Abstract
It is important to study the effect of Fe(III) on the positive electrolyte, in order to provide some practical guidance for the preparation and use of vanadium electrolyte. The effect of Fe(III) on the thermal stability and electrochemical behaviour of the positive electrolyte for the vanadium redox flow battery (VRFB) was investigated. When the Fe(III) concentration was above 0.0196 mol l−1, the thermal stability of V(V) electrolyte was impaired, the diffusion coefficient of V(IV) species decreased from (2.06–3.33) × 10−6 cm2 s−1 to (1.78–2.88) × 10−6 cm2 s−1, and the positive electrolyte exhibited a higher electrolyte resistance and a charge transfer resistance. Furthermore, Fe(III) could result in the side reaction and capacity fading, which would have a detrimental effect on battery application. With the increase of Fe(III), the collision probability of vanadium ions with Fe(III) and the competition with the redox reaction was aggravated, which would interfere with the electrode reaction, the diffusion of vanadium ions and the performance of VRFB. Therefore, this study provides some practical guidance that it is best to bring the impurity of Fe(III) below 0.0196 mol l−1 during the preparation and use of vanadium electrolyte.
Highlights
With the ongoing environmental pollution and energy crisis, the vanadium redox flow battery (VRFB) has been considered as an efficient and environmentally-friendly storage& 2019 The Authors
We studied in detail different concentrations of Fe(III) as impurity ions for VRFB anolytes and investigated its effect on the thermal stability and electrochemical performance
The Cyclic voltammetry (CV) measurements indicated that better reaction kinetics were achieved by adding 0.0196 mol l21 Fe(III), resulting in the improvement of the V(IV) diffusion coefficient, and better reversibility of the electrode reaction compared with the pristine electrolyte
Summary
With the ongoing environmental pollution and energy crisis, the vanadium redox flow battery (VRFB) has been considered as an efficient and environmentally-friendly storage. VRFBs are installed as the positive and negative electrolytes of energy storage materials in two liquid storage tanks, which means they have many advantages, such as high efficiency, fast response, deep discharge ability, flexible module design and long lifetime [3,4,5]. Because of these merits, VRFB is widely commercially applied and researched. We studied in detail different concentrations of Fe(III) as impurity ions for VRFB anolytes and investigated its effect on the thermal stability and electrochemical performance. This study may provide some practical guidance for the preparation and use of vanadium electrolyte
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