Year-end Sale % OFF 
Abstract
The vanadium redox flow battery (VRFB) is one of the most mature and commercially available electrochemical technologies for large-scale energy storage applications. The VRFB has unique advantages, such as separation of power and energy capacity, long lifetime (>20 years), stable performance under deep discharge cycling, few safety issues and easy recyclability. Despite these benefits, practical VRFB operation suffers from electrolyte imbalance, which is primarily due to the transfer of water and vanadium ions through the ion-exchange membranes. This can cause a cumulative capacity loss if the electrolytes are not rebalanced. In commercial systems, periodic complete or partial remixing of electrolyte is performed using a by-pass line. However, frequent mixing impacts the usable energy and requires extra hardware. To address this problem, research has focused on developing new membranes with higher selectivity and minimal crossover. In contrast, this study presents two alternative concepts to minimize capacity fade that would be of great practical benefit and are easy to implement: (1) introducing a hydraulic shunt between the electrolyte tanks and (2) having stacks containing both anion and cation exchange membranes. It will be shown that the hydraulic shunt is effective in passively resolving the continuous capacity loss without detrimentally influencing the energy efficiency. Similarly, the combination of anion and cation exchange membranes reduced the net electrolyte flux, reducing capacity loss. Both approaches work efficiently and passively to reduce capacity fade during operation of a flow battery system.
Highlights
Vanadium redox flow batteries (VRFBs) are attractive for large-scale energy storage application due to their long life, environmentally-friendly chemistry, stable and high roundtrip efficiency and cheapest levelized cost per kWh compared to other available battery technologies [1,2].Batteries 2018, 4, 48; doi:10.3390/batteries4040048 www.mdpi.com/journal/batteriesThe anolyte and catholyte solutions in a vanadium redox flow battery (VRFB) are hindered from mixing by means of ion exchange membranes, which facilitate the ionic transport necessary to maintain the electrochemical reactions.The ion exchange membrane has to be efficient in proton conductivity and ion selectivity [3]
For a cell assembled with cation exchange membranes (CEMs) (Nafion 117), Schafner et al [21] observed that the overflow of the excess electrolyte effectively rebalanced the capacity, for extended period of cycling, a complete remixing will be needed for complete balancing of concentration and oxidation states of vanadium and sulfate ions
The auto-rebalancing of electrolyte was accomplished reversible capacity loss in VRFB
Summary
Vanadium redox flow batteries (VRFBs) are attractive for large-scale energy storage application due to their long life, environmentally-friendly chemistry, stable and high roundtrip efficiency and cheapest levelized cost per kWh compared to other available battery technologies [1,2]. In another work by Qingtao et al [8], the relationship between the electrochemical performance of VRFBs and electrolyte composition was studied They reported that one reason for capacity fading over repeated charge/discharge cycles was the resulting asymmetrical valency of vanadium ions in positive and negative electrolytes. Sukkar and Skyllas-Kazacos [12] investigated the use of different types of polyelectrolytes (both anionic and cationic) to improve the selectivity and stability of the membrane Both membranes exhibited improved water transfer properties, but these were not maintained upon longer exposure to vanadium electrolyte. Reported that by transferring surplus positive vanadium species back to the negative half-cell in a cell assembled with Nafion membrane, the lost capacity due to crossover during cycling can be restored, enabling long-term operation to be carried out without substantial loss of energy from the periodic total remixing of electrolyte.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
