Currently, the use of automobiles is growing steadily. New energy electric vehicles represent a key direction for the future development of the automotive industry.
Power batteries serve as the “heart” of new energy vehicles, while adhesives act as the “muscular tissue” that enables this “heart” to deliver sustained power output. Currently, the wave of electrification is sweeping across the globe, driving explosive growth in demand for power batteries, and the adhesives market is expanding in tandem.
It is understood that CTP-based battery packs used in new energy vehicles are designed to eliminate or significantly reduce intermediate module components, instead utilizing large amounts of adhesive to bond and secure the cells. The application of these adhesives primarily serves two major purposes: the first category consists of structural adhesives, which are primarily used for structural bonding while also providing a certain degree of thermal conductivity; the second category comprises thermal conductive adhesives, which are primarily designed for thermal conductive bonding – the adhesive is used to conduct the heat generated by the cells during operation to external heat dissipation components, thereby fulfilling part of the thermal management function while also meeting structural bonding requirements.
Structural adhesives are adhesives designed for bonding load-bearing structural components, capable of withstanding significant dynamic and static loads and being suitable for long-term use. They serve as an alternative to bolts, rivets, or welding when joining structural components made of metals, plastics, glass, wood, or other materials; these adhesives are engineered to maintain reliable performance even under prolonged exposure to high loads.
Thermal conductive adhesive is primarily used to facilitate thermal conduction between battery cells themselves, as well as between battery cells and liquid cooling pipes; its specific applications include use as a gasket, for encapsulation, or for filling.
Application of thermal conductive adhesive in battery packs – between cells
1 Structural Adhesive
Structural adhesives are designed to reliably connect and secure the battery cell to the pack housing, replacing the mechanical connections used in traditional module architectures; this imposes stringent performance requirements on strength, flexibility, aging resistance, flame retardancy and insulation properties, as well as thermal conductivity.
Power battery pack structural adhesives primarily include polyurethane structural adhesives, acrylic structural adhesives, silicone adhesives, epoxy structural adhesives, UV-curable adhesives, and high-temperature resistant hot-melt adhesives; depending on their respective characteristics, they are applied in different scenarios.
For different types of structural adhesives, three specific indicators are used to evaluate their bonding performance: joint strength, failure mode (cohesive failure is the ideal mode, as it corresponds to the maximum strength of the material at the joint), and the adhesive’s fracture elongation (which reflects the elasticity of the adhesive).
2 Thermal adhesive
Thermal conductive adhesives are primarily composed of a resin matrix (e.g., epoxy resin, silicone, and polyurethane) and thermal conductive fillers (used to enhance thermal conductivity; examples include aluminum nitride (AlN), boron nitride (BN), silicon nitride (Si₃N₄), aluminum oxide (Al₂O₃), magnesium oxide (MgO), and zinc oxide (ZnO)). Amid the evolving CTP (Cell-to-Pack) industry trends, battery manufacturers have a high demand for thermal conductive adhesives alongside ongoing cost reduction requirements; meanwhile, the simplification of structural design necessitates adhesives capable of providing high bonding strength (greater than 10 MPa). Consequently, polyurethane thermal conductive structural adhesives, which offer superior bonding strength and cost-effectiveness, have become the preferred choice for thermal management applications. Follow the official WeChat account: Battery BMS!
Due to the narrow optimal operating temperature range for battery cells (20–40°C), the thermal conductive adhesive in the CTP architecture enables balanced heat dissipation between the cells and between the cells and the liquid cooling plate, thereby reducing the cell temperature and the temperature difference between cells by 1–2°C – a development that will significantly benefit the battery thermal management system.
A thermal conductive adhesive with a higher thermal conductivity coefficient is more effective at reducing the battery’s temperature rise and temperature gradient.
3 Adhesive Point Analysis for Power Batteries
The four major roles of adhesives in power batteries:
1. Provides protective protection for power batteries;
2. Achieve a safe and reliable lightweight design;
3. Thermal management;
4. Help the battery withstand more complex operating environments.
3.1 Battery cell bonding – Structural bonding
Substrate: Aluminum sheet with outer PET film coating
Requirements: Bonding and positioning; thermal conductivity; excellent adhesion to PET film and aluminum sheets.
Solution: Two-component polyurethane structural adhesive; single-component silicone sealant; two-component silicone sealant
3.2 Bonding of the conductive sheet to the module housing
Substrate: PC sheets and nickel/aluminum sheets; nickel/aluminum sheets and ABS/PC
Requirements: Bonding and positioning; temperature resistance (-40°C to 85°C); rapid positioning;
Recommended products: Two-component acrylic structural adhesive; High-temperature resistant hot-melt adhesive
3.3 Cell Packaging
Requirements: thermal conductivity, cell fixation, shock absorption, flame retardancy, enhanced safety, low density
Product Recommendation: Two-component thermal silicone sealant
3.4 Bonding and fixation of the cylindrical battery base
Application: Cable harness isolation plate; Welding point protection adhesive
Requirements: Flame retardant, low odor, non-corrosive to copper/aluminum/PVC/PP/silicone materials, and rapid curing time.
Recommended products: Flame-retardant rubber, UV-curable adhesive, Epoxy protective adhesive
3.5 Circular Battery Mounting Bracket Fixation
Performance requirements: Excellent aging resistance and superior flexibility
Product Recommendation: Acrylic Structural Adhesive
3.6 Thermal conduction between the base plate and the battery cell
Requirements: environmentally friendly; exhibits thixotropy; possesses good thermal conductivity; and solidifies rapidly at room temperature;
Product Recommendation: Thermal Conductive Epoxy Structural Adhesive; Two-Component Acrylic Structural Adhesive
3.7 Battery Thread Locking
Requirements: Capability to perform tests including vibration, mechanical shock, drop, inversion, and simulated collision tests.
Product Recommendation: Anaerobic Thread Locking Compound
3.8 Nameplate Adhesion
Substrate: Primarily aluminum alloys or steel components with surface treatment.
Requirements: Vibration resistance; the adhesive layer should possess toughness and strong initial adhesion; the adhesive should exhibit certain thixotropy and provide excellent adhesion to the substrate.
Product recommendations: Acrylic structural adhesive; Low-temperature curing epoxy adhesive.