title: LiNi(0.5)Mn(1.5)O4 high-voltage cathode coated with Li4Ti5O12: a hard X-ray photoelectron spectroscopy (HAXPES) study.
abstract: A Li4Ti5O12 (LTO) film was coated as buffer layer onto a LiNi0.5Mn1.5O4 (LNMO) high-voltage cathode, and after cycling of the cathode in a battery electrolyte, the LTO film was investigated by means of synchrotron radiation based hard X-ray photoelectron spectroscopy (HAXPES). By tuning the photon energy between 2 keV and 6 keV, we obtained non-destructive depth profiles of the coating material with probing depths ranging from 6 nm to 20 nm. The coating was found to be covered by a few nanometers thin surface layer resulting from electrolyte decomposition. This layer consisted predominantly of organic polymers as well as metal fluorides and fluorophosphates. A positive influence of the Li4Ti5O12 coating with regard to the size and stability of the surface layer was found. The coating itself consisted of a uniform mixture of Li(I), Ti(IV), Ni(II) and Mn(IV) oxides that most likely adopted a spinel structure by forming a solid solution of the two spinels LiNi0.5Mn1.5O4 and Li4Ti5O12 with Li, Mn, Ni and Ti cations mixing on the spinel octahedral sites. The diffusion of Ni and Mn ions into the Li4Ti5O12 lattice occurred during the heat treatment when preparing the cathode. The doping of Li4Ti5O12 with the open d-shell ions Ni(2+) (d(8)) and Mn(4+) (d(3)) should increase the electronic conductivity of the coating significantly, as was found in previous studies. The complex signal structure of the Ti 2p, Ni 2p and Mn 2p core levels provides insight into the chemical nature of the transition metal ions.
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032 Marburg, Germany. michael.gottfried@chemie.uni-marburg.de.
authors.forename: Malte
authors.initials: M
authors.lastname: Sachs
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032 Marburg, Germany. michael.gottfried@chemie.uni-marburg.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Gellert
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032 Marburg, Germany. michael.gottfried@chemie.uni-marburg.de.
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032 Marburg, Germany. michael.gottfried@chemie.uni-marburg.de.
authors.forename: Hans-Jörg
authors.initials: HJ
authors.lastname: Drescher
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032 Marburg, Germany. michael.gottfried@chemie.uni-marburg.de.
authors.forename: Stefan Renato
authors.initials: SR
authors.lastname: Kachel
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032 Marburg, Germany. michael.gottfried@chemie.uni-marburg.de.
authors.forename: Han
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032 Marburg, Germany. michael.gottfried@chemie.uni-marburg.de.
authors.forename: Malte
authors.initials: M
authors.lastname: Zugermeier
authors.affiliation: Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Straße 15, 12489 Berlin, Germany.
authors.forename: Mihaela
authors.initials: M
authors.lastname: Gorgoi
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032 Marburg, Germany. michael.gottfried@chemie.uni-marburg.de.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Roling
authors.affiliation: Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße 4, 35032 Marburg, Germany. michael.gottfried@chemie.uni-marburg.de.
authors.forename: J Michael
authors.initials: JM
authors.lastname: Gottfried