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 Li2O2 can cause excessive charge overpotential, eventually leading to the deactivation of the Li‐O2 battery. Here, a nanoflower structure (Fe3O4@NC) fabricated by coating Fe3O4 with N‐doped carbon was used as an effective catalyst for Li‐O2 cathode. The N‐doped defective carbon layer provides sufficient active sites for the formation of discharge intermediates and exhibits a coating effect on Fe3O4, thereby facilitating the maintenance of structural stability. The hierarchical structure of Fe3O4 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 Fe3O4 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 Fe3O4@NC induces the epitaxial growth of Li2O2 into uniform nanosheets, thereby increasing the utilization of cathode space and ultimately promoting the energy release of Li‐O2 batteries. The Li‐O2 battery with Fe3O4@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.