[en] Highlights: • An advanced atomic layer deposition strategy was developed to controllably synthesize RuO₂ catalyst. • The as-made catalysts just use 2.84 wt% RuO₂ but deliver a superior cycle life over 1700 h. • The grafted RuO₂ with modulated electronic structure can confine chemical disproportionation reactions of LiO₂. • The as-made catalyst enable the discharge product featuring the ultrathin nanosheet structure. Li-O₂ batteries with ultrahigh theoretical energy density have triggered worldwide research interests and hold the prospect for powering electric vehicles. However, the poor cycling stability and low energy efficiency of Li-O₂ batteries still remain and hamper their practical application. Configuring desirable porous cathodes with uniformly dispersed and highly active catalysts is a noteworthy and feasible approach to overcoming these critical obstacles. Herein, we report on a novel strategy for the fabrication of Mn₃O₄ nanowires and carbon nanotubes composite film (Mn₃O₄/CNTs film) with ultrafine RuO₂ nanoparticles (Mn₃O₄/CNTs-RuO₂ film), in which the Mn₃O₄/CNTs film was employed as a conductive and porous matrix and extremely low amount of RuO₂ (just 2.84 wt%) are uniformly dispersed onto this matrix by using atomic layer deposition method, and reveal its electrochemical behaviors as a free-standing air electrode for Li-O₂ batteries. The Mn₃O₄/CNTs-RuO₂ film delivers a high specific capacity, improved round-trip energy efficiency and ultra-long cycle life (251 cycles). The superior electrochemical performance can be attributed to the enhanced catalytic activity of the grafted RuO₂ with modulated electronic structure as the result of the interaction with substrate, which is evidenced by the corresponding X-ray absorption spectroscopy results and the unique nanosheet-shaped discharge product which can be smoothly decomposed.