Construction of KCu7S4@NiMoO4 three-dimensional core-shell hollow structure with high hole mobility and fast ion transport for high-performance hybrid supercapacitors

Abstract

The rational construction of hierarchical three-dimensional nanostructures with multiple metallic elements is of great importance for improving electrochemical energy storage. KCu7S4 is a first-rate candidate for electrode materials of supercapacitors, due to its unique quasi one-dimensional K+ alkali metal ion channels and extremely low resistance property. However, the limited ion contacted sites and single metal element composition restrain the extra upgrade of its electrochemical performance. We thereof have effectively prepared KCu7S4@NiMoO4 nanocomposites with a three-dimensional core-shell hollow structure by anchoring NiMoO4 nanosheet arrays uniformly on KCu7S4 nanorods. The incorporation of NiMoO4 nanosheet arrays increases the active sites and electrochemical stability. Due to the synergistic effect of NiMoO4 nanosheet arrays with Cu atomic vacancies and quasi one-dimensional K+ alkali metal ion channels in KCu7S4 nanorods, the prepared electrode has outstanding capacitance (1194.6 F g−1 (165.91 mAh g−1), 1 A g−1), significant equivalent series resistance (0.614 Ω), and high capacitance retention (92.3% after 10,000 cycles). In addition, the KCu7S4@NiMoO4//AC ASC prepared with KCu7S4@NiMoO4 cathode and activated carbon (AC) anode exhibits excellent energy density (55.9 Wh kg−1, 750 W kg−1) and outstanding capacitance retention (91.3% after 10,000cycles). Therefore, the new three-dimensional core-shell hollow structure electrode materials with KCu7S4 nanorods as the cores and binary metal molybdates as the shell materials have a broad research potential.