Mechanistic and Structural Investigation of LixMnO2 Cathodes during Cycling in Li-Ion Batteries

Monday, 6 October 2014: 11:50
Sunrise, 2nd Floor, Galactic Ballroom 4 (Moon Palace Resort)
S. W. Donne, W. M. Dose (University of Newcastle), and N. Sharma (School of Chemistry, The University of New South Wales, Sydney)
Increasingly there is demand for clean energy sources and suitable batteries to store this energy. Manganese dioxide and lithiated variants are a promising alternative to conventional Li-ion cathodes due to their cost, abundance, safety and electrochemical performance. Cathodes which operate by a single-phase lithium insertion/extraction process can offer some intrinsic advantages over those with two-phase processes. In this work, in-situ and ex-situ synchrotron X-ray diffraction (XRD) is used to investigate the structural evolution and lithium insertion/extraction mechanism of various LixMnO2 cathodes. Li0.30MnO2 is found to cycle solely with a single-phase mechanism, in contrast to previous literature reports, with only subtle changes in the crystal structure. However, a better cycling discharge capacity is realised through a two-step lithiation synthesis, thermally lithiated Li0.08MnO2 which is then electrochemically lithiated to Li0.33MnO2. After an irreversible two-phase reaction early in the first discharge, this material cycles by a single-phase reaction with good structural reversibility and a stable unoptimised cycling capacity of 120 mAh/g. Comparing cathodes using a combination of in-situ and ex-situ synchrotron XRD data allows us to rationalise cathodic performance with structure and thereby directing research into promising candidates.