Advanced Single Cell Thermal Runaway Initiation Techniques

Abstract

The evaluation of lithium ion battery safety has traditionally focused on the performance of single cells exposed to abusive conditions. As lithium ion batteries are fielded in increasingly large and complex systems, the system level safety performance is becoming of greater concern. Testing laboratories and battery end users have begun to consider the hazards associated with a localized thermal runaway event, a single cell or small group of cells, propagating to the bulk of a large battery system. Evaluating this propagating failure requires initiating thermal runaway of a single cell or group of cells and observing how that failure affects the surrounding system.Ultimately, testing cell to cell propagation requires a method for initiating or simulating single cell runaway while adding a minimum of excess energy into the system. Traditionally single cell failure is initiated with standard battery abuse tests, such as overcharge, thermal ramp and nail penetration tests. However, nail penetration tests can be difficult to perform in fully developed battery systems while overcharge and thermal ramp add a significant amount of excess energy into the battery system. Recent work at Sandia has looked at non-traditional thermal runaway triggers that can be applied to off-the-shelf cells. Single cells were initiated using a fiber coupled laser to create a localized failure on a cell. The ability to initiate single cell failure in both pouch and cylindrical cells is in multiple orientations is demonstrated. Limited cell to cell propagation initiated by the laser is performed as well, demonstrating the technique as a low energy initiation source for propagation testing.Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.