Reliability of Cylindrical Li-ion Battery Safety Vents

• Published in: IEEE access Vol. 8; pp. 101859 - 101866
• Main Authors: Yao, Xing-Yan, Kong, Lingxi, Pecht, Michael G.
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2020; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Case studies; Computed tomography; CT scan; cylindrical li-ion battery; explosive failure; Failure mechanisms; Heating systems; Lithium; Lithium-ion batteries; Product safety; Rechargeable batteries; Reliability; Rupture; Safety; Temperature distribution; Thermal runaway; Thermistors; Vent failure; Vents
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2020.2997792

Cylindrical Li-ion batteries (cells) typically have safety vents in the positive terminal to enable the release of gases that build up inside the battery and thus help reduce the effects of thermal runaway, including fire and explosion. However, the vents are not always effective, and it is critical to understand why. This paper overviews various vent designs and presents two case studies of vents in cylindrical Li-ion batteries that failed to operate properly. The first case study concerns a Sony VCT5 18650 Li-ion battery in which thermal runaway caused the cylindrical casing (can) to rupture. The second case study involves an Ampking 20700 Li-ion battery in which thermal runaway caused side-wall rupture of the casing. In both cases, the vents did not function as intended. Computed tomography (CT) scanning was used to investigate the internal structure of the battery to assess the failure mechanisms of the failed vents. These cases raise concerns about the efficiency, reliability, and safety of some current vent designs.