Thermal-Flow Analysis for Optimizing Thermal Management of Lithium-Ion Battery

摘要

Due to enhanced environmental regulations, a great attention has been paid to electric vehicles which are eco-friendly vehicles emitting no pollutants. According to Bloomberg's 'Electric Vehicle Outlook 2018' report, one of the ten cars sold in 2025 are expected to be electric cars. In line with the expansion of the electric vehicle market, it is necessary to improve short mileage and long charging time which delays market deployment of electric cars. For this purpose, research and development for increasing the energy density of a battery cell and fast-charging of an electric vehicle have been actively conducted. However, energy density of a battery and the use of high-current fast-charging lead to extensive local heat generation. This results in excessive cell temperature hence decreases the battery's performance, efficiency and lifespan. Since the electrochemical reaction takes place substantially in the vicinity of current collecting tabs, a large temperature gradient appears in the direction of width and length. As a result, the temperature gradient is established in a battery module composed of several battery cells. The temperature gradient inside the battery module deteriorates its performance and structural stability. To tackle this issue, it is necessary to perform thermal management considering spatially-resolved heat generation of the battery cell according to its electrochemical behavior under various operating conditions. In this study, thermal-flow analysis is performed by using a three-dimensional, physical model which resolves spatially a battery module and accounts for heat generation characteristics of a pouch type lithium ion battery. Assuming a battery module composed of 12 cells, thermal flow analysis for air-cooling or water-cooling method is performed. Based on the analysis, an effective cooling method to secure the performance and stability of the battery module is derived. The results developed in this study can be used for thermal management in a battery pack.