Crystal structure, microstructure and electrochemical properties of hydrothermally synthesised LiMn2O4. Issue 11 (25th February 2016)

• Record Type: Journal Article
• Authors: Christiansen, Troels Lindahl; Bøjesen, Espen D.; Søndergaard, Martin; Birgisson, Steinar; Becker, Jacob; Iversen, Bo B.
• Is Part Of: CrystEngComm. Volume 18:Issue 11(2016)
• Page Start: 1996
• Page End: 2004
• Publication Date: 2016-02-25
• Subjects: Crystals -- Periodicals; Crystal growth -- Periodicals; Crystallography -- Periodicals; Cristaux -- Périodiques; Cristaux -- Croissance -- Périodiques; Cristallographie -- Périodiques; 548
• DOI: 10.1039/c5ce02358k
• Languages: English
• ISSNs: 1466-8033

Abstract

Abstract : Hydrothermal synthesis offers an environmentally benign method for synthesis of LiMn2 O4 anode material, but characterization is challenging due to structurally related impurity phases such as Li x Mn y O2 and Mn3 O4, whose presence may explain the inconsistent properties in published literature. 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 LiMn2 O4, 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 LiMn2 O4 was formed together with a Mn3 O4 impurity. At high LiOH concentration the layered Li x Mn y O2 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 Mn3 O4 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 LiMn2 O4 phase can easily be mistaken for the layered Li x Mn y O2 phase. The present study therefore highlights the importance of thorough structural characterization in studies of battery materials.