ABSTRACT
NiCo metal-organic framework (MOF) electrodes were prepared by a simple hydrothermal method. The flower-like NiCo MOF electrode exhibited an exciting potential window of 1.2 V and an excellent specific capacitance of 927.1 F g-1 at 1 A g-1. The flower-like NiCo MOF//activated carbon (AC) device delivered a high energy density of 28.5 W hkg-1 at a power density of 400.5 W kg-1 and good cycle stability (95.4% after 5000 cycles at 10 A g-1). Based on the flower-like NiCo MOF electrode, the asymmetric quasi-solid-state flexible supercapacitor (AFSC) was prepared and exhibited good capacitance retention after bending (79% after 100 bends and 64.4% after 200 bends). Furthermore, two AFSCs in series successfully lit up ten parallel red LED lights, showing great application potential in flexible and wearable energy storage devices.
ABSTRACT
In the past decades, the energy consumption of nonrenewable fossil fuels has been increasing, which severely threatens human life. Thus, it is very urgent to develop renewable and reliable energy storage devices with features of environmental harmlessness and low cost. High power density, excellent cycle stability, and a fast charge/discharge process make supercapacitors a promising energy device. However, the energy density of supercapacitors is still less than that of ordinary batteries. As is known to all, the electrochemical performance of supercapacitors is largely dependent on electrode materials. In this review, we firstly introduced six typical transition metal oxides (TMOs) for supercapacitor electrodes, including RuO2, Co3O4, MnO2, ZnO, XCo2O4 (X = Mn, Cu, Ni), and AMoO4 (A = Co, Mn, Ni, Zn). Secondly, the problems of these TMOs in practical application are presented and the corresponding feasible solutions are clarified. Then, we summarize the latest developments of the six TMOs for supercapacitor electrodes. Finally, we discuss the developing trend of supercapacitors and give some recommendations for the future of supercapacitors.
