Quasi-Isothermal External Short Circuit Tests Applied to Lithium-Ion Cells: Part II. Modeling and Simulation

Abstract

Measurement data gained from quasi-isothermal external short circuit tests on single-layered pouch-type Li-ion cells presented in the first part of this combined work was used to validate a well-known homogenized physical-chemical model for different electrode loadings, cell temperatures, initial cell voltages, and external short circuit resistances. Accounting for diffusion-limited reaction kinetics, effective solid phase diffusion coefficients, and one representative active material particle size within each electrode, the model is capable of describing the experimentally observed characteristic change in magnitudes of current and heat generation rate throughout the short circuit. Underlying mechanisms for the observed characteristics are studied by evaluating the predicted concentration distribution across the electrodes and separator and by calculating the cell polarization due to ohmic losses, diffusion processes, and reaction kinetics. The importance of mass transport in the solid and liquid phase limiting reaction kinetics is discussed and evaluated in the context of a sensitivity analysis. Concentration dependent transport properties, electrode tortuosity, particle size, and electrode energy density are affecting different stages of a short circuit. Simulation results suggest a strong impact of electrode design on the short circuit dynamics allowing for an optimization regarding a cell's energy and power characteristics whilst guaranteeing a high short circuit tolerance.

On The Impact of the Locality on Short-Circuit Characteristics: Experimental Analysis and Multiphysics Simulation of External and Local Short-Circuits Applied to Lithium-Ion Batteries

“…0 V as well as 5, 50, and 500 mΩ), are using the terminal voltage for a first, simple correlation as the current flux is not measureable for the LSC tests. As shown in our previous works 31,32 investigating P1-type ESC tests, the cell's polarization correlates to the electrochemical Regarding the terminal voltage in Fig. 4c, the different stages appear similarly for the P1-LSC results.…”

“…Correction of LSC polarization effects.-As discussed before, comparing the terminal voltages may incorporate a certain error due to the expected high local polarization around the penetration site in the LSC tests as indicated by the local potential measurements (see To do so, a multidimensional multiphysics model [39][40][41][42][43][44] previously validated for the P1-type cells 32 is presented in the supplementary material and used to simulate an exemplary ESC and LSC case, which reveal a similar current flux either through the tabs or the internally shorted area in the simulation model. As the same current flux is simulated, similar shorting resistances are expected and most likely both scenarios occur at the same short-circuit condition and shorting intensity.…”

“…temperature) for calculating the heat rate is not directly affected of the local polarization effects due to the expected thermal uniformity in the copper bars as shown in our previous works. 31,32 Hence, the P1-type ESC and P1-LSC shorting scenarios can be analyzed regarding the plateau and transition zones of the heat rate, which appears similarly to the current flux, terminal voltage, and local electrical potential (see Figs. 4a-4c) only with a certain delay in time 31 due to the inertia of heat transport phenomena and the calorimetric test bench.…”

“…<1 s) and the subsequent, various electrochemical rate limitation effects (i.e. >1 s), 31,32 which are caused by either the anode or the cathode within the tested cells. To further study various LSC conditions in a stacked electrode configuration, nail/needle penetration were further applied to cells with two electrode stacks with and without a hole within one of the electrode stacks.…”

Research Status and Analysis for Battery Safety Accidents in Electric Vehicles

“…(3) 德国慕尼黑工业大学。慕尼黑工业大学的 RHEINFELD 教授团队也针对外部短路情况下的电池 安全特性开展了研究。该团队重点针对准等温情况下 的外部短路进行研究，包括进行了不同测试条件下 的短路试验研究，观察短路过程中的电池特性及内 部变化机理，并进一步开展了建模与仿真研究 [40][41] 。 此外，还有部分学者开展了相关研究 [34,42] ，目 前外部短路的研究尚处于起步阶段，尽管当前的研 究在一定程度上阐明了外部短路的电热特性，但试 验数据的完备性仍须进一步提高，尤其外部短路与 其他故障并发复杂情况的试验分析仍匮缺。 3.5 挤压/碰撞特性研究 锂离子电池的车载应用具有一定的特殊性，由 于汽车碰撞是难以避免的现象，很多学者开展了电 池挤压穿刺等机械滥用试验。这里列举部分主要的 研发团队如下。…”