Issue 11, 2016

Crystal structure, microstructure and electrochemical properties of hydrothermally synthesised LiMn2O4

Abstract

The hydrothermal synthesis method offers an environmentally benign way of synthesizing Li-ion battery materials with strong control of particle size and morphology, and thereby also the electrochemical performance. Here we present an in depth investigation of the crystal structure, microstructure and electrochemical properties of hydrothermally synthesized LiMn2O4, which is a widely used cathode material. A range of samples were synthesized by a simple, single-step hydrothermal route, and the products were characterized by elaborate Rietveld refinement of powder X-ray diffraction data, electron microscopy and electrochemical analysis. A distinct bimodal crystallite size distribution of LiMn2O4 was formed together with a Mn3O4 impurity. At high LiOH concentration the layered LixMnyO2 phase was formed. The crystallite sizes and impurity weight fractions were found to be highly synthesis dependent, and the amount of spinel impurity phase was found to correlate with deterioration of the electrochemical performance. The Mn3O4 phase can be very difficult to quantify in standard powder X-ray diffraction and due to peak overlap and X-ray fluorescence impurity levels of more than 10% are easily hidden. Furthermore, the spinel LiMn2O4 phase can easily be mistaken for the layered LixMnyO2 phase. The present study therefore highlights the importance of thorough structural characterization in studies of battery materials.

Graphical abstract: Crystal structure, microstructure and electrochemical properties of hydrothermally synthesised LiMn2O4

Supplementary files

Article information

Article type
Paper
Submitted
02 Dec 2015
Accepted
17 Feb 2016
First published
17 Feb 2016

CrystEngComm, 2016,18, 1996-2004

Author version available

Crystal structure, microstructure and electrochemical properties of hydrothermally synthesised LiMn2O4

T. L. Christiansen, E. D. Bøjesen, M. Søndergaard, S. Birgisson, J. Becker and B. B. Iversen, CrystEngComm, 2016, 18, 1996 DOI: 10.1039/C5CE02358K

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