5. Electrochemical energy storage systems (ORNL, UT Austin)

Research thrusts: Fast & reliable solution of multiphysics/multiscale problems; Validation, adaptation, and management of models
Research sub-thrusts: Accurate, robust discretizations; Error estimation; Inadequacy modeling

Figure 8: Electrochemical impedance spectra over a representative range of frequencies for a higher-fidelity model (solid blue line) and its equivalent cicuit (dashed green).

ORNL developed software to support the research in electrochemical energy storage systems. The code is open source, available on github. It provides a straightforward API that aligns well with real-world electrochemical experiments and is designed to ease development and testing of numerical models for energy storage devices. In collaboration with UT Austin, ORNL examined the inadequacy of lower-fidelity equivalent circuit models for predicting the behavior of the supercapacitor double-layer. For that purpose, we investigated various techniques to characterize the electrochemical behavior of storage systems which lead us to perform full impedance spectroscopy analysis on our high-fidelity models (a unique capability!). Fig. 8 plots the frequency response of the finite-element model next to a simple resistor-capacitor equivalent circuit, demonstrating that the equivalent circuit model is unable to capure the higher frequency behavior of supercapacitors.