As a promising candidate for next generation energy storage system, Li-air battery has generated a great deal of interest over the past decade. However, realization of the practical Li-air battery is a formidable challenge, and is impeded by some fundamental key issues including the degraded capacity, limited cycle life, notoriously low round-trip efficiency and limited stability of battery components, which are currently being tackled by numerous approaches. From the viewpoint of fundamental study, a better understanding of the oxygen electrode reactions in aprotic electrolyte will be beneficial to the realization of Li-air batteries with improved electrochemical performances. Here, a mechanistic study of oxygen electrochemistry in aprotic Li⁺ electrolyte has been conducted using Raman spectroelectrochemistry coupled with density functional theory calculations. By spectroscopic identification of oxygen intermediates under various operating conditions, different routes for Li₂O₂ formation have been revealed.