MOF-derived Fe2O3 decorated with MnO2 nanosheet arrays as anode for high energy density hybrid supercapacitor

The development of high-performance anode materials to match the fast-burgeoning cathodes is essential for the fabrication of high-energy–density supercapacitors. Hematite Fe2O3, with ultra-high theoretical capacitance, has been considered as a promising anode candidate, but the insufficient utilization of the energy storage potential range (mainly in −1.1 V ~ -0.5 V) creates obstacles for further expansion of its electrochemical performance. In this work, a pinecone-like core–shell composite, with vertically grown MnO2 nanosheet arrays decorated on the M−Fe2O3 prepared via sacrificing the Fe-MOF (MIL-88A) template, was synthesized to achieve the excellent energy storage effect at a wide potential range from −1.1 V to 0.3 V. As adjusting the MnO2 coating amount to a suitable level, the M−Fe2O3@MnO2 composite exhibits a prominent specific capacitance up to 908.5F g−1 as well as excellent cycle stability. Pseudocapacitance analysis interprets the essence of the kinetics process of composite materials in the energy storage process. The hybrid supercapacitor (HSC), assembled with pinecone-like M−Fe2O3@MnO2 as the anode and urchin-like NiCo2O4 as the cathode, delivers a high energy density of 86.8 Wh kg−1 at 804.1 W kg−1. Unsurprisingly, 25 parallel blue LEDs powered by two HSC devices can illuminate for over an astonishing 210 min. This work fabricates a promising anode material for high-energy–density hybrid supercapacitors, and the strategy of complementary energy storage potential provides a novel approach for constructing high-performance energy storage systems.