Simulation Study on Thermal Runaway of Lithiumion Batteries in Different Aging States

The continuous promotion of electric vehicles and large-scale energy storage power plants is hampered by the safety issues brought on by thermal runaway of lithium-ion batteries. The severity of the thermal runaway issue is made worse by the rise in battery energy density and the progression of age. To study the thermal runaway of high energy density lithium-ion batteries in different ageing states, 21700 cylindrical lithium-ion batterie with Li (Ni
0.8
Co
0.15
Al
0.05
) O
2
(NCA) as the cathode material were chosen as the object of study, and a thermal runaway model was developed based on the electrochemical and ageing mechanisms. Based on the model simulation, the thermal runaway characteristics of different aging states were analyzed, it was determined that as the ageing degree increases, the thermal runaway time of the 21700 NCA battery accelerates, the maximum temperature decreases, and the proportion of heat generated by the reaction between the anode and the electrolyte and the decomposition of SEI increases, while that of the decomposition of the cathode and the short-circuit decreases. By further analysing the heat generation power of the side reaction, the relationship between the ageing degradation mechanism of the battery and the evolution of the safety performance is summarised, laying the groundwork for optimising the safety of lithium-ion batteries throughout their entire life cycle.