Study On Safety Performance Of 18650 Lithium Ion Battery Under Mechanical Abuse

Lithium-ion battery,as the power source of electric vehicle,if extrusion occurs serious deformation in traffic accidents,it is easy to cause internal short circuit or even the risk of thermal runaway,resulting in personal and property losses.Therefore,it is of great significance for the safe application of power lithium-ion batteries to study the mechanical response and safety performance of power lithium-ion batteries under mechanical abuse.In this paper,the 18650 power lithium-ion batteries are taken as the research object,and the safety performance of the battery under mechanical abuse is studied by experiment and simulation.In the experiment,the battery was loaded by quasi-static compression and dynamic impact.The mechanical response,voltage change,temperature change and failure mode of the lithium-ion battery during the loading of different working conditions were studied.In addition,the finite element simulation method was used to simulate the failure of the internal components of the lithium-ion battery under mechanical abuse.In the quasi-static compression experiment,the batteries were compressed from both the radial and axial directions by varying the SOC and loading speed.The results show that when the battery is deformed greatly,electrolyte leakage and internal short circuit may occur,and the battery temperature will rise sharply in a short time.In the axial compression experiments,the heat is released after the buckling of the battery,but there is no serious thermal runaway such as explosion.In the radial compression experiment,when the SOC is high and the loading speed is fast,the battery will undergo severe thermal runaway such as explosion and fire after deformation.The thermal runaway of the battery is the result of the combination of loading direction,loading rate and SOC,the essence is the rapid and massive accumulation of heat.In addition,the batteries after deformation were cyclically charged and discharged,and the effect of four different deformation quantities on battery life were studied by monitoring the capacity attenuation.In the dynamic impact test,the dynamic compression and dynamic indentation experiments of lithium ion batteries were carried out by using the drop hammer tester.The effects of SOC,impact energy and impact mass changes on the safety performance of the battery under two impact modes were studied,and the experimental results of the impact mode were analyzed and compared.The results show that in the dynamic compression experiment,the battery is deformed but no internal short circuit occurs.In the dynamic indentation experiment,all the batteries have voltage drop and temperature rise.When the SOC reaches 80%,the battery may even have serious thermal runaway such as explosion and fire,and the maximum temperature reaches 600℃.Comparing the effects of two different impact modes on the safety performance of the battery,it was found that the battery was more damaged when the local deformation occurred compared to the overall pressure,and the battery was more likely to be dangerous.Finally,the finite element simulation method was used to simulate the failure of the battery under different working conditions.A finite element model of the battery was built and loaded in both static and dynamic ways.The simulation found that whether in the static compression or dynamic impact,the casing of the battery is the first to fail and the casing can resist the main external force in the early stage of loading,which can protect the jellyroll.The dynamic impact simulation also found that the anode current collector first failed after the battery casing yielded.The negative electrode has a large impact on the safety performance of the jellyroll.