Hierarchical Cu(OH)2/Co2(OH)2CO3 nanohybrid arrays grown on copper foam for high-performance battery-type supercapacitors

Abstract

Hierarchical Cu(OH)2/Co2(OH)2CO3 nanohybrid arrays grown on copper foam were realized by a simple two-step solution route for the first time, Cu(OH)2 nanowires were utilized as a scaffold to form Cu(OH)2 nanowire/Co2(OH)2CO3 nanoneedle core–shell structures and upper dispersed Co2(OH)2CO3 ball-flowers structures. And time gradient experiments were also considered to understand the growth mechanism for the Cu(OH)2/Co2(OH)2CO3 nanohybrid arrays, the optimized hierarchical architecture electrode of Cu(OH)2/Co2(OH)2CO3 yields a high areal capacitance of 1.31 F cm−2 at 2 mA cm−2, which is more than three times higher than that of single Cu(OH)2 electrode (0.37 F cm−2) and also superior than that of Co2(OH)2CO3, an excellent rate property (0.74 F cm−2 at 50 mA cm−2), and good cycling stability (91.5% capacity retention after 5000 cycles). Also, the hierarchical Cu(OH)2/Co2(OH)2CO3 nanohybrid arrays//active carbon asymmetric supercapacitors (ASCs) were fabricated, exhibiting a high energy density of 656 mWh cm−2 with a power density of 28.8 W cm−2. And three different colors (two red, two yellow, two green) of LED indicators can be lighted up by two ASC devices in series, which demonstrate that the hierarchical Cu(OH)2/Co2(OH)2CO3 nanohybrid arrays on copper foam are promising candidate electrode materials for supercapacitors.