Key Takeaways & Executive Findings
- •• Critically analyses the ion transport mechanisms of various membranes and compares them, highlighting the challenges for vanadium redox flow battery (VRFB) applications. • Provides in-depth analysis and discussion of the best strategies for membranes to achieve high-performance VRFBs. • Prospective approaches to realising high-performance, sustainable VRFB membranes are outlined. • Emphasizes the trade-off between membrane efficiency and durability, and the need for cost-effective solutions.
Abstract
While being a promising candidate for large-scale energy storage, the current market penetration of vanadium redox flow batteries (VRFBs) is still limited by several challenges. As one of the key components in VRFBs, a membrane is employed to separate the catholyte and anolyte to prevent the vanadium ions from cross-mixing while allowing the proton conduction to maintain charge balance in the system during operation. To overcome the weakness of commercial membranes, various types of membranes, ranging from ion exchange membranes with diverse functional groups to non-ionic porous membranes, have been designed and reported to achieve higher ionic conductivity while maintaining low vanadium ion permeability, thus enhancing efficiency. In addition, besides overall efficiency, stability and cost-effectiveness of the membrane are also critical aspects that determine the practical applicability of the membranes and thus VRFBs. In this article, we have offered comprehensive insights into the mechanism of ion transportation in membranes of VRFBs that contribute to the challenges and issues of VRFB applications. We have further discussed optimal strategies for solving the trade-off between the membrane efficiency and its durability in VRFB applications. The development of state-of-the-art membranes through various material and structure engineering is demonstrated to reveal the relationship of properties-structure-performance.
1. Introduction
The increasing worldwide energy demand, environmental challenges stemming from the extensive consumption of fossil fuels, and the urgency to meet carbon emission targets are propelling the development of renewable energy technologies utilizing clean energy sources, such as solar and wind [1–6]. However, due to their inherent unpredictability and intermittency [7, 8], the electricity generated from renewable sources is difficult to be utilised directly and efficiently in practice. Large-scale energy storage systems are the key to facilitate the implementation of renewable energies by storing and then releasing a reliable energy supply when needed. Among the various storage technologies, redox flow batteries (RFBs) are anticipated to become a viable candidate for large-scale and long-duration applications. Initially conceptualised in the early 1980s, RFBs emerged as an innovative alternative to conventional battery systems due to their ability to decouple energy storage and power generation [9]. Unlike traditional batteries, where the electrochemical reactions take place within a single cell, RFBs rely on liquid electrolytes that are stored externally and circulated through electrochemical cells, allowing for easy scaling of both capacity and power [10]. The development of RFBs has been a significant advancement in the field of energy storage technologies. This expectation is based on their distinct features, including the ability of delivering both high energy capacity and high-power output, adaptable design, minimal toxicity, and extended cycle life [11–13]. To date, a variety of RFB systems have been developed, such as all-vanadium RFBs [14–16], zinc-based RFBs [17–19], iron-based RFBs [20], sodium-based RFBs [21], polysulfide-based RFBs [22], nitrobenzene-iodine RFBs [23], and aqueous organic RFBs [24]. Among them, the vanadium redox flow battery (VRFB) represents the most commercially viable RFBs.
VRFB was first proposed by Skyllas-Kazacos and colleagues in 1984 [25]. While the research and initial development of VRFBs began in the 1980s-1990s, their progress and commercial viability rose dramatically in the 2010s and especially recently, driven by the growing need for long-duration energy storage to support renewable energy integration and grid stability. Possessing all the typical properties of RFBs, VRFB also has the advantage of being environmentally friendly and economically efficient, making it suitable for large-scale energy storage applications. Unlike other RFBs, such as Zn-based or Fe-based batteries, VRFBs do not suffer from cross-contamination issues since they use vanadium ions on both positive and negative sides [26]. A VRFB consists of three critical components: electrodes, electrolytes, and a membrane. Numerous factors can affect the performance of VRFBs, including reactivity of the electrode [27–29], concentration and flow rate of the electrolyte [30, 31], operating temperature [32], stability of components, ionic conductivity, and vanadium ion permeability.
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Tan Trung Kien Huynh, Tong Yang, Nayanthara P S, Yang Yang, Jiaye Ye, Hongxia Wang (2025). Construction of High-Performance Membranes for Vanadium Redox Flow Batteries: Challenges, Development, and Perspectives. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01736-x
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Frequently Asked Questions
What is the role of a membrane in a vanadium redox flow battery (VRFB)?
The membrane in a VRFB separates the catholyte and anolyte to prevent vanadium ions from cross-mixing while allowing proton conduction to maintain charge balance during operation.
What are the main challenges for membranes in VRFBs?
Key challenges include achieving high ionic conductivity while maintaining low vanadium ion permeability, ensuring long-term stability and durability, and balancing performance with cost-effectiveness.
What types of membranes are discussed in the article?
The article discusses various types of membranes, including ion exchange membranes with diverse functional groups and non-ionic porous membranes, designed to improve performance.
What strategies are proposed to improve membrane performance?
Optimal strategies include material and structure engineering to solve the trade-off between membrane efficiency and durability, as well as developing state-of-the-art membranes with enhanced properties.
Why are VRFBs considered promising for large-scale energy storage?
VRFBs offer high energy capacity, high-power output, adaptable design, minimal toxicity, and extended cycle life, making them suitable for large-scale and long-duration energy storage applications.
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