A techno-economic model was developed to investigate the influence of components on the system costs of redox flow batteries. Sensitivity analyses were carried out based on an example of a 10 kW/120 kWh vanadium redox flow battery system, and the costs of the individual components were analyzed. Particular consideration was given to the influence of the material costs and resistances of bipolar plates and energy storage media as well as voltages and electric currents. Based on the developed model, it was possible to formulate statements about the targeted optimization of a developed non-commercial vanadium redox flow battery system and general aspects for future developments of redox flow batteries.

In this study, 1.6 M vanadium electrolytes in the oxidation forms V(III) and V(V) were prepared from V(IV) in sulfuric (4.7 M total sulphate), V(IV) in hydrochloric (6.1 M total chloride) acids, as well as from 1:1 mol mixture of V(III) and V(IV) (denoted as V^3.5+) in hydrochloric (7.6 M total chloride) acid. These electrolyte solutions were investigated in terms of performance in vanadium redox flow battery (VRFB). The half-wave potentials of the V(III)/V(II) and V(V)/V(IV) couples, determined by cyclic voltammetry, and the electronic spectra of V(III) and V(IV) electrolyte samples, are discussed to reveal the effect of electrolyte matrix on charge-discharge behavior of a 40 cm² cell operated with 1.6 M V^3.5+ electrolytes in sulfuric and hydrochloric acids. Provided that the total vanadium concentration and the conductivity of electrolytes are comparable for both acids, respective energy efficiencies of 77% and 72–75% were attained at a current density of 50 mA∙cm⁻². All electrolytes in the oxidation state V(V) were examined for chemical stability at room temperature and +45 °C by titrimetric determination of the molar ratio V(V):V(IV) and total vanadium concentration.

A series of vanadium redox‐flow battery (VRFB) electrolytes at 1.55 m vanadium and 4.5 m total sulfate concentration are prepared from vanadyl sulfate solution and tested under conditions of appearance of “power drop” effect (discharge at high current density from high state‐of‐charge). A correlation between the initial electrolyte composition, the thermal stability of catholyte, and the susceptibility of VRFB to exhibit a “power drop” effect is derived. The increase in total acidity to 3 m, expressed as concentration of sulfuric acid in precursor vanadyl sulfate solution, enables “power drop”‐free operation of VRFB at least at 75 mA cm⁻². Thermally‐induced degradation of electrolyte is evaluated based on decrease in vanadium concentration in the electrolyte series after exposure to the temperature of 45 °C and based on characterization of catholytes series using ⁵¹V, ¹⁷O, and ¹H nuclear magnetic resonance spectroscopy.

A techno-economic model was developed to investigate the influence of components on the system costs of redox flow batteries. Sensitivity analyses were carried out based on a example of a 10 kW/120 kWh vanadium redox flow battery system and the costs of the individual components were analyzed. Particular consideration was given to the influence of material costs and resistances of bipolar plates and energy storage media as well as voltages and electric currents. Based on the developed model it was possible to formulate statements about the targeted optimization of existing battery systems and general aspects for future developments of redox flow batteries.

This case study investigates practical approaches for evaluating commercially available vanadium electrolytes (VEL) for vanadium flow battery applications. From the perspective of a potential electrolyte customer, a range of wet chemical and instrumental analytical methods was applied to characterize commercial electrolyte samples obtained from multiple suppliers. The results demonstrate that potentiometric titration, inductively coupled plasma optical emission spectroscopy (ICP‐OES), and inductively coupled plasma mass spectrometry (ICP‐MS) provide a robust analytical framework for determining the main electrolyte components and inorganic impurities, although method‐dependent deviations were observed for selected parameters. In contrast, short‐term galvanostatic charge–discharge testing showed limited sensitivity for differentiating electrolytes of similar composition and purity. Thermal stability testing of electrolyte at high states of charge revealed clear differences between samples and indicated that phosphate concentration and the ratio of total vanadium to sulfate concentration ( C _V / C _S ) are important parameters influencing electrolyte stability. Furthermore, gas phase analysis of hydrogen evolution from vanadium(II)‐containing electrolytes proved to be a useful method for detecting impurity‐related effects that are not captured by conventional electrochemical testing. Overall, the study identifies a set of practical analytical metrics and complementary testing approaches that enable a more structured and application relevant assessment of vanadium electrolyte quality in a developing commercial market.