Physics-Driven Modeling of Sodium-Ion Batteries Incorporating Synergistic Adsorption-Insertion Dynamics

Abstract With the accelerated commercialization of sodium-ion batteries (SIBs), the development of accurate physical models has become crucial for optimizing design and supporting commercial development. Traditional SIB modeling often simplifies complex physical processes, failing to accurately capture the battery internal reactions due to the neglect of the adsorption-desorption mechanism in hard carbon (HC). This study introduces a comprehensive Na+ storage model based on a full physical understanding, integrating both the adsorption-desorption (Langmuir kinetics and modified Butler-Volmer equation) and insertion-extraction (Fick diffusion and Butler-Volmer equation) mechanisms for the first time. This dual-mechanism model enables a more precise description of the sodium storage behavior in HC. Validation results show that the model's discharge capacity error is less than 3%, significantly outperforming the single-mechanism model (errors up to 12%). Based on this model, the influence of key parameters in HC electrode design can be accurately analyzed. Moreover, by decoupling the desorption and extraction processes, it is found that adsorption-desorption behavior exhibits faster charge migration characteristics, which will gradually dominate the electrode reaction at high rates or with larger particle sizes. This work not only establishes a full-physics model for SIBs but also provides a reliable simulation tool for battery performance prediction and parameter optimization.