High-Specific-Surface-Area Octahedral Iron–Nickel Spinel Oxides for High-Performance Li–O ₂ Batteries

Li–O 2 batteries have attracted great attention due to their extremely high theoretical energy density. However, they suffer from a short cycle life and low capacity in practical applications. These problems stem from the inability to fully decompose the Li 2 O 2 generated during the discharge process. In this study, NiFe 2 O 4 catalysts with two different morphologies, octahedral and microflowers, were prepared by a simple hydrothermal method. The effects of NiFe 2 O 4 cathodes with different morphologies on the performance of Li–O 2 batteries were investigated. Theoretical calculations reveal that the overpotentials of the oxygen reduction reaction and oxygen evolution reaction of the battery with NiFe 2 O 4 are 0.52 and 0.65 V, respectively. The results show that the octahedral Super-P/NiFe 2 O 4 cathode exhibits high catalytic activity and shows a large specific surface area and a reasonable pore structure, resulting in the reduction in charge/discharge potential difference. The battery equipped with an octahedral Super-P/NiFe 2 O 4 cathode exhibits the best cycle life of 125 cycles at a current density of 500 mA·g –1 and presents the highest discharge capacity of 9427 mAh·g –1 at a current density of 100 mA·g –1 .