Kyu, Cho T.
M.S. (Master of Science)
Department of Mechanical Engineering
The demand of electrical energy system is increasing rapidly these days for diverse applications from portable electronics and electrical vehicles to grid-scale energy storage. Lithium-ion battery has been utilized for most of those applications, but due to high cost (about $600/ kWh) and lower energy density (0.37 kWh/kg), the advent of low cost and high performing battery system is required. In this study, we will revisit aluminum-air battery as a promising system which has excellent features such as high energy density of 2.8 kWh/kg, low cost, and safe in nature, but it was abandoned due to challenging issues. One of the key issues is the parasitic corrosion of aluminum anode to evolve hydrogen gas, which significantly decreases the aluminum-air battery’s efficiency.
This research focused on building physics-based mathematical model to define the key controlling parameters for the performance of aluminum-air battery. Especially, the side reaction (i.e. self-corrosion of aluminum to generate hydrogen gas) was analyzed in detail to understand its effect on mass-transfer boundary layer, conductivity of electrolyte, surface concentration of reactive species, and reactive surface area of electrode. Fraction of electrode surface area occupied by the H2 gas bubble was calculated by combing physics-based analytic relations with experimental results. The relations include the physical components such as contact angle formed by bubble on the electrode surface, critical diameter of bubble detached from the surface which was calculated from the force balance among gravity, buoyancy, drag, and surface tension forces, bubble generation rate, Fourier, and Jacob number. And also, the effect of bubble coverage on kinetics was considered by modifying active reactive area in Butler-Volmer equation.
It was found that the effect of side reaction on the cell performance was significant. Due to the self-corrosion of aluminum electrode, open circuit voltage was decreased significantly from theoretical value of 2.7 V to 1.9V. And the side reaction was found to be decreased as main cell current increased. The effect of bubble coverage was significant in the kinetic loss, and it could be reduced by minimizing contact angle formed by gas bubble on the electrode by using hydrophilic material or by using higher flow rate of electrolyte. In the presentation, all the detailed research works conducted for this project will be addressed along with analysis of key results, and it is expected that the results from this fundamental research will not only advance knowledge of bubble dynamics and two-phase flow in the battery system, but also guide future research in this field.
Zhou, Chong, "Analysis of Aluminum-Air Battery By Physics-Based Mathematical Model" (2018). Graduate Research Theses & Dissertations. 7804.
Northern Illinois University
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