Thangadurai, VenkataramanAbraham, Akhil Mammoottil2023-05-112022-06-22Abraham, A. M. (2022). High Sulfur Content, Fast Charging, and Extended Life Cathode for Lithium Sulfur Battery (Doctoral thesis). University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca .http://hdl.handle.net/1880/116295Beyond lithium-ion batteries (LIB) are required to meet high energy density applications of modern society. Lithium-sulfur (Li-S) battery technology offers a theoretical energy density of 2500 Wh kg-1, which is around 5 times that of existing LIBs. However, at a cell level energy density of >350 Wh kg-1 (where sulfur loading >5 mg cm-2) at room temperature, the Li-S battery demonstrates severe capacity fade, limited cyclability, and poor rate performance. In this thesis, in-situ sulfur cathodes, MoS3 and WS3, are explored as solutions to improve the rate performance of Li-S batteries. Presence of S22- disulfide ligands in MoS3 or WS3, provides an alternative sulfur source to electronically insulating S8. The Li-S battery with MoS3 cathode demonstrated a high reversible capacity of ~1500 mAh g-1 in the first cycle at a rate of 0.3 C, indicating a high sulfur utilization percent of ~89%. Furthermore, when cycled long term at a rate of 2 C (~1000 mAh g-1 in the first cycle), the device was cyclable close to 200 cycles with a capacity fade rate of 0.13% per cycle. The analogous WS3 cathode delivered similar performance. The device was rate capable up to a C-rate of 2C with a specific capacity of ~600 mAh g-1. On long-term cycling the WS3 cathode exhibited a capacity fade rate of ~0.02% per cycle. To increase the sulfur loading tolerance of cathode architecture, a freestanding electrode is investigated. Into this electrode matrix a hybrid MoS2-WS2 anchoring material is incorporated. The novel cathode design maximizes the geometric coverage for anchoring-conversion of polysulfides to restrain shuttle effect at practical sulfur (S) loadings. The strategy presented in chapter 6 prevents the accumulation of polysulfide molecules at a localized site of the anchoring surface. Our systematic analysis (5 – 50 mg cm-2 of S-loadings) reveals that the unique cathode architecture exhibits reversible S-loading tolerance up to 28 mg cm-2. A high initial areal capacity of 32 mAh cm-2 with an area specific energy density of 67 mWh cm-2 is achieved, which is highest among the hybrid composites reported till date. The approach can unlock high S-loading Li-S cells with extended cyclability and rate performance. Finally, we propose a computational aided design principle to screen an ideal surface for polysulfide electrocatalysis.EnglishBatterysulfurenergylithiummetal sulfideselectrocatalysisenergy densitryChemistry--Generaldoctoral thesis