Large-capacity energy storage batteries exhibit thermal behaviors markedly different from conventional cylindrical or pouch cells. Due to their multilayer electrode structure, they show pronounced anisotropy in thermal conductivity between through-thickness and in-plane directions. This results in uneven heat diffusion and internal–external temperature gradients that surface sensors cannot capture. Moreover, heat generation varies with temperature and state of charge (SOC) owing to changes in internal resistance. To address these challenges, an equivalent circuit and anisotropic electrothermal coupled model were established, with heat generation and transfer processes analytically derived. Parameter identification was performed through capacity calibration, specific heat and entropy measurements, hybrid pulse power characterization (HPPC), and constant-current charging tests. Results reveal strong temperature dependence of resistance and capacitances, SOC-dependent entropy heat effects, and significant anisotropic thermal resistance arising from the winding structure. The model achieved high predictive accuracy, with surface temperature RMSE below 0.3°C, demonstrating its reliability for thermal behavior prediction of large-capacity storage cells.