Experimental Investigation of Air Cooling on LiFePO4 Pouch Cells: Effects of Temperature Distribution on Discharge Performance

Abstract

Abstract. The increasing demand for Li-ion batteries in electric vehicles (EVs), electronics, and drones underscores the critical need for effective thermal management to prevent performance degradation. While extensive research exists on cooling methods, a significant gap remains regarding the direct impact of surface temperature gradients on discharge duration. This study experimentally investigates the discharge performance of a LiFePO4 pouch cell by analyzing its surface temperature distribution. The cell was discharged at rates from 0.5 C to 2.5 C under varying convective cooling conditions. This study prioritizes discharge performance because low-power two-wheeler EVs and drones experience high thermal stress during discharge. Using infrared thermography, we precisely mapped surface and tab temperatures to locate hotspots and quantify thermal non-uniformity. Key findings reveal that increasing air flow from 0.0054 m3/s to 0.0189 m3/s effectively limits the surface temperature gradient to below 5 °C, mitigating thermal hotspots and significantly enhancing discharge duration. This controlled cooling resulted in up to a 7% improvement in cell discharge capacity for a voltage drop to 80% of the rated capacity. The study demonstrates that discharge performance is critically influenced by temperature non-uniformity, cooling rate, and state of charge. Thermographic imaging at a 1.75 C load under natural convection, for instance, revealed significant surface temperature variations of 0.5–6 °C within just 10 min. This work provides a detailed thermographic analysis of temperature distribution in LiFePO4 cells, offering critical insights for optimizing thermal management strategies to improve battery performance and longevity.