Key Points Regarding Electrical Safety in Small Cylindrical Li-ion Cell Assemblies During Overcharge or Partial Short-Circuit

Abstract:
Safety of lithium-ion batteries is a key criterion for large-scale deployment as for electrical vehicles. When Li-ion cells are abused, serious consequences can occur, the worst-case scenario being the thermal runaway. Although easy to manage for small devices, electrical safety is a new challenge for increasingly powerful systems. However, standards for electrical design and abusive testing do not always seem to be appropriate for these high power systems. In this work, an improved scheme of the overcharge test has been proposed, allowing representative stresses of the system to be applied to a cell. Tests on 18650 size cylindrical cells equipped with Current Interrupt Devices CID have made it possible to trace the beginning of the safety zone of this element for the first time. This work investigates the relationship between the size of a battery system, the electrical architecture, the constraints on cells in case of electrical defect and the switching capacity of the integrated elements of the cells.