Fe-based hybrid electrocatalysts for nonaqueous lithium-oxygen batteries

Lithium-oxygen batteries promise high energy densities, but are confronted with challenges, such as high overpotentials and sudden death during discharge-charge cycling, because the oxygen electrode is covered with the insulating discharge product, Li₂O₂. Here, we synthesized low-cost Fe-based nanocomposites via an electrical wire pulse process, as a hybrid electrocatalyst for the oxygen electrode of Li-O₂ batteries. Fe₃O₄-Fe nanohybrids-containing electrodes exhibited a high discharge capacity (13,890 mA h g_c ^-1 at a current density of 500 mA g_c ^-1), long cycle stability (100 cycles at a current rate of 500 mA g_c ^-1 and fixed capacity regime of 1,000 mA h g_c ^-1), and low overpotential (1.39 V at 40 cycles). This superior performance resulted from the good electrical conductivity of the Fe metal nanoparticles during discharge-charge cycling, which could enhance the oxygen reduction reaction and oxygen evolution reaction activities. We have demonstrated the increased electrical conductivity of the Fe₃O₄-Fe nanohybrids using electrochemical impedance spectroscopy.