FeSe hollow spheroids as electrocatalysts for high-rate Li–O2 battery cathodes

Highlights: • FeSe hollow spheroids were fabricated via hydrothermal and thermal selenization using a silk–fibroin. • The FeSe hollow spheroids were applied to electrocatalysts for Li–O₂ batteries. • The electrocatalytic activity of FeSe is due to disordered Fe³⁺ formation and proper oxygen affinity. • The FeSe hollow spheroids cathode exhibited high–rate performance with stable cycle retention. -- Abstract: In this study, FeSe hollow spheroids were prepared for application as cathode electrocatalysts in Li–O₂ batteries. The hollow spheroids were synthesized through hydrothermal and thermal selenization processing based on a silk–fibroin template. At the high current rate of 1000 mA g⁻¹, the FeSe spheroids exhibited higher reversibility (100 cycles) and a similar voltage gap to that at 200 mA g⁻¹. Therefore, FeSe hollow spheroids exhibit high oxygen reduction/evolution catalytic efficiency for high–rate Li–O₂ batteries. This result was demonstrated via comparison of the oxygen reduction/evolution kinetics of FeSe and Fe₂O₃ hollow spheroids using electrochemical impedance spectroscopy.