Date of Award

8-2022

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Materials Science and Engineering

Committee Chair/Advisor

Ulf D. Schiller

Committee Member

Rajendra K. Bordia

Committee Member

Jianhua Tong

Abstract

Modern electric vehicles and consumer electronics applications demand high specific energy from Li-ion batteries, which can be charged and discharged faster. In the search for high specific energy, researchers have tried to make thicker battery electrodes which contain a greater proportion of active material. While chemical and structural modification of electrodes can help to increase the electronic conductivity of active material, the microstructure of porous electrodes can be engineered to enhance ion transport for fast charge and discharge. Previous research has shown that macropores introduced by directional freeze tape casting can enhance the performance of thick porous electrodes. For instance, Azami-Ghadkolai et al. have studied freeze tape cast molybdenum doped lithium titanate cathodes and demonstrated that macropores in an anisotropic hierarchical structure can mitigate the depletion of lithium salt at the current collector side of the electrode. Their study also highlighted the utility of numerical simulations of charge transport in porous electrodes. However, they only considered macrochannels of the same width as the active material
columns.


The main research goal of this thesis is a numerical investigation of the impact
of the channel width on rate capability and specific energy of hierarchical porous
electrodes. By leveraging the finite element software COMSOL, we developed three different models with channel widths equal to, half, and double the width of the cathode walls, respectively, while the total width of the cathode was kept constant. The numerical results indicate that the narrow channel model exhibits the best performance in terms of specific energy at high discharge rate amongst the three models. The thinness where there is equivalent mass loading makes the narrow channel model a promising microstructure that can be targeted in experimental electrode fabrication.

Available for download on Saturday, August 12, 2023

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