Abstract
Lithium-doped vanadates (V2−xLixO5−δ (0.15 ≤ x ≤ 0.30)) are synthesized by melt-quench method. The physical, structural, optical, thermal and conducting properties of as-quenched samples are investigated using various experimental techniques to study their suitability for electrolyte in battery/solid oxide fuel cell application. X-ray diffraction (XRD) patterns confirm the formation of three different crystalline phases. FTIR and Raman spectra indicate that the doping of Li2O into V2O5 leads to a transition from VO5 into VO4 structural unit. The optical diffused reflectance spectra revealed that the optical band gap (Eg) decreases from 2.2 to 2.08 eV while Urbach energy (EU) increases (0.31–0.41 eV) with the addition of Li2O content in place of vanadium. The thermal stability is studied by thermogravimetric analyser (TGA). The DC conductivity of the present samples is increased from 0.08 to 0.12 Scm−1 at 450 °C with Li2O doping. These materials can be used as electrolyte for battery/solid oxide fuel cell due to their good conductivity (~0.12 Scm−1) at 450 °C.
Highlights
Solid oxide fuel cells (SOFCs) are most efficient electrochemical devices which convert chemical energy into electricity with heat and water as a by-product
The V2−xLixO5−δ (x = 0.15–0.30) systems have been synthesized by melt-quench followed by various characterization techniques to study their structural, optical, thermal and electrical properties to check their suitability as electrolytes for SOFCs applications
The increase in molar volume is ascribed to the rearrangement of the lattice which leads to creating oxygen vacancies due to VO5 → VO4 conversion with the substitution of Li1+ for V5+18
Summary
Solid oxide fuel cells (SOFCs) are most efficient electrochemical devices which convert chemical energy into electricity with heat and water as a by-product. The chemical nature and concentration of dopants play a vital role to change the oxidation state of vanadium which leads to a creation of oxygen vacancies to maintain overall electrical neutrality of the vanadate systems[5,9,10]. In most of the cases, these doped systems are prepared by solid-state reaction/chemical method followed by slow cooling which leads to lower the conductivity due to ordering in oxygen vacancies[5]. It has been reported by some research groups that quenched samples have higher disordering/defects which leads to increase in the overall electrical conductivity.
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