1. Structural Adhesive
Structural adhesive plays a role in reliably connecting and fixing the battery cells to the pack housing, replacing the mechanical connections in the original module structure. It has high - performance requirements for strength, flexibility, aging resistance, flame retardancy, insulation, and thermal conductivity.
The main types of structural adhesives for power battery packs include polyurethane structural adhesive, acrylic structural adhesive, silicone rubber, epoxy structural adhesive, UV adhesive, and high - temperature - resistant hot - melt adhesive. They are applied in different scenarios according to their different characteristics.
For different types of structural adhesives, there are three specific indicators to evaluate their bonding performance: the strength of the joint, the failure mode (cohesive failure is the most ideal mode, achieving the maximum strength of the material at the joint), and the elongation at break of the adhesive (reflecting the elasticity of the colloid).
2. Thermal Conductive Adhesive
Thermal conductive adhesive is mainly composed of a resin matrix (such as epoxy resin, silicone, and polyurethane) and thermal conductive fillers (to improve thermal conductivity, including aluminum nitride (AlN), boron nitride (BN), silicon nitride (Si₃N₄), aluminum oxide (Al₂O₃), magnesium oxide (MgO), zinc oxide (ZnO), etc.). Under the development trend of CTP in battery packs, battery manufacturers have a large demand for thermal conductive adhesives and a continuous need to reduce costs. At the same time, the reduction in the design of structural components also creates a demand for bonding and fixing with high strength (greater than 10 MPa). Therefore, polyurethane thermal conductive structural adhesive, which has advantages in bonding strength and economic cost, has become the mainstream choice for thermal conductive adhesives. Follow the official account "Power Battery BMS"!
Since the optimal operating temperature range of battery cells is relatively narrow (20 - 40°C), under the CTP structure, the thermal conductive adhesive can achieve uniform heat dissipation between the battery cells and between the battery cells and the liquid - cooling plate. Thus, reducing the temperature of the battery cells and the temperature difference between the cells by 1 - 2°C will be extremely beneficial to the battery thermal management system.
The higher the thermal conductivity of the thermal conductive adhesive, the more obvious the effect on reducing the temperature rise and temperature difference of the battery.
3. Analysis of Bonding Points for Power Batteries
The four major functions of adhesives in power batteries are as follows:
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Provide protection for power batteries.
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Achieve a safe and reliable lightweight design.
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Conduct thermal management.
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Help the battery cope with more complex usage environments.
3.1 Bonding between Battery Cells - Structural Bonding
Substrates: Aluminum plates and outer - wrapped PET films.
Requirements: Bonding and positioning, thermal conductivity, and good adhesion to PET films and aluminum plates.
Solutions: Two - component polyurethane structural adhesive, one - component silicone rubber, and two - component silicone rubber.
