At last, the Na-doped Li 2 O 2 decomposition has been studied. The removal of the second LiO 2 intermediate is found to be the limiting step during charge, in both Na-doped and pristine Li 2 O 2 surfaces. We have found that Na-doping decreases the energy barrier of the limiting step, contributing to a reduction of the charging overpotential, in line with the experimental results. Our calculations indicate that the origin of this decrease are the lattice distortions associated with doping that weaken the LiO 2 binding, and not the emergence of surface metallic states as previously reported.