Study On The Safety Of Ternary Lithium Ion Battery In Combustion And Explosion Disaster

In this paper,the damage mechanism and thermal runaway law of lithium-ion battery in combustion and explosion environment are studied by combining experiment and simulation.The battery temperature,gas production pressure and type,mass loss,appearance performance change,electrical performance change and energy parameters are tested in various test environments,and the thermal runaway of battery in radiation environment is simulated to promote the mechanism analysis.Firstly,by changing the received heat flux of lithium-ion battery,the variation of main performance with heating time under different heat radiation flux was studied.Under low radiation,the battery temperature is stable and low;Under moderate radiation,the safety valve is damaged before the battery thermal runaway,and the temperature reaches 500℃～550℃;Gas production flow rate reaches 40m/S～60m/S;The main types of gases are H₂（0.81%）,C₂H₂（0.24%）and other combustible gases;The mass loss is between 240g and 255g.Under high radiation,the battery heat is out of control and has combustion,and the temperature reaches 610℃～650℃;The gas production flow rate reaches 70m/S～80m/S;The main gases are pyrolysis gases such as CO₂（4%）and CO（1.2%）.Secondly,the battery simulation model is constructed to further study the mechanism of battery thermal runaway under the action of thermal radiation.In the process of thermal runaway,the reaction begins to produce heat in the order of SEI film,negative material,positive material and electrolyte.The heat production rate of cathode material is the highest and that of SEI film is the lowest;The shell temperature corresponding to the peak heat production rate of active material increases with the increase of heat flux.With the increase of heat flux,the start time and peak time of active material heat production rate decrease,and the peak heat production rate increases.Finally,the effects of the magnitude and form of input overpressure on the appearance and electrical properties of lithium-ion batteries are studied.The damage of explosion shock to the safety valve mainly comes from impulse.The initial air pressure inside the high-capacity battery is larger and can withstand higher impact.The capacity of the lithium-ion battery whose safety valve is damaged by the explosion impact has a large attenuation（up to 10%）.At this time,the internal structure has been damaged.The extrusion effect of the explosion impact increases the contact area between the electrode and the electrolyte,so that the lithium ion is embedded into the negative electrode,which is similar to the charging process.Therefore,the voltage increases and the internal resistance decreases.