Experimental analysis of short-circuit scenarios applied to silicon-graphite/nickel-rich lithium-ion batteries
Résumé
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 silicongraphite
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 a maximum, 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.
