Year

2019

Degree Name

Doctor of Philosophy

Department

Institute for Superconducting and Electronic Materials

Abstract

The emerging global energy shortage and climate change has been a critical issue in recent years. More effective power generation with clean energy sources are in strong demand especially for large-scale energy storage systems. Currently, lithium-ion batteries (LIBs) have been widely used as power sources for electronic devices and vehicles. Since the volume of energy storage system is restrictedly limited in most portable devices and electric vehicles, the energy density is a decisive factor when making the whole systems. One effective way to increase the energy density is to pursue electrodes that can work at high potentials. High voltage (5 V–class) spinel LiCr0.2Ni0.4Mn1.4O4 is one of the most promising cathode materials to meet the energy requirements of lithium-ion batteries for electric vehicles and hybrid electric vehicles. For the mass production of this material (1 kg or higher), different synthesis routes will lead to different electrochemical performances, even with similar morphology and similar crystal structure obtained from laboratory X-ray diffraction, and the reason for this issue is still not clear. Taking advantage of the high-resolution X-ray beam in synchrotron Xray diffraction, various phase composition as well as the generated impurities, rather than the particle distribution, are likely to be the main reasons for the detected electrochemical variations. A higher amount of impurities will result in greater charge transfer resistance, inferior cycling stability, and more oxygen/lithium vacancies. Therefore, it is very important to obtain a deeper understanding with the help of higher-resolution X-rays and to provide better guidance for mass production of this cathode material for practical applications.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.