With standard potentials calculated from the change in free energy (SI-7). For the first reaction (peak at 1.7-2 V) we note that the H2 partial current was only ~0.1. Considering the AFM images (Figure ) after holding the potential at 1.7 V, this corresponds to -1 mC/cm 2 for the hydrogen generating reaction. Strikingly, the expected volume of LiOH or Li2O for this amount of charge following reaction (2) or ( ) is ~0.17 µm 3 and ~0.08 µm , respectively, where we obtain a very similar value of 0.065 µm 3 from the AFM images. We therefore consider it likely that the observed particles are either LiOH and/or Li2O, which have also previously been observed in our electrolyte system . We emphasize that this does not rule out the formation of additional (potentially corroding) Lithium or organic species (SI-7), as a large part of the total current remains unaccounted for. For the second reaction (peak at 1.3 V) no particles are observed in Figure . In fact, the total volume of the patches after holding at 1.2 V is ~0.018 µm 3 , despite the partial current being > 0.3 at this concentration of the H2O additive, which would result in a larger volume of material following reactions (2) or (3). We therefore attribute this peak to the hydrogen evolution reaction (HER), reaction (1), similar to what was argued in a LP30 electrolyte .