Facile fabrication of hierarchical ZnCo₂O₄/NiO core/shell nanowire arrays with improved lithium-ion battery performance

We report a facile and controllable strategy for the fabrication of three-dimensional (3D) ZnCo₂O₄/NiO core/shell nanowire arrays (ZCO/NiO NWs) on nickel (Ni) foam substrates by a simple, cost-effective, two-step, solution-based method. Ultra-thin NiO nanosheets are revealed to grow uniformly on the porous ZnCo₂O₄ nanowires with many interparticle mesopores, resulting in the formation of 3D core/shell nanowire arrays with hierarchical architecture. In comparison with the pristine ZnCo₂O₄ nanowire arrays (ZCO NWs), the ZCO/NiO NWs exhibit significantly improved Li storage properties, in terms of higher capacity, enhanced rate capability and improved cycling stability when applied as binders and additive-free anode materials for lithium-ion batteries. The superior Li storage performance of the ZCO/NiO NWs could be attributed to the synergetic effect between the ZnCo₂O₄ core and the NiO shell, as well as its unique hierarchical architecture, which ensures a large specific surface area and good conductivity. Our results may offer very useful guidelines in scrupulously designing 3D core/shell nanowire-array electrodes using cheap, earth-abundant materials in energy storage applications.