Ultrasonic Spraying in Flow Battery Sector?

Can ultrasonic thin-film spraying equipment be used in the flow battery sector?

Ultrasonic thin-film spraying equipment is not only applicable to the flow battery sector but is also becoming a core process choice for preparing functional coatings on electrodes and separators. This technology is most maturely applied in the R&D and industrialization of all-vanadium flow batteries (VRFBs) and is expanding to other flow battery chemistries, such as zinc-based and iron-based systems.

Core Application Scenarios

Surface modification of graphite felt/carbon felt electrodes (Primary application)

Graphite felt and carbon felt are the core electrode materials for flow batteries; however, the raw materials suffer from issues such as poor hydrophilicity, low electrochemical activity, and sluggish reaction kinetics. Surface coating modification is essential to enhance their performance.

1. Carbon-based functional coatings: Spraying conductive nanomaterials—such as carbon nanotubes, graphene, and carbon black—to form a 3D conductive network. This reduces charge transfer resistance (by approximately 60%) and lowers the contact angle from 120° to below 30°, significantly improving hydrophilicity and electrolyte wettability.
2. Metal/metal oxide catalytic coatings: Applying catalysts such as TiO₂, MnO₂, and V₂O₅ to accelerate vanadium ion redox reaction rates, thereby boosting battery energy efficiency and power density.
3. Surface activation treatment: Spraying functional coatings following acid treatment or plasma pre-treatment to further optimize electrode surface structure and active sites.
4. Comparative advantages: Compared to traditional dipping or brush-coating methods, ultrasonic spraying increases material utilization by over 50% (reaching 90%+), ensures uniform and controllable coating thickness (±1 μm), prevents damage to carbon felt fibers through non-contact spraying, and is suitable for large-scale continuous production.

Preparation of functional coatings for ion-exchange membranes/separators (Key technological breakthrough)

The separator is a core component of flow batteries; its performance directly impacts vanadium ion permeability (cross-contamination), ion conductivity, and battery lifespan.

1. Selective barrier coatings: Ultrasonic spraying is used to deposit composite coatings—comprising graphene, graphene oxide, and polyelectrolytes—onto the surface of Nafion or porous polymer membranes. These coatings create ion-sieving channels that significantly reduce vanadium ion permeability (by over 80%) while maintaining high proton conductivity.
2. Anti-fouling/corrosion-resistant coatings: Spraying sulfuric acid-resistant ceramic or functional polymer coatings enhances the membrane’s stability and service life in highly acidic electrolytes.
3. Research progress: Studies conducted between 2024 and 2025 demonstrate that membranes with selectively applied coatings (via ultrasonic spraying) can extend the cycle life of all-vanadium redox flow batteries by more than 40%; the technology has progressed from laboratory research to the pilot-scale testing stage.

Coatings for other key components

1. Bipolar plate coatings: Spraying conductive, anti-corrosive coatings (such as carbon-based or metal nitride coatings) reduces contact resistance and improves the bipolar plate’s corrosion resistance in highly acidic environments.
2. Current collector surface treatment: Spraying conductive coatings optimizes the contact interface between the current collector and the electrode, thereby reducing interfacial impedance.
3. Zinc-based flow battery anode coatings: Spraying functional coatings (such as carbon nanotube/polymer composites) onto the zinc anode surface inhibits zinc dendrite growth; this addresses short-circuit issues caused by dendrites puncturing the membrane and extends the battery’s cycle life.

