| Lithium ion battery has the advantages of high specific energy and high working voltage,which makes it applied in more and more fields and become the leader of new energy field.However,it also leads to a certain degree of danger.Under the condition of abuse,the battery will lose control of heat and even explode.In the lithium-ion battery pack,the thermal runaway of a single battery will spread to the surrounding area,which will lead to the thermal runaway of the surrounding normal battery,chain reaction and more serious consequences.Therefore,the research on the law of thermal runaway spread of lithium-ion batteries and its control methods can clarify the behavior and specific hazards of thermal runaway spread of lithium-ion batteries,grasp the law of thermal runaway spread of lithium-ion batteries,determine the influencing factors of thermal runaway spread,and compare the inhibition effect of different fire extinguishing agents on fire and spread of lithium-ion batteries.So we can find the way to restrain the thermal runaway spread of lithium-ion batteries,reduce the possibility of the thermal runaway spread of batteries,and provide the theoretical basis and technical support for the promotion and application of lithium-ion batteries.The main contents and research progress of this paper are as follows:(1)The thermal runaway experiment platform of lithium-ion battery was improved to study the influence of SOC and environment atmosphere on the thermal runaway of lithium-ion battery caused by short circuit.It is found that the temperature of the battery rises rapidly when the battery is short circuited,and the heating rate of the positive and(2)negative electrodes is very different,and the heating rate of the negative electrode is much higher than that of the positive electrode.The state of charge has a great influence on the thermal runaway of battery short-circuit: the process of thermal runaway of 18650lithium-ion battery short-circuit with the state of charge of 100% SOC can be divided into three stages: the first is the continuous rise of battery temperature;the second is the initial explosion due to the rupture of the positive relief valve of battery;the third is the explosion of battery.The temperature of 50% SOC battery will rise rapidly,but it will not be out of control completely.(3)The influence of ambience on thermal runaway of lithium-ion battery caused by external short-circuit is weak.There is no significant difference in the surface temperature change of battery,the temperature inside the device,the over-pressure and gas output when explosion occurs under the condition of vacuum and atmospheric pressure.(4)The effects of SOC,ambient temperature,the number of thermal runaway batteries around normal batteries and the way of battery stacking on the thermal runaway spread of18650 Li-ion batteries were studied by using the test platform.It is found that the higher the ambient temperature is,the higher the state of charge of the battery is,the more the number of thermal runaway batteries in the same area is,and the easier the thermal runaway spread in the battery pack is;the diamond stacking battery pack is more likely to generate thermal runaway spread than the square stacking battery pack.(5)By using the improved thermal runaway test platform of lithium-ion battery,the thermal runaway and its spread of 18650 lithium-ion battery pack,which is represented by the lithium-ion battery,are restrained by different kinds of fire extinguishing agents.The test results show that the three extinguishing agents,such as water,perfluorohexanone(Novec1230)and water film foam extinguishing agent(MPQ),can quickly and effectively extinguish the open fire caused by thermal runaway of lithium ion batteries and prevent their reburning.And these three kinds of fire extinguishing agents can effectively prevent the temperature rise of the surrounding normal battery,quickly reduce the battery temperature below the safety threshold,and prevent the runaway heat from continuing to spread.The cooling effects of these three kinds of extinguishing agents are as follows:perfluorohexanone > water > water film forming foam extinguishing agent. |
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