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The practical implementation of supercapacitors is hindered by low utilization and poor structural stability of electrode materials. Herein, to surmount these critical challenges, a three-dimensional hierarchical α-Co(OH)2/α-Ni(OH)2 heterojunction nanorods are built in situ on Ni foam through a mild two-step growth reaction. The unique lamellar crystal structure and abundant intercalated anions of α-M(OH)2 (M = Co or Ni) and the ideal electronic conductivity of α-Co(OH)2 construct numerous cross-linked ion and electron transport paths in heterojunction nanorods. The deformation stresses exerted by α-Co(OH)2 and α-Ni(OH)2 on each other guarantee the excellent structural stability of this heterojunction nanorods. Using nickel foam with a three-dimensional network conductive framework as the template ensures the rapidly transfer of electrons between this heterojunction nanorods and current collector. Three-dimensional hierarchical structure of α-Co(OH)2/α-Ni(OH)2 heterojunction nanorods provides a large liquid interface area. These result together in the high utilization rate and excellent structure stability of the α-Co(OH)2/α-Ni(OH)2 heterojunction nanorods. And the capacitance retention rate is up to 93.4% at 1 A g-1 from three-electrode system to two-electrode system. The α-Co(OH)2/α-Ni(OH)2//AC device also present a long cycle life (the capacitance retention rate is 123.6% at 5 A g-1 for 10000 cycles), a high specific capacitance (207.2 F g-1 at 1 A g-1), and high energy density and power density (72.6 Wh kg-1 at 196.4 W kg-1 and 40.9 Wh kg-1 at 3491.8 W kg-1), exhibiting a fascinating potential for supercapacitor in large-scale applications.
Zhou et al. (Wed,) studied this question.