Cho, Kyu Taek
M.S. (Master of Science)
Department of Mechanical Engineering
There has been a renewed interest in flow batteries, particularly those based on the bromate reduction reaction mediated by fast redox reaction of Br2/Br- which employs highly soluble aqueous multi-electron oxidants, characterized by auto-catalytic accelerated mechanism. This enables, in theory, very high energy densities, in the range of 1000 Ah/kg, which is not only ideal for application in the stationary energy storage sector, but also holds promise for the transport industry, where it can provide a comparable driving range of 500 km, but in less than half the weight of the battery system under use presently (209 kg compared to 450 kg as used in a Tesla Roadster) (Tolmachev). However, the primary research conducted so far for this system is component-level analysis under steady state and ideal operating conditions (employed with an RDE), which does not provide insight into the cell behavior in the actual conditions including variation of reactant concentration and reaction time effects (Tolmachev). In this study, research has been conducted systematically through computational analysis combined with full-cell test to understand the effect of coupled catalytic reaction on the cell behaviors under realistic conditions. From the full-cell based test, a unique behavior induced by the auto-catalytic reaction was found for the first time, and to understand the underlying physics and nature of the system, fundamental study has been conducted through model and actual systems. Characteristic behaviors of three mechanisms (E, EC, and EC') were investigated with modeled systems and the results were compared with respect to reaction time and concentration which are key factors in EC' mechanism. Furthermore, the effect of stoichiometric coefficients of reactants on concentration profiles of reactants and products, and cell potentials was investigated. As a final step, the effect of catalytic reaction was generalized through analytic relations including a non-dimensional parameter which includes key parameters in EC' reaction such as reaction kinetic constant, reactant concentration, and reaction time. In particular, the analytic relations provide conditions for limiting-case analysis i.e. diffusion-limited zone (i.e. general E mechanism is dominant) and kinetic-limited zone (i.e. EC' mechanism is dominant).
Razaulla, Talha, "Study of redox-mediated bromate-based electrochemical energy system" (2018). Graduate Research Theses & Dissertations. 5117.
Northern Illinois University
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