title: Layered-to-Tunnel Structure Transformation and Oxygen Redox Chemistry in LiRhO2 upon Li Extraction and Insertion.
abstract: Layered Li(M,Li)O2 (where M is a transition metal) ordered rock-salt-type structures are used in advanced metal-ion batteries as one of the best hosts for the reversible intercalation of Li ions. Besides the conventional redox reaction involving oxidation/reduction of the M cation upon Li extraction/insertion, creating oxygen-located holes because of the partial oxygen oxidation increases capacity while maintaining the oxidized oxygen species in the lattice through high covalency of the M-O bonding. Typical degradation mechanism of the Li(M,Li)O2 electrodes involves partially irreversible M cation migration toward the Li positions, resulting in gradual capacity/voltage fade. Here, using LiRhO2 as a model system (isostructural and isoelectronic to LiCoO2), for the first time, we demonstrate an intimate coupling between the oxygen redox and M cation migration. A formation of the oxidized oxygen species upon electrochemical Li extraction coincides with transformation of the layered Li1-xRhO2 structure into the γ-MnO2-type rutile-ramsdellite intergrowth LiyRh3O6 structure with rutile-like [1 × 1] channels along with bigger ramsdellite-like [2 × 1] tunnels through massive and concerted Rh migration toward the empty positions in the Li layers. The oxidized oxygen dimers with the O-O distances as short as 2.26 Å are stabilized in this structure via the local Rh-O configuration reminiscent to that in the μ-peroxo-μ-hydroxo Rh complexes. The LiyRh3O6 structure is remarkably stable upon electrochemical cycling illustrating that proper structural implementation of the oxidized oxygen species can open a pathway toward deliberate employment of the anion redox chemistry in high-capacity/high-voltage positive electrodes for metal-ion batteries.
authors.affiliation: Karlsruhe Institute of Technology (KIT) , Institute for Applied Materials (IAM), Hermann-von- Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany.|IFW Dresden , Institute for Complex Materials, Helmholtzstr. 20, D-01069 Dresden, Germany.|Max Planck Institute for Chemical Physics of Solids , Nöthnitzer Str. 40, D-01187 Dresden, Germany.
authors.forename: Daria
authors.initials: D
authors.lastname: Mikhailova
authors.affiliation: EMAT, University of Antwerp , Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
authors.forename: Olesia M
authors.initials: OM
authors.lastname: Karakulina
authors.affiliation: EMAT, University of Antwerp , Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Batuk
authors.affiliation: EMAT, University of Antwerp , Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
authors.forename: Joke
authors.initials: J
authors.lastname: Hadermann
authors.affiliation: EMAT, University of Antwerp , Groenenborgerlaan 171, B-2020 Antwerp, Belgium.|Skoltech Center for Electrochemical Energy Storage, Skolkovo Institute of Science and Technology , 143026 Moscow, Russia.
authors.forename: Artem M
authors.initials: AM
authors.lastname: Abakumov
authors.affiliation: IFW Dresden , Institute for Complex Materials, Helmholtzstr. 20, D-01069 Dresden, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Herklotz
authors.affiliation: National Institute of Chemical Physics and Biophysics , Akadeemia tee 23, 12618 Tallinn, Estonia.|Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg , Universitaetsstr. 1, 86159 Augsburg, Germany.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Tsirlin
authors.affiliation: IFW Dresden , Institute for Complex Materials, Helmholtzstr. 20, D-01069 Dresden, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Oswald
authors.affiliation: IFW Dresden , Institute for Complex Materials, Helmholtzstr. 20, D-01069 Dresden, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Giebeler
authors.affiliation: Max Planck Institute for Chemical Physics of Solids , Nöthnitzer Str. 40, D-01187 Dresden, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Schmidt
authors.affiliation: Erich Schmid Institute of Materials Science, Austrian Academy of Sciences , Jahnstraße 12, A-8700 Leoben, Austria.|Department of Materials Physics, Montanuniversität Leoben , Jahnstraße 12, A-8700 Leoben, Austria.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Eckert
authors.affiliation: Karlsruhe Institute of Technology (KIT) , Institute for Applied Materials (IAM), Hermann-von- Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Knapp
authors.affiliation: Karlsruhe Institute of Technology (KIT) , Institute for Applied Materials (IAM), Hermann-von- Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Helmut
authors.initials: H
authors.lastname: Ehrenberg