Vanadium Pentoxide with H2O, K+, and Na+Spacer between Layered Nanostructures for High-Performance Symmetric Electrochemical Capacitors
Vanadium oxide 2D layered nanostructures with the hydrous form of potassium (K + ) and sodium (Na + ) are synthesized via hydrothermal reaction between VOSO 4 ·xH 2 O and different persulfate oxidants ((NH 4 ) 2 S 2 O 8 , K 2 S 2 O 8 , and Na 2 S 2 O 8 ). The physicochemical characterization suggests that the synthesized V 2 O 5 ·3H 2 O nanostructures possess layered morphology with considerable amount of water molecules accommodated between the interlayer spacing of nanostructures. Moreover, samples obtained using K 2 S 2 O 8 and Na 2 S 2 O 8 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 Na 2 SO 4 electrolyte. The fabricated device with bare V 2 O 5 ·3H 2 O samples shows maximum specific capacitance ( > 60%) than that of heat-treated V 2 O 5 samples, which represents the positive influence of water molecule on electrochemical behavior of V 2 O 5 . Moreover, the bare sample V 2 O 5 ·3H 2 O (using (NH 4 ) 2 S 2 O 8 ) symmetric supercapacitor exhibits an excellent cyclic stability with high capacitance retention of ≈97% after 25 000 cycles.