Improving Battery Pack Safety with an Innovative Fluid for Thermal Management 2021-01-1250

Efficient and safe Lithium-Ion Batteries have undoubtedly become the Holy Grail of the electric vehicle industry. Any OEM’s technical roadmap is currently focused on increasing battery lifetime, energy density, or above all on safety. The battery is definitively becoming a way to differentiate electric vehicle performance. Battery safety is central; any fire is unacceptable and can damage OEM’s image and Battery Electric Vehicle (BEV) acceptance. Therefore, solutions must be developed to cope with this dramatic issue. This paper presents a battery thermal management system, helping to increase battery lifetime, but, above all, making the battery pack safer. This system relies on the use of an innovative dielectric fluid in direct contact with electrochemical cells. Fluid physical properties are designed to accurately maintain the battery pack at a specific temperature in a daily life (fast charging and fast acceleration). Experimental and numerical results demonstrate the performance and the versatility of this solution. The key innovation relies on the fluid behavior when exposed to extreme heat generated during a battery thermal runaway event. Its specific chemical structure prevents fire propagation, even in a severe scenario where common fluids are getting ignite and catch on fire. Electrochemical cells abuse tests have been carried out on several types of cells, such as 21700 cylindrical cells or pouch cells with higher capacity. During nail penetration and overcharging events triggered in tests, it was demonstrated thermal events were avoided. The solution developed is ready to be implemented on a large scale and can be used by any battery pack designer as a tool to improve safety.