Hierarchical FeCo₂ S₄ @FeNi₂ S₄ Core/Shell Nanostructures on Ni Foam for High-Performance Supercapacitors

The design of electrode materials with rational core/shell structures is promising for improving the electrochemical properties of supercapacitors. Hence, hierarchical FeCo₂ S₄ @FeNi₂ S₄ core/shell nanostructures on Ni foam were fabricated by a simple hydrothermal method. Owing to their structure and synergistic effect, they deliver an excellent specific capacitance of 2393 F g^-1 at 1 A g^-1 and long cycle lifespan as positive electrode materials. An asymmetric supercapacitor device with FeCo₂ S₄ @FeNi₂ S₄ as positive electrode and graphene as negative electrode exhibited a specific capacitance of 133.2 F g^-1 at 1 A g^-1 and a high energy density of 47.37 W h kg^-1 at a power density of 800 W kg^-1 . Moreover, the device showed remarkable cycling stability with 87.0 % specific-capacitance retention after 5000 cycles at 2 A g^-1 . These results demonstrate that the hierarchical FeCo₂ S₄ @FeNi₂ S₄ core/shell structures have great potential in the field of electrochemical energy storage.