title: Elucidation of the Conversion Reaction of CoMnFeO4 Nanoparticles in Lithium Ion Battery Anode via Operando Studies.
abstract: Conversion reactions deliver much higher capacities than intercalation/deintercalation reactions of commercial Li ion batteries. However, the complex reaction pathways of conversion reactions occurring during Li uptake and release are not entirely understood, especially the irreversible capacity loss of Mn(III)-containing oxidic spinels. Here, we report for the first time on the electrochemical Li uptake and release of Co(II)Mn(III)Fe(III)O4 spinel nanoparticles and the conversion reaction mechanisms elucidated by combined operando X-ray diffraction, operando and ex-situ X-ray absorption spectroscopy, transmission electron microscopy, (7)Li NMR, and molecular dynamics simulation. The combination of these techniques enabled uncovering the pronounced electronic changes and structural alterations on different length scales in a unique way. The spinel nanoparticles undergo a successive phase transition into a mixed monoxide caused by a movement of the reduced cations from tetrahedral to octahedral positions. While the redox reactions Fe(3+) ↔ Fe(0) and Co(2+) ↔ Co(0) occur for many charge/discharge cycles, metallic Mn nanoparticles formed during the first discharge can only be oxidized to Mn(2+) during charge. This finding explains the partial capacity loss reported for Mn(III)-based spinels. Furthermore, the results of the investigations evidence that the reaction mechanisms on the nanoscale are very different from pathways of microcrystalline materials.
authors.affiliation: Institute of Inorganic Chemistry, University of Kiel , Max-Eyth-Straße 2, 24118 Kiel, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Permien
authors.affiliation: Institute for Applied Materials, Karlsruhe Institute of Technology , P.O. Box 3640, 76021 Karlsruhe, Germany.
authors.forename: Sylvio
authors.initials: S
authors.lastname: Indris
authors.affiliation: Institute of Inorganic Chemistry, University of Kiel , Max-Eyth-Straße 2, 24118 Kiel, Germany.
authors.forename: Anna-Lena
authors.initials: AL
authors.lastname: Hansen
authors.affiliation: Institute for Applied Materials, Karlsruhe Institute of Technology , P.O. Box 3640, 76021 Karlsruhe, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Scheuermann
authors.affiliation: Chair for theoretical Chemistry/Computer Chemistry Centrum, Friedrich-Alexander University Erlangen-Nürnberg , Nagelsbachstraße 25, 91052 Erlangen, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Zahn
authors.affiliation: Institute for Materials Science, University of Kiel , Kaiserstraße 2, 24143 Kiel, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schürmann
authors.affiliation: Institute for Materials Science, University of Kiel , Kaiserstraße 2, 24143 Kiel, Germany.
authors.forename: Gero
authors.initials: G
authors.lastname: Neubüser
authors.affiliation: Institute for Materials Science, University of Kiel , Kaiserstraße 2, 24143 Kiel, Germany.
authors.forename: Lorenz
authors.initials: L
authors.lastname: Kienle
authors.affiliation: Institute of Inorganic Chemistry, University of Kiel , Max-Eyth-Straße 2, 24118 Kiel, Germany.
authors.forename: Eugen
authors.initials: E
authors.lastname: Yegudin
authors.affiliation: Institute of Inorganic Chemistry, University of Kiel , Max-Eyth-Straße 2, 24118 Kiel, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bensch
keywords: anode; conversion; lithium ion battery; operando XAS; operando XRD; spinel oxide