Redox Flow Battery Technologies and Energy Storage Systems

Redox flow batteries (RFBs) are electrochemical energy storage systems in which the power and energy capacities are decoupled by storing redox‐active species in external tanks and circulating them through a central cell stack. This architecture enables independent scaling of energy (tank volume) and power (cell area), making RFBs particularly attractive for long‐duration grid stabilisation, renewable integration and large‐scale industrial applications. Aqueous vanadium systems remain the most mature, owing to their symmetric redox chemistry and inherently low crossover, but research now spans nonaqueous solvents, metal coordination complexes and organic molecules to achieve higher cell voltages, increased energy density and lower cost. Advances in ion‐selective membranes, flow‐field engineering and electrode materials have boosted both coulombic and energy efficiencies, while emerging chemistries such as quinones, flavins and transition‐metal complexes offer structural tunability and sustainability. Ongoing challenges include ensuring long‐term chemical stability, minimising crossover of active species, improving conductivity and reducing materials costs. Collectively, these developments point to a versatile platform capable of addressing global needs for flexible, safe and cost‐effective stationary energy storage.

Research from Nature Portfolio

Recent studies have demonstrated biomimetic organic electrolytes such as flavin mononucleotide paired with ferrocyanide in strongly alkaline media, achieving stable cycling over 100 charges and discharges with more than 99% capacity retention; this work underlines the importance of hydrotropic agents in enhancing aqueous solubility and resonance stabilisation of redox‐active biomolecules. Complementary efforts have systematically screened and characterised over thirty quinone and hydroquinone derivatives, quantifying how side-group position governs redox potential, solubility and chemical stability, and mapping degradation pathways that inform the molecular design of more robust all-organic aqueous flow systems.

Redox Flow Battery Technologies and Energy Storage Systems publication trend

The graph below shows the total number of articles in redox flow battery technologies and energy storage systems across all publications each year (not limited to Nature Index journals).

Technical terms

Redox couple: A pair of chemical species that undergo reversible oxidation and reduction at the electrodes, defining the cell voltage.

Coulombic efficiency: The ratio of charge extracted during discharge to charge supplied during charging, indicating parasitic losses.

Energy density: The amount of energy stored per unit volume or mass of electrolyte, determining the footprint of a storage system.

Anolyte/Catholyte: The negative and positive electrolytes, respectively, that store electrons during charging and deliver them during discharging.

Ion‐exchange membrane: A selective barrier that permits charge‐balancing ion transport while preventing mixing of anolyte and catholyte.

Flow field: The internal pathway structure within the cell stack that directs electrolyte distribution over the electrode surfaces.

References

1. Recent Advances in Redox Flow Batteries Employing Metal Coordination Complexes as Redox-Active Species. Electrochemical Energy Reviews (2024).
2. Zinc–Bromine Rechargeable Batteries: From Device Configuration, Electrochemistry, Material to Performance Evaluation. Nano-Micro Letters (2023).
3. Pathways to low-cost electrochemical energy storage: a comparison of aqueous and nonaqueous flow batteries. Energy & Environmental Science (2014).
4. Redox flow batteries: Status and perspective towards sustainable stationary energy storage. Journal of Power Sources (2021).
5. A biomimetic redox flow battery based on flavin mononucleotide. Nature Communications (2016).
6. Organic Redox Species in Aqueous Flow Batteries: Redox Potentials, Chemical Stability and Solubility. Scientific Reports (2016).