Qiming Tang

Date of Award

Spring 2022

Document Type

Open Access Dissertation

Department

Mechanical Engineering

First Advisor

Kevin Huang

Abstract

Climate change caused by anthropogenic greenhouse gas (GHG) emissions such as the burning of fossil fuels for power generation and industrial processing is affecting the global climate. To address this critical issue, a transition from fossil energy to renewable energy, especially wind and solar, is necessary. However, to successfully realize this transition, a cost-effective and large-scale stationary electricity storage system is indispensable. In this work, a new type of solid-oxide iron-air battery (SOIAB) operated on high-temperature oxide-ion chemistry is studied for this purpose due to its unique cycling characteristics suitable for large-scale Long Duration Electricity Storage (LDES) applications.

In the first part of the thesis, the reduction kinetics of iron oxides to metallic iron with hydrogen as the reducing agent is investigated. Aimed at understanding and ultimately improving the kinetics of FeOx reduction, it covers the kinetic studies on isothermal H2-reduction of iron oxides (derived from Fe2O3) as oxygen carrier in a Chemical Looping Hydrogen (CLH) and SOIAB environments. ZrO2 is purposely mixed with FeOx to prevent Fe particles from sintering, thus obtaining reliable kinetic data. It was found that the reduction of Fe3O4 to Fe follows two consecutive steps and can be reasonably described by phenomenological chemical-controlled and diffusion-controlled kinetic models. In addition, guided by thermodynamics, the desirable starting oxide phases, i.e., Fe3O4 and FeO, were obtained by precisely controlling the ratio of partial pressures of H2O and H2. The kinetics of the two one-step reduction reactions follows nicely the Johnson-Mehl-Avrami (JMA) phase transformation model. The results show that FeO-to-Fe reduction exhibits two orders of magnitude higher rate constant than Fe3O4-to-Fe with half the activation energy. The obtained kinetic parameters provide firsthand data for engineering and design of practical SOIABs.

In the second part of the thesis, the Reversible Solid Oxide Cell (RSOC) in the SOIAB, a critical component determining the performance and lifetime, is studied. In order to improve the electrochemical performance and stability of the battery, a new battery vessel with a better gas tightness has been redesigned, and the anode supported thin electrolyte layer was made by dip-coating technology and modified by Gadolinium Doped Cerium (GDC) infiltration. The electrochemical performance testing results suggest that the modified RSOFC is an important step in improving the battery performance. Compared to dry-pressed cells, the dip coated cells show a power enhancement of 30%.

In the third part of the thesis, two types of new energy storage unit (ESU) materials were designed to enhance reduction kinetics. The slow FeOx reduction kinetics is significantly improved by IrO2 nanoparticles in Fe-based ESU, achieving high cycle efficiency of 73% at a high-power density of 50 mA cm-2 . Furthermore, BaZr0.4 Ce0.4Y0.1Yb0.1O3-δ (BZC4YYb), a proton-conducting perovskite, was also studied as support for Fe particles in ESU. Compared to the traditional oxide support ZrO2, this new support significantly enhances the kinetics of redox reactions, achieving a high round trip efficiency (RTE) of ~65% at 1.5 C (75 mA cm-2 ).

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© 2022, Qiming Tang

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