Experimental Analysis of Short-Circuit Scenarios Applied to Silicon-Graphite/Nickel-Rich Lithium-Ion Batteries

Short-circuit incidents pose a severe safety threat to lithium-ion batteries during lifetime. Understanding the underlying electrochemical behavior can help to mitigate safety risks. The electrochemically-caused rate-limiting behavior is analyzed using a quasi-isothermal test-bench, where external and local short-circuit conditions are applied to single-layered pouch cells (50 mAh). The cell voltage, the heat generation rate, and either the short-circuit current or a local electrical potential are measured and used to characterize the short-circuit intensity. The results of 35 custom-built silicon-graphite SiC/NCA and SiC/NMC-811 cells with 2.5 wt.-% silicon are benchmarked to previously studied graphite G/NMC-111 cells. An additional current plateau appears for the silicon-graphite/nickel-rich cells, which is ascribed to the anode-limited electrode balancing. At amaximum, 29% of the total dissipated heat is caused during over-discharge. The effect of cyclic aging on the impact of the short-circuit behavior is investigated with aged single-layered pouch cells (SoH 80%), which revealed nearly the same levels of over-discharge as non-aged cells. A lithium reference electrode is used to visualize polarization effects in the anode during ESCs and to evaluate the onset of copper dissolution (3.2 V vs Li/Li+), which could be estimated up to 20% of the negative current collector mass.