System-scale short-circuit behavior of small cylindrical Li-ion cells

Unprotected short-circuits, stemming from situations such as double insulation faults for example, represent a major concern for Li-ion battery packs safety, often culminating in thermal runaway of the cells. The severity of this scenario escalates with the size of the battery, due to the resultant surge in fault currents and voltages, which can be orders of magnitude higher than those encountered in single-cell instances. In such cases, the internal elements of the cells, such as tabs, are tasked with interrupting the current flow, yet information regarding their breaking capacity remains elusive from manufacturers’ datasheets or scientific knowledge. In this study, a novel methodology coupled with an innovative test bench have been set up to replicate, on a single Li-ion cell, the current and voltage constraints characteristic of a battery pack. Short-circuit tests, reaching a maximum of 92.4 V and 1200 A, were conducted on a commercial 3Ah NCA cylindrical (21700-format) Li-ion cell to evaluate the breaking capacity of its internal components and elucidate safety implications.