Changes in the crystal and electronic structure of LiCoO2 and LiNiO2 upon Li intercalation and de-intercalation

Sonja Laubach; Stefan Laubach; Peter C. Schmidt; David Ensling; Stefan Schmid; Wolfram Jaegermann; Andreas Thißen; Kristian Nikolowski; Helmut Ehrenberg

doi:10.1039/B901200A

Changes in the crystal and electronic structure of LiCoO₂ and LiNiO₂ upon Li intercalation and de-intercalation

Sonja Laubach,^a Stefan Laubach,^a Peter C. Schmidt,*^a David Ensling,^b Stefan Schmid,^b Wolfram Jaegermann,^b Andreas Thißen,^c Kristian Nikolowski^d and Helmut Ehrenberg^e

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* Corresponding authors

^a Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, Petersenstraße 21, D-64287 Darmstadt, Germany

^b Fachbereich Material- und Geowissenschaften, Fachgebiet Oberflächenforschung, Technische Universität Darmstadt, Petersenstraße 23, D-64287 Darmstadt, Germany

^c SPECS GmbH, Voltastrasse 5, Berlin, Germany

^d Fachbereich Material- und Geowissenschaften, Fachgebiet Strukturforschung, Technische Universität Darmstadt, Petersenstraße 23, D-64287 Darmstadt, Germany

^e Institut für Komplexe Materialien, IFW Dresden, Helmholtzstraße 20, D-01069 Dresden, Germany

Abstract

Li_xCoO₂ and Li_xNiO₂ (0.5 < x < 1) are used as prototype cathode materials in lithium ion batteries. Both systems show degradation and fatigue when used as cathode material during electrochemical cycling. In order to analyze the change of the structure and the electronic structure of Li_xCoO₂ and Li_xNiO₂ as a function of Li content x in detail, we have performed X-ray diffraction studies, photoelectron spectroscopy (PES) investigations and band structure calculations for a series of compounds Li_x(Co,Ni)O₂ (0 < x⩽ 1). The calculated density of states (DOS) are weighted by theoretical photoionization cross sections and compared with the DOS gained from the PES experiments. Consistently, the experimental and calculated DOS show a broadening of the Co/Ni 3d states upon lithium de-intercalation. The change of the shape of the experimental PES curves with decreasing lithium concentration can be interpreted from the calculated partial DOS as an increasing energetic overlap of the Co/Ni 3d and O 2p states and a change in the orbital overlap of Co/Ni and O wave functions.

This article is part of the themed collection: Physical chemistry of solids - The science behind materials engineering

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https://doi.org/10.1039/B901200A

Article type

Paper

Submitted

21 Jan 2009

Accepted

05 Mar 2009

First published

25 Mar 2009

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Phys. Chem. Chem. Phys., 2009,11, 3278-3289

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Changes in the crystal and electronic structure of LiCoO₂ and LiNiO₂ upon Li intercalation and de-intercalation

S. Laubach, S. Laubach, P. C. Schmidt, D. Ensling, S. Schmid, W. Jaegermann, A. Thißen, K. Nikolowski and H. Ehrenberg, Phys. Chem. Chem. Phys., 2009, 11, 3278 DOI: 10.1039/B901200A

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Physical Chemistry Chemical Physics

Changes in the crystal and electronic structure of LiCoO₂ and LiNiO₂ upon Li intercalation and de-intercalation

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Changes in the crystal and electronic structure of LiCoO₂ and LiNiO₂ upon Li intercalation and de-intercalation

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