Lithium-ion battery technology is a critical enabling technology to the advancement of electric propulsion transportation. Cost, Life, Performance, and Safety have been the main impediments for the application of batteries for use in Automotive and Aviation markets. Cost, life, and performance have been improving for the last decade.¹ However, safety with respect to thermal runaway propensity continues to be a challenge for both automotive and especially aviation electric propulsion due to the energetic nature of the technology. Complete thermal runaway containment is required to obtain FAA certification for passenger safety for aviation applications. Consequently, an evaluation of the thermal runaway characteristics will be discussed.

Thermal runaway propagation analysis at the cell and module level was performed on a suite of Samsung 30Q 18650 cylindrical cells. Measurements such as cell enthalpy, maximum thermal runaway temperature, and thermal runaway onset and initiation temperatures (shown in Figure 1 & 2) were collected and shown to be consistent by means of accelerated rate calorimetry (ARC). Results for ten 30Q cells are shown in Figure 3. This study showed, using the X-57 module billet as a thermal runaway propagation mitigation strategy, wherein the cell energy was successfully absorbed during a failure event in the module and prevented thermal runaway propagation from between cells.

The results show the 30Q cell average maximum temperature is 375°C and the average initiation temperature is 195°C. The average mass lost was 33.1 grams. The stochastic nature of the results indicates the need to test a larger than normal sample to obtain a good statistical sample. These values become critical design points for the module containment strategy. Module level, cell to cell propagation tests will also be evaluated, showing the fulfillment of the module design strategy to eliminate cell to cell propagation.

References

1. courtesy of Bloomberg NEF 2021