Investigation On The Thermal Runaway And Propagation Characteristics Of Batteries Under The Heating Condition

The widespread use of battery vehicles is restricted by battery safety issues.When the battery is under the extreme condition of high temperature heating,decomposition of the battery materials within the battery system may cause the accumulation of heat,further touch the battery thermal runaway.If this phenomenon occurred in a battery module,it may induce the thermal runaway propagation,which will have a bad effect on the surrounding batteries.Therefore,the mechanism of the above phenomena is studied in this paper to provide data and method support for battery materials and thermal barrier technology,so as to improve the safety of electric vehicles.A kind of 18650 nickel-cobalt-manganese lithium-ion battery produced by a battery factory was chosen to be investigated.All the work was carried out as follows:First of all,according to the existing research results,the internal mechanism of thermal runaway of power battery was analyzed theoretically,and parameters of the battery materials,such as the pre-factor,activation energy,and decomposition heat,etc.,were obtained for simulation calculations.Secondly,thermal runaway experiment was carried out by using the electric heating wire to heat the single battery.Otherwise,the two-dimensional non-stratified and two-dimensional layered geometric model of the cell was established for the simulation analysis.The results showed that the temperature curve obtained by the experiment and the two modeling methods are consistent,which proves that the two simulation models are feasible.It also was found that the non-stratified modeling method can reduce the amount of calculation while ensuring the accuracy of the simulation analysis.Then,the simulation model of the 3×3 battery module with the M-type diversionstructure was established to explore the mechanism of thermal runaway propagation,mainly calculated by two calculation ways,one of which was to calculate heat flux transferred by only one heat transfer path(heat conduction,heat convection or heat radiation),and the other of which was to calculate the total heat flux by the three heat transfer paths.The results showed that when calculated by the first calculation way,the temperature of each battery in the battery module decreases with the increase of the distance between batteries,and in different heat transfer paths,the battery number with the highest temperature is different.When the second calculation way is adopted,the temperature value of battery 8 is the highest,and the heat flux between battery 8 and battery 5 is mainly transferred by heat convection.Furthermore,in comparison of resultsby the two calculation ways,it was found that the order of influence level of heat transfer path on battery 8 are the same,heat convection > heat conduction > heat radiation.Finally,the simulation of the thermal runaway propagation in the battery module with three different monolithic diversion structures was carried out.It can be seen that the battery 8 is affected differently by different heat transfer modes under different diversion structures,and the nickel plate type and the BONDING line type diversion structure can effectively reduce the influence of the diversion structure on the heat propagation between the batteries,and the safety is high.