Thermal Management Optimization of a Lithium-Ion Battery Module with Graphite Sheet Fins and Liquid Cold Plates

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Thermal Management Optimization of a Lithium‑Ion Battery Module with Graphite Sheet Fins and Liquid Cold Plates Guohua Wang1,3 · Qing Gao1 · Yuying Yan2 · Yongzhen Wang1 Received: 25 February 2020 / Accepted: 22 October 2020 © China Society of Automotive Engineers (China SAE) 2020

Abstract Temperature uniformity of lithium-ion batteries and maintaining the temperature within the range for efficient operation are addressed. First, Liquid cold plates are placed on the sides of a prismatic battery, and fins made of aluminum alloy or graphite sheets are applied between battery cells to improve the heat transfer performance. Then a simulation model is built with 70 battery cells and 6 liquid cold plates, and the performance is analyzed according to the flow rate, liquid temperature, and discharge rate. Finally, the results show that temperature differences are mainly caused by the liquid cold plates. The fin surface determines the equivalent thermal conductivity of the battery. The graphite sheets have heterogeneous thermal conductivity, which help improve temperature uniformity and reduce the temperature gradient. With lower density than the aluminum alloy, they offer a lower gravimetric power density for the same heat transfer capacity. In addition to the equivalent thermal conductivity, the temperature difference between the cooling liquid and battery surface is an important parameter for temperature uniformity. Optimizing the fin thickness is found to be an effective way to reduce the temperature difference between the liquid and battery during cooling and improve the temperature uniformity. Keywords  Thermal management · Lithium-ion battery · Liquid cold plate · Temperature uniformity

1 Introduction Powertrain electrification has been promoted as a potential approach to reducing greenhouse gas emissions [1]. Electric vehicles are predicted to reduce greenhouse gas emissions by up to 20% as a direct replacement of conventional vehicles, which leads to an additional 40% reduction if the electricity is generated by renewable energy [2]. Lithium-ion batteries serve as the power source of EVs; they offer a high energy/power density, long service life, and environmental friendliness. The battery performance is largely affected by temperature [3]. Various strategies have been proposed for battery thermal management to ensure that the operating temperature is in the optimum range [4]. These strategies * Guohua Wang [email protected] 1



State Key Laboratory of Automotive Simulation and Control, Jilin University, Changchun 130025, China

2



Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK

3

Department of Thermal Engineering, Jilin Univeristy, Nanling Campus, Changchun 130022, China



can be divided into five categories based on the medium: air cooling/heating, liquid cooling/heating, phase change materials (PCM), heat pipes, and a combination of the above strategies. With air cooling, the optimum temperature is maintained by adjusting the air volume and temperature. He et al. [5] and He an