*4.2. Model Results*

Kinetic parameters have been calculated from the ARC tests. Results are presented in the following paragraphs and compared to the results of the post-mortem analysis summarised in Table 2.


**Table 2.** Summary of the conclusion of the tests.

#### 4.2.1. Onset Temperature

The onset temperature was calculated for each cell (Figure 7) thanks to the criteria described before. The instant when *T*<sup>0</sup> is measured represents the start of the reaction. Once the beginning of the reaction is defined, the fractional degree of conversion of reactants *α*<sup>0</sup> and the temperature rate (*β*0) can be evaluated.

Two groups appear. One group has a lower temperature onset than the fresh cells: cells aged at (0 ◦C, −20 ◦C). A second group has a higher onset temperature than the fresh cells: cells aged at (25 ◦C, 45 ◦C) and cells aged by a calendar process. The fractional degree of conversion of reactants follows the same order, which is totally normal in adiabatic conditions.

Notice that the dispersion of the fractional degree of conversion of reactants for cells aged at 45 ◦C is more pronounced even if the temperature onset is identical. One more temperature pulse has been applied to one of the cells, which explains a larger degree of conversion. Yet it has no impact on the measure of the onset temperature.

The temperature rate is quasi-identical at the beginning of the reaction for each test. Reactions start at the same speed.

**Figure 7.** Onset temperature for different ageing conditions (new/fresh, 0 ◦C, −20 ◦C, 45 ◦C, 25 ◦C, at constant voltage (calendar ageing) at 4.2 V and OCV after charge at 4.2 V at room temperature). Fractional degree of conversion (*α*0) of reactants at *t*<sup>0</sup> and temperature rate (*β*0) at *t*0.
