Development of an on-Demand Internal Short Circuit (NREL/NASA)

NREL, in conjunction with NASA, has developed an internal short circuit (ISC) device that can be placed anywhere within the battery and may be used with both spirally wound and flat-plate cells.  The internal short device is small compared to other shorting techniques being developed by industry and does not rely on mechanical pressure deforming the battery to activate the short as do most of the other “internal shorts” being developed.  The battery can be used and cycled within normal operating conditions without activating the internal short device.  This allows for the battery to be aged prior to activation of the internal short.  Another unique feature of NREL’s internal short device is that the resistance of the short can be tuned to simulate a hard (more energetic) or soft (less energetic) short. Once the short is activated, the positive and negative components of the battery are internally connected within the cell and internal short circuit begins.  NREL’s ISC can simulate all four types of shorts within a cell – collector to collector, collector to anode, collector to cathode and collector to collector.

NREL uses the internal short circuit device to better understand the failure modes of Li-ion cells and to validate NREL’s abuse models.  The internal short produced by NREL’s device is consistent and is being developed as an analysis tool for battery manufacturers and other national laboratories as well as OEMs. This has broad-reaching applications as automakers bring electrified vehicles to market in larger

Over the past three years, NREL has implanted their ISC into cylindrical 18650 LiCoO₂ cells to determine the effectiveness of a shutdown separator with regards to ISC type – in particular, we compared a collector to collector ISC versus a collector to aluminum ISC.  NREL has also been using the ISC to determine the effectiveness of a non-flammable electrolyte in LiMnO₄ pouch cells.  During our presentation, we will update the battery community on the effectiveness of the ISC in understanding the behavior of these safety devices incorporated into these two cell types and chemistries.  We will also show how the ISC can be used for propogation testing in modules and packs.