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Many studies on Li-O2 batteries have addressed the chemical and morphological evolution of the device as a function of electrode material, electrolyte, and discharge current density. Here we report that simple operating conditions can also affect discharge product formation. Results show the formation of Li2O2 and LiOH in experiments using continuous O2 flow (open system) and without it (closed system), and an additional more complex chemistry including LiOOH•H2O, Li2O and LiO2 in the closed system. This unexpected difference was also examined during charging of the Li-O2 cell, in which the LiOOH•H2O is preferably reversed in comparison to LiOH. Beside the influence in the reaction routes, the O2 flow and pressure impact on the cell performance. The total discharge capacity varies from 1,459 mA g − 1 to 2,460 mA g − 1 decreasing the O2 flow. In contrast, when using the closed pressurized system, the discharge capacity increased up to 5,851 mA g − 1 with the same electrode in the best result, as the electrolyte loss due to evaporation was avoided.