(Invited) Calorimetry of Cell Failure in Multiple Formats and Capacity

Abstract

Accelerating Rate Calorimetry (ARC) has previously been used to evaluate differences observed in various active materials with a typical comparison shown in the figure below. This evaluation is usually performed on small cells of roughly the same capacity (~1 AH) to allow for an easy comparison of active materials as they are developed. However, this and similar calorimetry methods present a means to perform more quantitative measurements of the heat generated and kinetics of thermal runaway. Sandia National Laboratories has performed testing on cells in the 10s of amp hours and analyzed the thermal runaway behavior of these cells.This work uses accelerating rate calorimetry to evaluate the impact of cell chemistry, state of charge, cell capacity, and ultimately cell energy density on the total energy release and peak heating rates observed during thermal runaway of Li-ion batteries. This work seeks to better understand how applicable small cell data is to understand the thermal runaway behavior of large cells as well as determine if thermal runaway behaviors can be more generally tied to aspects of lithium-ion cells such as total stored energy and specific energy. We have found a strong linear correlation between the total enthalpy of the thermal runaway process and the stored energy of the cell, apparently independent of cell size and state of charge. We have also shown that peak heating rates and peak temperatures reached during thermal runaway events are more closely tied to specific energy, increasing exponentially in the case of peak heating rates.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. Figure 1