Degree Type

Thesis

Date of Award

2020

Degree Name

Doctor of Philosophy

Department

Materials Science and Engineering

Major

Material Science and Engineering

First Advisor

Steve W Martin

Abstract

With the rapidly changing shift in energy storage paradigm, solid state sodium system have gained a lot of attention as an reliable, safe, and low cost option for grid scale energy storage by enabling the use of high energy density of sodium metal anodes. To achieve this effort, a solid state electrolyte must be developed that exhibits a high ionic conductivity, sable in contact with sodium metal, and is cost-effective to produce at an industrial scale. Where poly-crystalline materials exhibit ionic conductivities greater than 10-4 (Ωcm)-1 at room temperature, these materials lack the stability and processability needed for commercialization. Glassy solid state electrolytes offer a comparable ionic conductivity, with superior resistance to dendrites, improved stability and processability. The properties of glassy materials are directly related to the underlying short range order (SRO) structure, which can be modified through compositional changes to ultimately engineer the properties required electrolyte applications. This compositional dependence is strongly observed in mixed anion systems, such as mixed oxy-sulfide (MOS), and mixed-oxy-sulfide-nitride (MOSN) glasses which has been related SRO glass structure. The addition of oxygen to Na4P2S7-xOx glass system improved the thermal, chemical, and electrochemical stability, while negatively impacting the ionic conductivity. Nitrogen was incorporated into the MOS glasses via the ammonolysis process to produce a range of MOSN glass chemistries, Na4P2S7-xOx-3yN2y, with improved stability. The SRO structure of these materials were investigated with FT-IR, Raman, and 31P NMR spectroscopies to provide a clear structure-property relationship in these mixed-anion glasses.

DOI

https://doi.org/10.31274/etd-20200624-70

Copyright Owner

Steven James Kmiec

Language

en

File Format

application/pdf

File Size

311 pages

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