Innovative Application of Ultrasonic Cleaning Technology in Bipolar Plate Preparation for Hydrogen Fuel Cells

Against the backdrop of global energy transition, hydrogen energy has become an important direction for energy transformation as an efficient and clean form of energy. Hydrogen fuel cells, as a key technology for hydrogen energy applications, are receiving increasing attention, with their performance and cost-effectiveness being the core factors driving the development of the hydrogen energy industry.

A hydrogen fuel cell is a device that converts chemical energy into electrical energy by the chemical reaction of hydrogen and oxygen within the fuel cell stack, without involving combustion and producing water as the byproduct. Therefore, fuel cells have advantages such as zero emissions, high efficiency, and low noise compared to traditional internal combustion engines.

The fuel cell stack typically consists of multiple fuel cell units stacked in series to improve overall power output. Within the stack, the bipolar plates and membrane electrodes are interleaved, embedded with seals, and clamped by end plates.

Among them, the bipolar plate serves as the backbone of the fuel cell, performing multiple tasks such as gas distribution, electrical and thermal conduction, supporting membrane electrodes, and removing byproducts. Its cost accounts for approximately 20-40% of the fuel cell stack. Depending on the material, bipolar plates can be categorized into three major types: metal, graphite, and composite materials.

With the continuous development of manufacturing technology, metal bipolar plates are becoming the mainstream choice for fuel cell bipolar plates due to their excellent performance, durability, and cost advantages. The production process for metal bipolar plates mainly includes stamping, edging, cleaning, welding, coating, and encapsulation steps.

Single plate stamping and cutting: Flow fields, three-chamber ports, and auxiliary structures are prepared on metal sheet coils through stamping forming molds. Excess flash and port remnants are removed by trimming molds.

Single plate cleaning: Metal bipolar plates are formed by welding two single plates, the cathode plate, and the anode plate. The welding process requires consideration of factors such as sealing, robustness, consistency, durability, and flatness, with strict requirements for cleanliness on the welding area surface. Therefore, pre-cleaning of single plates is a necessary step to improve welding quality.

Bipolar plate welding: Two single plates are welded together to form a bipolar plate using a high-speed laser welding system, which relies on laser fusion to achieve the connection at the welding area.

Bipolar plate cleaning: Bipolar plates need to have corrosion resistance in the acidic and humid environment of fuel cells, and they require good compatibility with other fuel cell components and materials. Therefore, the surface of bipolar plates undergoes multi-material and multi-layer coating treatments to achieve good corrosion resistance, high conductivity, and low contact resistance. Precise cleaning of the plates is necessary before the coating process to avoid any negative impact on the coating quality and performance.

Bipolar plate coating: Conductive and corrosion-resistant coatings are prepared on the surface of bipolar plates using magnetron sputtering in a vacuum coating system.

Bipolar plate encapsulation: Adhesive layers are pre-applied to the surface of the bipolar plates using automated encapsulation equipment. Seal components are placed and positioned, and the bipolar plates are connected to the seal components using the adhesive layer.

Testing and shipping: The conductivity of the bipolar plates is tested using a contact resistance testing device. After sealing, leakage tests are conducted on the hydrogen chamber, oxygen/air chamber, and coolant chamber of the bipolar plates using an airtightness testing device to ensure the airtight state. Visual inspections are performed, and the final inspection report is generated in preparation for shipping.

Hydrogen fuel cells hold immense potential and bring exciting opportunities. However, there are significant challenges on the path to practical application, with bipolar plate cleaning being a highly challenging task.

Compared to traditional cleaning methods, ultrasonic cleaning technology offers advantages such as high cleaning efficiency, excellent cleaning results, and non-destructive cleaning. It utilizes the cavitation effect generated by ultrasonic waves in the liquid to penetrate into the tiny gaps and pores on the surface of metal bipolar plates, effectively removing impurities such as dust, stamping particles, oil, and organic substances, providing a clean surface for welding and coating processes, thereby enhancing the conductivity and corrosion resistance of the bipolar plates.

Furthermore, ultrasonic cleaning technology is easy to implement for full-process automation control. Whether applied to individual process applications or integrated into the entire production line, it ensures high cleanliness and consistency of the cleaning results. Moreover, ultrasonic cleaning technology is suitable for cleaning objects of various materials and sizes, enabling it to meet the cleaning requirements of bipolar plates with different production scales, materials, and sizes, making it an ideal choice for cleaning metal bipolar plates.

The development prospects of the hydrogen energy industry are broad, and many countries worldwide have recognized hydrogen energy and fuel cells as important components of energy transition, providing policy support and investment. With technological advancements and cost reductions, hydrogen fuel cells are expected to be widely used in various fields such as transportation, aviation, aerospace, industrial clean energy applications, and power generation.

In conclusion, the innovative application of ultrasonic cleaning technology in the preparation of bipolar plates for hydrogen fuel cells offers significant advantages in terms of cleaning efficiency, cleaning results, automation control, and compatibility with different plate materials and sizes. By utilizing ultrasonic waves and the cavitation effect, this technology ensures the cleanliness, conductivity, and corrosion resistance of the bipolar plates, which are crucial for the performance and durability of fuel cells. With the growing importance of hydrogen energy and fuel cell technology, the implementation of ultrasonic cleaning technology in the manufacturing process of bipolar plates contributes to the advancement and widespread adoption of hydrogen fuel cells in various industries.