Date(s) - 10/04/2021
9:35 am - 10:30 am
Ankur Gupta, Ph.D.
Assistant Professor of Chemical and Biological Engineering
University of Colorado Boulder
Title: Charging Dynamics of Electrochemical Capacitors
Abstract: Electrochemical capacitors, such as supercapacitors and pseudocapacitors, are energy storage devices characterized by their high-power densities. They consist of porous electrodes, typically made of dispersions of activated carbon spheres, immersed in aqueous, organic, or ionic electrolytes. These devices store energy primarily through physical adsorption of ions, commonly referred to as the electrical double layers. However, the electrode material may also consist of a metallic oxide to store additional energy through an oxidation/reduction mechanism. Over the past two decades, there have been significant advancements in materials of electrodes and electrolytes for electrochemical capacitors. The field has tended to focus on finding different combinations of materials to optimize the energy and power densities. However, an understanding of various transport processes that govern the dynamics of charging/discharging remains unclear.
In this talk, I will first describe a theoretical framework that my group is developing to understand the charging dynamics of electrochemical capacitors. Recently, we analyzed the electrical double layers inside a cylindrical pore of arbitrary radius for an ideally blocking electrode. By utilizing perturbation analysis and direct numerical simulations of the Poisson-Nernsnt-Planck equations, we are able to predict the evolution of electrical potential and ion concentrations in both the radial and axial directions. Our analysis yields two main characteristic features of arbitrary pore sizes: i) a monotonic decrease of the charging timescale with an increase in relative pore size (pore size relative to Debye length); ii) a region of large potential gradients at the mouth of the pore due to charge conservation. We have also extended our analysis for asymmetric ion diffusivities and ion valences. Finally, I will also briefly describe the impact of faradaic reactions on the charging of electrical double layers.
Bio: Ankur Gupta is currently an Assistant Professor in the Department of Chemical and Biological Engineering at the University of Colorado, Boulder, where he is the principal investigator of Laboratory of Interfaces, Flow and Electrokinetics (LIFE). He pursued his postdoctoral research in the Department of Mechanical and Aerospace Engineering at Princeton University. Prior to his postdoctoral position, Ankur completed his PhD in Chemical Engineering from Massachusetts Institute of Technology and his BTech in Chemical Engineering from Indian Institute of Technology (IIT), Delhi. His research interests include interfacial phenomena, complex fluids, multiphase flows and electrokinetics. His work has applications in energy storage, desalination, and lab-on-a-chip technologies. He is the recipient of Outstanding Graduate Teaching Award in Chemical and Biological Engineering at CU-Boulder, Publons Peer-Review Award, Hugh Hampton Young Fellowship, Dow Travel Award and President’s Gold Medal (IIT Delhi).