An investigation on thermal runaway behaviour of a cylindrical lithium-ion battery under different states of charge based on thermal tests and a three-dimensional thermal runaway model

A significant risk for lithium-ion batteries (LIBs) is fire and explosions caused by thermal runaway (TR). A TR model for LIBs with various states of charge (SOCs) can help design safer battery modules. In this work, the TR mechanism of a commercial Li[Ni5Co2Mn3]O2/graphite 18650 type cylindrical battery with various SOCs has been investigated through differential scanning calorimetry (DSC) tests on the single and mixed components. Then, a three-dimensional (3D) TR model is developed to predict the battery TR behaviours under different SOCs. This model fits well with the accelerating rate calorimetry (ARC) test results of the batteries with various SOCs. Furthermore, the validated model and ARC experiment results are employed to investigate the TR mechanism of different SOC batteries. The results show that the reaction onset temperature for cathode-anode and anode-electrolyte roughly advances as the SOC increases and the reaction enthalpy of the cathode-anode, anode-electrolyte and cathode increases with the increase of SOC. Cathode-anode, anode-electrolyte are the main heat generation in the process of battery TR, and their proportion of heat generation will decrease with the decrease of SOC.