Incorporation of α-MnO2 Nanoflowers into Zinc-Terephthalate Metal-Organic Frameworks for High-Performance Asymmetric Supercapacitors.

Herein, we report the synthesis of α-MnO2 nanoflower-incorporated zinc-terephthalate MOFs (MnO2@Zn-MOFs) via the conventional solution phase synthesis technique as an electrode material for supercapacitor applications. The material was characterized by powder-X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy techniques. The prepared electrode material exhibited a specific capacitance of 880.58 F g-1 at 5 A g-1, which is higher than the pure Zn-BDC (610.83 F g-1) and pure α-MnO2 (541.69 F g-1). Also, it showed a 94% capacitance retention of its initial value after 10,000 cycles at 10 A g-1. The improved performance is attributed to the increased number of reactive sites and improved redox activity due to MnO2 inclusion. Moreover, an asymmetric supercapacitor assembled using MnO2@Zn-MOF as the anode and carbon black as the cathode delivered a specific capacitance of 160 F g-1 at 3 A g-1 with a high energy density of 40.68 W h kg-1 at a power density of 20.24 kW kg-1 with an operating potential of 0-1.35 V. The ASC also exhibited a good cycle stability of 90% of its initial capacitance.