“…After 10 scans, we observe a significant loss in current density, as expected with the growth of a passivating layer resulting from known electrolyte TFSI − decomposition. 24,28,29,33,34 Figure 5b shows that by adding the MgI 2 SEI ex situ, the onset potential for Mg stripping does not increase, while the onset potential for deposition does decrease over 10 scans, and there remains a decrease in current density after 10 scans. Figure 5c shows that after adding 5 mM I 2 to the Mg(TFSI) 2 electrolyte, a decrease in the onset potential for Mg deposition (from ∼−0.3 to ∼−0.2 V for the first scan, from ∼−1.2 to −0.1 V for the 10th scan) and stripping (from ∼0.6 to ∼0.4 V for the first scan, from ∼0.9 to ∼0.1 V for the 10th scan) is observed when compared to cells with no additive.…”