Figure shows the same current density vs. time and AFM image when the CA reaches 2300 seconds. The current density approaches zero as a consequence of the total oxidation of the Li2O2 deposit. Figure shows the AFM image of the HOPG surface free of Li 2 O 2 deposits, a fact that is also evident observing the topographic profile (Figure ). Starting with a clean HOPG surface (Figure ), a CA was performed at a reduction potential of 2.7 V during 150 seconds (Figure ). In this case the current does not vanish either, suggesting that still exist uncovered HOPG regions where the O2 can be reduced to O 2-. The AFM image in Figure shows the HOPG surface covered with Li 2 O 2 nanoparticles (~20 nm height) with small holes (marked with white circles) or interstitial sites that are possible regions where the O 2 reduction could still proceed. . A zoom on Figure allows to observe the detailed morphology of the Li 2 O 2 nanoparticles (Figure ). The worn-like nanoparticles observed in this AFM image differ from the rod-shaped nanoplates formed on HOPG, reported by Byon et al. using an electrolyte based on the TEGDME solvent, These alternative morphologies may be the evidence of the occurrence of two different formation mechanisms of the discharge products. On one hand, the use of a solvent with a high donor number Starting with a clean HOPG surface, the CV described in Figures and was repeated, this time at a scan rate of 5 mV/s. Figure shows the corresponding voltagram where two cathodic peaks at 2.57 and 2.43 V are observed, while three anodic peaks at 3.5 V, 4.0 V, and 4.3 V are present. It is worth mentioning that at a slower scan rate the oxidation peaks become closer because the O 2 molecules have more time for diffusing toward the cathode, continuing the ORR. Moreover, the LiO 2 has now enough time to diffuse in the electrolyte, reducing the chance of being reduced again to Li 2 O 2 on the cathode surface. In addition, the low intensity of the cathodic peaks is a signal of the asymmetry of the ORR and OER. Figures and, show the in-situ AFM images taken during the CV, after the cathodic scan, at 2.0 V and the anodic scan at 4.8 V. During the cathodic scan, a number of nanoparticles ~100 nm in diameter and ~30 nm height, cover the HOPG surface (Figure ). After the anodic scan a reduction in the size of the nanoparticles on the surface size was observed (Figure ). The topographic profiles shown in Figure , reveal an scenario similar to that previously described, where the OER on the bigger size Li 2 O 2 nanoparticles initiates at the lateral walls. However, in this case it is also observed a remarkable diminishing of the particles height.