Although H2 trapping in the pores, as discussed by Escher and Geisler, could occur in parallel, we propose, based on our observations, that oxidation of NaH in the SEI is a more likely explanation . accepted that PBAs release both HCN and (CN)2 during thermal runaway and high temperature abuse . However, cyanogen has only been observed in PW via OEMS/DEMS in overcharge regimes and we therefore further studied PW|HC cells cycled in an increased voltage window. Slightly unbalanced full-cells based on PW|HC (N/P ratio of 0.92) were then cycled in an increased voltage window (0 -4.0 V) in order to determine the gas evolution on over-oxidation of PW and over-reduction of HC. Figure shows the voltage profile as well as gas evolution rates, n, for the observed CO, CO2, C2H4, H2, and (CN)2 gases during galvanostatic cycling (0.1C). Increasing the upper cut-off does not impact SEI formation or early impurity oxidation and there is therefore barely no change in their respective gassing (C2H4, CO2 and H2 at 2.3 V).