Abstract

Lithium sulfur batteries (LSBs) are attracting attention as a next generation energy storage device because of their high energy density (2670WhKg-1), high specific capacity (1675 mAhg-1), low cost and environmental friendliness. However, there are several challenges that need to be overcome before LSBs can be implemented in general applications. This is due to the low electric conductivities of sulfur and lithium sulfide and large volume changes during charge/discharge cycling. Also, most importantly, the dissolution of lithium polysulfides into the electrolyte during cycling leads to capacity decay and low coulombic efficiency. Additionally, these lithium polysulfides can diffuse to the lithium anode through the electrolyte and cause parasitic reactions at the anode (shuttle effect). The objective of this dissertation study is to develop LSB cathode composites to suppress the polysulfide dissolution, improve the performance of the LSB, and study the underlying mechanisms. Here, we employed two strategies: 1) physical confinement and 2) chemical adsorption of the polysulfide species. A nano-porous composite was developed using vat dye particles that confined the polysulfides and accommodated the large volume changes during the charge/discharge process. A gallium-based liquid metal was introduced as an electrocatalyst and a self-healing anchor to adsorb lithium polysulfides and prevent the shuttle effect. The electrochemical performance test showed improved performance using these methods. A variety of characterization techniques, such as X-ray photoelectron spectroscopy, in situ transmission electron microscopy, and theoretical modeling, were used to reveal the fundamental effects of the two strategies proposed. The results obtained in this work provide insights and suggest new research directions towards the fundamental understanding and the development of LSB technologies.

Notes

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Graduation Date

2022

Semester

Spring

Advisor

Kushima, Akihiro

Degree

Doctor of Philosophy (Ph.D.)

College

College of Engineering and Computer Science

Department

Materials Science and Engineering

Degree Program

Materials Science and Engineering

Format

application/pdf

Identifier

CFE0008977; DP0026310

URL

https://purls.library.ucf.edu/go/DP0026310

Language

English

Release Date

May 2022

Length of Campus-only Access

None

Access Status

Doctoral Dissertation (Open Access)

Restricted to the UCF community until May 2022; it will then be open access.

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