Effect of neutral electrolytes on vanadium dioxide microspheres-based electrode materials for asymmetric supercapacitors

Different neutral electrolytes (0.5 M K2SO4, 1 M Li2SO4, 1 M Na2SO4, and 1 M NaNO3) were used to investigate the electrochemical performances of vanadium dioxide (VO2) successfully synthesized via a solvothermal process. X-ray diffraction (XRD) results for the VO2 material revealed a monoclinic crystal structure phase A and field emission scanning electron microscopy (FESEM) images showed that the sample is formed of microspheres-like morphology with an assembly of nanograins on their surfaces. Electrochemical investigation of as-prepared sample was done in three-electrode configurations. The highest specific capacitance of 163.1 F g(-1) was recorded with 0.5 M of K2SO4 and the lowest value of 44.5 F g(-1) with 1 M Li2SO4 at a specific current of 0.5 A g(-1) in a stable potential window of 0.8 V. The synthesized vanadium dioxide (VO2 (A)) as a positive electrode and peanut shell derived activated carbon (PS-AC) as a negative electrode were used to assemble asymmetric supercapacitors (VO2//PS-AC) in 0.5 M K2SO4 electrolyte. This asymmetric device recorded a specific energy of 25.8 W h kg(-1) with a corresponding specific power of 425 W kg(-1) at 0.5 A g(-1) in a cell potential of 1.7 V. It also showed a good columbic efficiency of 99.8% and a capacitance retention of 75% up to 10,000 charge-discharge cycles at a specific current of 5 A g(-1). Overall, the VO2 microspheres//PS-AC asymmetric supercapacitor revealed excellent electrochemical performance in the neutral medium electrolyte and thus a potential candidate for use in other integrated energy systems.

Automated summary

Different neutral electrolytes were used to investigate the electrochemical performances of vanadium dioxide synthesized via a solvothermal process. Among them, the material showed the highest specific capacitance in 0.5 M K2SO4. The asymmetric supercapacitor (VO2//PS-AC) demonstrated excellent performance at 0.5 A g(-1) in the neutral medium electrolyte.