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APPLICATION OF GRAPHENE-BASED 2D MATERIALS AND EXPLORATION OF LITHIUM POLYSULFIDES SOLID PHASES – FIRST-PRINCIPLES STUDY BASED ON DENSITY FUNCTIONAL THEORY
Date of Award
Campus Access Dissertation
Doctor of Philosophy in Physics (PhD)
Administrative Home Department
Department of Physics
Kah Chun Lau
Committee Member 1
Committee Member 2
Committee Member 3
In my Ph. D. thesis, the work performed can be divided into two parts: the first part is related to graphene-based heterostructures and the second part is associated with the Li-S battery in which state-of-the-art density functional theory (DFT) was employed.
Graphene is the most versatile 2D material due to its unique properties. However, the absence of a finite bandgap has impeded it from practical applications. To open up the bandgap via the interfacial interactions, we investigated the van der Waals heterostructures composed of graphene and SnO layers. In such stacked heterostructures a sizable bandgap is predicted, and the bandgap is so robust that can bear an external electric field up to ~0.3 x 010 V/m. When removed one of the SnO layers, a Schottky junction is formed. The contact type could be tuned by an external electric field. Next, we discussed the potential applications for 2D materials as protective coatings for Uranium metal. Graphene, TMDs (MoS2/MoSe2), and Ti2C-based MXenes all show good affinity with Uranium surfaces.
The Lithium-sulfur battery is considered a promising substitute for the current Lithium-ion battery due to its high theoretical energy density and relatively low cost. With a well-engineered cathode microstructure, the lithium polysulfides could be confined within the cathode without dissolving into the electrolytes. This provides the feasibility of solid polysulfides formation. Because of the complexity of intermediate polysulfides products, the discharge progress is still not fully understood. In the second part of the thesis, we have performed a comprehensive characterization of the intermediate lithium polysulfide solid phases in terms of stability and mechanical properties, thus establishing an important baseline study for the design and fabrication of advanced cathodes with high coulombic efficiency and a long lifespan.
Guo, Qing, "APPLICATION OF GRAPHENE-BASED 2D MATERIALS AND EXPLORATION OF LITHIUM POLYSULFIDES SOLID PHASES – FIRST-PRINCIPLES STUDY BASED ON DENSITY FUNCTIONAL THEORY", Campus Access Dissertation, Michigan Technological University, 2021.