Evaluation of Large-Format Lithium-Ion Cell Thermal Runaway Response Triggered by Nail Penetration using Novel Fractional Thermal Runaway Calorimetry and Gas Collection Methodology

To simultaneously optimize the battery design, reduce risk, and maintain safety margin, it is important to design from the ground up based on test determined cell-specific thermal runaway behavior as a function of heat output and analysis of the expelled gases. These data will inform the analytical models used for design optimization. Here we analyze the thermal runaway behavior of the 134 A-h GS Yuasa Li-ion cell (LSE134) using a novel large format fractional thermal runaway calorimeter and gas collection methodology. Results indicate an average total thermal runaway energy yield of 2.86 MJ, or 1.6 times the stored electrochemical energy; this follows an assertion commonly found in literature that energy yield scales linearly with capacity. The average fractional energy distribution was 2% through the cell body, 53% through the electrode winding, and 45% through the ejecta material and gases. Lot-to-lot variability in heat output was also identified. Additionally, it was found that an average of 416.6 SL of gas was generated which is approximately 3.1 l A-h ⁻¹ . The exhaust gas was determined to be a mixture of carbon dioxide, methane, ethane, oxygen, hydrogen, and other short chain hydrocarbons. Carbon dioxide was the largest component by volume with a range of 41% to 52% followed by hydrogen which ranged from 28% to 41%. Larger cells appear to result in strong ejecta flow driven events with higher fractions of the total energy delivered via the flow as compared to smaller format Li-ion cells (e.g. 18650 and 21700).