Electrochemical impedance spectroscopy (EIS) is an established technique for monitoring and testing of electrochemical systems, including batteries. Parameters related to electrochemical phenomena such as charge-transfer kinetics and mass transport can be estimated from the impedance response over a range of frequencies¹.

The classical description for impedance of an electrochemical system, subjected to a periodic input perturbation, depends upon achieving a steady periodic output state². However, there may be value in analyzing the joint time-frequency response of a dynamic impedance-like output signal under conditions that are not steady periodic³. For example, it has been shown that using a dynamic impedance-like response allows parameter estimation to be carried out in shorter times than waiting for a steady periodic state to be reached⁴. This may be particularly valuable for accessing low frequency (slow) phenomena such as thermodynamic and diffusion effects. As a result, dynamic impedance-like signals may be a valuable tool for real time diagnostics of battery degradation processes.

The objective of this study is to develop time and frequency dependent solutions for existing battery models to further investigate the full dynamic response of the system. Devan et al. has performed transient voltage analysis for a porous electrode model⁵ and short-time current density response for an intercalation particle model⁴. A comparison to the steady periodic response for parameter estimation and the choice of optimum frequencies for measurements will be explored. While the analysis will begin with a simple physics-based model, the goal is to develop a fast and efficient tool for porous electrode 2D models. In particular, the focus will be on the gain in estimating parameters with specific confidence intervals, and mechanism validation from using the transient data compared to steady state models.

References

1. Yu, B. N. Popov, J. A. Ritter, and R. E. White, Journal of The Electrochemical Society, 146, 8 (1999).
2. Ceder, M. Doyle, P. Arora, and Y. Fuentes, MRS Bulletin, 27, 619–623 (2002).
3. Doyle and J. Newman, in Tutorials in Electrochemical Engineering—Mathematical Modeling, edited by R.F. Savinell, J.M. Fenton, A.C. West, S.L. Scanlon, and J. Weidner (The Electrochemical Society, Seattle, 1999) p. 144.
4. Devan and R. E. White, Journal of The Electrochemical Society, 154(2007).
5. Devan, V. R. Subramanian, and R. E. White, Journal of The Electrochemical Society, 152 (2005).