The polaron formation at the O-rich surface emerges as a consequence of a surface reconstruction, which in Ref. 14 was blocked by using a 1x1 supercell. Breaking the symmetry using a 2x1 unit cell, the reconstruction is now possible and the polaron is stabilized being 30.3 meV/Å 2 more stable than the delocalized configuration. The same effect occurs for Li 2 O 2 bulk, where the extra charge also prefers to be localized at the oxygen dimers. On the other hand, Figure presents the DOS calculated within GGA (black line) and HSE (solid red) for the whole 1st and 2nd layers of the [1 100] ST-3 surface, the one with the lowest γ using HSE. Unlike the O-rich surfaces, in the ST ones there are not extra charge that can be self-trapped to produce polarons. In this case, it can be observed an insulating behavior with both methods (GGA and HSE), and the same happens to all stoichiometric situations. Non of the studied surfaces are metallic within HSE. These results confirm the strong insulating character of Li 2 O 2 , that is one of the main drawbacks of the LOB.