The early detection of micro internal short circuit (ISCr) cells can provide sufficient response time for preventing accidents such as spontaneous thermal runaway in battery packs of electric vehicles, and greatly improve safety. Because the existing models describing ISCr are mainly equivalent circuit models and three-dimensional physics-based models, we build a pseudo-two-dimensional model of micro ISCr cells to make up for the gaps. Using the calculation results of this model, we reveal the phenomenon of electric quantity depletion and the variation of internal electrochemical parameters when a micro ISCr occurs in the cell. We find the effective electrical conductivity of the separator is a crucial parameter describing the ISCr severity and determine reasonable values for this effective conductivity for fault diagnosis and battery design. Moreover, we propose an impedance-identification method that can be used for ISCr diagnostics. Through the simulation and experimental results, we find that the impedance of micro ISCr cells is different from that of normal cells and shows a certain regularity with the increase of ISCr severity.

微型内部短路（ISCr）电池的早期检测可以提供足够的响应时间，以防止发生诸如电动汽车电池组中的自发性热失控之类的事故，并大大提高安全性。由于现有描述ISCr的模型主要是等效电路模型和基于三维物理学的模型，因此我们建立了一个微型ISCr单元的伪二维模型来弥补这一空白。使用该模型的计算结果，我们揭示了当电池中出现微ISCr时电量耗尽现象和内部电化学参数的变化。我们发现隔板的有效电导率是描述ISCr严重性的关键参数，并为故障诊断和电池设计确定该有效电导率的合理值。此外，我们提出了一种可用于ISCr诊断的阻抗识别方法。通过仿真和实验结果，我们发现微ISCr细胞的阻抗与正常细胞的阻抗不同，并且随着ISCr严重程度的增加呈现出一定的规律性。