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Guided by the mechanism exploration via the density functional theory (DFT) calculations, the chromium (Cr) doped CoFe 2 O 4 nanoflowers (Cr-CoFe 2 O 4) are designed and directly constructed on nickel foam as a bifunctional electrocatalyst for LOB, which can achieve low overpotential (0.48 V), high discharge capacity (22030 mA h g−1) and long-term cycling durability (over 500 cycles at 300 mA g−1). [Display omitted] Tailored electrocatalysts that can modulate their electronic structure are highly desirable to facilitate the reaction kinetics of oxygen evolution reaction (OER) and oxidation reduction reaction (ORR) in lithium-oxygen batteries (LOB). Although octahedron predominant inverse spinels (e.g., CoFe 2 O 4) have been proposed as promising candidates for catalytic reactions, their performance has remained unsatisfactory. Herein, the chromium (Cr) doped CoFe 2 O 4 nanoflowers (Cr-CoFe 2 O 4) are elaborately constructed on nickel foam as a bifunctional electrocatalyst that drastically improves the performance of LOB. The results show that the partially oxidized Cr6+ stabilizes the cobalt (Co) sites at high-valence and regulates the electronic structure of Co sites, facilitating the oxygen redox kinetics of LOB due to their strong electron-withdrawing capability. Moreover, DFT calculations and ultraviolet photoelectron spectrometer (UPS) results consistently demonstrate that Cr doping optimizes the e g electron filling state of the active octahedral Co sites, significantly improves the covalency of Co-O bonds, and enhances the degree of Co 3d-O 2p hybrids. As a result, Cr-CoFe 2 O 4 catalyzed LOB can achieve low overpotential (0.48 V), high discharge capacity (22030 mA h g−1) and long-term cycling durability (over 500 cycles at 300 mA g−1). This work promotes the oxygen redox reaction and accelerates the electron transfer between Co ions and oxygen-containing intermediates, highlighting the potential of Cr-CoFe 2 O 4 nanoflowers as bifunctional electrocatalysts for LOB. [ABSTRACT FROM AUTHOR]