Date of Award

Fall 2020

Document Type

Open Access Dissertation

Department

Chemical Engineering

First Advisor

Ralph E. White

Abstract

Energy storage market transformed by utilization of lithium-ion batteries, will demand high and affordable deliverable energy in the near future which it would be impossible for the current employed technologies to meet those needs Among new generation of lithium batteries, high theoretical energy density, good low-temperature performance, and abundance of inexpensive nontoxic raw material, make the lithium-sulfur batteries (LiS) a promising candidate to outperform the current lithium-ion batteries and transform the technology of the future. However, the problems and challenges that LiS batteries are currently facing with, which stem from the inherent complex mechanism of these cells, are hindering their successful development, commercialization, and implementation.

In this regard, mathematical models can be used as a powerful tool to provide a better mechanistic understanding, address the issues and challenges, clarify the existing misconceptions and guide experimental studies toward an optimum configuration and performance. In the present research study, different aspects of the performance of LiS cells including lithium capacity loss, multicomponent transport, phase change and precipitation, porosity and volume change of the cathode, and the shuttling process are thoroughly studied through proposing mathematical models to gain a mechanistic understanding of the phenomena occurring inside the cell. First, the focus will be on the anode side of the cell and developing a mechanistic model for the solid electrolyte

interphase (SEI) growth on the anode surface. As dissolution, diffusion, and shuttling of the dissolved polysulfides result in parasitic reactions and substantial capacity loss for LiS cells, in the second step and in order to study the shuttling phenomena as the main performance issue and source of capacity loss of the LiS cells, a 1D porous electrode model is developed for the entire LiS cell which uses a semi-empirical loss approximations for the shuttling induced capacity fade mechanism to dig deeper into the underlying mechanism and investigate this process. Finally, by focusing on the future of the LiS cells, a simple lumped model with minimum number of parameters is proposed and developed based on the idea of having an empirical state of charge (SOC) expression for the LiS cells.

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