title: Evidence for anionic redox activity in a tridimensional-ordered Li-rich positive electrode β-Li2IrO3.
abstract: Lithium-ion battery cathode materials have relied on cationic redox reactions until the recent discovery of anionic redox activity in Li-rich layered compounds which enables capacities as high as 300 mAh g-1. In the quest for new high-capacity electrodes with anionic redox, a still unanswered question was remaining regarding the importance of the structural dimensionality. The present manuscript provides an answer. We herein report on a β-Li2IrO3phase which, in spite of having the Ir arranged in a tridimensional (3D) framework instead of the typical two-dimensional (2D) layers seen in other Li-rich oxides, can reversibly exchange 2.5 e-per Ir, the highest value ever reported for any insertion reaction involving d-metals. We show that such a large activity results from joint reversible cationic (Mn+) and anionic (O2)n-redox processes, the latter being visualized via complementary transmission electron microscopy and neutron diffraction experiments, and confirmed by density functional theory calculations. Moreover, β-Li2IrO3presents a good cycling behaviour while showing neither cationic migration nor shearing of atomic layers as seen in 2D-layered Li-rich materials. Remarkably, the anionic redox process occurs jointly with the oxidation of Ir4+at potentials as low as 3.4 V versus Li+/Li0, as equivalently observed in the layered α-Li2IrO3polymorph. Theoretical calculations elucidate the electrochemical similarities and differences of the 3D versus 2D polymorphs in terms of structural, electronic and mechanical descriptors. Our findings free the structural dimensionality constraint and broaden the possibilities in designing high-energy-density electrodes for the next generation of Li-ion batteries.
authors.affiliation: Collège de France, Chimie du Solide et de l'Energie, UMR 8260, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France.|Réseau sur le Stockage Electrochimique de l'Energie (RS2E), FR CNRS 3459, 80039 Amiens Cedex, France.|Sorbonne Universités-UPMC Univ Paris 06, 4 Place Jussieu, F-75005 Paris, France.
authors.forename: Paul E
authors.initials: PE
authors.lastname: Pearce
authors.affiliation: Collège de France, Chimie du Solide et de l'Energie, UMR 8260, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France.|Réseau sur le Stockage Electrochimique de l'Energie (RS2E), FR CNRS 3459, 80039 Amiens Cedex, France.|Sorbonne Universités-UPMC Univ Paris 06, 4 Place Jussieu, F-75005 Paris, France.
authors.forename: Arnaud J
authors.initials: AJ
authors.lastname: Perez
authors.affiliation: Collège de France, Chimie du Solide et de l'Energie, UMR 8260, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France.|Réseau sur le Stockage Electrochimique de l'Energie (RS2E), FR CNRS 3459, 80039 Amiens Cedex, France.|Sorbonne Universités-UPMC Univ Paris 06, 4 Place Jussieu, F-75005 Paris, France.
authors.forename: Gwenaelle
authors.initials: G
authors.lastname: Rousse
authors.affiliation: Réseau sur le Stockage Electrochimique de l'Energie (RS2E), FR CNRS 3459, 80039 Amiens Cedex, France.|Institut Charles Gerhardt, UMR 5253, CNRS and Université de Montpellier, Place Eugène Bataillon, F-34095 Montpellier, France.
authors.forename: Mathieu
authors.identifier: 0000-0002-9900-6175
authors.initials: M
authors.lastname: Saubanère
authors.affiliation: Collège de France, Chimie du Solide et de l'Energie, UMR 8260, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France.|EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerp, Belgium.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Batuk
authors.affiliation: Réseau sur le Stockage Electrochimique de l'Energie (RS2E), FR CNRS 3459, 80039 Amiens Cedex, France.|IPREM/ECP (UMR 5254), Université de Pau, 2 Avenue Pierre Angot, 64053 Pau Cedex 9, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Foix
authors.affiliation: Collège de France, Chimie du Solide et de l'Energie, UMR 8260, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France.|Réseau sur le Stockage Electrochimique de l'Energie (RS2E), FR CNRS 3459, 80039 Amiens Cedex, France.|CEMS, University of Minnesota, 421 Washington Avenue, Minneapolis, Minnesota 55455, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: McCalla
authors.affiliation: EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerp, Belgium.|Skolkovo Institute of Science and Technology, 3 Nobel Street, 143026 Moscow, Russia.
authors.forename: Artem M
authors.initials: AM
authors.lastname: Abakumov
authors.affiliation: EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020, Antwerp, Belgium.
authors.forename: Gustaaf
authors.initials: G
authors.lastname: Van Tendeloo
authors.affiliation: Réseau sur le Stockage Electrochimique de l'Energie (RS2E), FR CNRS 3459, 80039 Amiens Cedex, France.|Institut Charles Gerhardt, UMR 5253, CNRS and Université de Montpellier, Place Eugène Bataillon, F-34095 Montpellier, France.
authors.forename: Marie-Liesse
authors.initials: ML
authors.lastname: Doublet
authors.affiliation: Collège de France, Chimie du Solide et de l'Energie, UMR 8260, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France.|Réseau sur le Stockage Electrochimique de l'Energie (RS2E), FR CNRS 3459, 80039 Amiens Cedex, France.|Sorbonne Universités-UPMC Univ Paris 06, 4 Place Jussieu, F-75005 Paris, France.
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Tarascon