A pseudo-2-dimensional model of the nonlinear impedance response of a nickel-iron battery

Abstract

Pseudo-2-dimensional (P2D) models are computationally efficient tools for accurately predicting the battery’s performance. These models have been widely used to simulate lithium-ion batteries, but their application can be extended to other battery chemistries. Nickel-iron batteries are one type of storage that is regaining attention due to their durability and large theoretical specific capacity. However, their tendency to form an irreversible passivation layer and hydrogen gas leads to lower overall specific capacity and charging efficiency. Physics-based models of impedance spectra can help understand and interpret mass transport, thermodynamic, and reaction processes in a system. Batteries, being nonlinear systems in nature, can be better evaluated through nonlinear electrochemical impedance spectroscopy (NLEIS), an extension of the traditional electrochemical impedance spectroscopy (EIS), to break the degeneracy of a linear model. Base case parameters were used to generate the impedance spectra by applying moderate-amplitude current modulations. This work compared the first harmonic linear response and the second harmonic nonlinear response simulated through a P2D model. Unlike EIS, the nonlinear response shows sensitivity to charge transfer symmetry. At the negative electrode, the nonlinear response demonstrates strong dependence on the kinetic properties, suggesting that the overall battery performance is mainly influenced by the processes at the negative electrode-electrolyte interface.