Thermal analysis of high specific energy NCM-21700 Li-ion battery cell under hybrid battery thermal management system for EV applications

Electric vehicles (EVs) have revolutionized the transportation sector by offering a sustainable alternative to conventional internal combustion engine vehicles. Lithium -ion (Li -ion) batteries, particularly the high specific energy Nickel -Cobalt -Manganese (NCM)-21,700 battery cell, have emerged as the leading energy storage solution for EVs due to their high energy density and extended lifespan. However, the efficient operation of NCM21700 cells demands effective thermal management to address the challenges associated with heat generation during charge and discharge cycles. The accumulation of heat within the battery cell can lead to hazards, reduced performance, and accelerated ageing. Therefore, maintaining the temperature within a permissible range is crucial to ensure safe and reliable operation, extending the battery's lifespan and maximizing its performance. This study provides a numerical investigation of the thermal behaviour of NCM-21700 Li -ion battery cells for EV applications. The heat generation of an NCM-21700 cell is estimated experimentally within an insulated environment and this data is used to predict the heat transfer under natural convection through numerical modelling. Based on the heat generation data, we perform a numerical study to evaluate the performance of a Hybrid Battery Thermal Management System (HBTMS) which effectively combines Phase Change Material (PCM) as a passive cooling mechanism and air cooling as an active cooling technique to efficiently manage heat during charge and discharge cycles. The cell spacing, fin spacing, and fin length are optimized for an HBTMS to mitigate heat dissipation. The findings contribute to a better understanding of efficient thermal management strategies, promoting safety, extending battery lifespan, and maximizing performance in EVs.