V2O5 nanosheet arrays/Co3O4 nanoneedle arrays composite for supercapacitor with enhanced energy density

In this work, two-dimensional V2O5 nanosheet arrays/one-dimensional Co3O4 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 V2O5 monocrystal with a layered structure grafting by Co3O4 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 (Cs) 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 Cs 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 (Ed) 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 Ed of supercapacitors.