Limitation of Discharge Capacity and Mechanisms of Air‐Electrode Deactivation in Silicon–Air Batteries

Abstract

The electrocatalytical process at the air cathode in novel silicon-air batteries using the room-temperature ionic liquid hydrophilic 1-ethyl-3-methylimidazolium oligofluorohydrogenate [EMI⋅2.3 HF⋅F] as electrolyte and highly doped silicon wafers as anodes is investigated by electrochemical means, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) spectroscopy. The results obtained by XPS and EPR provide a model to describe the limited discharge capacity by means of a mechanism of air-electrode deactivation. In that respect, upon discharge the silicon-air battery's cathode is not only blocked by silicon oxide reduction products, but also experiences a major modification in the MnO₂ catalyst nature. The proposed modification of the MnO₂ catalyst by means of a MnF₂ surface layer greatly impacts the Si-air performance and describes a mechanism relevant for other metal-air batteries, such as the lithium-air. Moreover, the ability for this deactivation layer to form is greatly impacted by water in the electrolyte.

Analysis on discharge behavior and performance of As- and B-doped silicon anodes in non-aqueous Si–air batteries under pulsed discharge operation

“…The development of Si-air batteries with EMIm(HF) 2.3 F electrolyte started in 2009, when the proof of concept was established [23] and, subsequently, the discharge capacities up to 26.7 mAh from a cell with 0.5 cm 2 anode surface area were corroborated [13]. Since then, focus of the further research was on electrochemical mechanisms, on factors influencing the end of discharge [24,25], andwith respect to material selection-on performance investigations depending on silicon anode type [26]. In general, pore clogging by silicon oxide deposits at the cathode side [13,25] and enhanced resistivity at the anode interface [24] were identified as factors contributing to the discharge limitations.…”

“…Since then, focus of the further research was on electrochemical mechanisms, on factors influencing the end of discharge [24,25], andwith respect to material selection-on performance investigations depending on silicon anode type [26]. In general, pore clogging by silicon oxide deposits at the cathode side [13,25] and enhanced resistivity at the anode interface [24] were identified as factors contributing to the discharge limitations. However, the mechanisms that lead to the discharge termination are still under discussion.…”

Influence of Dopant Type and Orientation of Silicon Anodes on Performance, Efficiency and Corrosion of Silicon–Air Cells with EMIm(HF)2.3F Electrolyte

“…Subsequent detailed work -comprising the analysis of long run discharge behavior, 11 the mechanisms that * Electrochemical Society Member. z E-mail: y.durmus@fz-juelich.de lead to a discharge termination 12,13 and the effects of humidity on the discharge characteristics 14 -was focusing exclusively on cells with 100 oriented As-doped Si anodes.…”

Silicon and Iron as Resource-Efficient Anode Materials for Ambient-Temperature Metal-Air Batteries: A Review

“…Basing on the promising results such as low corrosion rates and an average working potential of 1.0 -1.2 V under relatively high current densities of up to 300 µA/cm 2 , the new concept Si-air was introduced [123]. Further studies by Cohn et al led to new insights into the understanding of the Si-air battery behavior [53,140,[142][143][144]. More recently, Aslanbas et al also reported the effect of alloying of Si and Al on the discharge and corrosion behavior of cells with EMIm(HF)2.3F [165].…”

“…The discharge termination mechanism was further analyzed by Jakes et al, who performed electron magnetic resonance spectroscopy (EPR) and XPS on the air cathode [143]. In addition to pore clogging by SiO2 reaction products, the results obtained by EPR and XPS on the air electrode after cell discharge revealed another mechanism for discharge termination; modification of the catalyst (MnO2) in the air cathode.…”