Hierarchical design of hollow Co-Ni LDH nanocages strung by MnO2 nanowire with enhanced pseudocapacitive properties

Core-sheath hierarchical-architectured materials have attracted much attention due to their extensive application in energy storage devices. However, as to multi-dimensional hierarchical core-sheath architectures, relative study has rarely been reported. In this work, a unique sugar gourd-like architecture is designed for the first time with hollow Co-Ni LDH nanocages uniformly strung by MnO2 nanowire (MnO2@Co-Ni LDH). Meanwhile, its forming mechanism is also systematically studied. Beneficial from this unique architecture, the designed MnO2@Co-Ni LDH possesses highly micro-structural integrity, abundant electrochemical-active sites and developed 3D diffusion path for electrolyte ions. When evaluated as positive electrode for pseudocapacitor, this material exhibits large specific capacitance of 1436 F g−1 at a current density of 1 A g−1, excellent rate capability (e.g., 1080 F g−1 at 20 A g−1) and high cycling stability (96.1% retention after 10,000 cycles). To assess practical functionality, a hybrid supercapacitor based on MnO2@Co-Ni LDH and active carbon nanoparticle is fabricated, which exhibits a high energy density of 40.9 Wh kg−1 along with remarkable long-term cyclic stability (81.8% retention after 20,000 cycles), demonstrating its potential application in the feld of energy storage devices. More importantly, the novel structural design can be easily extended to the synthesis of other functional materials for widespread applications.