Hierarchical NiMoO4@Co3V2O8 hybrid nanorod/nanosphere clusters as advanced electrodes for high-performance electrochemical energy storage

Herein, a synergistic strategy to construct hierarchical NiMoO4@Co3V2O8 (denoted as NMO@CVO) hybrid nanorod/nanosphere clusters is proposed for the first time, where Co3V2O8 nanospheres (denoted as CVO) have been uniformly immobilized on the surface of the NiMoO4 nanorods (denoted as NMO) via a facile two-step hydrothermal method. Due to the surface recombination effect between NMO and CVO, the as-prepared NMO@CVO effectively avoids the aggregation of CVO nanosphere clusters. The unique hybrid architecture can make the most of the large interfacial area and abundant active sites for storing charge, which is greatly beneficial for the rapid diffusion of electrolyte ions and fast electron transport. The optimized NMO@CVO-8 composite nanostructure displays battery-like behavior with a maximum specific capacity of 357 C g-1, excellent rate capability (77.8% retention with the current density increasing by 10 times) and remarkable cycling stability. In addition, an aqueous asymmetric energy storage device is assembled based on the NMO@CVO-8 hybrid nanorod/nanosphere clusters and activated carbon. The device shows an ultrahigh energy density of 48.5 W h kg-1 at a power density of 839.1 W kg-1, good rate capability (20.9 W h kg-1 even at 7833.7 W kg-1) and excellent cycling stability (83.5% capacitance retention after 5000 cycles). More notably, two charged devices in series can light up a red light-emitting diode (LED) for 20 min, demonstrating its potential in future energy storage applications. This work indicates that the hierarchical NiMoO4@Co3V2O8-8 hybrid nanorod/nanosphere clusters are promising energy storage materials for future practical applications and also provides a rational strategy for fabricating novel nanostructured materials for high-performance energy storage.