Measurement of heat generation rate in lithium-ion battery cell under extreme environments

Abstract

Accurate heat-generation data are essential for designing battery thermal management systems (BTMS), yet experimental measurements under extreme conditions defined here as sub-zero ambient temperatures (−20 °C) combined with high discharge loads (≥10C-rate) remain limited in the literature. This study addresses this gap by quantifying surface heat flux (heat flow per unit area in W m−2) and heat-generation rate of a 5.5 Ah LiMn₂O₄/graphite pouch cell discharged at 2C, 5C, 10C, and 20C-rate (C-rate denotes the normalized discharge rate as 1C-rate corresponds to a 1-h full discharge, 2C-rate to a 30-min discharge, and 20C-rate to a 3-min discharge) in an environmental chamber at −20 °C, 0 °C, and 20 °C. Sensor placement was determined through emissivity-corrected thermal imaging, and measurements were obtained using a calibrated thermoelectric heat-flux sensor with ±3% accuracy. Peak heat flux reached 839.2 W m−2 at −20 °C and 20C-rate, while the minimum was 38.7 W m−2 at 20 °C and 2C-rate, with overall uncertainty within ±4–6%. Total heat and average heat-generation rates were calculated by integrating the measured flux over discharge time, and a physics-guided polynomial fit was applied for interpolation across the tested temperature C-rate space. The results provide reliable, design-ready heat-generation data for modelling BTMS performance in high-power and cold-climate applications, where existing literature remains limited.