Hierarchical Cu(OH)2@Ni2(OH)2CO3 core/shell nanowire arrays in situ grown on three-dimensional copper foam for high-performance solid-state supercapacitors

Abstract

Well-aligned hierarchical Cu(OH)₂@Ni₂(OH)₂CO₃ core/shell nanowire arrays were prepared on conductive copper foam via a simple in situ oxidation reaction and subsequent hydrothermal method for high-performance solid-state supercapacitors. Such novel hierarchical architectures integrate the merits of macroporous copper foam and the core/shell nanowire arrays such as superior electrical conductivity, enlarged surface area, and fast charge transport and ion diffusion. The areal capacitance of this typical hierarchical Cu(OH)₂@Ni₂(OH)₂CO₃ core/shell nanowire array reaches 1.09 F cm⁻² at a current density of 1.0 mA cm⁻², much higher than that of pristine Cu(OH)₂ nanowire arrays (0.36 F cm⁻²). In addition, a remarkable rate capability (0.91 F cm⁻² at a current density of 25 mA cm⁻²) and excellent cycling stability (86.1% after 10 000 cycles) were observed. Moreover, the hierarchical Cu(OH)₂@Ni₂(OH)₂CO₃ core/shell nanowire arrays were also used as the positive electrodes to fabricate solid-state asymmetric supercapacitor devices, exhibiting a high cell voltage of 1.6 V and largely enhanced energy density up to 1.01 W h cm⁻². The improvement in electrochemical behaviors is attributed to the unique hierarchical architecture and the component synergistic effect. This work provides a scalable and promising strategy for the synthesis of well-defined core/shell nanoarrays as energy storage and conversion devices.