Energy storage materials with both high capacity and high charge/discharge rate enable applications that require long life, high power, and rapid charge. Capacitors offer high power and battery electrodes offer relatively high capacity but the combination requires advanced materials. While nanostructures have dominated this emerging field, there are well-known issues of cost, stability, scalability, and safety of nanoparticles for battery applications. Recently, we have demonstrated and characterised complex oxide structures from facile solid-state synthetic methods with promising rate, capacity, and stability for reversible Li intercalation. Dense particles with high packing density of non-nanostructured T-Nb2O5 were shown to intercalate Li at high rates with capacity performance and retention similar to the best nanostructured analogues; a mechanistic investigation was undertaken to explain this novel behavior. The results and implications for the field of energy storage and inorganic materials design will be discussed. T-Nb2O5 bronze type and other novel complex structures with advanced energy storage properties feature low symmetry, large unit cells, site disorder, superstructure, second–order Jahn–Teller distortions, and mobile Li+, which create severe challenges and interesting opportunities for experimental and computational investigations. Herein, we discuss the structure and properties of i.) crystallographic shear compounds (e.g. TiNb2O7) and ii.) tungsten bronze-type phases (e.g. T-Nb2O5). Electrochemical results are interpreted with insights from 6/7Li, 93Nb, and 17O solid-state NMR spectroscopy, in situ x-ray absorption spectroscopy & diffraction, bond valence sum mapping, and density functional theory. There is a focus on understanding these important structure families and the applicability of advanced characterization techniques to complex functional oxides.

Elucidating the mechanism of high-rate and high-capacity lithium-ion intercalation in bulk complex transition metal oxides

253rd National Meeting (2017)

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