Synthesis of Cubic Ni(OH)2 Nanocages Through Coordinating Etching and Precipitating Route for High-Performance Supercapacitors.

Rational design of cage-like structure is an effective method for the improvement of the capacitive performance of transition metal hydroxides. In this work, cubic Ni(OH)2 nanocages (Ni(OH)2 NCs) were constructed through a coordinating etching and precipitating (CEP) route. Ni(OH)2 NCs possess abundant active sites, sufficient diffusion channels, and accelerated electron transfer rate, which are beneficial for electrochemical kinetics. As a positive electrode for supercapacitors, the Ni(OH)2 NCs/Ni foam (NF) electrode presents a high specific capacitance of 539.8 F g-1 at 1 A g-1, which is much larger than that of broken Ni(OH)2 NCs/NF (Ni(OH)2 BNCs/NF, 87.3 F g-1 at 1 A g-1). In addition, the Ni(OH)2 NCs/NF electrode still retains 96.9% of its initial specific capacitance after 2000 cycles. The asymmetric supercapacitor (ASC) devices were assembled using Ni(OH)2 NCs/NF and activated carbon (AC)/NF as positive and negative electrodes, respectively. The ASC exhibits a higher energy density of 23.3 Wh kg-1 at a power density of 800 W kg-1 compared to Ni(OH)2 BNCs/NF (3 Wh kg-1 at 880 W kg-1). These results demonstrate that the Ni(OH)2 NCs/NF electrode presents potential applications in the field of energy storage. The design of cage-like structure paves an effective way to achieve high-performance electrode materials.