Flow Battery Supports New Development of Long-Duration Energy Storage / Stack / Electrolyte

Flow batteries boast unique advantages of high safety, long service life and flexible adjustability, showing broad prospects in the large-scale long-duration energy storage sector. Guided by the "dual carbon" goals, flow battery technology is entering a critical breakthrough phase. This paper reviews the mainstream technical routes of flow batteries, focuses on key material bottlenecks and cutting-edge breakthroughs, analyzes future development trends, and provides an important reference for the continuous advancement of flow batteries.

Flow battery technologies are developing in a diversified manner, including iron-chromium, all-vanadium, all-iron, zinc-based (e.g., zinc-bromine, zinc-iron) and aqueous organic systems. Among them, the all-vanadium system is the most mature, while new low-cost systems such as all-iron and aqueous organic are developing rapidly. Nevertheless, high system cost remains the major bottleneck for the industrialization of flow batteries. The core to reducing costs and improving efficiency lies in the innovation of key materials.

1.Stack (Power Module):

Image: Ion Exchange Membrane

As a core component of flow batteries, the flow battery membrane must simultaneously achieve ion-selective conduction and active species blocking functions. It is mainly classified into three categories:

Ion-exchange membranes conduct ions via fixed charged groups. Traditional perfluorosulfonic acid membranes offer good stability but suffer from poor ion selectivity and high cost, while non-fluorinated membranes greatly reduce costs and have demonstrated high efficiency and long-term stability in kilowatt-scale stacks.

Porous membranes rely on porous channels for ion conduction and sieving, with performance enhanced by pore structure regulation. They are divided into intrinsic porous membranes and post-formed porous membranes based on how the pores are created.

Ordered-channel membranes (e.g., zeolites, MOFs, COFs) achieve precise and efficient sieving through uniform pore sizes. For instance, two-dimensional MFI-type zeolite membranes can synergistically improve ionic conductivity and selectivity, thereby significantly optimizing flow battery performance.

Image:Classification of Flow Battery Membranes

As the site for electrochemical reactions, the mainstream graphite felt electrodes suffer from insufficient hydrophilicity and activity. Studies have improved their performance through surface pore formation, introduction of active functional groups, catalyst loading, and design of gradient-structured electrodes. Lightweight and ultra-thin structures represent the future development trend.

Bipolar plates collect and conduct electrons, while also supporting the electrodes and distributing the electrolyte. Optimized flow field designs (such as dead-zone compensated flow fields and multi-stage distribution channels) can greatly improve the uniformity of electrolyte distribution, reduce flow resistance, and enhance stack efficiency and power density.

Image: Flow Battery Membrane Production Equipment

(Equipment Supplier: DRON)

2.Electrolyte (Capacity Module)The core objective of electrolyte modification is to develop electrolyte systems with high concentration, high stability, and low cost. Among fully dissolved systems, all-vanadium is relatively mature but limited by vanadium resources; research focuses on improving concentration and stability. New low-cost inorganic systems, such as fully dissolved all-iron batteries and sulfur-based batteries, are developing rapidly and showing promising application potential. Aqueous organic systems regulate potential via molecular design, improve solubility, enable multi-electron reactions, and enhance stability, with continuous improvements in energy density and cycle life. For deposition-dissolution batteries such as zinc-based and acidic all-iron systems, strategies including electrolyte additives are needed to suppress dendrite growth on the negative electrode and promote uniform metal deposition.

Future Outlook:In the future development of flow batteries, material innovation remains the core driving force: developing membranes with high selectivity, conductivity, and stability; electrodes with high activity and low resistance; bipolar plates with high conductivity, high strength, and low cost; and exploring new low-cost, high-stability, high-energy-density electrolyte systems based on abundant elements (Fe/Zn/Mn) or organic molecules. Artificial intelligence will accelerate material research and development. At the system level, intelligent control, hydrodynamic optimization, and modular design will improve operational efficiency and deployment flexibility. With policy support, industrial chain collaboration, and cost reduction driven by large-scale production, flow batteries will play an important role in power-side, grid-side, and user-side scenarios, providing critical long-duration energy storage support for building a new energy system and achieving the "dual carbon" goals.

20 Years of Equipment Experience – DRON Casting Production Line

SOFC (Solid Oxide Fuel Cell) Membrane Full Line:Optimized processes from Slurry Preparation → casting → drying → cutting, suitable for green sheets with thickness of 10–500 μm.

Water Electrolysis Hydrogen Production PEM/AEM Membrane Production Line:Compatible with proton exchange membrane / anion exchange membrane materials, film thickness uniformity: ±1 μm + 2%.