摘要
A self-assembled mesoporous silica sphere templating process was developed to create hierarchical continuous porous coral reef like N-doped carbon nanostructures on stainless steel meshes as bifunctional electrodes for ultrahigh performance lithium ion based energy storage devices. The coral reef like carbon nanostructure achieved a high specific surface area of 1229 m 2 g −1 and a large specific pore volume of 2.21 cm 3 g −1 , without application of chemical activations. The electrode, when serving as an anode for lithium ion batteries (LIB) or lithium ion capacitors (LIC), delivered an ultrahigh specific capacity of 2058 mAh g −1 at 0.2 A g −1 . If used as a cathode for LICs, it generated a high specific capacity of 125 mAh g −1 at 0.1 A g −1 . The LICs assembled from using the electrode as both the cathode and anode, exhibited a high energy density of 145 Wh kg −1 at a power density of 1.4 kW kg −1 and maintained an energy density of 58 Wh kg −1 under an ultrahigh power density of 27.3 kW kg −1 , among the top tie of the state-of-the-art LICs. The cycling stability of the LIC was outstanding with a 85% capacity retention after 5000 cycle operations at 5 A g −1 . The hierarchical continuous porous coral reef like N-doped carbonaceous nanostructure provides micropores as micro-reservoirs of Li ions for local and fast Li ion intercalation/de-intercalation, edge N-doping for additional redox pseudo-capacitances, and large pore volumes to accommodate the volume expansion/shrinkage at the charge/discharge cycles and to offer fast mass transfer path for electrolyte ions, altogether leading to the successful applications as bifunctional electrodes for Li ion based energy storage devices.