Study On The Law Of Thermal Runaway Of Lithium-ion Batteries And Its Suppression With Water Mist

In recent years,with the vigorous development of the new energy industry in China,lithium-ion battery has occupied most of the battery industry market due to its advantages of high energy ratio,low memory,high output voltage,etc.However,the lithium-ion battery is prone to thermal runaway when it is squeezed,punctured,overcharged and overheated,releasing flammable,explosive,toxic and harmful gases,and releasing a large amount of heat,causing the thermal runaway to propagate in the battery pack,resulting in fire and even explosion,posing a serious threat to the lives and property of the people.Therefore,it is of great significance to study the law of thermal runaway of lithium-ion batteries and the suppression technology of thermal runaway to protect the lives and property of the people.In this paper,the thermal runaway experiment of lithium-ion battery was conducted in the laboratory,18650 lithium-ion battety with NCM was selected as the research object,the self-buit experimental instalation to study the thermal runaway law of lithium-ion baatteries in a semi-enclosed space.The experimental study on thermal runaway of single lithium-ion battery in calibration under different SOC showed that when the SOC of lithium-ion battery reaches 100%,the safe exhaust temperature of single lithium-ion battery is 145.11℃,and the critical thermal runaway temperature is 205.00℃.It is the lowest value among the tested lithium-ion batteries with different SOC,and the maximum mass loss is 25.84 g.The thermal runaway hazard is the highest.For the thermal runaway propagation experiment of unconnected lithium battery pack,it was found that the energy generated by the thermal runaway of a single lithium-ion battery is insufficient to cause the thermal runaway propagation in the battery pack.In the thermal runaway experiment of parallel lithium-ion battery pack,it was found that in parallel circuit due to thermal runaway of the battery,the temperature of ots adjacent battery rises rapidly to the temperature sufficient to open the safety valve.Sparks were generated at the battery connector,which ignited the gas discharged above the positive pole and eventually causing the prapagation of thermal runaway.With the propagation of thermal runaway,the critical thermal runaway temperature of lithium-ion battery decreased,which reduced the time interval of thermal runaway propagation between adjacent lithium-ion batteries and increased the control difficulty.In view of the thermal runaway characteristics of lithium-ion battery,pure water mist was applied to suppress the thermal runaway.It is found that in the parallel battery pack,applying pure water mist after the thermal runaway of the first lithium-ion battery can effectively control the thermal runaway propagation,and control the surface temperature of other batteries below 100℃.Experiments of suppressing thermal runaway of lithiumion battery with different surface temperatures using pure water mist were conducted.The results showed that when the surface temperature of the lithium-ion battery reaches 165℃or below,the pure water mias can successfully control the thermal runaway of the lithiumion battery.When the surface temperature of lithium-ion battery reaches 170℃,its thermal runaway can not be suppressed by pure water mist.In order to improve the effect of water mist on suppressing the thermal runaway of lithium-ion battery,four additives of different concentrations,namely sodium dodecylbenzene sulfonate,Tween 20,urea and potassium carbonate,were added into water to conduct the experiment of water mist for suppressing the thermal runaway of lithium-ion battery.The results showed that the optimal concentrations of additives in water mist for the thermal runaway of lithium-ion battery was 1.5%,0.02%,12% and 11% respectively.The experiment of thermal runaway suppression with water mist with composite additives,showed that the best composite formula for suppressing thermal runaway was 12% urea,0.02% Tween 20 and 87.98%distilled water.By reducing the droplet size and blocking the chemical reaction chain,using the composite additives water mist the controllable temperature of lithium-ion battery for thermal runaway can be increased to 175℃.Figure [35] Table [15] Reference [54]...