Hierarchical Mn-doped Fe2O3@rGO hollow core-shell spheres for high-performance hybrid capacitor

Herein, we use a facile one-step hydrothermal growth process to achieve hollow spheres assembled from Mn-doped Fe2O3 nanoparticles (NPs) coated by reduced graphene oxide (rGO) layers. This unique 3D nanostructure enables electrochemical reactions to occur easily and efficiently, increasing the active regions of redox reactions where remarkable electrochemical properties with specific capacity of 285 mAh g−1 (5.7 mAh cm−2) at 1 A g−1 (20 mA cm−2) with a high area loading of 20 mg cm−2. Cycle performance of 83.4% at 1 A g−1 over 1000 cycles is achieved, confirming high stability of the Mn-doped Fe2O3@rGO hollow sphere after the redox reaction. Even under high current density of 16 A g−1, capacity retention of 64.4% is demonstrated, representing good rate capability. Furthermore, hybrid capacitor (HC) devices consisting of the as-prepared 3D Mn-doped Fe2O3@rGO as the anode electrode and NiAl-LDH nanosheets as the cathode electrode with an superior maximum energy density of 102.0 Wh kg−1 at the power density of 1.1 kW kg−1 were demonstrated and the energy density of 56.0 Wh kg−1 remains at the power density of 10.1 kW kg−1.