When aprotic Li-O_2 batteries recharge, the solid Li_2O_2 in the positive electrode is oxidized, which often exhibits a continuous or step increase in the charging potential as a function of the charging capacity, and its origin remains incompletely understood.Here, we report a model study of electro-oxidation of a Li_2O_2 film on an Au electrode using voltammetry coupled with in situ Raman spectroscopy. It was found that the charging reaction initializes at the positive electrode|Li_2O_2 interface, instead of the previously presumed Li_2O_2 surface, and consists of two temporally and spatially separated Li_2O_2 oxidation processes, accounting for the potential rise during charging of Li-O_2 batteries. Moreover, the electrode surface-initialized oxidation can disintegrate the Li_2O_2 film resulting in a loss of Li_2O_2 into electrolyte solution, which drastically decreases the charging efficiency and highlights the importance of using soluble electro-catalyst for the complete charging of Li-O_2 batteries. When aprotic Li-O_2 batteries recharge, the solid Li 2 O 2 in the positive electrode is oxidized, which often exhibits a continuous or step increase in the charging potential as a function of the charging capacity, and its origin remains incompletely understood. Here, we report a model study of electro-oxidation of a Li_2O_2 film on an Au electrode using voltammetry coupled with in situ Raman spectroscopy. It was found that the charging reaction initializes at the positive electrode | Li_2O_2 interface, instead of the previously presumed Li_2O_2 surface, and consists of Two temporally and spatially separated Li 2 O 2 oxidation processes, accounting for the potential rise during charging of Li-O 2 batteries. Moreover, the electrode surface-initialized oxidation can disintegrate the Li 2 O 2 film resulting in a loss of Li 2 O 2 into electrolyte solution, which drastically decreases the charging efficiency and highlights the importance of using soluble electro-catalyst for the complete charging of Li-O_2 batteries.