The effects of molecular composition on thermal, electrochemical, and mechanical properties of hyperbranched polymer electrolytes

Bolar-Gastony, Maria Mercedes (2022) The effects of molecular composition on thermal, electrochemical, and mechanical properties of hyperbranched polymer electrolytes. Doctoral thesis, Northern Arizona University.

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Abstract

This dissertation examines how changing the hyperbranching density and structure of polymer host backbones affects the physical properties of solid state polymer electrolytes. The structure of interest in this dissertation is the hyperbranching polymer backbone, which includes tetrabranching and tribranching architectures of varying hyperbranching densities. For a series of poly(ethylene glycol)-based polymers, we consider how molecular architecture impacts the electrochemical, thermal, and mechanical properties of the electrolytes on both the bulk and macromolecular scales. For both architectures, decreasing hyperbranching densities lead to improved conductivities (tetra- at 9.45 • 10-4 S/cm and tri- at 1.95 • 10-3 S/cm at 80 ºC) and improved shear storage moduli (tetra- at 0.63 MPa and tri- at 1.24 at 90 ºC). While having superior ionic conductivity and shear strength, the tribranching electrolytes were not compatible with lithium, which is a necessity for lithium-ion battery application. Following successful synthesis and material characterization, the tetrabranching electrolytes of various hyperbranching densities and structures are further probed as electrolytes in lithium-ion batteries. This series showed improved cycling performance with decreasing hyperbranching density (specific capacity of 1175 mAh/gSi after 50 cycles), with improved energy storage capabilities relative to the liquid control electrolyte (763 mAh/gSi after 50 cycles). Ultimately, the solid state polymer electrolytes synthesized in this work are promising candidates for further use in energy storage devices due to their observed thermal, electrochemical, and mechanical stabilities.

Item Type:	Thesis (Doctoral)
Publisher’s Statement:	© Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords:	Hyperbranched Polymers; Lithium-Ion Batteries; Lithium-Ion Transport; Polymer Branching Density; Polymer Electrolytes
Subjects:	Q Science > QC Physics
NAU Depositing Author Academic Status:	Student
Department/Unit:	Graduate College > Theses and Dissertations College of Engineering, Informatics, and Applied Sciences > Civil Engineering, Construction Management and Environmental Engineering
Date Deposited:	08 Jun 2023 15:50
Last Modified:	04 Jul 2023 08:30
URI:	https://openknowledge.nau.edu/id/eprint/5986

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