Although Li–O2 batteries can potentially achieve greater than two-fold higher energy densities than Li-ion batteries, the basic performance of Li–O2 batteries remains poor. In particular, the large over-potential of positive electrode reactions during the charging process results in low round-trip energy efficiency and limited cycle life, and is therefore the main barrier to the practical use of rechargeable Li–O2 batteries. In the present study, we demonstrate that the charging performance of Li–O2 batteries can be significantly improved by simply adding barium (Ba) ions into the electrolyte. Elemental analysis revealed that Ba-incorporated Li2O2 was obtained as the main discharge product of a Li–O2 cell operated in the presence of Ba2+. Notably, the improvement of charging performance was confirmed to originate from the Ba-incorporated Li2O2 deposits, rather than the Ba2+ present in the electrolyte. The present results suggest that the incorporation of heteroatoms into the discharge product is an effective approach for improving the charging performance of Li–O2 batteries.