Mastering battery thermal management: a major challenge
Khadija El Kadri Benkara is a research scientist at UTC-Roberval Laboratory and is responsible for all electrical energy research platforms. One of her areas of research is dedicated to optimising battery performance and lifespan. She is working on several battery research projects (CALIX, HIPOBAT, etc.) and is currently supervising a thesis on the thermal aspects of batteries.
“Batteries as a source of energy storage have contributed significantly to the development of our technological devices such as mobile phones and computers, renewable energy networks and electric mobility (electric vehicles, electric trains, electric planes, electric bikes, etc.), which are contributing to the global energy transition,” she says.
However, batteries are not without risk. For example, lithium-ion batteries, which are the most widely used, can cause fires due to uncontrolled heating. “In our studies, our goal is to fully understand these heat transfer phenomena and the thermal behaviour of batteries. To do this, we use calorimetry, the science of measuring heat exchanged during a physical process,” she says.
Numerous studies show that temperature is one of the main factors influencing, among other things, ageing and therefore battery life. “Batteries do not like extreme temperatures. They function best at around 25°C, much like the human body (at 37°C). If the temperature rises significantly, there is a risk of overheating, and if the temperature drops below 0°C, the battery loses its performance. Temperature therefore has a direct impact on what is known as the SOH (state of health) and SOC (state of charge) of the battery,” explains Khadija El Kadri Benkara.
Detailed study of battery thermal behaviour
How can ‘heat’ be measured in concrete terms? “First, we set up surface temperature measurements using thermocouples or infrared cameras. We also implemented a temperature measurement inside the battery, as surface measurements are not always representative of the actual temperature of the battery. However, accessing the internal temperature of the battery remains a delicate and intrusive method. In addition, the temperature distribution within the battery is far from uniform. To obtain an accurate temperature measurement, we need to increase the number of measurement points and therefore the number of sensors. To this end, we are collaborating with the Collège de France, which is integrating fibre optic temperature measurement inside the battery as part of the HIPOBAT project. Finally, we have developed tools to directly measure the heat flow generated by the battery. Measuring heat during battery operation is an important step. We use flow meters with calibration methods to improve the accuracy of our measurements. This work is being carried out as part of a thesis co-funded by the Hauts-de-France Region (the ETHERION project) and the international research project IRP ADONIS in partnership with the Lebanese University,” she explains.
Temperature is a key parameter for understanding how batteries work, in terms of their lifespan, health and performance. The laboratory recently acquired an isothermal calorimeter.
This equipment, funded by CPER EE4.0 (CALIX project), was recently developed by THT (Thermal Hazard Technology) for pocket, prismatic and cylindrical batteries. “Very few laboratories have this type of equipment, so it will be extremely useful for developing our platforms and testing methods. Isothermal calorimetry will enable us to analyse electrochemical phenomena in isothermal conditions (i.e., with the battery temperature controlled at a constant value) in greater detail. This makes it possible to control the battery temperature and to carry out tests under conditions conducive to model validation, by decoupling the phenomena and maintaining real control over the temperature,” she explains.
The state-of-the-art calorimeter will enable the team to take their experiments further. “We will be able to continue developing our knowledge of batteries for applications with high constraints, such as high-power or fast-charging batteries. In these two cases in particular, the thermal behaviour of the battery has a significant impact on its performance and battery service life. We can also use calorimetric measurement to obtain proof of concept for the SEI Solid Electrolyte Interface formation model. This formation is very important in the battery cell production phase in the development of gigafactories,” concludes Khadija El Kadri Benkara.
MSD
