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[Display omitted] • Co 3 O 4 nanoneedle arrays is grafted on V 2 O 5 nanosheet arrays to form VNSAs/CNNAs. • The VNSAs/CNNAs composite shows a high C s value of 1023 F g−1at 5 mV s−1. • The VNSAs/CNNAs composite can work under a large voltage window of 1.6 V. • The VNSAs/CNNAs composite has a high E d value of 127.3 Wh kg−1 at 400 W kg−1. • The high performance is ascribed to the synergistic effect of V 2 O 5 and Co 3 O 4. In this work, two-dimensional V 2 O 5 nanosheet arrays/one-dimensional Co 3 O 4 nanoneedle arrays (2D VNSAs/1D CNNAs) composite is successfully prepared on nickel foam substrate. A variety of structural characterization techniques (SEM, XRD, EDS, TEM, and XPS) show that the as-prepared composite is V 2 O 5 monocrystal with a layered structure grafting by Co 3 O 4 polycrystal with a 1D needle-like structure. The VNSAs/CNNAs composite is used as supercapacitor electrode material. In a three-electrodes system, it shows high specific capacitance (C s) values (1023 F g−1@5 mV s−1 from CV curve and 826 F g−1@0.5 A/g from GCD curve), a high coulombic efficiency (98.6 %@10 A/g), a good cyclic stability (92.7 % after 6000 cycles), a low charge transfer resistance (2.7 Ω), and a fast ionic diffusion rate (2.01 × 10−8 cm2 s−1). In a two-electrodes system, the assembled VNSAs/CNNAs//VNSAs/CNNAs symmetric supercapacitor has C s values of 445 F g−1@5 mV s−1 and 363 F g−1@0.5 A/g. Its cycle stability and rate capability could reach up to 92.3 % and 90.7 % after 6000 cycels, respectively. It also shows a high energy density (E d) of 127.3 Wh kg−1@400 W kg−1 and can retain 72.2 Wh kg−1@8000 W kg−1. The excellent electrochemical properties indicate that VNSAs/CNNAs composite can greatly increase the E d of supercapacitors. [ABSTRACT FROM AUTHOR]

In this paper, porous NiO nanoflake arrays@V 2 O 5 nanoparticles (PNFAs@VNPs) composite is fabricated on Ni foam through a facile hydrothermal process. The PNFAs@VNPs composite has an ordered array structure, a large active surface, and favorable physical stability. Based on the CV profile, the specific capacitance can achieve 950 F g−1 and remain stable at 95.8 % of the original value after 5000 loops. When the PNFAs@VNPs composite is assembled into a symmetric supercapacitor, the energy density can reach 67.0 W h kg−1 at a power density of 550 W kg−1. Even if the power density rises to 11,000 W kg−1, the energy density can still be held at 25.3 W h kg−1. The high supercapacitive property of the PNFAs@VNPs composite is owed to the synergic action of the PNFAs and VNPs. The PNFAs@VNPs composite with the advantages of battery-type and capacitive-type pseudocapacitances has higher charge transfer dynamics, making it a potential supercapacitive electrode material. [Display omitted] • Porous NiO nanoflake arrays (PNFAs) is successfully prepared on nickel foam. • V 2 O 5 nanoparticles (VNPs) are loaded on the PNFAs to form a hierarchical structure. • The PNFAs@VNPs has the advantages of Faraday and intercalation type pseudocapacitor. • The PNFAs@VNPs shows a specific capacitance of 950 F g−1at 5 mV s−1. • The PNFAs@VNPs supercapacitor has an energy density of 67.0 W h kg−1 at 550 W kg−1. [ABSTRACT FROM AUTHOR]