Author: Gaurav Assat

Publisher:

Published: 2018

Total Pages: 0

ISBN-13:

Our increasing dependence on lithium-ion batteries for energy storage applications calls for continual performance improvements of their positive electrodes, which have so far relied solely on cationic redox of transition-metal ions for driving the electrochemical reactions. Great hope has recently been placed on the emergence of anionic redox - a transformational approach for designing Li-rich positive electrodes as it leads to a near-doubling of capacity - hence generating worldwide research interest. However, questions have been raised on the fundamental origins of anionic redox and whether its full potential can be realised in applications. This is exactly what this thesis aims to answer by using the knowledge from the fields of solid-state chemistry, electrochemistry, X-ray spectroscopy, and thermochemistry. We first provide a comprehensive historical account, a theoretical framework, some materials' design rules, and a survey of characterization techniques specific to anionic redox. Then, through comprehensive experimental studies that were performed in parallel on one 'model' (4d metal based) and one 'practical' (3d metal based) material, we highlight how the fundamental interplay between cationic and anionic redox processes governs the application-wise important properties of these promising battery materials (i.e. voltage hysteresis, rate performance, voltage decay, and heat generation,). Finally, using these results, we outline possible approaches for improving such materials and for designing novel ones. We also summarize their chances for market implementation in face of the competing nickel-based layered cathodes that are prevalent today.