High energy electrode materials for lithium sulfur batteries
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This thesis described the research work on high energy electrode materials for lithium sulfur batteries. The literature review of high energy electrode materials was presented, including the advantages and disadvantages of different anode and cathode materials and related synthesis techniques. The lithium-sulfur battery and sulphur cathode are the major focus due to their advantages in energy density, cost and environmental sustainability. Different sulphur cathodes based on amorphous carbon, graphene and mesoporous carbon were synthesized to study the correlation between morphology of carbonaceous material and the performance of the sulphur cathode. The as-prepared electrode materials have been characterized by X-ray diffraction, field emission scanning electron microscopy, backscattered imaging, energy disperse spectroscopy element mapping and thermogravimetric analysis. The synthesized sulphur composites are tested as cathode materials in subsequent electrochemical tests. The electrochemical tests performed on sulfur cathodes include cyclic voltammetry, galvanostatic charge-discharge cycle tests and electrochemical impedance measurements. The synthesized graphene-sulfur composite was tested as cathode material and achieved both high sulphur utilization rate with a high specific capacity of 1593 mAh /g and good rate capability at 1.0 C and 2.0 C discharge rates. Graphene within the sulphur composite greatly improved the electrochemical performance of Li-S battery. The effect of sulphur particle size and size distribution within the cathode to the performance of Li-S battery was investigated through the synthesis of carbon-sulfur nanocomposite by an innovative solution-based synthesis technique. The modification of synthesis method has helped to reduce the particle size of sulphur to the level of about 200 nm. The as-prepared sulphur nanocomposite with a homogeneous dispersion of sulphur particles was applied as the cathode material in Li-S battery and exhibited a high reversible capacity of 1220 mAh/g and maintained favourable cycle stability.
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