Investigation of electrochemical-mechanical-thermal coupling characteristics during lithium-ion battery charging based on an enhanced single-particle model

This study develops an electrochemical-mechanical-thermal enhanced single-particle model (ESPM) to describe the coupled behavior of lithium-ion batteries during charging. The model integrates stress-assisted solid diffusion, diffusion-induced stress, electrode-decoupled expansion reconstruction, and lumped thermal correction. The cathode and anode volume changes are separately mapped to cell-level expansion using experimentally constrained structural coefficients, while temperature effects are considered through heat generation, temperature-dependent kinetics, thermal expansion, and mechanical softening. The model was parameterized and validated using a commercial 40 Ah prismatic NCM622/graphite cell. Under the held-out charging rates of 0.7C to 1.5C, the voltage RMSE ranges from 23.43 mV to 31.46 mV, and the temperature RMSE ranges from 0.1553 °C to 0.2677 °C. The RMSE values of free expansion and constrained expansion force range from 11.50% to 17.46% and from 234.14 N to 319.95 N, respectively. Comparisons with SPM and SPMe further indicate that stress-assisted diffusion affects solid-phase concentration redistribution. The proposed ESPM provides a reduced-order framework for analyzing coupled electrical, thermal, and mechanical responses during battery charging.