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  4. Novel electrolyte rebalancing method for vanadium redox flow batteries
 
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2021
Journal Article
Title

Novel electrolyte rebalancing method for vanadium redox flow batteries

Abstract
A new method is proposed that restores the battery energy and capacity of a Vanadium Redox Flow Battery, by counteracting the charge imbalance caused by air-oxidation and hydrogen evolution in the negative electrolyte. The process makes use of a regeneration system specifically designed and successfully tested. This system is built around an electrolysis cell, that is called ""regeneration cell"", where an electro-reduction reaction of V(V) is coupled with an oxygen evolution reaction catalyzed by a Ti-IrO2 electrode. The rebalancing of three different unbalanced electrolytes was tested: V3.55+, V3.60+ and V3.65+, namely: 45% V(III)/55% V(IV), 40% V(III)/60% V(IV) and 35% V(III)/65% V(IV) respectively. The behavior of the VRFB cell during the rebalancing process was investigated both numerically and experimentally. An end-point strategy for the rebalancing process without additional sensors has been developed by using of a specific mathematical model capable of simulating the current response and concentrations profile during the rebalancing process. This strategy allowed to improve the performance of the rebalancing process. After rebalancing, the resulting electrolyte oxidation states were respectively: V3.483+, V3.482+, V3.484+. Since a perfectly balanced electrolyte is V3.50+ (50% V(III), 50% (VIV) such results demonstrated that the electrolyte imbalance was drastically reduced and the rebalancing process was successful.
Author(s)
Poli, Nicola
Schäffer, Michael  orcid-logo
Fraunhofer-Institut für Chemische Technologie ICT  
Trovò, Andrea
Noack, Jens  
Fraunhofer-Institut für Chemische Technologie ICT  
Guarnieri, Massimo
Fischer, Peter  
Fraunhofer-Institut für Chemische Technologie ICT  
Journal
The chemical engineering journal  
DOI
10.1016/j.cej.2020.126583
Language
English
Fraunhofer-Institut für Chemische Technologie ICT  
Keyword(s)
  • vanadium redox-flow battery

  • electrolyte imbalance

  • electrolyte concentration

  • capacity decay

  • rebalance

  • capacity loss

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