Lithium–oxygen (Li–O₂) batteries have attracted significant attention due to their ultrahigh theoretical energy density, but are obstructed by the sluggish reaction kinetics at the cathode and high overpotential. Our previous researches have proved that energy fields such as light, force, and heat are effective strategies to improve the reaction kinetics of Li–O₂ batteries. Herein, we proposed a novel magnetic field-assisted Li–O₂ batteries via a spin polarization strategy. By doping magnetic Mn²⁺ ions with spin polarization characteristics into CsPbBr₃ (Mn–CsPbBr₃) perovskite, a magnetic field-responsive cathode was designed and prepared. The incorporation of Mn²⁺ ions drives the charge redistribution and spin polarization of CsPbBr₃, which remarkably improve the carrier separation efficiency and the oxygen species adsorption energy. The Increased spin-polarization of the magnetic elements by Zeeman effect in an external magnetic field results in the enhanced oxygen reduction and evolution reaction. In the magnetic field, a low overpotential of 0.40 V was obtained for Li–O₂ batteries with Mn–CsPbBr₃ cathodes, demonstrating an ultralow overpotential of 0.12 V and an ultrahigh energy efficiency of 96.3% with the further illumination. The introduction of magnetic fields into the Li–O₂ battery system provides a new avenue for improving the reaction kinetics of rechargeable Li–O₂ battery.