不同循环周期锂离子动力电池热失控特性分析

热失控作为锂离子电池的失效方式之一,对研究动力电池的热安全性具有至关重要的作用。以26 Ah软包型锂离子动力电池为研究对象,结合混合动力脉冲能力特性(HPPC)测试和交流阻抗测试两种方法,利用扩展加速量热仪(EV+ARC)来研究不同循环周期下动力电池的电化学行为和热失控行为,并进一步考察电池的热稳定性和安全性。结果表明,电池经过常温下1 000周循环后容量下降至83%,直流内阻随循环次数增加而增大。从热失控曲线来看,随着循环次数的增加,电池自产热温度呈现总体下降,说明不断循环老化的电池SEI膜热稳定性逐渐变差。交流阻抗谱显示,SEI膜与电解液的阻抗随着循环次数增加而增大,说明SEI膜与电解液结构和成分随着循环周期的变化是影响其热稳定性的关键因素。

Analysis of thermal runaway characteristics for lithium ion power battery in various cycles

As one failure mode of lithium ion battery,thermal runaway plays a vital role in the research on thermal safety of power battery.A type of 26 Ah soft package lithium-ion battery in various life cycles was studied.Two electrochemical methods of HPPC and AC impedance were tested in order to study the thermal behavior and safety of the batteries using extended volume-accelerating rate calorimetry (EV+ARC).The results show that the cell cycled at normal temperature drops to 83％ after 1 000 cycles and the resistance increases with cycle number increasing.The overall decline in onset temperature of cell is shown in thermal runaway curve,which suggests thermal stability of SEI film decreases with cycle number increasing.The electrochemical impedance spectra shows the resistance of SEI film and electrolyte increases with cycle number increasing,indicating that composition and structure change of SEI film and electrolyte are key factors affecting thermal stability of the cell.