Abstract: Understanding reaction coupled transport in a porous media is very critical for the design and operation of electrochemical engineering systems such as batteries, fuel cells, and electrolyzers. The macro-homogeneous approximation of the porous media results in averaged quantities such as porosity and tortuosity. Traditionally, Bruggeman’s relation is used to estimate the tortuosity of porous media as a function of porosity. Such estimations are not suitable for porous battery electrodes as they grossly underpredict the transport losses in the porous media and are incapable of predicting tortuosity values as a function of various properties of the constituents of the porous media (particle shape, size distribution, binder content, specific surface area).
This talk is focused on electrochemical impedance spectroscopy (EIS) based techniques to (1) experimentally measure the in-plane tortuosity of a porous electrode and its dependence on porosity (2) develop the mathematical analysis in the presence of tortuosity, porosity and double-layer capacitance gradient, and (3) determine the tortuosity and porosity distribution in the through-plane direction. With our EIS based methods, it is possible to quickly screen porous electrodes for their homogeneity, and determine the impact of various manufacturing steps on the transport parameters. For example, the manufacturing of porous electrodes or diffusion media often involve a slurry drying step where fast solvent evaporation may lead to inhomogeneous distribution of binder or other constituents, leading to inhomogeneity in the ionic resistance. Such inhomogeneities are detrimental to the performance of the electrochemical systems and lead to capacity fade. While numerical simulation based methods using 3D reconstructions of X-ray tomography and/or FIB-SEM data of battery electrodes exist, the accuracy of such methods is limited due to their inability to resolve the binder and conductive carbon. Our EIS based method provides a much faster and easier way to measure such parameters and the inhomogeneity associated with them.
Bio: Dr. Bharatkumar Suthar is currently working as a postdoctoral researcher at the Technical University of Munich. He received his undergraduate education from the Department of chemical engineering at IIT-Bombay (2005-09) and worked for two years in ONGC as an Assistant Executive Engineer (2009-11). He received his M.S. and Ph.D. from Washington University in St. Louis, USA, and was also a recipient of the McDonnell International Scholarship during his graduate studies (2011-15). For his Ph.D., he worked under the supervision of Prof. Venkat Subramanian, working on continuum level battery modeling, efficient numerical simulation, and nonlinear optimization methods to derive optimal charging profiles considering various capacity fade mechanisms. After completing his Ph.D., he joined Prof. Paul Kohl at Georgia Tech as a postdoctoral researcher for two years (2015-17), working on control-oriented models for Li-ion batteries suitable for mixed integer linear programming (MILP). In September 2017, he joined Prof. Hubert Gasteiger’s lab at Technical University of Munich (TUM), Germany where he is working on developing EIS-based experimental techniques to determine transport, kinetic, and geometric parameters relevant for electrochemical systems.
This seminar is compulsory for students registered for course CL 702 or CL 704.