Beyond Lithium-Ion Technology: Lithium-Sulfur and Potassium-Ion for Better and Cheaper Batteries

Large-scale energy storage is one of the key components to power a sustainable future. While lithium-ion batteries (LIBs) have revolutionised our modern lifestyles, the cost of lithium resources and limited energy density that can be safely accessed have limited their potential as large-scale energy storage systems. Lithium-sulfur batteries (LSBs) and potassium-ion batteries (KIBs) are studied as the alternatives due to the high energy density sulfur and cheaper potassium. In the first part of this PhD project, metal oxides are in situ integrated with conductive and flexible carbon framework as the LSBs interlayer, for the first time, to mitigate active material loss. The composite prepared has a large TiO2 content that can chemically trap polysulfides and a high porosity CNF scaffold for physically hosting the polysulfides. The combined results in the interlayer increase initial discharge capacity and prolong the cycle life as compared to the cell without this interlayer. In the next part of this PhD project, a new ion storing mechanism is designed to compete for the diffusion limitation and the structural deterioration of KIB electrodes. Unlike a rigid oxide electrode, the oxygen deficient loose-layered potassium titanates (LL-KTO) anode delaminates and restacks reversibly upon charging and discharging, to name it, stacked ↔ sliced structural transformation. This mechanism allows for large storage of K+ ions in the electrode with net-zero structural deterioration during cycling. Subsequently, layered sodium titanates (L-NTO) are prepared to examine whether stacked ↔ sliced structural transformation mechanism can be engineered in sodium-ion storage. Nevertheless, as evidenced by the electrochemical performances, L-NTO stored sodium with intercalation. The work conducted in this PhD project provided essential knowledge on methods for mitigating active material loss in a sulfur based battery and mechanism on how to efficiently store potassium.Studying Abroad Scholarship, Ministry of Education, Taiwa