Background: ARC undertook a pouch film benchmarking study to compare the sealing performance of a European pouch film supplier against an established reference film for Li-ion pouch cell battery applications. The work focused on how pouch film selection affects pouch-to-polymer and pouch-to-pouch seal strength before and after electrolyte exposure, providing evidence to support material selection for future pouch cell development.
Challenge: The key challenge was to determine whether the alternative pouch film could deliver equivalent or improved sealing performance without introducing new failure risks after electrolyte exposure. ARC needed to assess whether pouch-to-polymer seals remained intact across different polymer sealants, whether pouch-to-pouch seals retained sufficient strength after ageing, and whether observed failure modes indicated robust bonding or weakness at the internal laminate interfaces.
Solution: ARC designed a comparative test programme covering seal strength, electrolyte ageing and failure-mode assessment. The benchmark compared pouch film performance using multiple polymer sealant options and generated both quantitative peel-strength data and qualitative failure-mode evidence to determine whether the alternative film provided a stronger or more stable seal system.
- Pouch-to-Polymer Seal Testing: ARC measured yield and necking strength for pouch-to-polymer seals using multiple polymer variants before and after electrolyte ageing. This allowed ARC to determine whether the pouch film itself affected seal formation or whether polymer choice was the dominant driver of seal strength.
- Pouch-to-Pouch Seal Testing: ARC compared pouch-to-pouch seal strength before and after electrolyte exposure. Initial seal strength was similar between films, while post-electrolyte results were used to assess strength retention and resistance to degradation.
- Electrolyte Ageing Assessment: Samples were evaluated after electrolyte exposure to identify whether ageing reduced peak yield strength, caused peeling at the pouch-to-polymer interface, or changed the way the laminate failed under mechanical loading.
- Failure-Mode Review: ARC examined the failed samples to distinguish between adhesive failure at the seal interface and cohesive or laminate-related failure within the pouch structure. This assessment helped determine whether the seal itself remained intact or whether failure occurred through tearing, delamination or layer separation.
Results: The benchmarking study showed that both pouch films performed similarly before electrolyte exposure, with no pouch-to-polymer peeling observed across the polymer variants tested. After electrolyte exposure, the European supplied pouch film showed higher pouch-to-pouch yield strength and failure modes that indicated a more vigorous and stable seal system.
- No significant pouch-to-polymer weakness identified: Across the polymer variants tested, ARC observed no peeling from the pouch-to-polymer seal, indicating that both pouch films could form compatible seals with the evaluated polymers.
- Similar pre-ageing performance: Both pouch films showed comparable pouch-to-pouch seal strength before electrolyte exposure, supporting the view that the alternative film was not disadvantaged at initial seal formation.
- Improved post-electrolyte strength retention: After electrolyte exposure, the alternative pouch film retained a stronger pouch-to-pouch seal at yield, indicating better resistance to electrolyte-related degradation.
- More robust failure behaviour: Failure-mode assessment showed fewer signs of polymer ripping or separation in the alternative film and more evidence of fracture through stronger bonded layers, suggesting improved seal stability after ageing.
Conclusion: ARC demonstrated that the European supplied pouch film is a credible candidate for Li-ion pouch cell battery development. The benchmark showed equivalent initial sealing behaviour, no observed pouch-to-polymer peeling, and stronger pouch-to-pouch performance after electrolyte exposure. The results indicate that pouch film selection can influence long-term seal stability, and that the European supplied film should be considered for further validation in representative cell formats and process conditions.