Junling Xu

3D binder-free Cu2O@Cu nanoneedle arrays for high-performance asymmetric supercapacitors

Nanostructured Cu oxides/hydroxides are promising materials for supercapacitors because of their high theoretical capacitance, low cost and friendliness to environment. However, the development of commercially viable Cu oxides/hydroxides with superior capacitive performance is still challenging. Here, 3D binder-free Cu2O@Cu nanoneedle arrays electrode was developed via facile electrochemistry. The electrode exhibits a high capacitance of 862.4 F g−1 and excellent cycling stability (20 000 cycles). Furthermore, we have successfully constructed a Cu2O@Cu//AC asymmetric supercapacitor, which can achieve an energy density of 35.6 W h kg−1 at 0.9 kW kg−1 and excellent stability with a capacitance retention of 92% after 10 000 cycles. After being charged for dozens of seconds, the in-series Cu2O@Cu//AC supercapacitors can light up LED arrays and even charge a mobile phone. These fascinating performances reasonably indicate their potential in commercial applications for energy storage.

Facile and scalable fabrication of three-dimensional Cu(OH)2 nanoporous nanorods for solid-state supercapacitors

A facile and scalable one-step anodization method has been developed to fabricate three-dimensional (3-D) Cu(OH)2 nanoporous nanorods on a copper foil substrate, a product that can be used directly as a binder-free electrode for supercapacitors. The unique morphology of the nanorods provides a large amount of active sites for redox reactions, which can be easily accessed by electrolyte ions. Benefiting from that, a high capacitance of 213 mF cm−2 is obtained, and superior rate capability (62.3% capacitance retention when the scan rate is increased to 10 times) and excellent cyclability (92.0% capacitance retention after 5000 cycles) are achieved. In addition, a flexible and foldable solid-state asymmetric supercapacitor is assembled using the Cu(OH)2 and activated carbon as the positive and negative electrodes, respectively. The devices deliver a high energy density of 3.68 mW h cm−3 and a high power density of 5314 mW cm−3, demonstrating great potential for next-generation high-rate energy storage systems.

Anodization driven synthesis of nickel oxalate nanostructures with excellent performance for asymmetric supercapacitors

Here we report a facile efficient anodization approach to fabricate nickel oxalate nanostructures on nickel foam (NON@NF). The NON@NF electrode exhibits high specific capacitance and excellent cycling performance. Moreover, an assembled asymmetric supercapacitor based upon NON@NF and activated carbon shows excellent performance with high energy/power density and long cycling stability.

Hybridizing Fe3O4 nanocrystals with nitrogen-doped carbon nanowires for high-performance supercapacitors

This study develops a facile approach to anchor Fe3O4 nanocrystals uniformly onto nitrogen-doped carbon nanowires (NCN). The influence of the ratio of Fe3O4 to NCN on the structure and pseudocapacitance performance of the nanocomposite is investigated systematically. It is found that the best performance is realized when the mass percentage of Fe3O4 is 65.9%. Benefiting from the synergistic effect of the nanostructure and conductive matrix, the optimized nanocomposite delivers high specific capacitance (541.7 F g−1 at 1 A g−1), superior rate capability (337.1 F g−1 at 10 A g−1), as well as good cyclability. This nanocomposite is also used as the anode material for assembling an asymmetric supercapacitor, which exhibits a high specific energy of 59.1 W h kg−1 and high specific power of 17.85 kW kg−1. The results manifest the great potential of this nanocomposite for next-generation high-power applications.