By Max VanRaaphorst, Avery Dennison.
The transition toward electrification has boosted the demand for high-performance batteries, which in turn has accelerated the need for scalable thermal management solutions. This is especially true as the industry pushes for higher density and faster charging, both of which heighten the effects of faults such as thermal runaway.
Finding and implementing thermal solutions is a significant engineering challenge. Modern battery packs are dense and complex. Added materials must be effective, lightweight and easy to integrate into production processes. Durable and versatile pressure-sensitive adhesive (PSA) tapes, such as those manufactured by Avery Dennison Performance Tapes, are emerging as a material of choice.
A primer on PSA tapes
PSA tapes have a long track record of success in many industries. They are chosen for many applications thanks to their versatility, durability, light weight, thinness and scalability. Their instant cure allows rapid application via manual or automated assembly lines.
The foundation of a PSA tape is the adhesive, which can be engineered with specific formulations to offer unique profiles for strength and durability. These adhesives are designed to withstand challenging stressors, including heat, chemicals and mechanical force.
Tapes are also customizable, and can provide multiple benefits. For instance, a tape can be laminated to a mica sheet to create a flame barrier, or to a dielectric film to create an electrical insulator. Furthermore, these tapes can be stamped and die-cut to align with the design requirements of any battery pack.
Battery pack engineers have devised numerous applications for PSA tapes. These include cell connection systems, wrapping, venting, compression padding, electrical insulation, gasketing, bonding, sealing and wire management. Increasingly, tapes’ most critical application is thermal management.
Key thermal management challenges
To effectively design for safety and longevity, engineers must overcome three fundamental thermal management challenges. While these are not exhaustive, they are closely related to battery effectiveness, durability and safety.
1. Promoting heat flow while ensuring dielectric strength
Heat needs a low-resistance pathway from cells to cooling components (e.g., cold plates or cooling fins). However, these pathways must simultaneously electrically isolate high-voltage cells to prevent arcing and fire.
Heat transfer is governed by Fourier’s Law of Heat Conduction: Q = k * A * T/X. Conductive thermal resistance (Rth ) is directly proportional to thickness (X). Minimizing thickness while maintaining thermal conductivity (k) is essential to maximize heat transfer rate (Q).
Balancing thermal conductivity with dielectric performance is a classic materials engineering challenge, as the properties that improve conductivity often conflict with those needed for electrical insulation. Engineers need thermal management materials that optimize both characteristics without sacrificing manufacturability.
2. Isolating cells during thermal runaway
Modern battery packs offer minimal room for physical barriers or air gaps between cells. This makes isolating a compromised cell difficult. Engineers need thin materials that can slow or prevent heat transfer long enough for safety systems to respond, minimizing the likelihood of a pack-level catastrophe. Materials like mica are excellent insulators. But they are often frangible and difficult to integrate into automated assembly.
3. Managing vented gases and flames
When a cell fails, internal pressure rises, forcing hot gases, flames and particulates to vent. If this is not managed, additional cells can become compromised and create dangerous pressure levels within the pack. Engineers need flame-resistant barriers that allow controlled pressure relief while reducing the likelihood that a single cell failure escalates into a catastrophic event.
A three-part strategy for prevention and mitigation
Engineers need a multifaceted thermal strategy that improves heat transfer, isolates components, contains runaway events and manages venting.
1. Improving heat transfer while maintaining electrical isolation
The Avery Dennison Volt Tough
line of tape products offers a solution by featuring a dielectric film carrier and acrylic adhesive suitable for bonding between cells, modules and cooling components.
Thermosetting dielectric powder coatings typically require 250 µm thickness to ensure coverage. Dielectric PSA tapes with PET or polyimide films, however, can achieve equivalent or superior breakdown voltage at a thickness of only 85 µm. Assuming comparable thermal conductivity, the 85 µm tape delivers a ~66% reduction in conductive thermal resistance compared to coating. This enables heat to transfer nearly three times faster from the cell casing to the cooling fluid, effectively suppressing peak cell temperatures during fast-charging.
2. Creating barriers that mitigate thermal runaway
Low-thermal-conductivity PSA tapes can laminate and encapsulate insulative materials like mica, aerogel or ceramic paper. This results in a robust construction that provides a superior balance of thermal insulation and mechanical strength. Adhesives capable of withstanding temperatures approaching 500℃ for short durations provide reliable bonding.
Avery Dennison offers specialized, low-release liner formulations that enable these tapes to be used in high-speed, automated assembly without damaging any frangible substrates.
3. Managing vented gases and flames during cell failure
Avery Dennison anisotropic venting tapes offer an elegant solution to managing cell failure. These tapes are strategically adhered to cell vent ports. Using a flame-retardant coating, each side has different burst properties when exposed to flame. During a thermal event, the tape bursts to allow gases and flames to escape into the venting channel, while simultaneously preventing those same gases from affecting nearby cells.
Thermodynamic impact: NMC vs. LFP chemistries
Tape performance must be aligned with the thermodynamic failure modes of the cell chemistry.
- Nickel manganese cobalt (NMC): These cathodes exhibit lower thermal stability and trigger thermal runaway at lower temperatures. Upon failure, the cathode decomposes exothermically, releasing oxygen that feeds combustion, leading to surface temperatures of 800-1050℃. Venting strategies must prioritize flame channeling and particle deflection. Tapes such as Avery Dennison ES 3505 burn through rapidly to divert high-velocity jets into exhaust ducts. Ceramic-rubber hybrid tapes like ES 3507 prevent ejecta from puncturing structural dividers.
- Lithium iron phosphate (LFP): LFP cathodes feature strong covalent bonds, providing high thermal stability with an onset threshold of 270-300℃. They do not release oxygen, resulting in lower peak temperatures (620-700℃). However, these events produce high concentrations of hydrogen, which can accumulate and create an explosion hazard. Venting strategies must focus on rapidly exhausting non-combusted gases. Because LFP events produce minimal abrasive ejecta, lightweight, pressure-actuated die-cut burst valves are highly effective.
Why Avery Dennison?
Avery Dennison combines an extensive portfolio of PSA products with support that manufacturers can rely on to develop bespoke thermal management solutions. Our portfolio is engineered to solve the most common challenges in battery design, including reducing flammability (UL® 94 V-0), boosting dielectric strength and optimizing assembly.
We also offer deep support, including access to testing facilities and collaboration with subject matter experts. And as a U.S.-based manufacturer with a strong presence in all global regions, we ensure access to both domestic and international supply chains.
Summary
Thermal runaway prevention and mitigation remains a critical engineering challenge with no simple, singular solution. Success requires a multifaceted strategy that addresses heat transference, thermal insulation, and the management of vented materials. PSA tapes integrated with functional materials should be the foundation of that strategy.
We welcome the opportunity to discuss your battery design challenges and explore thermal management strategies using PSA tapes.
To take the next step, please contact me directly at max.vanraaphorst@averydennison.com. You can also visit www.tapes.averydennison.com/evbattery for more information.
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