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.
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机译：重要的是研究Fe（III）对正电解质的影响，以便为钒电解质的制备和使用提供一些实用指导。研究了Fe（III）对钒还原液流电池（VRFB）的正电解质的热稳定性和电化学行为的影响。当Fe（III）的浓度高于0.0196 mol l −1 时，V（V）电解质的热稳定性受到损害，V（IV）物质的扩散系数从（2.06-3.33）降低×10 −6 cm 2 s -1 至（1.78–2.88）×10 -6 cm 2 s -1 ，正电解质表现出较高的电解质电阻和电荷转移电阻。此外，Fe（III）可能导致副反应和容量衰减，这将对电池应用产生不利影响。随着Fe（III）含量的增加，钒离子与Fe（III）的碰撞几率增大，并且与氧化还原反应的竞争加剧，从而干扰了电极反应，钒离子的扩散和VRFB的性能。因此，本研究提供了一些实践指导，即在钒电解液的制备和使用过程中，最好使Fe（III）的杂质含量低于0.0196 mol l -1 。
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