Effects Of Pressure And Temperature Changes On Thermal Runaway Law And Products Of 18650 Lithium Ion Battery

Lithium-ion batteries are widely used in civil aviation due to their high energy density and high cycle life,but increasingly serious safety issues hinder their further development.In this paper,taking 18650 lithium-ion battery as the research object,the effects of pressure and temperature changes on the thermal runaway peak temperature,thermal runaway time,CO concentration,and mass loss of lithium-ion batteries were carried out.Conducted research on thermal degradation behavior analysis,and conducted thermal propagation mechanism analysis,which provided support for understanding the thermal runaway mechanism of lithium-ion batteries,improving the transportation standards for lithium-ion batteries in the civil aviation industry,safety protection technology for lithium-ion batteries in high-altitude cargo compartments,and the formulation of safety warning strategies.Taking the 18650 lithium-ion battery as the research object in a confined space,the thermal runaway of the lithium-ion battery is triggered by heating by an external heat source,and the external pressure and temperature are studied at 0°C,a variable pressure environment,20 k Pa,a variable temperature environment,and a variable temperature and variable pressure environment.Effects of changing conditions on thermal runaway laws and products.First of all,two state of charge(SOC)lithium-ion batteries were selected in the experiment,one is that the lithium-ion battery for air transportation should not exceed the 30% SOC standard,and the other is that the battery of portable electronic equipment is fully charged to 100% SOC situation.Through comparative analysis,the influence of each single variable on the thermal runaway of lithium-ion batteries with different SOC cells,and which variable has a greater impact when multivariate influences are obtained.Secondly,by analyzing the types of thermal runaway residues under different working conditions,and conducting phase analysis and thermal degradation behavior analysis,the properties of lithium-ion battery residues with different SOC sells were judged.Finally,the thermal runaway analysis of the lithium-ion battery under the variable temperature and pressure environment is carried out to further explore the thermal runaway mechanism.The research results show that when the single factor of pressure or temperature is affected,the thermal runaway time increases continuously with the increase of pressure or the lower the temperature.When the pressure and temperature are under the synergistic effect,the thermal runaway time increases continuously with the decrease of pressure and temperature,and it is found that the effect of temperature change on the thermal runaway time is more obvious.By affecting the internal resistance of the battery,the temperature accelerates the electrochemical reaction speed and increases the heat release during the thermal runaway of the lithium-ion battery.Among them,the thermal runaway temperature of the lithium-ion battery with 30%SOC changes significantly,but there is a threshold for the temperature effect;100% SOC Lithium-ion batteries have more internal energy storage,and the temperature has little effect on the thermal runaway temperature.Pressure is positively correlated with the oxygen mass concentration in the air.Temperature and pressure affect the thermal runaway process of lithium-ion batteries,and affect the critical temperature and reaction time of material generation,resulting in differences in the types of thermal runaway residues in lithium-ion batteries with different SOC cells.The lithium-ion battery with 30% SOC has less content of high-valent nickel ions and cobalt ions,the NCM material is more stable,and there are more oxides in the residue.