Li–O₂ battery offers a dramatic increase in theoretical energy density relative to Li–ion cells, opening up the possibility of electric vehicles and renewable high energy systems. However, the sluggish kinetics at air cathode during discharge and charge processes requires the development of a promising bifunctional electrocatalysts to simultaneously improve the oxygen reduction and oxidation (ORR and OER) kinetics, resulting in increased reversibility of the battery. In this work, three dimensional (3D) α–MnO₂/RuO₂ mixed oxides at different ratios were synthesized using a simple hydrothermal method. The 3D mixed oxides were designed to be applied as suitable bifunctional electrocatalysts for Li–O₂ batteries. The morphology of the mixed oxides changed from sea urchin shaped nanostructures to nanospheres with the increase of RuO₂ content in the mixed oxides. The bifunctional catalytic properties were analyzed using oxygen reduction and evolution reactions (ORR and OER) in a rotating ring disc electrode system. It was found that α–MnO₂ and RuO₂ significantly served as ORR and OER catalysts, respectively, confirming that the mixed oxide is a suitable bifunctional catalyst for Li–O₂ battery. Among the four different α–MnO₂/RuO₂ composition ratios, (75:25) appeared to be the optimum ratio for the mixed oxides with superior activity for both ORR and OER. The superior performance of α–MnO₂/RuO₂ (75:25) could be attributed to its structural and compositional design which aid in the better catalytic performance. When applied in Li–O₂ battery system, the (75:25) ratio exhibited excellent performance with a maximum capacity of >8100 mAh g^-1 with high columbic efficiency and cyclability.