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Hossein Yadegari, PhD
Department of Mechanical and Industrial Engineering
University of Toronto
h.yadegari[at]utoronto.ca
Research
Operando spectroscopy for degradation mechanisms studies
Cycling life is one of the key aspects in energy storage and conversion systems regarding their practical applications. The cycle life of a battery, for example, is generally restricted by gradual degradation of electrode materials and/or cell electrolyte during consecutive discharge-charge cycles. Various degradation mechanisms may occur in different systems depending on their specific characteristics. The chemical mechanisms governing the degradation reactions should be understood in order to prevent these reactions to occur. As a major part of my research, I design and develop in-situ and in-operando analytical techniques to reveal the chemical and electrochemical reaction mechanisms in these systems.
Advanced electrode materials for energy storage and conversion
The demand for renewable energy resources has been increasing as a consequence of fossil fuels depletion and global warming. As a result, there is an instant need for high-efficiency energy storage devices (i.e. batteries and supercapacitors) to store the energy from renewable resources such as solar and wind when they are available and deliver them on demand. However, currently available battery systems fail to meet the required demands for energy storage. A part of my research is therefore focused on design and develop advanced electrode materials to enhance the efficiency and performance of these systems. The primary purpose of my research is to develop high-performance electrode materials for application in metal-O2 batteries and electrochemical supercapacitors. I design and fabricate 2D and 3D air electrodes with mesoporous microstructure to enhance the energy efficiency and cycle life in Na- and Li-O2 cells. In addition, I design and fabricate efficient and low-cost catalysts for application in metal-O2 batteries.
Electrocatalysis in non-aqueous electrolytes
Alkali metal–oxygen (Li– and Na–O2) batteries have attracted a great deal of attention over the past decade. The high theoretical energy density of these battery systems which is comparable with that of gasoline makes them desirable candidates for potential applications in electrical transportation. However, multiple basic challenges associated with the working mechanisms of alkali metal–oxygen cells limit their cycle life and hinder them from further development. The large overpotential required for charging the cells with a peroxide discharge product is among the major challenges facing the alkali metal–oxygen batteries. An extensive amount of effort has been devoted to develop and employ solid-state catalysts in order to reduce the charging overpotential and improve the cycling stability of the cells. Nevertheless, the underlying mechanism behind the catalytic activity remains controversial due to the different nature of oxygen reduction and evolutions reactions (ORR, OER) in non-aqueous cells compared to those in classic aqueous based reactions. I use analytical spectroscopic techniques to provide insight toward the mechanism of catalytic activity in non-aqueous systems. The results of these studies contribute to develop more efficient air electrodes for peroxide alkali metal-oxygen batteries.
