高能量密度21700型锂离子电池热失控行为研究

Research on Thermal Runaway Behavior of High-Energy-Density 21700 Lithium-Ion Batteries

锂离子电池安全性至关重要,利用加速绝热量热仪对荷电状态分别为0%、25%、50%、75%、100%的21700型锂离子电池进行热失控行为探究,同时对隔膜进行热稳定性分析。研究表明:荷电量越大发生副反应的初始温度点越低、热失控的起始温度点越低、最高温度越高;荷电量越大发生热失控时温升速率越大、反应越剧烈且质量损失越多。该结果表明隔膜破裂引发内短路不是导致锂离子电池热失控的根本原因,电池短路释放的热量会加速副反应的发生,热失控的根本原因是电极材料与电解液之间的反应以及后续各种放热副反应释放的热量。

The safety of lithium-ion batteries is very important.In this study,the adiabatic rate calorimeter was used to explore the thermal runaway behavior of 21700 lithium-ion batteries with states of charge(SOC)of 0%,25%,50%,75%and 100%respectively.Meanwhile,the thermal stability of the separator was analyzed.It was demonstrated that with the increasing of SOC,the onset temperature of side reaction was lower,the initial temperature point of the thermal runaway was lower,and the maximum temperature was higher.The higher the SOC,the higher the temperature rise rate when thermal runaway occurred,the more violent the reaction,and the more mass loss.The results showed that the internal short circuit caused by the separator melting was not the underlying reason for the thermal runaway of lithium-ion batteries.The heat released by the short circuit would accelerate the occurrence of side reactions.The underlying reason for the thermal runaway is the reaction between the electrode material and electrolyte,and the heat released by subsequent exothermic side reactions.