Details

Autor(en) / Beteiligte

• Jakes , Peter
• Cohn, Gil
• Ein-Eli, Yair
• Scheiba, Frieder
• Ehrenberg, Helmut
• Eichel , Rüdiger-A.

Titel

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

Ist Teil von

• ChemSusChem, 2012-11, Vol.5 (11), p.2278-2285

Ort / Verlag

Weinheim: WILEY-VCH Verlag

Erscheinungsjahr

2012

Quelle

Wiley InterScience Journals

Beschreibungen/Notizen

• 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. Mechanism of catalyst deactivation: Electrocatalytic oxygen reduction at the air cathode in silicon–air batteries critically impacts battery performance. We describe a mechanism of air‐electrode deactivation: upon discharge, the MnO2 catalyst is modified by the formation of of a MnF2 surface layer formation that is catalytically inactive for the oxygen reduction reaction and limits the discharge capacity. The ability for this deactivation layer to form is greatly impacted by the water content of the electrolyte.