| The globalization of electric vehicles has become a trend,but the safety of ternary lithium batteries has seriously hampered the vigorous development of my country’s electric vehicle industry.Therefore,they directly attacked the technical pain points of ternary lithium batteries and mastered the law of thermal runaway under the abuse of ternary lithium batteries.Through the intrinsic safety design of the battery,the passive safety design,and the active safety design,the risk control research of the thermal runaway of the ternary lithium battery is carried out.In this paper,the prismatic NCM ternary lithium battery for vehicles is the research object,the basic principle and thermal runaway mechanism of the lithium battery are studied,and the simulation model of the NCM ternary lithium battery is established.First,the electrochemistry of the NCM lithium battery is analyzed through the WLTC working conditions-Thermal characteristics,and optimized the structure of the battery lug,established the optimized battery acupuncture thermal runaway model,and compared the temperature of the acupuncture battery before and after the optimization of the lug based on the thermal runaway mechanism.Secondly,through the lithium battery acupuncture model,the effects of acupuncture factors such as acupuncture diameter,acupuncture position,acupuncture level,and state of charge on the thermal runaway of the battery are separately studied.Finally,the battery’s acupuncture influence factors build a battery’s extreme abuse acupuncture model,realize battery temperature management and graded warning through passive safety design and active safety design,respectively,and put forward relevant safety recommendations for the out-of-control acupuncture heat of lithium batteries.research shows:(1)According to the composition structure and working principle of the lithium-ion battery: the incentives for thermal runaway of a lithium-ion battery are divided into artificial unreasonable operation,physical attack of the external environment,and chemical attack of the external environment.The form of the internal short circuit is divided into instantaneous reaction and the Stacking effect.(2)According to the electrochemical-thermal coupling model under WLTC operating conditions: when the discharge rate is from 0.5C to 2C,the maximum voltage difference rises from 0.225 V to 0.712 V,and the maximum temperature rise of the battery rises from 0.464°C to At 12.241°C,the maximum temperature difference increased from 0.067°C to 1.359°C.The intrinsic safety of the battery is optimized.When the width of the positive electrode ear is 0.03 m,the width of the negative electrode ear is 0.05 m,and the distance between the positive and negative electrode ears is 0.05 m,the battery temperature field uniformity is the best.The optimized battery acupuncture thermal runaway model was established,and the non-linear fitting comparison showed that the peak temperature of the battery after the optimization was14% lower than the temperature before the optimization,which proved the effectiveness of the optimization of the battery tabs.(3)By simulating the influencing factors of different acupuncture conditions on battery thermal runaway: when the acupuncture diameter increases from 6mm to 18 mm,the peak temperature of the battery drops from 323.7℃ to 221.5℃;when the acupuncture positions are different,the battery The peak temperature of the battery has a small change(309.4℃-349.1℃);when the acupuncture level is to pierce the negative electrode and the diaphragm layer,the peak temperature of the battery is up to 731.4℃;when the state of charge of the battery drops from 100% to 0%,The peak temperature of the battery dropped from 309.4°C to 201.4°C.Under acupuncture conditions,the thermal runaway time when the NCM lithium battery is completely pierced is 1.67 s,and the battery’s diaphragm layer is pierced is the critical condition for thermal runaway of the NCM lithium battery.(4)Through the extreme abuse acupuncture model of battery thermal runaway: the paraffin/graphene phase change composite material is used to superimpose the battery surface to build a passive safety battery thermal management system model so that the peak temperature of the battery acupuncture thermal runaway is reduced from 383.35℃To 195.03°C.According to the thermal runaway mechanism,the non-linear fitting of the temperature curve of the acupuncture battery before and after thermal management is performed to prove the effectiveness of the thermal management system;the program flowchart of the battery management system is drawn through the active safety design to realize the graded warning of the severity of battery acupuncture,and Proposals for battery thermal runaway risk control from the three dimensions of battery intrinsic safety,passive safety,and active safety are put forward to prevent the occurrence of battery thermal run away from the source,and fundamentally avoid battery needle stick safety accidents. |
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