One line of development to establish resource-efficient metal–air batteries is focusing on silicon materials as anode electrodes. While operation of primary Si–air batteries with ionic liquid electrolytes is one possible approach [1], employing conventional alkaline electrolyte is also considered by the recent investigations [2]. At the current state of development, the alkaline Si–air batteries suffer from high corrosion rates that reduce the theoretical specific capacity of 3820 mAh/g to 120 mAh/g [3]. Thereby, corrosion as being the major challenge has to be overcome in order to establish practical application of primary alkaline Si–air batteries.

The objective of the present work is to investigate the corrosion behavior of highly As-doped <100> oriented silicon wafer anodes in alkaline solutions for a scope of conditions that may arise in battery operation. Firstly, the influence of the immersion times on the open-circuit corrosion rates are discussed in combination with the surface morphology development in 72 h. Secondly, the impact of KOH electrolyte concentration on the open-circuit corrosion rates is investigated and three ranges of KOH concentrations are identified with different limiting mechanisms. Moreover, basing on the electrochemical corrosion rates obtained from potentiodynamic polarization method, the comparison between the chemical and electrochemical corrosion mechanisms are pointed out. Further investigations are carried out on the corrosion behavior of Si wafers under anodic voltages as present during the discharge of batteries. The dependency of the discharge characteristics as the discharge voltage, corrosion rates, and mass conversion efficiencies on the KOH concentrations and current densities are analyzed and accordingly, optimum conditions for the battery application are discussed.

References:

[1] Cohn, G., Ein-Eli, Y., Journal of Power Sources, 195, 4963–4970 (2010).

[2] Zhong, X., Zhang, H., Liu, Y., Bai, J., Liao, L., Huang, Y., Duan, X., ChemSusChem 5, 177–180 (2012).

[3] Durmus, Y.E., Montiel Guerrero, S.S., Aslanbas, Ö., Tempel, H., Hausen, F., de Haart, L.G.J., Ein-Eli, Y., Eichel, R.-A., Kungl, H., Electrochimica Acta 265, 292–302 (2018).