Epitaxial Growth of Li2O2 Achieved by a Rational Designed Fe3O4@N‐doped Carbon Nanoflower Structure for Improving the Performance of Li−O2 Batteries

Abstract The insulated and insoluble discharge product Li 2 O 2 can cause excessive charge overpotential, eventually leading to the deactivation of the Li−O 2 battery. Here, a nanoflower structure (Fe 3 O 4 @NC) fabricated by coating Fe 3 O 4 with N‐doped carbon was used as an effective catalyst for Li−O 2 cathode. The N‐doped defective carbon layer provides sufficient active sites for the formation of discharge intermediates and exhibits a coating effect on Fe 3 O 4 , thereby facilitating the maintenance of structural stability. The hierarchical structure of Fe 3 O 4 can effectively mitigate the agglomeration of the carbon layer, thus promoting a homogeneous distribution and optimal utilization of active sites on the carbon layer. As a result, the synergistic effect of Fe 3 O 4 combined with the N‐doped carbon layer enhances the Li + /e − transfer rate and effectively accelerates the kinetic of oxygen reduction/evolution reaction (ORR/OER). Furthermore, the unique functionality of Fe 3 O 4 @NC induces the epitaxial growth of Li 2 O 2 into uniform nanosheets, thereby increasing the utilization of cathode space and ultimately promoting the energy release of Li−O 2 batteries. The Li−O 2 battery with Fe 3 O 4 @NC cathode exhibits remarkable full discharge capacity of 16495 mAh g −1 and significantly improved round‐trip performances for 120 cycles at a cutoff capacity of 1000 mAh g −1 with a current density of 200 mA g −1 .