Using Lix (Ni0.80Co0.15Al0.05)O2 (NCA) battery vent gas (BVG) as an archetypical multi-component mixture, a comprehensive computational investigation with detailed chemical kinetics is conducted on its pressure-temperature explosion limits response characteristics under different states of charge (SOC) and equivalence ratios conditions. The results show that the BVG explosion limits exhibit the characteristics Z-shaped curve under all of the SOC conditions, which demonstrates the dominance of H2 in the explosion response of the BVG. Furthermore, with increasing SOC, the explosion limit of the BVG mixture moves significantly to the lower temperature regime at high pressures condition. That is because the proportion of C2H4 in the BVG increases with increasing SOC, and the nonlinear characteristics of the C2H4 on the third explosion limit become more prominent. The more intriguing result is that with increasing equivalence ratio, the explosion limit curve rotates counterclockwise around a crossover point, and it is determined by the chain branching reaction with oxygen and the chain propagation reactions related to H2 and C2H4 for the low- and high-pressure conditions, respectively. To elucidate the key controlling mechanisms, the sensitivity and reaction path analyses under the conditions near the explosion limits of the typical battery vent gas are performed. The dominant kinetic pathways are found to be these of H2 and CO with the highly reactive H2O2 kinetics dominating. Moreover, the small amount of C2 species in BVG has been found to significantly influence the explosion boundary especially at elevated pressures. Results of this study are expected to offer potential options in the anti-fire BVG mixture design strategies, and provide useful guidance for the safety valve control strategy as well as the post-processing of the lithium-ion battery catch on fire.

中文翻译：

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关于 NCA 电池排气的爆炸极限


以 Lix （Ni0.80Co0.15Al0.05）O2 （NCA） 电池排气气体 （BVG） 为原型多组分混合物，对其在不同荷电状态 （SOC） 和等效比条件下的压力-温度爆炸极限响应特性进行了详细的化学动力学综合计算研究。结果表明，在所有SOC条件下，BVG爆炸极限均表现出Z形曲线特征，表明H2在BVG爆炸响应中占主导地位。此外，随着 SOC 的增加，BVG 混合物的爆炸极限在高压条件下显着移动到较低的温度状态。这是因为 C2H4 在 BVG 中的比例随着 SOC 的增加而增加，并且 C2H4 在第三爆炸极限上的非线性特性变得更加突出。更有趣的结果是，随着等效比的增加，爆炸极限曲线围绕交叉点逆时针旋转，它分别由低压和高压条件下与氧的链支链反应和与 H2 和 C2H4 相关的链传播反应决定。为了阐明关键的控制机制，在接近典型电池排气气体爆炸极限的条件下进行了灵敏度和反应路径分析。发现主要的动力学途径是 H2 和 CO 的这些，其中高反应性 H2O2 动力学占主导地位。此外，已发现 BVG 中少量的 C2 物质对爆炸边界有显著影响，尤其是在高压下。 本研究结果有望为防火 BVG 混合物设计策略提供潜在选择，并为安全阀控制策略以及锂离子电池着火的后处理提供有益指导。