Contribution of Ti insertion on nano-crystalline rich oxygen vacancy V₂O₅’s performance for supercapacitor electrodes

The sol–gel film method was employed to produce pure and Ti-doped V₂O₅ in varying concentrations (1, 2, 3, and 4 mol%). The resulting materials were characterized using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDX), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface area analysis, and X-ray photoelectron spectroscopy (XPS) to assess their crystal structure, morphology, surface characteristics, and elemental composition. XRD results indicated that all samples, whether pure or doped, crystallized in the orthorhombic phase with a preferred orientation along the (101) plane. The introduction of doping reduced the crystallite size, which fell below 10 nm. SEM analysis revealed that the V₂O₅ appeared as nanosheets. The impact of doping on electrochemical performance was evaluated using galvanostatic charge/discharge (GCD), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) in a 1 M LiNO₃ electrolyte. The electrochemical tests demonstrated surface redox pseudocapacitive behavior with reversible charge/discharge capabilities, and specific capacitance values ranged from 254.6 to 352.3 F/g, depending on the sample composition, as determined by CV. The presence of dopants enhanced the electrochemical performance due to the multiple oxidation states of V and Ti, as well as the presence of oxygen vacancies (V_O^··). Specifically, the 4% Ti-doped V₂O₅ exhibited a specific capacitance (C_sp) of 352.3 F/g, energy density (E_d) of 43.3 Wh/kg, power density (P_d) of 554.2 W/kg, and maintained 69.1% cycling stability over 10,000 cycles at 1 A/g.