Hierarchical supercapacitor electrodes based on metallized glass fiber for ultrahigh areal capacitance

The limited charge storage of supercapacitors at the surface region results in its high power density but low energy density. It still remains a great challenge to realize supercapacitor electrodes with both bulk-like charge storage (high energy density) and surface-like fast electron/ion kinetics (high power density). Here we demonstrate scalable and hierarchical electrodes by metalizing 3D glass fiber (GF) frameworks and loading with 2D mixed-valence metal oxides. The resulting GF-Ni-Au@NiO _x cathode and GF-Ni-Au@FeO _x anode allow fast electron transportation through the conductive networks and unimpeded ion transport through the micrometer channels over long distance, provide large specific surface area with the hierarchical nanostructures, and exhibit ultrahigh areal capacitances (3.57 F cm ^-2 for cathode and 3.34 F cm ^-2 for anode at the current density of 3 mA cm ^-2 ). The asymmetric supercapacitor is assembled by employing industrial printed circuit board packaging techniques, showing high areal (1.67 F cm ^-2 ) and volumetric (13.92 F cm ^-3 ) capacitances. Remarkably, the device exhibits a maximum energy density of 6.19 mW h cm ^-3 and a maximum power density of 334.15 mW cm ^-3 based on the total packaged volume of the device. Furthermore, the device shows superior stability during a 400-h continuous test. This hierarchical electrode shows great potential for maintaining high capacity and fast kinetics simultaneously, and can be further extended to other electrochemical energy storage or conversion devices.