Vanadium pentoxide nanosheets with rich oxygen vacancies as a high-performance electrode for supercapacitors

Vanadium pentoxide (V 2 O 5 ), as a common supercapacitor electrode material, has unsatisfactory electrochemical performance due to its low conductivity and ionic diffusion rate, especially its specific capacitance and rate capability, which limits its practical use. In this work, V 2 O 5 rich in oxygen vacancies is successfully prepared by a controllable two-step reduction method. A variety of advanced characterization techniques, especially X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) spectra, have been used to qualitatively monitor changes in oxygen vacancy content. Compared with the untreated hydrated V 2 O 5 nanosheets, the oxygen vacancy V 2 O 5 (Vö V 2 O 5 ) has a larger specific surface area (4.002 m 2  g −1 ); besides, its specific capacitance (619.5 F g −1 in 1 A g −1 ) being not only better than that of V 2 O 5 without oxygen vacancy treatment (308.0 F g −1 in 1 A g −1 ) but also its cycle stability being improved (70.7% capacity retention after 1000 cycles), it is possible to develop high-performance supercapacitors by using it as an electrode material.