Thermally Conductive Adhesives

When we look at the battery pack design for a vehicle we want to minimise the overall weight and hence need the cells to work structurally as part of the pack design. This leads us to Thermally Conductive Adhesives (TCAs) as a means of fixing cells to cooling systems and bonding them into a battery pack. A Thermal Interface Material and an Adhesive.

There are three primary chemical options for TCAs, each offering a different balance of thermal conductivity, flexibility, and structural strength:

1. Silicone Adhesives – known for their excellent thermal stability (operating from -50°C to 200°C) and extremely low modulus:

• Pros:
  • high flexibility allows them to absorb thermal cycling stresses and dampen vibrations, protecting fragile components like pouch cells from mechanical damage
  • exhibit strong resistance to “pump-out” (being squeezed out by vibrations) compared to non-curing silicone greases
• Cons:
  • don’o’t provide the high structural bond strength of other chemistries
  • potential outgassing of siloxanes can interfere with sensitive electronics

2. Epoxy-based Adhesives – designed for rigid structural bonding and are frequently used in Cell-to-Module (CTM) and structural battery pack assemblies:

• Pros:
  • high mechanical strength (high modulus) and exceptional shear and peel strengths, often exceeding 20 MPa on metals
  • can act as protective barriers and firewalls, contributing to the pack’s crashworthiness
• Cons:
  • epoxies are generally brittle, particularly at low temperatures, and will transfer mechanical stress to the battery cells during thermal cycling
  • their permanent, high-strength bonds make pack rework or disassembly very difficult

3. Polyurethane (Urethane) – these adhesives serve as a balanced mid-point between the high strength of epoxies and the flexibility of silicones:

• Pros:
  • provide a medium modulus, offering a blend of elastomeric flexibility to absorb stress and sufficient structural strength to maintain joint integrity
  • lower density also makes them ideal for lightweighting applications in Module-to-Pack bonding
• Cons:
  • limited to moderate operating temperatures (generally capped around 130°C)
  • can be sensitive to moisture during the uncured application phase

Below is a comparative table of general Thermally Conductive Adhesives (TCAs). Categories giving a range of thermal conductivity and a general strength/modulus description. Plus some specific commercial formulations detailing their thermal conductivity versus their modulus/strength profiles:

References

1. Thermally Conductive Adhesives (TCAs) for EV Battery Packs: A Technical Guide for Design Engineers, GLUESPEC
2. Adhesives and Sealants in Battery and Hybrid Electric Vehicles, ASC
3. Debonding-on-Demand Adhesives for EV Battery Modules Market, FMI
4. Rodrigues, V.C.M.B.; Kasaei, M.M.; Marques, E.A.S.; Carbas, R.J.C.; Szymanski, R.; Olive, M.; da Silva, L.F.M. Thermally Triggered Interfacial Debonding for Lid-to-Frame Disassembly in Electric Vehicle Battery Packs. World Electr. Veh. J. 2026, 17, 59.