On In–situ Redox Balancing of Vanadium Redox Flow Battery Using D‐Fructose as Negative Electrolyte Additive

Abstract

Vanadium redox flow battery (VRFB) is an energy storage system, wherein V2+/V3+ and VO2+/VO2+ are used as negative and positive electrolyte respectively. It is well known that, V2+/V3+ redox reaction is sluggish in comparison to that of VO2+/VO2+ reaction. As the redox potential of V2+/V3+ redox‐couple is more negative to that of H+/H2 redox‐couple, during the V2+ formation hydrogen evolution occurs concomitantly, which affects the capacity retention of VRFB inducing redox couples concentration imbalance between the positive and negative electrolytes. In this study, we have explored the beneficial effect of D‐fructose as an additive to the negative electrolyte. D‐fructose (i) enhances the interfacial area of the graphite felt negative electrode‐electrolyte interface by wetting, thereby the current due to V2+/V3+ redox reaction at a given overpotential, (ii) suppresses the H2 evolution at negative electrode during charging of VRFB (iii) controls the VO2+ accumulation at the positive electrolyte and (iv) chemically reduces the VO2+ arriving at negative electrode side through crossover, thereby avoiding the direct reaction between V2+ and VO2+. A capacity retention of 86 % and 25 % is achieved at the end of the 25th cycle in the presence and absence of D‐fructose in the negative electrolyte, respectively. This way of in‐situ redox balancing alleviates the requirement for external redox balancing of the electrolyte, and help VRFB to deliver constant capacity with cycles.

Improving a Redox Flow Battery Working under Realistic Conditions by Using of Graphene based Nanofluids

“…This cell allows changing chemical energy into electricity and vice versa by the oxidation and reduction reactions of electrolyte employed. Moreover, the concentration of the redox species and the volume of the tanks determine the amount of stored energy and the power is determined by the rate of reaction at each electrode and their total surface area . Among the different types of RFBs, the all vanadium redox flow batteries (VRFBs) are a very promising energy storage system since they employ the same ion on both electrolytes but in different oxidation states minimizing the cross‐contamination (in the positive tank: VO 2 + /VO 2+ redox couple; in the negative tank: V 2+ /V 3+ redox couple) ,.…”

On Capacity Upgradation and In Situ Capacity Rebalancing in Anthrarufin-Based Alkaline Redox Flow Batteries

“…Diethylenetriamine- and oxygen-rich phosphate group-modified carbon felt electrodes are some techniques incorporated for minimizing H 2 evolution. A number of organic additives such as dl -malic acid, l -aspartic acid, and d -fructose are known to minimize capacity fading in the VRFB application. , Oxygen-rich functional groups of the additives can attract electrons from neighboring carbon atoms and make them electron-deficient. Having these additives in the anolyte, the extent of chemisorption of H + or H 2 O on the carbon felt surface can be minimized.…”

N‐ and P‐co‐doped Graphite Felt Electrode for Improving Positive Electrode Chemistry of the Vanadium Redox Flow Battery

“…To avoid the direct reaction between V 2+ and , in our earlier study, D‐fructose was used as a negative electrolyte additive . D‐fructose plays a dual role, one is to reduce the H 2 evolution at the negative electrode during charging and other is to reduce the into before it reacts with V 2+ .…”