Modelling thermal runaway of cylindrical battery under sub-atmospheric pressure

The storage and transportation of lithium-ion batteries under reduced ambient pressure have critical safety concerns. This work develops a model to simulate and understand the thermal runaway of a cylindrical battery cell at different sub-atmospheric pressures. A lumped heat transfer model for batteries is upgraded by considering the increasing electrolyte loss observed in experiments as pressure decreases. Using the model, we examine the impacts of ambient pressure, cell heating rate, and safety-venting threshold on battery thermal failure, with a particular focus on safety venting and thermal runaway. Before safety venting, the internal cell pressure is raised initially by electrolyte vaporisation and then by gases produced from chemical reactions. As the safety valve threshold rises from 1.2 MPa to 2.2 MPa, the gas from SEI decomposition increases from 73.5 % to 82.3 % at the moment of safety venting. The incubation period between venting and thermal runaway increases as the ambient pressure decreases. In other words, lowering the ambient pressure allows more emergency response time before thermal runaway. The developed model approach and simulations improve our understanding of thermal runaway under low ambient pressures and provide novel insights for ensuring battery safety in storage and transportation. • A numerical model simulates battery thermal runaway under sub-atmospheric pressure. • Analyse the impact of safety valve threshold on battery internal pressure evolution. • Quantify pressure and gas composition from SEI decomposition at the venting point. • Examine coupled ambient-pressure effect of cell heating rate and convective cooling.