times than flat Si wafer anodes because of their larger specific surface areas and superior resistance to the passivation caused by SiO2 deposition. It is also demonstrated that a KOH electrolyte concentration of 1.9 M is the lowest threshold for the p < 100 > Si anode at a current density of 0.03 mA/cm2, and the p < 100 > Si anode can discharge for more than 400 h. Furthermore, n < 100 > Si NWs anodes performed best with a discharge time of more than 500 h at higher current density of 0.05 mA/cm2 with an electrolyte concentration of 6 M. This work can aid in understanding the electrochemical properties of silicon anodes with different configurations and doping types in Si-air batteries and provide direction for the operation of Si-air batteries at appropriate conditions.