Introduction
Engineers in electric vehicle battery module and cell bonding face an increasingly prominent core contradiction: the adhesive must possess sufficiently high thermal conductivity to address fast-charging heat dissipation issues, while also providing adequate structural strength to withstand crash safety requirements. At the same time, it must accommodate the process window and cost control demands of mass production. Traditional solutions often require trade-offs between thermally conductive fillers (sacrificing mechanical properties) and toughening agents (sacrificing thermal conductivity and heat resistance). This article provides an in-depth analysis of the latest advancements in structural thermally conductive adhesive technology, exploring how material innovations can simplify processes and enhance comprehensive performance, offering engineers a systematic technical reference.
1. Technological Evolution: From Simple Thermal Conductivity to "Structural-Thermal" Integration
Early thermally conductive adhesives focused primarily on thermal conductivity, but second and third-generation products have begun to emphasize maximizing mechanical properties to meet the efficiency and durability requirements of new battery designs. The BETAMATE™ series of structural adhesives developed by DuPont has been validated in projects like the Volkswagen MEB (Modular Electric Drive Matrix) platform, successfully applied in the battery pack manufacturing of models such as the ID.3. Through high elastic modulus and tensile strength, these materials integrate the battery pack into a single structural component while transferring heat, ensuring the stiffness, durability, and crash resistance of the battery frame. This also replaces some mechanical fasteners, achieving lightweighting and process simplification.
Research indicates that thermally conductive adhesives for power batteries play a crucial role within the battery system, and their performance directly impacts the driving performance and occupant safety of electric vehicles. Traditional welding or mechanical connections cannot provide a continuous bond line and struggle to achieve ideal cycle times. The emergence of structural thermally conductive adhesives precisely addresses these pain points.
2. Primerless and Cold-Curing Technologies: Core Breakthroughs in Process Simplification
At the process level, the most significant advancements in next-generation structural adhesives are reflected in two aspects: simplified surface pretreatment and innovative curing methods.
The maturation of Primerless technology allows adhesives to achieve handling strength within 20 minutes on aluminum profiles or high-strength steel without complex surface pretreatment, supporting robotic or manual application. DuPont BETAMATE 2090 leverages this very characteristic to help Volkswagen reduce production steps, shorten cycle times, and lower costs.
Cold-curing technology addresses the challenge of assembly lines lacking ovens. Traditional structural adhesives often require high-temperature oven curing, whereas new materials can complete the cross-linking reaction at room temperature while maintaining excellent mechanical properties. Darbond DA-1500, a one-component silicone thermally conductive adhesive, utilizes a rapid heat-curing process, fully curing in 30 minutes at 125°C, achieving a shear strength of 6.0 MPa, making it suitable for batch production. This curing flexibility provides engineers with a broader process window.
3. Key Performance Data: Balancing Thermal Conductivity and Electrical Insulation
Innovation in thermally conductive filler systems is key to achieving the balance between high thermal conductivity and electrical insulation. Through hybrid compounding techniques using fillers like spherical alumina and boron nitride, new silicone or epoxy-based thermally conductive adhesives can achieve precise thermal performance in different directions:
WEVO-CHEMIE GmbH's WEVOSIL 28015 FL, a two-component RTV silicone, achieves a thermal conductivity of 1.5 W/m·K, Shore hardness of 70, elastic modulus up to 60 N/mm², and maintains an elongation at break of 20%-25%. This satisfies structural bonding requirements while effectively compensating for thermal stress from temperature cycling. The product operates across a wide temperature range from -60°C to 200°C, maintaining stable performance under extreme conditions.
Shenzhen Darbond's DA-1500 thermally conductive adhesive features a thermal conductivity of 1.54 W/m·K, a dielectric breakdown strength of 21.0 kV/mm, and a UL94 V-0 flammability rating, perfectly balancing thermal efficiency and electrical safety. Its thermal resistance at 50°C and 40psi is only 0.269°C·cm²/W, efficiently dissipating heat from components.
4. Reliability Under Extreme Conditions: Thermal Runaway Protection and Aging Resistance
Addressing the core concern of battery safety, the performance of next-generation thermally conductive structural adhesives under extreme conditions is particularly outstanding:
Ceramifying technology has become a crucial direction for thermal runaway protection. Jinling Tongda's modified epoxy ceramifying thermally conductive structural adhesive, XK-CD12, with a thermal conductivity of 1.2 W/m·K, undergoes a ceramifying transformation when exposed to extreme high temperatures: at 450°C, the material converts into an insulating ceramic body with hardness greater than 2H; within the range of 830-860°C, it remains bonded to the metal substrate as a single unit, with a maximum temperature resistance exceeding 1200°C. This "ceramifying upon fire" characteristic can isolate flames and prevent short circuits in thermal runaway scenarios.
Regarding aging resistance, high-quality thermally conductive structural adhesives demonstrate very stable bonding performance in tests involving low-temperature shock at -40°C and high-temperature aging at 125°C. Jinling Tongda's XK-D20 series thermally conductive structural adhesive boasts a service life exceeding 25 years at 60°C, a UL94-V0 flammability rating, a breakdown strength ≥10 kV/mm, and an operating temperature range of -45°C to 175°C. Such materials have been applied in the production of several new energy vehicles by manufacturers like Tianjin Lishen, Shanxi Dayun, and Dongfeng Motor, enhancing battery safety and longevity.
5. Innovations in Fast Curing for Automated Production
To match highly automated production lines in the automotive and electronics industries, fast-curing technology has become a research hotspot. WEVOSIL 28015 FL achieves an initial adhesion force exceeding 2 MPa within minutes using infrared (IR) or laser curing technology, significantly shortening production cycle times. Its unique curing system design effectively prevents shrinkage and gap formation during curing, ensuring bond sealing and reliability even inside enclosed components or housings.
The thixotropic properties of Darbond DA-1500 allow flexible adaptation to dispensing processes, making it suitable for automated assembly lines. Jinling Tongda's XK series products also emphasize suitability for dispensing processes, meeting the demands of high-volume automated factory production.
Conclusion
From structural-thermal integrated design to primerless cold-curing processes, and further to ceramifying protection under extreme conditions, a new generation of thermally conductive structural adhesives is redefining the technical boundaries of battery assembly. For process engineers, understanding these material characteristics and conducting targeted selection will be key to enhancing product competitiveness and optimizing production efficiency. With the proliferation of 800V high-voltage platforms and CTC (Cell-to-Chassis) technologies, innovation in thermally conductive structural adhesives will continue to evolve, providing even more solid guarantees for the safety and performance of electric vehicles.
References:
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WEVO-CHEMIE GmbH. WEVOSIL 28015 FL – Thermally conductive silicone adhesive for battery modules and power electronics: https://www.wevo-chemie.com/en/products/wevosil-28015-fl/
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European Rubber Journal. Wevo develops thermally conductive silicone adhesive for EV battery modules, electronics: https://www.european-rubber-journal.com/article/2098267/wevo-develops-thermally-conductive-silicone-adhesive-for-ev-battery-modules-electronics
