Hierarchical 3D structured nanoporous Co9S8@Nix:Moy-Se core-shell nanowire array electrodes for high-performance asymmetric supercapacitors

The rational design of free-standing hierarchical core-shell nanoporous architectures is a good strategy for fabricating next-generation electrode materials for application in electrochemical energy conversion/storage systems. Herein, hierarchical core-shell 3D Co9S8@Ni-x:Mo-y-Se nanowire arrays (NWAs) are constructed by a low-cost, straightforward two-step hydrothermal method and an effective electrodeposition process. The optimal 3D Co9S8@Ni0.5Mo0.5-Se NWA electrode displays an excellent specific capacity of 460.81 mA h g(-1) with a corresponding areal capacity of 0.93 mA h cm(-2) at 1.5 mA cm(-2). It also demonstrates superb rate capability (similar to 68.4% capacity retention at 20 mA cm(-2)) and remarkable cycling stability (similar to 94.3% capacity retention after 10 000 charge and discharge cycles). Additionally, an asymmetric supercapacitor (ASC) is assembled using the hierarchical 3D Co9S8@Ni0.5Mo0.5-Se NWAs as the positive electrode, and the as-obtained Fe2O3@PANNFs/N-rGO aerogel as the negative electrode. The assembled Co9S8@Ni0.5Mo0.5-Se//Fe2O3@PANNFs/N-rGO ASC shows a larger operating voltage range of 1.7 V, a high electrochemical energy storage capability (96.90 W h kg(-1) at 1158 W kg(-1)), and excellent cycling stability (similar to 94.47% retention of the original capacity after 10 000 cycles). The all-solid-state ASC device that is also fabricated exhibits a high output working potential window of similar to 1.8 V, and an outstanding energy density of similar to 102.94 W h kg(-1) at similar to 1534 W kg(-1), demonstrating that the hierarchical 3D Co9S8@Ni0.5Mo0.5-Se NWA electrode material is a potential candidate for high-performance energy storage devices.