Elucidating Rate- and State-Dependent Intercalation Mechanisms in Zn/NaV₃O₈ Aqueous Batteries via Coupled Physics-Based Modeling and Experiment

A physics-based continuum model is developed for analysis of the electrochemical behavior of Zn/NaV₃O₈ aqueous batteries by combining experimental Galvanostatic Intermittent Titration Technique (GITT) data with numerical simulations. The model is calibrated using discharge open-circuit potential (OCP) data and validated over a wide range of current densities from 50 to 2000 mA g⁻¹. Comparison of different OCP formulations shows that the discharge-derived OCP provides the best agreement with experimental voltage profiles, while charge and averaged OCP models result in larger fitting errors. Parameter estimation using Sobol sampling reveals well-constrained reaction rate constants for Zn²⁺ and H⁺ intercalation, with Zn²⁺ insertion dominating the discharge process at the tested operating conditions. The model accurately reproduces discharge voltage behavior across all tested rates, demonstrating strong predictive capability for rate-dependent performance. However, the model cannot capture the large voltage hysteresis observed during charge, suggesting a path-dependent nature of intercalation in Zn/NaV₃O₈. These results show that discharge-based modeling provides reliable discharge predictions while indicating the need for hysteresis-aware approaches to achieve full-cycle simulation accuracy.