What role do thermal interface materials (TIMs) play in EV battery systems?

Automotive manufacturers rely on thermal interface materials (TIMs) to prevent overheating in electric vehicle (EV) batteries. TIMs improve thermal regulation across traction packs by optimizing heat transfer between key components and supporting effective dissipation.

This article discusses where and how TIMs are applied in EV battery packs to enable faster, safer charging, maximize range, and extend battery life. It highlights TIMs commonly used in battery systems — from gap fillers and thermal pastes to flexible graphite sheets and thermally conductive adhesives and tapes. It also explores key design considerations and integration challenges while spotlighting emerging solutions and application-specific materials.

Where TIMs are applied in EV battery packs

As shown in Figure 1, EV manufacturers apply TIMs at critical thermal interfaces to minimize temperature gradients and prevent overheating.

Figure 1. An illustration of TIM placement between EV battery modules and a liquid-cooled cold plate. The TIM layer improves thermal contact, facilitating efficient heat transfer from the battery cells to the active cooling system. (Image: IDTECHEX)

TIMs are placed between cells, modules, and cooling plates to optimize heat transfer and between battery enclosures and thermal management components to facilitate pack-level dissipation.

TIMs can replace mechanical fasteners in certain structural battery designs, improving heat conduction and integration in cell-to-chassis architectures. Although embedding battery packs into the chassis reduces weight and frees up space, precise thermal and mechanical coupling is required to ensure structural integrity and maintain reliable thermal performance.

Types of TIMs used in EV battery systems

Suppliers offer many different types of EV battery TIMs. As shown in Figure 2, gap fillers conform to uneven surfaces, displace air pockets, and reduce thermal resistance between cells, modules, and cooling components.

Figure 2. An illustration of a thermal gap filler applied between a heat-generating component and a cooling element. The TIM layer conducts heat away from the component, improving thermal contact and enabling uniform dissipation. (Image: Saint-Gobain)

Depending on the formulation, gap fillers offer thermal conductivities up to 3.5 W/m·K, with varying performance between 1 and 2K chemistries. Gap fillers facilitate uniform heat dissipation, prevent localized hotspots, dampen vibration, and support cell compression — significantly improving mechanical stability and reducing structural stress.

Additional TIM types used in EV batteries include:

Thermal pastes and greases fill microscopic air gaps between tightly interfacing surfaces such as battery cells and cooling plates. These viscous compounds improve interfacial contact and increase thermal transfer efficiency in compact assemblies.
Thermally conductive adhesives and tapes bond cells to cooling plates in structural battery designs while providing dielectric insulation and mechanical stability. Notably, adhesives eliminate the need for fasteners and maintain consistent thermal contact under dynamic conditions.
Flexible graphite sheets provide high in-plane thermal conductivity. These materials isolate heat between adjacent components and limit thermal propagation during rapid charging or abnormal operating conditions. They maintain consistent thermal paths while compensating for manufacturing tolerances. Although still used in some applications, liquid-dispensed gap fillers increasingly replace gap pads in high-volume EV manufacturing.

As shown in Figure 3, thermal or gap pads are conformable solid or semi-solid sheets placed between components with surface irregularities.

Figure 3. Pre-cut thermal pads conform to surface irregularities and maintain consistent heat transfer across component interfaces. (Image: BatteryDesign)

Design considerations and integration challenges

Achieving uniform thermal performance with TIMs can be challenging in densely packed traction packs. Variations in geometry, surface finish, and assembly tolerances disrupt consistent thermal contact and reduce heat transfer efficiency across interfaces.

Maintaining contact during high-speed manufacturing is difficult even with well-matched materials, particularly when precise placement is required. Excessive compression or misalignment can further degrade thermal interfaces and damage sensitive components.

Another concern is long-term reliability. Thermal cycling, vibration, and exposure to coolants such as glycol can degrade TIM properties over time, increasing thermal resistance and reducing heat transfer efficiency.

Thermal cross-talk between adjacent cells presents additional challenges. In high-density packs, lateral heat transfer can raise the temperature of neighboring cells and increase the likelihood of cascading failure. As a result, TIMs must conduct heat efficiently to cooling systems while limiting lateral propagation and maintaining dielectric isolation.

Emerging solutions and application-specific TIMs

Many automotive manufacturers are integrating hybrid TIMs with metallic fillers or embedded heat pipes into EV battery traction packs to address these challenges. This approach increases thermal conductivity while maintaining mechanical compliance and production compatibility. These materials are often combined with encapsulants, dielectric coatings, and foams as part of integrated thermal management systems.

Suppliers such as Sika, Saint-Gobain, and 3M offer TIMs engineered for EV applications. Their solutions span silicone-free gap fillers for glycol-exposed environments, UL94 V-0 fire-rated materials that meet automotive safety standards, and custom die-cut solutions for irregular surfaces and complex battery geometries.

Summary

TIMs integrated into EV battery traction packs help manage temperature, prevent overheating, and optimize charging performance. Applied at key battery interfaces, they support uniform heat transfer and structural integration, particularly in cell-to-chassis designs. TIMs span a range of chemistries and formats, such as gap fillers, thermal pastes, graphite sheets, and adhesives.