Sustainable Energy System Utilizing High‐Voltage‐Stable and Energy‐dense Supercapacitors Based on Porous Fe2O3@Graphene Electrode in Ionic Liquid Electrolyte

Abstract Energy‐dense supercapacitors (SCs) based on metal oxides@graphene electrode and ionic liquid (IL) electrolyte hold great promise in sustainable energy system. However, these types of SCs suffer from poor cycling stability, especially at high working voltage. Herein, a porous ferric oxide/graphene (P−Fe 2 O 3 /G) electrode has been developed, in which Fe 2 O 3 nanoparticles exhibit abundant and suitable mesoporous channels. This structure ensures the high ionic diffusion kinetics of the IL ions during the repeated charging‐discharging processes, thereby providing the P−Fe 2 O 3 /G electrode with outastanding capacitance behavior and cycling performance in IL electrolyte. As a result, an ingenious asymmetric electrode concept has been put forward to fabricate energy‐dense SCs based on this P−Fe 2 O 3 /G as negative electrode, carbon dodecahedrons/graphene (CDs/G) as positive electrode and IL electrolyte. Remarkably, the fabricated devices exhibit superior high‐voltage cycling stability with 95 % retention after 20 000 cycles, which are much better than that of most previously reported SCs based on metal oxides/graphene electrode and IL electrolyte. On this basis, a sustainable energy system combining wind harvesting with asymmetric SCs has been established, wherein the asymmetric SCs can be effectively recharged by harvesting sustainable wind power and repeatedly supply power without decline of electrochemical performance. Therefore, this work can provide a promising porous electrode for high performance SCs in sustainable energy system.