Deterioration behavior of aluminum pouch film used as packaging materials for pouch-type lithium-ion batteries

Pouch-type lithium-ion batteries are packed into an aluminum pouch film (Al-Pouch). They are used as power sources for large-scale energy storage systems or electric vehicles because of their attractive features. However, the packaging materials of Al-pouch are prone to contamination from electrolyte containing lithium salt during the electrolyte injection process, a key part of their manufacturing process. This electrolyte contamination can be fatal to the long-term reliability or durability of pouch-type LiBs. Here, therefore, we study of how Al-pouch are damaged by electrolyte contamination; understanding this mechanism is critical for ensuring the long-term reliability and durability of pouch-type LiBs. We find that the nylon film comprising the outer layer of Al-pouch is damaged when it reacts with an electrolyte containing lithium salt in the presence of atmospheric moisture. This leads to cracking, followed by nylon locally peeling off from the Al-pouch. This peeling exposes the underlying thin aluminum film that comprises the middle layer of Al-pouch. Once partially exposed to the atmosphere, severe pitting corrosion occurs on the thin aluminum film. High volumes of moisture to easily penetrate pouch-type LiBs through these corroded pits, showing the detrimental effects of electrolyte contamination on pouch-type LiBs’ long-term cycle life and reliability.