Determining the effects of non-catastrophic nail puncture on the operational performance and service life of small soft case commercial Li-ion prismatic cells

Abstract

This work focused on the operational effects of Li-ion batteries (LIBs) that had been partially damaged and were allowed to continue operating afterwards. The intent was to simulate the operation of a damaged cell in an abusive environment, such as that found in electric vehicles and hybrid-electric vehicles. A test rig implementing a drop hammer with a nail attached was used to puncture approximately halfway through cycling LIBs to determine how their operation was affected. For all LIBs tested, the puncture caused a rapid spike in temperature. The dynamic impact immediately caused an initial drop in capacity of approximately 11%, and capacity continued to decrease throughout the remainder of the cycles. The cells also reached their end of life within an average of 43 cycles after the puncture, much sooner than the rated lifetime. Postmortem analysis of the punctured LIBs presented impact induced physical damage to the electrodes, oxidation of the electrolyte, and degradation of the interior components of the cells. This caused a decrease in discharge capacity and shortened useful lifetime due to hindering the charge capability of the cells. The degradation mechanism of the cells was further determined using peak tracking of the incremental capacity curves throughout their lifetimes.