Spatial heat generation and temperature distribution in cylindrical lithium-ion batteries: Insights from a multi-domain electrochemical-thermal model

Lithium-ion batteries (LIBs) are widely used for power and energy storage, yet their performance is highly sensitive to operating temperature. Most existing models oversimplify heterogeneous heat generation across different components, thereby failing to capture the spatial variability of heat distribution and leading to misidentification of local hotspots. To address these issues, this work develops a multi-domain electrochemical-thermal coupled model for the cross-section of multi-layer structures in cylindrical LIBs. At the microscopic scale, local hotspots emerge at the negative electrode-separator interface, acting as one of the major triggering factors for thermal runaway. At the macroscopic scale, under natural convection conditions, the core-to-surface temperature difference increases from 0.36 °C at 0.5C to 2.07 °C at 2C. Under enhanced cooling, this temperature difference rises further to 3.55 °C at 2C. As the discharge rate increases, the dominant heat source shifts from reaction heat to ohmic heat. Based on quantified internal temperature differences and peak temperatures, the uniform and safe regions are defined. The overlapping range of convective heat-transfer coefficients from the two regions provides a practical design window for heat-dissipation strategy optimization. By selecting cooling conditions within this window, LIBs can maintain highly uniform operating temperatures while ensuring safety. These findings improve the accuracy of battery thermal management systems and lower thermal runaway risk under practical operating conditions.