Vanadium Pentoxide with H2O, K+, and Na+ Spacer between Layered Nanostructures for High‐Performance Symmetric Electrochemical Capacitors

Abstract

AbstractVanadium oxide 2D layered nanostructures with the hydrous form of potassium (K+) and sodium (Na+) are synthesized via hydrothermal reaction between VOSO4 · xH2O and different persulfate oxidants ((NH4)2S2O8, K2S2O8, and Na2S2O8). The physicochemical characterization suggests that the synthesized V2O5 · 3H2O nanostructures possess layered morphology with considerable amount of water molecules accommodated between the interlayer spacing of nanostructures. Moreover, samples obtained using K2S2O8 and Na2S2O8 oxidants have K+ (6.41%) and Na+ (0.38%) ions intercalated on the 2D nanostructure along with the water molecules. Subsequently, the synthesized samples are heat‐treated at 400 °C for 3 h in the air and it is observed that the structural and morphological aspects are highly affected due to the removal of surface‐ and lattice‐bonded water molecules. The electrochemical properties of the samples are studied by assembling symmetric supercapacitor devices utilizing the bare and heat‐treated samples in 1 m Na2SO4 electrolyte. The fabricated device with bare V2O5 · 3H2O samples shows maximum specific capacitance (>60%) than that of heat‐treated V2O5 samples, which represents the positive influence of water molecule on electrochemical behavior of V2O5. Moreover, the bare sample V2O5 · 3H2O (using (NH4)2S2O8) symmetric supercapacitor exhibits an excellent cyclic stability with high capacitance retention of ≈97% after 25 000 cycles.