Sputter-coated copper on silicon wafers was used as a working electrode (150 nm copper + 10 nm titanium on boron doped silicon (ρ = 1-30 Ωm, Si-Mat). Samples were prepared by cleaving the wafer and cleaning with isopropanol. Samples were contacted from the top by folding aluminium foil around the edges, outside the region of the O-ring, which were then placed on a conducting base for contacting the potentiostat. Metallic lithium ribbon was used as counter-, and reference electrodes (99.9%, Sigma-Aldrich), which was scraped clean using a toothbrush before use. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, 99.9% under Argon, Solvionic) and LiClO4 (99.99%, battery grade, dry, Sigma-Aldrich) were used as electrolytes in Tetraethylene glycol dimethyl ether (4G, 99%, Sigma-Aldrich), which was dried over 4 Å molecular sieves before use (Thermo Scientific). The water additive was produced at high purity (18.2 MΩ⸱cm), but stored in a buffertank without a nitrogen blanket. Prior to exsitu imaging (SEM/AFM) samples were rinsed with Propylene carbonate (99.7% anhydrous, Sigma-Aldrich) and dried in vacuum.