Analyzing Thermal Runaway Propagation in Lithium-Ion Battery Modules with Reduced Flammability Electrolyte Cells

A thorough analysis of thermal runaway propagation was conducted, focusing on both module and cell levels, using a range of standard flammability and reduced flammability electrolytes in 18650 cells sourced from Eagle-Picher Technologies. Utilizing techniques such as accelerated rate calorimetry; cell enthalpy, maximum thermal runaway temperature, and thermal runaway onset and initiation temperatures were evaluated, consistently demonstrating their reliability. Employing the NASA X-57 module billet as a strategy for mitigating thermal runaway propagation, the absorption of cell energy during failure events was observed, effectively preventing the spread of thermal runaway between cells. Notably, the use of reduced flammability electrolyte resulted in an average reduction of 104 °C in maximum thermal runaway temperature at the module level, thereby offering decreased risk in preventing thermal runaway propagation during failures. Note the relatively modest 51 °C difference observed between reduced flammability and standard flammability cells during individual cell tests. This underscores the importance of conducting tests at both the cell and module levels in the development of systems for certification, where the cell-level data indicate a 51 °C discrepancy, while the module-level analysis shows a more substantial 104 °C differentiation.