Capacity fade-aware parameter identification of zero-dimensional model for vanadium redox flow batteries

Abstract

This study proposes a framework for evaluating the electrochemical performance of a vanadium redox flow battery (VRFB) system. First, a numerical solver for redox flow battery is constructed to represent the multi-physics system through systems of ordinary differential equations, which describe the mass conservation of existing vanadium ions. The present numerical model is validated regarding the voltage by comparing its results with the experimental results of previous studies. Second, we identify the parameters in the governing equations using a genetic algorithm with the present numerical model. We select seven parameters by considering the physical meaning of each parameter related to the electrochemical performance. The voltage for the first charging/discharging cycle and capacity fade data are used to identify the selected parameters. The voltage and capacity fade estimated by the parameters identified using the numerical model align with the previous studies. Finally, we analyze the global sensitivity of the identified parameters in terms of the voltage and capacity fade using the total Sobol’ indices because the high sensitivity confirms that the identified parameters have reliable values. As expected, voltage- and capacity-related parameters show high total Sobol’ indices for the voltage and discharging capacity, respectively. Furthermore, we predict the performance of the VRFBs using the identified parameter set and numerical model during 30-cycle operations. Additionally, the performance is compared according to the current density and vanadium concentration in the electrolyte. The proposed framework can be used to evaluate the electrochemical characteristics of developed VRFBs by identifying parameters related to physical performance, such as voltage and capacity fade. Moreover, the identified parameters can be utilized to predict voltage and capacity performance, enabling the optimization of operating conditions and configurations of VRFBs.