Date of Award

August 2026

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Physics & Astrophysics

First Advisor

Dr. Deniz Cakir

Abstract

Lithium-sulfur (Li-S) batteries have become a promising choice for next-generation energy storage because of their high theoretical energy density, low material cost, and environmental friendliness. However, their commercialization faces significant challenges due to the poor conductivity of the cathode and the ‘shuttle effect’ caused by lithium polysulfides (LiPSs). During operation, the highly soluble lithium polysulfides, which are byproducts of sulfur reduction, dissolve into the electrolyte and can migrate between the anode and cathode. This migration results in loss of active material, reduced coulombic efficiency, and rapid capacity fading. To address these challenges, developing effective cathode host materials that can absorb polysulfides and prevent their diffusion is crucial. Two-dimensional (2D) materials such as molybdenum disulfide (MoS2), vanadium disulfide (VS2), and graphene are of interest due to their high surface area, tunable physical and electrical properties, and strong affinity for sulfur species. Using first-principles methods, this study explores the potential of graphene/MoS2 and VS2/MoS2 heterostructures as effective cathode host materials to improve lithium-sulfur (Li-S) battery performance. We aim to reduce the polysulfide shuttle effect by introducing effective anchoring materials into cathodes for Li-S batteries to enhance the cycling stability. It was found that the graphene/MoS2 and VS2/MoS2 heterostructures show stronger adsorption ability for lithium polysulfides than monolayer MoS2, VS2, and graphene. The resulting stronger adsorption strength effectively suppresses the dissolution of LiPSs while preserving the structural stability of the Li2Sn clusters. The charge transfer analysis further confirms the strong chemical interactions between lithium polysulfides and the host heterostructures. Ab initio molecular dynamics (AIMD) simulations reveal that the adsorbed configurations remain thermally stable under finite -temperature conditions. These findings demonstrate that both graphene/MoS2 and VS2/MoS2 heterostructures are effective anchoring materials to improve the electrochemical performance in Li-S batteries. This work provides fundamental insights and theoretical guidance for designing effective heterostructure electrode materials for next-generation high-performance Li-S battery applications.

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Available for download on Monday, March 08, 2027

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