Li-O₂ batteries with high energy density hold significant promise as next-generation energy storage systems. However, Li-O₂ batteries have poor cycling performance at high current densities and large capacities, primarily due to the high impedance caused by the instability of the lithium anode and the sluggish kinetics in the discharge products decomposition on the cathode. Herein, we investigated a bifunctional nitrile additive (2-methoxy benzonitrile (2-MBN)) with good chemical/electrochemical stability to improve the performances of Li-O₂ batteries. The 2-MBN could actively modify the anode by ensuring uniform Li⁺ deposition and optimizing the composition of solid electrolyte interphase (SEI). Meanwhile, it could also facilitate the decomposition of discharge products by inducing the formation of sheet-like Li₂O₂, significantly reducing the battery charge overpotential. The bifunctional effects of 2-MBN for the anode and cathode enable Li-O₂ batteries to achieve a stable lifetime of 97 cycles at a current density of 600 mA·g⁻¹ with a fixed capacity of 2000 mAh·g⁻¹, much better than that of Li-O₂ batteries without 2-MBN (28 cycles). The inclusion of 2-MBN provides an effective approach for attaining high-performance Li-O₂ batteries.