Investigation on Electrochemical–Thermal Characteristics of a Large-Capacity LiFePO4 Energy Storage Battery During Charge

The increasing deployment of renewable energy systems has driven the demand for large-scale energy storage, where large-capacity lithium-ion batteries are widely adopted owing to their high energy density. However, thermal safety and degradation remain critical challenges. In this study, an electrochemical–thermal coupled model for a 314 Ah LiFePO4 energy storage battery is developed and experimentally validated to investigate the electrochemical behavior, thermal performance, and charge efficiency during the charge process. The results show that the positive electrode exhibits a substantially higher overpotential than the negative electrode, making it the dominant source of polarization losses during charge. The stacked structure of the prismatic battery induces anisotropic heat conduction, resulting in a non-uniform surface temperature distribution. As the charge rate increases from 0.25 C to 1.00 C, the peak temperature rise increases from 4.2 °C to 15.0 °C, while charge efficiency decreases by 2.43%. Low-temperature operation significantly enhances irreversible heat generation, which accounts for around 80% of the total heat generation. Preheating from −5 °C to 10 °C yields the most significant improvement in charge efficiency. Increasing the negative-to-positive capacity ratio (N/P ratio) from 0.9 to 1.2 reduces the total heat generation rate by 10.68% with only a marginal effect on charge efficiency. These findings provide valuable guidance for the electrochemical and thermal optimization of large-capacity energy storage batteries under practical operating conditions.