Thermal Runaway Behavior And Early Warning System Of Ternary Lithium Battery Under Overcharge And Overheating Conditions

Ternary lithium battery,because of its long cycle life,high specific energy and environmental protection,has gradually become the most competitive new energy.However,there are still many potential safety hazards and accidents.Overcharge and overheating of ternary lithium battery are the main reasons for the uncontrolled spread of thermal runaway,which leads to explosion accidents of battery.It poses serious threats to the safety of public life and property.Therefore,there is important practical significance to analyze the thermal runaway behavior of ternary lithium battery under overcharge and overheating conditions,extract the characteristic parameters and research the technology of early warning.Taking the common commercial ternary lithium-ion battery as the research object,this paper mainly uses battery testing system(BTS8.0),temperature acquisition system(EX3008),and temperature control system(KFR-72LW/(72566)Aa-2)for experimental research,and analyzes the thermal runaway behavior and characteristic parameters of ternary lithium-ion battery under overcharge and overheating conditions,establishes the early warning criterion and develops a reliable early warning system.The main research work is summarized as follows:1.The thermal runaway behavior of ternary lithium battery under various overcharge conditions.The homemade thermal runaway experimental platform of ternary lithium battery was carried out overcharge experiment on ternary lithium battery with initial SOC(battery charge)of 25%,50%,75% and 100% at the rate of 0.5C,1C and 3C.The phenomenon of thermal runaway and its influencing factors under overcharge conditions were analyzed.Meanwhile,monitoring the battery voltage and surface temperature parameters in real time,combining with the variation law of them with time and SOC,the parameter characteristics were analyzed and the relevant characteristic parameters were extracted.The results show that the higher the charging rate is,the shorter the thermal runaway time is,and the higher the probability of combustion explosion is.However,the initial charge of the battery has no obvious relationship with the thermal runaway of overcharge.2.The thermal runaway behavior of ternary lithium battery under various overheating conditions.The homemade thermal runaway experimental platform of ternary lithium battery was carried out overheating experiment on ternary lithium battery with initial SOC(battery charge)of 25%,50%,75% and 100% at 80 ℃,140 ℃,200 ℃ and 260 ℃.The phenomenon of thermal runaway and its influencing factors under overheating conditions were analyzed.Meanwhile,monitoring the battery voltage and surface temperature parameters in real time,combining with the variation law of them with time and SOC,the parameter characteristics were analyzed and the relevant characteristic parameters were extracted.The results show that the external temperature determines whether the thermal runaway occurs,and the higher the external temperature and the initial charge,the easier the thermal runaway occurs.3.Based on the variation characteristics of voltage and surface temperature of ternary lithium battery under overcharge and overheating conditions,the process of thermal runaway under overcharge and overheating was divided into three different stages,and the risk degree of different stages was analyzed.It’s pointed out that there was no obvious change in the appearance of the battery in the first stage.In the second stage,the battery had the phenomena of shell opening and bulging.And in the third stage,the battery burned and exploded.On this basis,the early-warning criteria of overcharge and overheating runaway of ternary lithium battery based on characteristic parameters were established.4.An early warning system of thermal runaway for overcharge and overheating of ternary lithium battery was designed.Combining with the established thermal runaway early warning criterion to build an overall architecture of the early warning system,selecting pertinent system hardware module,completing the software writing of the platform layer,and combining software with hardware,a complete early warning system was constructed.And the designed early warning criterion and system were verified by experiments of thermal runaway for overcharge and overheating.The results show that,the scheme and system can precisely judge the three stages of overcharge and overheating of ternary lithium battery.The early warning criterion of thermal runaway is reasonable,and the early warning judgment of the device is reliable and effective.