Abstract: With the aim to shed more light on the reaction mechanism of rechargeable Li/S batteries, a three electrode set-up and a two electrode coil cell were assembled to identify the possible oxidation process of polysulfides at the surface of mesoporous carbon material. Cyclic Voltammograms and galvanostatic potential profile were examined in high or low sulfur concentrations. The color change in electrolyte and at the surface of positive electrode of a three electrode set-up were studied in the redox process. Factors impact peak current at 2.6 V (vs. Li⁺/Li)include concentration of sulfur, component of electrolyte, specific area of carbon matrix were studied. It is necessary to maintain super-saturation of sulfur in electrolyte to complete the charging process;Sulfur is reduced to polysulfides and it dissolves into electrolyte at the discharging process. Polysulfides is oxidized to elemental sulfur , at the same time, it generateselemental sulfur through disproportionation at the charging process. The anodic peak current increases at enhanced area of carbon matrix. It decreases in carbonate electrolyte because the carbonate electrolyte has rather low solubility to sulfur and polysulfides; With the increase of the concentration of sulfur in electrolyte, the anodic peak current first increases proportionally, then decreases dramatically when concentration of sulfur exceeds a certain value. The appropriate total sulfur concentration in ether electrolyte is 0.125 mol/L.

Key words: mesoporous materials, cyclic voltammetry, electrochemical behavior, lithium cells