Electrochemical–thermal correlation for assessing potential thermal runaway in automotive pouch cells via 3D numerical simulations

Electrochemical and thermal deviations in lithium-ion batteries under harsh C-rate conditions can lead to spatial differences in thermal runaway risk, highlighting the need to understand temporal and spatial distributions of electrochemical–thermal characteristics. In this study, a comprehensive three-dimensional model is established for a 58.3 Ah commercial automotive pouch-type cell to investigate local electrochemical–thermal characteristics under such conditions. The model is rigorously validated by comparing simulation results with experimental voltage and temperature profiles, as well as spatially resolved data from IR-based temperature mapping and MFI-based current density measurements. Simulation results demonstrate that higher C-rates cause greater temperature rises—24.48 °C (1C), 54.88 °C (3C), and 81.08 °C (5C)—and larger local temperature deviations—0.65 °C (1C), 5.23 °C (3C), 13.25 °C (5C)—highlighting the significant thermal effects associated with higher C-rates. By correlating overpotential with heat generation, the analysis reveals the electrochemical origins of temperature rise and thermal inhomogeneity. Component-specific analysis shows that, as the C-rate increases, heat generation in the electrodes—particularly reaction and ionic ohmic heat in the positive electrode, which together account for 51.31 % of the total—becomes more prominent. Moreover, reversible heat significantly rises towards the end of discharge, reaching 59.23 W, comparable to reaction heat. Meanwhile, in-plane distribution analysis reveals that temperature deviations are driven by variations in electrical current density near the tab connections, resulting in localized increases in electronic ohmic heat. The electronic ohmic heat near the tab connections is approximately 2.37 times higher than average, highlighting significant localized thermal effects in these areas.