What kind of foam material is needed for power batteries?

Foam can provide excellent insulation, cushioning, flame retardancy, sealing, support, shock absorption, and other functions in power battery packs to use the foam in different areas of the battery pack.

Foam can provide insulation and buffering between battery cells when they experience thermal expansion and contraction. When the battery cell experiences thermal runaway, foam can prevent heat transfer and has flame-retardant properties. Foam can provide support and shock absorption in the battery pack, located under the liquid cooling plate or adjacent to the upper and lower box covers. It can also be used as a battery-sealing ring.

There are many types of foam, including PU, EVA, PE, CR, ECR, silicone foam, etc. In the practical application process of battery systems, the foam suitable for the cell-to-cell interface is generally made of materials such as PE and PU. The foam used for supporting and shock-absorbing in the battery pack box is generally EVA, PE, ECR, EVA+CR, silicone foam, and other materials. The foam used for battery sealing rings is usually made of silicone foam.

Battery cells are the energy source for electric vehicles, and the safety issues of battery cells directly affect the safety of the entire car. During operation, battery cells generate a certain amount of heat, which undergoes thermal expansion and contraction at different temperatures. Battery cells experience specific swelling, and long-term contact friction between them may lead to battery damage, failure, and even loss of control.

The performance requirements for foam products between battery cells in new energy power batteries are as follows:

• Low hardness and high rebound, able to absorb stress caused by thermal expansion and contraction, and play a buffering role;
• Low thermal conductivity, capable of insulation, suppressing heat diffusion, and delaying accidents in the event of thermal runaway;
• Flame retardant performance: when the battery cell catches fire, the flame retardant effect can delay the spread of the fire;
• Excellent rebound performance, with a wide compression ratio for positioning;
• It is small in thickness, occupies less space, and has a long lifespan.

Thermal management plays a crucial role in power batteries, directly affecting the safety of the battery pack and the entire vehicle. The cooling system inside the battery pack has been transformed from traditional air cooling to liquid cooling. Heat is transmitted between the battery pack and the liquid cooling plate through thermal conductive silicone. However, due to the poor elasticity of the thermally conductive silicone, it loses thickness after long-term use, resulting in insufficient contact between the liquid cooling plate and the battery pack, which affects the thermal conductivity effect. The solution can be to install springs or foam as supporting materials below the liquid cooling plate to ensure good contact between the liquid cooling plate, thermal silicone, and module.

The performance requirements for battery pack box support foam include the following:

• Stable support and good shock absorption effect
• Excellent temperature resistance and durability
• Compression permanent deformation and slight loss of stress relaxation
• It has excellent flame retardant performance, ensuring combustion safety
• The application of foam in the sealing ring of power batteries

The battery pack is the core energy source of new energy vehicles, providing driving power for the entire car. To protect the internal components of the battery pack from dust, rain, and other erosion, the shell seal of the battery pack must reach a certain level of dust and water resistance.
The industry generally requires battery packs to have a protection level of IP67 or IP6 in terms of dust and water resistance.