Which Is Better for EV Batteries: MPP Foam or Silicone Foam?

Choosing a battery foam only by density or temperature rating can leave the cell stack with the wrong compression force, excessive permanent set or unnecessary material cost.

Compare MPP foam and silicone foam against the actual battery pressure, temperature, thickness and flame requirements. MPP generally refers to microcellular polypropylene foam, while silicone foam belongs to a different elastomer family with different aging and thermal behavior.

Neither material is automatically better. For EV battery cushioning and compression management, the correct decision comes from the finished pad's compression curve, thickness, long-term recovery and environmental validation.

What Is the Main Difference Between MPP Foam and Silicone Foam?

Substituting one foam for another without checking its mechanical curve can change the pressure applied to pouch or prismatic cells.

Use MPP when a lightweight microcellular polyolefin construction fits the mechanical and environmental window; use silicone when temperature stability, flame performance or long-term elastomeric recovery becomes more important.

Microcellular polypropylene can be produced with supercritical carbon dioxide to create a fine cellular structure, while silicone foams are formulated as cellular silicone elastomers. The exact performance of both materials remains grade-specific.^[1]

Which Foam Is Better for Cell Compression?

A pad that is too stiff can overload the cell, while a pad that relaxes too quickly can lose the intended stack pressure during battery life.

Compare compression force deflection, compression set and stress relaxation at the actual working thickness. The correct material should maintain the required pressure window as the cell breathes and gradually swells.

Saint-Gobain similarly recommends starting from cell chemistry, gap, compression range, beginning-of-life and end-of-life pressure targets rather than selecting a battery compression pad by chemistry alone.^[2]

When Does Silicone Foam Make More Sense?

Using a lower-temperature foam in a demanding battery location can reduce mechanical stability and force a redesign late in validation.

Silicone foam becomes attractive when elevated-temperature aging, low compression set or stringent flame requirements dominate the design.

For comparison, certain Rogers BISCO silicone grades publish operation up to 200°C with UL 94 V-0 performance and low compression-set values, but these numbers apply to those specific grades and should not be generalized to every silicone foam.^[3]

What Should You Send to a Foam Supplier Before Requesting Samples?

Asking for “3 mm battery foam” without pressure and temperature requirements usually leads to irrelevant samples and repeated testing.

Provide the cell format, nominal gap, minimum and maximum compression, pressure target, operating temperature, flame requirement, dimensions and adhesive requirement.

This makes it possible to compare MPP and silicone using the actual finished die-cut part rather than generic raw-material datasheets.

Comparing MPP Foam and Silicone Foam?

Send Fuqiang your cell drawing, available gap, compression range, temperature requirement and target pad thickness. We can compare material options and prepare die-cut samples for assembly and pressure testing.

FAQ

What is MPP foam?

MPP foam commonly refers to microcellular polypropylene foam, a lightweight cellular polyolefin material that can be engineered for cushioning, insulation and compression applications.

Is MPP foam better than silicone foam?

Not universally. MPP can be attractive for lightweight compression applications, while silicone may be preferred where high-temperature aging, flame performance or elastomeric recovery is more demanding.

Can MPP foam be used between EV battery cells?

Yes, if the selected grade meets the required compression, electrical, temperature, aging and flammability specifications.

Does silicone foam prevent thermal runaway?

Standard silicone compression foam should not automatically be treated as a thermal-runaway barrier. Specialized composite or ceramifiable constructions are used when thermal propagation protection is required.

What data is most important when comparing battery foams?

Start with compression force deflection, compression set, stress relaxation, thickness, temperature performance, flammability and dielectric requirements.

A 15-Year Automotive Wire Harness and Battery Materials Perspective

After 15 years working with automotive electrical and battery components, I recommend comparing the finished pad under its real compression window rather than selecting a foam from material names alone. Thickness, force retention and assembly conditions usually decide whether the material will work in production.

Authoritative References

[1] The Journal of Supercritical Fluids — Microcellular Foaming of Polypropylene Using Supercritical CO₂

[2] Saint-Gobain — EV Battery Cell Swelling and Compression Management

[3] Rogers Corporation — BISCO Silicone Foam Properties