Experimental simulation of internal short circuit in Li-ion and Li-ion-polymer cells

► A multi-parameter controlled pinch test was developed to study the occurrence of internal short circuits in Li-ion and Li-ion-polymer cells. ► This study shows that the improved pinch test can reproducibly create ∼1–2 mm size internal short circuit in one or two inner layers of a cell anode and cathode, possibly mimicking the type of internal short that may occur during service. ► This study also shows that the improved pinch test could be used to assess the risk of alternate cell designs to thermal runaway and rank them accordingly. A multi-parameter controlled pinch test was developed to study the occurrence of internal short circuits in Li-ion and Li-ion-polymer cells. By tuning the control parameters (i.e., cell voltage as well as pinching area, load, and speed), the pinch test can reproducibly create an internal short between a cell jelly-roll's inner layer electrodes as small as 1-mm wide. This recreates conditions similar to those that may occur during service. In this paper we demonstrate the use of the pinch test as a means to assess design and manufacturing changes in Li-ion-polymer cells on their thermal stability and to identify features or characteristics that lower risk of potential thermal events created by internal short circuits.