title: 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.
authors.affiliation: Forschungszentrum Jülich, Institut für Energie- und Klimaforschung, IEK-9, 52452 Jülich, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Jakes
authors.forename: Gil
authors.initials: G
authors.lastname: Cohn
authors.forename: Yair
authors.initials: Y
authors.lastname: Ein-Eli
authors.forename: Frieder
authors.initials: F
authors.lastname: Scheiba
authors.forename: Helmut
authors.initials: H
authors.lastname: Ehrenberg
authors.forename: Rüdiger-A
authors.initials: RA
authors.lastname: Eichel
mesh_terms: D000388:Air; D011211:Electric Power Supplies; D004563:Electrochemistry; D004566:Electrodes; D012825:Silicon / Q000737:chemistry*; D013696:Temperature
chemical_list: D012825:Silicon