Heat Generation Characteristics of Lithium‐Ion Batteries for Grid‐Forming Energy Storage Under High Temperature Differences and High Discharge Rates

Grid‐forming energy storage system is often operated in environments with large temperature fluctuations and must meet both the requirements of conventional low‐rate scheduling and high‐rate grid support. These wide‐temperature‐range and multirate operating conditions can lead to changes in battery capacity degradation and heat generation mechanisms. This study developed a P2D electrochemical‐3D thermal coupling model for lithium‐ion batteries for grid‐forming energy storage system, distinguishing the physical parameters of the anode, cathode, and separator domains, and establishing separate heat sources for reversible heat, polarization heat, and Ohmic heat. After experimentally validating the model, the heat generation characteristics of the battery were analyzed under temperatures ranging from −15 to 45°C and discharge rates from 0.1 to 10 C. The results indicate that low temperatures significantly increase total heat generation and Ohmic heat in the separator; at high rates of discharge, polarization heat dominates, while reversible heat accounts for as much as 72% during discharge at 45°C and 0.1 C. In terms of spatial distribution, high rates of discharge cause extremely uneven internal heat generation, with the anode accounting for 66% of the heat generated. Furthermore, at −15°C and a 10 C discharge rate, the capacity dropped to 10% of that at room temperature; discharges at 6–10 C between 5 and 45°C all exceeded the 40°C safety threshold. These results reveal the heat generation and decay patterns under various operating conditions, providing a theoretical basis for evaluating extreme discharge capabilities and formulating thermal management strategies.