Beyond the nitrate, are there more additives? Could rational criteria be proposed for identifying appropriate additives? To answer these questions, we carried out a number of electrochemical experiments to employ a series of inorganic salts as additives to alter the ether solvent environment in EDLs (see Table for detailed classification of salts). Considering that involvement of I -hampers the packing of the NO3 -adsorption layer (Figure ), the oxidation tolerance of the anion itself is taken into account first; for instance, oxidation of N (III) in NO2 -rather than N (VI) in NO3 -is favored thermodynamically. As shown in Figures and, the LSV for NaNO2-containing ether electrolyte exhibited a weak current response early at ~3.9 V, with two new oxidation peaks appearing at high potentials. The detailed investigation suggests that the irreversible oxidation of NaNO2 salt accounts for the appearance of these peaks (Figures and). Even though the overall onset of oxidation of this NaNO2-containing ether electrolyte becomes ~0.2 V higher than in the presence of LiNO3 (Figure ), further attempts to test the cycling stability of this electrolyte in Li||LiCoO2 proved fruitless (Figure ). Meanwhile, better oxidation stability of LiClO4 than NaClO3 was experimentally confirmed by a higher onset potential of oxidation in the LiClO4-containing ether electrolytes (Figure ). As for the Na2SO4 with S (VI) and AlPO4 with P (V) (two types of soluble/slightly soluble salts with high valence state, Table ), they failed to enhance the oxidation stability of the ether electrolytes. But interestingly, KH2PO4 and K2HPO4 with P (V) enabled improved oxidation tolerance of the dilute ether electrolytes (Figure ). Finally, except for the undissolved salts in ethers, the oxidation stability was experimentally found to increase with the presence of five salts, including LiNO3, LiClO4, NaClO3, KH2PO4 and K2HPO4, where the maximum enhancement was obtained when LiClO4 salt was used (Table ).