What role does the safety valve play in the safety of lithium-ion cells? Part II. Cells with various states of health and formats

To demonstrate the role of safety valves in enhancing the safety characteristics of lithium-ion cells, this study conducts a set of abusive testing including accelerating rate calorimetry testing, overheating testing, and overcharge testing. Additionally, the influence of safety valves on cells with different states of health (100%, 90%, and 80% SOH) and formats (14,650, 18,650, and 22,650) is investigated. The results reveal that safety valves have a substantial influence on the thermal runaway behaviour of cells. They effectively mitigate the risks and hazards associated with thermal runaway during overheating and ARC conditions. Beyond that, the presence of a safety valve can prevent thermal runaway triggered by overcharge. It is observed that cells with lower SOH and/or smaller diameters are more prone to experiencing earlier thermal runaway. Furthermore, this research finds that the influence of safety valves is more pronounced in cells with less degradation and/or smaller formats.