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

Abstract

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@Ni_0.5Mo_0.5–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 (∼68.4% capacity retention at 20 mA cm⁻²) and remarkable cycling stability (∼94.3% capacity retention after 10 000 charge and discharge cycles). Additionally, an asymmetric supercapacitor (ASC) is assembled using the hierarchical 3D Co₉S₈@Ni_0.5Mo_0.5–Se NWAs as the positive electrode, and the as-obtained Fe₂O₃@PANNFs/N-rGO aerogel as the negative electrode. The assembled Co₉S₈@Ni_0.5Mo_0.5–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 (∼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 ∼1.8 V, and an outstanding energy density of ∼102.94 W h kg⁻¹ at ∼1534 W kg⁻¹, demonstrating that the hierarchical 3D Co₉S₈@Ni_0.5Mo_0.5–Se NWA electrode material is a potential candidate for high-performance energy storage devices.