Battery asynchronous fractional-order thermoelectric coupling modeling and state of charge estimation based on frequency characteristic separation at low temperatures

Due to the widespread application of lithium-ion batteries in new energy vehicles and energy storage fields, fractional-order theory and coupling modeling methods have developed rapidly in battery modeling. This paper proposes an asynchronous fractional-order hot zone coupling modeling method based on frequency domain separation to adapt to battery characteristics. Specifically, in the electrochemical impedance spectroscopy test, the behavior of the battery exhibits different frequency characteristics. Furthermore, a model parameter identification strategy based on frequency domain separation is constructed, and asynchronous parameter updates are achieved through mutually coupled sub-algorithms with different time scales. Additionally, the robustness of the asynchronous fractional-order thermal-electric coupling model (AFO-TCM) was validated under low ambient temperatures, along with its superiority in state of charge (SOC) estimation. Compared to models that do not consider frequency characteristics, the proposed model achieved a reduction in the root mean square error (RMSE) of SOC estimation results by 57 %, 52 %, and 45 % at 0 °C, −10 °C, and −20 °C environments, respectively, under the US06 Supplemental Federal Test Procedure Cycle (US06) driving cycle. This method provides a novel approach to addressing the interdependence between the order of fractional models and temperature.