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On In–situ Redox Balancing of Vanadium Redox Flow Battery Using D‐Fructose as Negative Electrolyte Additive
Author(s) -
Pasala Vasudevarao,
Ramanujam Kothandaraman
Publication year - 2017
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201601417
Subject(s) - redox , electrolyte , flow battery , vanadium , chemistry , overpotential , inorganic chemistry , electrode , electrochemistry
Vanadium redox flow battery (VRFB) is an energy storage system, wherein V 2+ /V 3+ and VO 2+ /VO 2 + are used as negative and positive electrolyte respectively. It is well known that, V 2+ /V 3+ redox reaction is sluggish in comparison to that of VO 2+ /VO 2 + reaction. As the redox potential of V 2+ /V 3+ redox‐couple is more negative to that of H + /H 2 redox‐couple, during the V 2+ 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 V 2+ /V 3+ redox reaction at a given overpotential, (ii) suppresses the H 2 evolution at negative electrode during charging of VRFB (iii) controls the VO 2 + accumulation at the positive electrolyte and (iv) chemically reduces the VO 2 + arriving at negative electrode side through crossover, thereby avoiding the direct reaction between V 2+ and VO 2 + . A capacity retention of 86 % and 25 % is achieved at the end of the 25 th 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.