Impact of external short circuit on lithium-ion batteries: a post-mortem case study

Abstract

This study presents the findings of post-mortem analysis on commercial 21700 lithium-ion cells with nickel-rich NCA|graphite chemistry subjected to external short-circuiting conditions, compared to a new cell discharged to 0 V. The aim was to identify the degradation mechanisms and to assess the evolution of the battery behavior influenced by abusive external short circuit testing. A comprehensive analysis was conducted using a range of spectroscopic techniques, including X-ray computed tomography, X-ray diffraction, and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. The results of this study indicated that ESC conditions induce structural deformation in the jelly roll and enhance crack formation in both the cathode and the anode surfaces. These cracks are pivotal in comprehending the loss of active material from the cathode and its migration toward the anode. Furthermore, the active materials present in the cathode (nickel-rich NCA) and anode (graphite) have undergone modifications in their lattice property after short-circuiting, which also alters the physical properties of the separator.