Abstract

Non-CO2-emitting sources of renewable energy, such as solar and wind, have become quite popular in recent years, and their electricity generation cost at scale has become comparable with that of gas- and coal-fired power plants. However, their intermittent output makes the resultant electricity hard to dispatch in a reliable manner in the absence of grid-scale electrical energy storage (EES) technologies. Redox-flow batteries (RFBs) are promising devices for medium- to large-scale electric energy storage. They are safe, reliable, and portable, and are designed with decoupled power and energy modules, which makes it easy and cost-effective to scale their output to meet user demands. However, a significant challenge in RFBs is low RFB efficiency, one key reason for which is short-circuiting due to active ion species crossover through the membrane between the electrolyte solutions.This dissertation focuses on resolving this obstacle and addresses the aforementioned issues in two parts. The first part focuses on the use of the boundary element method to model ion transfer and Donnan exclusion phenomena in both anion and cation exchange membranes. The results guided the membrane fabrication for homogeneous, heterogeneous, and asymmetric membranes. The second part of the dissertation focuses on studying the mechanism of ion selectivity in AEMs, especially the Donnan exclusion effect. Once the mechanism of the ion selectivity of membranes was well understood, modified AEMs with high ion selectivity were developed and applied in the V-Ce ED-RFB and Ti-Ce ED-RFB. 79% energy efficiency (EE) was obtained after 100 charge/discharge cycles at 50 mA/cm2 in V-Ce ED-RFB. The highly selective AEMs mentioned above exhibited < 0.4 % cation crossover over 1000 hours of operation. The ED-RFB showed 100% capacity retention over 1300 hours of charge/discharge cycles with >70% energy efficiency.

Committee Chair

Vijay K. Ramani

Committee Members

Marcus Foston

Degree

Doctor of Philosophy (PhD)

Author's Department

Energy, Environmental & Chemical Engineering

Author's School

McKelvey School of Engineering

Document Type

Dissertation

Date of Award

Winter 12-15-2021

Language

English (en)

Author's ORCID

http://orcid.org/0000-0002-6824-391X

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