Analysis of moisture penetration mechanism into the AI-pouch type lithium ion batteries

The moisture penetration mechanism into the pouch type lithium ion battery (LiB) is systematically investigated. In order to clarify the path for moisture penetration into pouch type LiB, we prepared dummy cells assembled with lead-tap and dummy cells assembled without lead-tap, in which there are only electrolyte. The change of amount of moisture inside the samples was tracked during 8 weeks by storing them under high humidity condition (RH 90%). As a result, a large amount of moisture is detected in the dummy cells assembled with lead-tap. To understand such phenomena, the microstructure of interface between lead-tab and lead film was observed by SEM. We found that a large amount of microvoids was existing on the interface between lead-tap and lead film. This result implies that such micro-void might act as the path of moisture penetration for the pouch type LiB.