Effect of organophosphorus compound additives for thermal stability on the positive electrolyte of a vanadium redox flow battery

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 cm 2 s −1 to (1.78–2.88) × 10 −6 cm 2 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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An electrolyte with high thermal stability for the vanadium redox flow battery

Advanced Materials, Mechanical and Structural Engineering ◽

10.1201/b19934-75 ◽

2016 ◽

pp. 383-388

Keyword(s):

Thermal Stability ◽

High Thermal Stability ◽

Vanadium Redox Flow Battery ◽

Redox Flow Battery ◽

Flow Battery ◽

Vanadium Redox

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Effect of Phosphate Additive for Thermal Stability in a Vanadium Redox Flow Battery

Journal of Electrochemical Energy Conversion and Storage ◽

10.1115/1.4038019 ◽

2017 ◽

Vol 14 (4) ◽

Cited By ~ 4

Author(s):

Sun-Hwa Yeon ◽

Jae Young So ◽

Jin Hee Yun ◽

Se-Kook Park ◽

Kyoung-Hee Shin ◽

...

Keyword(s):

Thermal Stability ◽

Precipitation Amount ◽

Inorganic Materials ◽

Vanadium Redox Flow Battery ◽

Redox Flow Battery ◽

Flow Battery ◽

H2so4 Concentration ◽

The Stability ◽

Vanadium Redox ◽

Blank Solution

Organic/inorganic materials are investigated as additives to improve the stability of a vanadium electrolyte for a vanadium redox flow battery (VRFB) at operating temperatures of 25 °C and 40 °C. Among these materials, the most effective additive is chosen based on the thermal stability and electrochemical performance with a long inhibition time. Through precipitation time and electrochemical measurements, the results show that the best inhibition effect is achieved by adding sodium pyrophosphate dibasic (SPD, H2Na2O7P2) as an additive at a considerably high H2SO4 concentration (3M) electrolyte, indicating an improved redox reversibility and electrochemical activity. Nonflow cell assembled with the SPD additive exhibits larger discharge capacity retentions of 40% than a blank solution with the retentions of 2% at 600 cycles at 40 °C. In the case of flow cell, the capacity retention on the SPD additive shows 55.4%, which is 5.3% higher than the blank solution at 40 °C and 180 cycles. The morphology of the precipitation is investigated by SEM, which exhibits more severe V2O5 precipitation amount on the carbon felt electrode used in the blank electrolyte at 40 °C, which causes larger capacity losses compared to cells assembled with the SPD additive electrolyte.

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