Cerium Oxide Based Interlayer and Cathode Materials for High Performance Lithium Sulfur Battery

Investigation of sluggish redox kinetics and polysulfide shuttling is crucial to design advanced lithium sulfur battery. Cerium oxide (CeO2) has remarkable polysulfide adsorption capability and has been recently investigated in lithium sulfur battery application and novel catalyst design. With the goal of bridging towards commercialization of lithium sulfur battery, several interlayer and cathode materials based on cerium oxide have been developed in this thesis. This literature involves understanding of the mechanism of CeO2 based materials in lithium sulfur battery. Chapter 3 focuses on cellulose paper derived carbon fiber decorated with CeO2 nanorods to be used as interlayer material for lithium sulfur battery. The carbon fiber provides physical confinement and the CeO2 adsorbs lithium polysulfides chemically to reduce shuttle effect to achieve long lifetime and high capacity for lithium sulfur battery. With a sulfur content of 2 mg, a high capacity of 1177 mAh/g was achieved. The improved performance is attributed to the binding of lithium polysulfides by the CeO2 and the blocking of polysulfide physically by the compact conducting carbon fiber. Chapter 4 is focused on Prussian blue derived carbon cubes and CeO2 nanorods co-decorated on carbon fiber as lithium sulfur battery interlayer. The carbon cubes provide room for sulfur to expand during battery cycling, further leading to excellent rate capability. The battery could last 350 cycles at high current rate of 1C. The superior performance was compared with other existing literatures as well and it could be shown that the performance improved a few folds. Chapter 5 describes the use of copper oxide (CuO) impregnated CeO2 as a cathode host material for lithium sulfur battery. The redox potential of CuO lies in the optimal range to convert lithium polysulfides to polythionate and thiosulfate species which helps to improve the battery kinetics. As a result, 10wt% of CuO impregnated in CeO2 nanorods maintain excellent discharge capacity of over 1100 mAh/g for at least 60 cycles. This catalytic effect of the material is exciting prospect for further research in Li-S battery.