Thermal performance analysis of liquid cooling system with hierarchically thermal conductive skeleton for large-scaled cylindrical battery module in harsh working conditions

Abstract

Liquid cooling (LC) technology is most widely used in battery thermal management systems. However, for cylindrical battery modules, tailor-made LC components with curved surface and complicated LC structures are required to match the curved surface of the cells. Herein, we design an easily-assembled LC structure by directly embedding thermal conductive silica gel (SG) into a 21.6 V/39Ah cylindrical battery module with thermal conductive plates (TCPs) connected to LC plates (LCPs). This LC strategy avoids the tedious and costly procedure of processing LC components with special specifications, and demonstrates excellent adaptability to battery modules with diversified specifications. By selecting copper plates and flexible SG with 2 wt% expanded graphite as the TCPs and embedding material respectively, a high-efficient thermal conductive skeleton can be constructed, endowing the module center with a greatly reduced thermal resistance of 1.27 × 10−2 m2∙K∙W − 1. In addition, the optimal water inlet velocity and cell distance are determined to be 0.2 m∙s − 1 and 7 mm, respectively. As a result, the maximum temperature (Tmax) and temperature difference (ΔTmax) of the battery module are well maintained within the optimal ranges of 28.9∼41.7 °C and 1.4∼4.7 °C under all working conditions, respectively. Remarkably, even under the harsh working conditions with a 3 C discharge rate under 25, 35 and 40 °C, the Tmax can be controlled below 31.6, 40.3 and 41.7 °C, while the corresponding ΔTmax are only 4.6, 3.8 and 3.8 °C, respectively.