Let’s talk about the adhesion performances of thermal management materials! In this blog post, we will dig deeper into why thermally conductive adhesives are an important point of focus for battery engineers.
If you’ve downloaded our eBook on Battery Thermal Management, you already know our point of view: silicone is the material to leverage for safer and more efficient EV batteries. Therefore, two questions are raised:
- Are adhesive materials important for thermal management?
- Can silicones be proper thermally conductive adhesives?
A polymer adhesive is simply an adhesive that cures or sets in this method, through a chemical reaction that involves small molecules reacting and connecting together. [credits to covascientific.com].
Are adhesive materials needed in thermal management?
As reviewed in our eBook on Thermal Management, there are two different types of battery design projects: one consists of insulating each battery cells (which is great to prevent heat propagation, also known as “thermal runaway”), the other focus on evacuating the heat. This second process is called thermal conduction (or thermal conductivity).
When battery engineers work on thermal conductivity, they always integrate a cooling system (such as a cooling plate) with cooling fluids. This commonly goes under the battery modules and aims to drastically reduce the heat generated by the battery cells.
Problem to solve is: how can I facilitate the conduction between the cell and the cooling plate? There’s one piece missing in this jigsaw.
Thermally conductive materials are then used as an interface between the cooling plate and the battery cells, filling of the roughness/cavities of the surface to prevent air voids. These materials have high thermally conductive capacities, so the heat is directly conducted down to the cooling system to be eliminated.
Battery Module illustration, represented with various type of thermal management materials, including thermally conductive adhesives.
Ok, but… are these materials necessarily adhesives?
The fact is that you really need your cells to be connected to your cooling plate to properly operate the thermal conduction. So the thermally conductive material you put in between should keep the bonding during the whole battery life to ensure the heat conduction when in use (driving, charging). You guessed it, to ensure a 24/24 7/7 bonding between these two elements, you better select thermally conductive adhesives!
Let’s connect the dots: by reading our eBook, you’ve understood that silicone materials are the highest performance technologies available for battery thermal management. In this blog post, you also get the point that thermal conduction can be achieved using thermally conductive adhesives.
The last question to solve is: can silicones be proper thermally conductive adhesives?
Originally, silicone adhesives have a very low thermal conductivity. However, for some applications, such as thermally conductive adhesives, a substantial increase in thermal conductivity is strongly desired. This can be achieved by adding thermally conductive fillers to the formulation while keeping bonding performances.
Specially designed silicone self-adhesives are therefore widely used to achieve these two goals. These silicone adhesives do not require the use of primers on the surfaces beforehand, they are stable and they resist aging across a wide range of temperatures. Silicones can also be purpose-designed to provide the right level of adhesion characteristics, as well as ensure greater safety, in particular, because they are not combustible and act as fire retardants.
Before discussing with an Elkem Silicones expert, you would probably like to explore more web-resources and other blog posts. That’s why we’ve been designing two reference collaterals to help you better understand how silicone can helps with your thermal management project.
The first one is a broad approach to EV Batteries Thermal Management and will help you see clearer how material science can play a role in your project. We also describe why silicone material offers better properties in a unique comparative table, and talk about battery engineering day-to-day challenges, without avoiding the question of volatile content.
The second is a focused expertise white paper that gives A Closer Look at Effects of Silicone Test Methods on Thermal Conductivity Results. We recommend this reading to help you better evaluate your material suppliers by adopting best in class test methods. In this paper, we compare different test methods with results examples made on thermally conductive silicones.