New Sealing Material For Safe Battery Cells

In the rapidly growing electric vehicle market, improved battery performance with shorter charging times, maximum temperature resistance and a longer battery life are key factors for success. To meet these demands, OEMs in Europe and the United States need materials that also comply with stricter national and international environmental standards. One high-performance material for such applications comes from the elastomer material group. Freudenberg Sealing Technologies has successfully developed a material that outperforms thermoplastics in the event of thermal runaway and takes battery applications in e-mobility to an entirely new level.

Using material advantages – elastomer seals instead of thermoplastics

Thermoplastics that are traditionally used for battery seals have macromolecules with long-chain molecular structures that are not chemically cross-linked but instead held together by weak intermolecular forces. While thermoplastics can be elastically deformed to some degree, the constant charging and discharging of the battery cell also causes them to undergo functionally relevant plastic deformation over time. This is different in elastomers whose molecular chains are chemically cross-linked. In their basic state, the polymer chains form a tangled ball that stretches or compresses under tensile and compressive loads. Due to the entropy elasticity, these cross-linked materials react elastically and reversibly, maintaining their shape exceptionally well during the cyclical volume change of the battery cells under load.

“Our O-rings made from the new elastomer therefore prevent electrolyte from leaking out of the battery cell or impurities from entering the cell,” explains David Kuhne, Application Engineer at Freudenberg Sealing Technologies. “You shouldn’t think of a battery cell as a rigid construct – it ‘breathes’. When the temperature in the battery cell rises from ambient levels to – as a rule – ranges of up to 60°C, the cell expands and then contracts in the same way as it cools. Elastomers show significant advantages over thermoplastics during this continuous stress.” explains Kuhne the charging and discharging process.