title: Electrochemical Reduction of Oxygen in Aprotic Ionic Liquids Containing Metal Cations: A Case Study on the Na-O2system.
abstract: Metal-air batteries are intensively studied because of their high theoretical energy-storage capability. However, the fundamental science of electrodes, electrolytes, and reaction products still needs to be better understood. In this work, the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) was chosen to study the influence of a wide range of metal cations (Mn+) on the electrochemical behavior of oxygen. The relevance of the theory of Lewis hard and soft acids and bases to predict satisfactorily the reduction potential of oxygen in electrolytes containing metal cations is demonstrated. Systems with soft and intermediate Mn+acidity are shown to facilitate oxygen reduction and metal oxide formation, whereas oxygen reduction is hampered by hard acid cations such as sodium and lithium. Furthermore, DFT calculations on the energy of formation of the resulting metal oxides rationalize the effect of Mn+on oxygen reduction. A case study on the Na-O2system is described in detail. Among other things, the Na+concentration of the electrolyte is shown to control the electrochemical pathway (solution precipitation vs. surface deposition) by which the discharge product grows. All in all, fundamental insights for the design of advanced electrolytes for metal-air batteries, and Na-air batteries in particular, are provided.
authors.affiliation: Nanomaterials Unit, IK4-Cidetec, Paseo Miramon 196, 20009, Donostia-SanSebastián, Spain.
authors.forename: Eneko
authors.initials: E
authors.lastname: Azaceta
authors.affiliation: Chemistry of Materials and Energy, College de France, Place Marcelin Berthelot 11, 75005, Paris, France.
authors.forename: Lukas
authors.initials: L
authors.lastname: Lutz
authors.affiliation: Chemistry of Materials and Energy, College de France, Place Marcelin Berthelot 11, 75005, Paris, France.
authors.forename: Alexis
authors.initials: A
authors.lastname: Grimaud
authors.affiliation: Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, Ctra. Utrera km 1, Seville, Spain.
authors.forename: Jose Manuel
authors.initials: JM
authors.lastname: Vicent-Luna
authors.affiliation: Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, Ctra. Utrera km 1, Seville, Spain.
authors.forename: Said
authors.initials: S
authors.lastname: Hamad
authors.affiliation: CIC-Biomagune, Paseo Miramón 182, 20009, Donostia-San Sebastián, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Yate
authors.affiliation: Nanomaterials Unit, IK4-Cidetec, Paseo Miramon 196, 20009, Donostia-SanSebastián, Spain.
authors.forename: German
authors.initials: G
authors.lastname: Cabañero
authors.affiliation: Nanomaterials Unit, IK4-Cidetec, Paseo Miramon 196, 20009, Donostia-SanSebastián, Spain.
authors.forename: Hans-Jurgen
authors.initials: HJ
authors.lastname: Grande
authors.affiliation: Department of Physical, Chemical and Natural Systems, Universidad Pablo de Olavide, Ctra. Utrera km 1, Seville, Spain.
authors.forename: Juan A
authors.initials: JA
authors.lastname: Anta
authors.affiliation: Chemistry of Materials and Energy, College de France, Place Marcelin Berthelot 11, 75005, Paris, France.
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Tarascon
authors.affiliation: Nanomaterials Unit, IK4-Cidetec, Paseo Miramon 196, 20009, Donostia-SanSebastián, Spain.
authors.forename: Ramon
authors.identifier: 0000-0002-1525-7760
authors.initials: R
authors.lastname: Tena-Zaera
mesh_terms: D011211:Electric Power Supplies; D004563:Electrochemistry; D004566:Electrodes; D052578:Ionic Liquids / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D011789:Quantum Theory; D012964:Sodium / Q000737:chemistry*
chemical_list: D052578:Ionic Liquids; D012964:Sodium; D010100:Oxygen
keywords: cations; electrochemistry; ionic liquids; metal-air batteries; oxygen reduction