Experimental investigation of thermal characteristics of a 12S1P Li-ion NMC-21700 battery module under different environments for EV applications

Abstract

The rapid growth of electric vehicles (EVs) has placed significant emphasis on the performance and safety of lithium-ion (Li-ion) batteries, which serve as the primary energy storage solution. Effective thermal management is crucial to ensure battery safety, longevity, and efficiency, particularly under high discharge rates where excessive heat generation can compromise performance. This study examines the thermal behaviour of a 4 × 3 Li-ion nickel-cobalt-manganese (NCM)-21,700 battery module with a 12S1P configuration. The focus of this study is to mitigate the challenges associated with heat generation at high discharge rates. Experiments are performed on a single NCM-21,700 cell to estimate the heat generation during charge and discharge. Based on this heat generation data, several experiments are performed on the 4 × 3 battery module under different thermal environments. These environments include natural convection, battery case, and phase change material (PCM) inside the battery case. The objectives of this study are to mitigate heat generation and ensure effective thermal management. The findings of these experiments demonstrate that despite being simple and economical, natural convection is insufficient as the temperature of the battery module rises significantly at high discharge rates. Although standard EV applications do not exceed the range of 0.3–0.6 C-rate, our study is focussed on extreme conditions of 1C and 2C rates. The maximum battery cell temperature in the battery module was found to be 48 °C and 53 °C for 1C and 2C discharge rates, respectively. The maximum temperature difference in the battery module was found to be 6 °Cand 13 °C for 1C and 2C discharge rates, respectively. The maximum temperature and maximum temperature difference of the battery module for PCM were reduced to 20 % and 45.45 % compared to conventional natural convection, respectively for a 1C discharge rate. PCM-based cooling provides better thermal uniformity across the battery module, helps to avoid thermal hotspots, and provides even performance across the battery module. The maximum temperature in any battery module is observed at the central cell due to the lesser space for heat dissipation. The results underscore the need for specialized cooling techniques for enhanced battery life, safety, and performance of high-energy Li-ion batteries in EV applications. This study also offers insights into efficient thermal management techniques for EV battery modules.