Experimental investigation of environmental test chamber resilience to unintended thermal runaway events in large-format prismatic lithium-ion batteries

Environmental test chambers are commonly used with battery cyclers to maintain specific temperature and humidity conditions during battery cycling and ageing tests. However, the resilience of these chambers during thermal runaway (TR) events involving large-format lithium-ion batteries remains inadequately understood. A thorough understanding of the risks and consequences of TR in large-format batteries is crucial for performing comprehensive risk assessments prior to conducting such cycling and ageing tests. In this study, large-format prismatic lithium-ion battery cells with nickel manganese cobalt oxide cathodes and capacities of approximately 100 Ah and 175 Ah were used to investigate chamber response and containment hazards during overcharge-induced TR. Overcharging was selected as it represents a realistic unintended abuse scenario during routine battery testing and can produce a severe failure condition. Such events may exceed the containment capability associated with EUCAR (European Council for Automotive R&D) hazard level 6 outcomes and, in severe cases, involve fire, explosion, and violent energy release. The effects of cell capacity, number of cells, test conditions, and chamber configurations on the chamber response during TR were assessed. Key indicators of TR were analysed, and the underlying TR mechanisms were explained. Finally, both guidance for the design of environmental test chambers to improve safety and response during TR events and a multi-level warning strategy integrating voltage and temperature monitoring with smoke detection were proposed.