Date of Graduation

7-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Chemistry (PhD)

Degree Level

Graduate

Department

Chemistry & Biochemistry

Advisor

Jie Xiao

Committee Member

Robert Coridan

Second Committee Member

Stefan Kilyanek

Third Committee Member

David Paul

Fourth Committee Member

Ryan Tian

Keywords

Batteries, Lithium Metal, Solid Electrolyte Interface, Tungsten Trioxide

Abstract

Li-ion batteries have started to reach the theoretical maximum energy. Next-generation batteries represent the future of portable energy sources for vehicle electrification and grid energy storage. Li metal battery is one of the most promising next-generation battery technologies that could potentially double the cell-level energy of conventional Li-ion batteries. However, Li metal has multiple drawbacks that require addressing before realization. These drawbacks include dendrite formation leading to internal short and increasing internal resistance due to the breakdown of electrolyte, leading to rapid cell death. These problems stem from the interfacial reactions occurring during the plating and stripping of Li metal. The plating of Li metal is impacted by the mass transport of ions within the electrolyte and surface conditions of the substrate it is plating on. The research presented here strives to understand the interfacial reactions due to the atomistic nature of the substrate, both in crystal type and facet selection, and the surface compounds present on the substrates with regards to surface oxides and other conversion materials. W was found to show a promising performance when compared to Cu. The SEI on W showed a more robust composition with an increase in inorganic component production. The crystal face present during plating causes the plated Li to match the crystal face; however, as the thickness of the plated Li increases, the crystal structure becomes anisotropic and starts to become unimodal. The unimodal texture showed that Li plates in the basis-oriented reproductive type (BR), with the zeta-fiber being the preferred texture. The surface compounds present were explored initially with WO3, as the oxygen content is controllable, and the WO3 undergoes multiple transformations. A first of its kind application of WO3 was found to impact the Li plating and stripping by changing the solid electrolyte interface (SEI) properties through participation in the electrochemical reactions. The presence of W, derived from WO3, within the SEI, creates a framework that helps to regenerate ”dead” Li. Additionally, the modified SEI changes the nature of Li nucleation and helps to form a denser inorganic layer by catalytically increasing the decomposition of the electrolyte. New insights have been provided in tailoring SEI properties formed on Li metal surfaces to inspire revolutionary ideas to address the grand challenges of rechargeable Li metal batteries.

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