Core advantages of ultrasonic thin-film spraying technology (tailored to flow battery requirements)

1. High-precision atomization and uniform deposition: High-frequency ultrasonic waves (typically 20–120 kHz) atomize nano-slurries into uniform droplets (50–200 nm), forming dense thin-film coatings with controllable thickness while avoiding the “coffee-ring” effect and particle agglomeration associated with traditional spraying methods.
2. 2. Extremely high material utilization: Non-contact spraying results in virtually no overspray; utilization rates for catalysts and functional materials exceed 90%, significantly reducing costs for expensive materials (such as carbon nanotubes, graphene, and catalysts).
3. Flexible and controllable process: Coating thickness (ranging from tens of nanometers to several micrometers) and areal density can be precisely controlled by adjusting spraying parameters (frequency, flow rate, temperature, and distance), meeting the specific requirements of various flow battery types.
4. Environmentally friendly and equipment-compatible: Operations can be conducted at ambient temperature and pressure without the need for a vacuum environment; the equipment integrates into existing production lines, supports roll-to-roll continuous spraying, and is suitable for mass production; the process generates no wastewater or exhaust gas pollution, aligning with green manufacturing standards.
5. Compatible with multiple systems: Suitable not only for all-vanadium flow batteries but also for electrode and membrane modification in other flow battery technologies, such as zinc-based (zinc-iron, zinc-bromine, zinc-manganese) and iron-based (iron-chromium, all-iron) systems.

Current Status of Technology Application and Development Trends

Current Application Status

1. R&D Stage: Leading flow battery companies and research institutions (such as the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences, Tsinghua University, and international firms like VRB Energy and Invinity) are utilizing ultrasonic spraying technology to research electrode and membrane modifications.
2. Industrialization Progress: Several domestic equipment manufacturers have launched specialized ultrasonic spraying equipment for flow battery electrodes; some all-vanadium flow battery production lines have adopted this technology for pilot-scale production (coating capacity exceeding 1,000 m²/day).
3. Cost and Efficiency: As the technology matures, the cost of ultrasonic spraying equipment has gradually decreased; the unit coating cost for mass production now approaches that of traditional processes, yet offers significant performance advantages (a 5–8% increase in battery energy efficiency and a more than 30% increase in cycle life).

Challenges and Future Directions

1. Core Challenges:
– Stable atomization of high-viscosity nano-slurries (e.g., graphene slurries, high-concentration catalyst slurries)
– Control of coating uniformity over large areas (matching tension and speed during roll-to-roll production)
– Optimization of interfacial bonding strength between the coating and the substrate (carbon felt/membrane)
2. Development Trends:
– Integrated ultrasonic spraying technology for multi-material composite coatings (e.g., carbon nanotubes + catalysts + polymers)
– Development of continuous production lines integrating in-situ spraying, drying, and curing
– Application of AI and machine vision technologies for online monitoring of coating quality
– Technological expansion from all-vanadium flow batteries to low-cost flow battery chemistries, such as zinc-based and iron-based systems

Summary and Recommendations

Ultrasonic thin-film spraying equipment offers clear value and broad prospects in the flow battery sector; it is a key process technology for enhancing performance, reducing costs, and driving large-scale application.

For flow battery R&D companies and equipment manufacturers, the following recommendations are made:
1. Prioritize the evaluation of ultrasonic spraying technology for graphite felt electrode surface modification projects, as it can significantly improve electrode performance and reduce material costs.
2. Conduct R&D on ultrasonic spraying processes for selective membrane coating technologies, as this is an effective approach to addressing cross-contamination issues in flow batteries.
3. Collaborate with ultrasonic spraying equipment manufacturers to develop customized equipment and process solutions tailored to flow battery production.

About Cheersonic

Cheersonic is the leading developer and manufacturer of ultrasonic coating systems for applying precise, thin film coatings to protect, strengthen or smooth surfaces on parts and components for the microelectronics/electronics, alternative energy, medical and industrial markets, including specialized glass applications in construction and automotive.

Our coating solutions are environmentally-friendly, efficient and highly reliable, and enable dramatic reductions in overspray, savings in raw material, water and energy usage and provide improved process repeatability, transfer efficiency, high uniformity and reduced emissions.

If you have any technical questions, customization demands, or procurement inquiries about ultrasonic atomization nozzles, feel free to contact our professional sales and technical team for detailed parameters, customized solutions, and industry application support.
Email: market2@cheersonic.com