Effective thermal management remains a persistent critical challenge in large-format lithium-ion batteries, primarily due to issues of internal temperature non-uniformity. Localized heating and pronounced thermal gradients within these systems significantly exacerbate safety hazards and accelerate performance degradation. To address this fundamental issue, this study develops an enhanced coupled electrochemical-thermal model. Grounded in a thermal equilibrium approach and implemented computationally using Python, this model is specifically designed to predict and analyze the spatiotemporal dynamics of thermal inhomogeneity within large-format cells. The computational framework discretizes the battery geometry into representative thermal cells and comprehensively integrates core electrochemical processes—governed by pseudo-two-dimensional (P2D) theory—with three-dimensional heat transfer physics. This coupled approach enables the precise prediction of temperature distributions across diverse operating scenarios. Validation against experimental measurements demonstrates exceptional agreement, with predicted temperature discrepancies consistently maintained below 5%. Collectively, this work provides valuable mechanistic insights and delivers a rigorously validated computational tool. These contributions facilitate the optimization of thermal management protocols and safety strategies throughout the operational lifecycle of large lithium-ion batteries, thereby enhancing their reliability and performance in practical applications.

Electrochemical-thermal model,Large-format batteries,Non-uniform heat,Thermal imbalance