Supplemental Information Intercalation of Solvated Na-ions into Graphite

Electrolytes were prepared by dissolving NaClO4 (Sigma Aldrich ACS reagent, ≥ 98.0 %) in ethylene glycol dimethyl ether (G1, Sigma Aldrich, anhydrous, 99.5 %), diethylene glycol dimethyl ether (G2, Sigma Aldrich, anhydrous, 99.5 %), triethylene glycol dimethyl ether (G3, Alfa Aesar, 99 %), tetraethylene glycol dimethyl ether (G4, Sigma Aldrich, ≥ 99 %) as well as in a 1:1 (volume) mixture of ethylene carbonate (EC, Sigma Aldrich, anhydrous, 99 %) and dimethyl carbonate (DMC, Sigma Aldrich, anhydrous, ≥ 99 %). Before use, the electrolytes were dried using 3 Å molecular sieves (Merck Millipore) for several days, which lowered the water content of all electrolytes well below 40 ppm (checked via Karl-Fischer titration measurements, Metrohm).