Bipolar plates are flat components within fuel cells that generate electricity. They may be found in hydrogen vehicles, back-up power generation units, and industrial solutions. Certain materials may be long-lasting but very expensive. Metal plates have great conductivity, graphite plates have typically better resistance to chemicals, and composite materials seem to sort of do both. So, what is selecting bipolar plate material really about? Finding the right balance to suit your particular application. This article will describe the major material types and help you select the proper material for your specific application.
What is Bipolar Plate?
Bipolar plates are flat, thin pieces that stack between the individual fuel cells to create complete power systems. These are important pieces that perform multiple functions in fuel cell stacks.
Some functions of bipolar plates include:
- Gas distribution: Distribute the hydrogen and oxygen gases evenly over the active area of the cells
- Electrical conduction: Conducts current from cell to cell, creating series connections
- Thermal management: Remove heat using the cooling channels designed into the plates
- Structural support: Provide a mechanical structure for the membrane assemblies
The name ‘bipolar’ describes how they behave electrically. One side of the plate acts positively for one cell, while the other side acts negatively for the adjacent cell. Most plates are 1-3 millimeters thick with very complex flow channels etched into the face of the plates. The flow channels distribute the gases while also getting rid of any water created during the reactions. Bipolar plates can also be made from a number of different materials. Each bipolar plate material offers different advantages for certain applications.
Common Bipolar Plate Material Option
When it comes to choosing bipolar plate material, it is not a matter of identifying a one-size-fits-all solution but rather matching material properties to specific application needs. Fuel cell bipolar plate material affects its performance.
Metals
Metals continue to be the dominant choice for bipolar plates because:
- Excellent conductivity for effective transport of electrical current,
- Adequate mechanical properties to withstand clamping force,
- Can be made thin to improve the packing density, and
- Established, scalable production systems to produce thick plates.
Of these, stainless steel is the most common in use, but titanium and aluminum bipolar plates are also used with protective coatings to mitigate corrosion of these substrates.
Graphite
Graphite has its benefits because of:
- Good chemical resistance in acidic or alkaline environments
- Coatings are not required, thus reducing processing operations
- However, it has less toughness than metals.
Composites
Composites provide the best of both worlds by integrating polymers with carbon fibers to demonstrate:
- Good chemical resistance on par with graphite
- Conductivities sufficient for energy applications, and
- Provide added benefits in situations where metals or graphite will not meet the needs directly.
Factors to Consider When Choosing Bipolar Plate Material
The material you choose for bipolar plates will impact their performance. Here are some of the key factors you should consider when choosing bipolar plate material:
- Corrosion Resistance: Materials should exhibit long-term stability when exposed to operating conditions to ensure reliable performance.
- Electrical and Thermal Conductivity: This factor is important for generating current and managing heat removal. Metallic materials have better electrical efficiency than graphite materials.
- Mechanical Strength: Plates must be strong enough to maintain the clamping forces keeping the fuel cell stack together. They must not break or deform upon assembly to the other components of the stack
- Cost: The cost of bipolar plates reaches significant proportions of the total stack costs. Therefore, the matter of material selection must be critically analyzed in terms of its impact on the commercial viability of fuel cell systems.
TMNetch Bipolar Plates: Advanced Materials for Optimal Performance
TMNetch makes high-precision bipolar plates, also referred to as flow field or current collector plates, for fuel cells and water electrolyzers. TMNetch has decades of etching experience and continues to produce components with high performance.
- Depth Channels: Twin depth channels (e.g., 0.6 mm & 0.4 mm on one side and 0.5 mm on the other) are etched to provide optimized gas distribution and conductivity.
- Advanced Coatings: Surface coatings such as platinum plating on one side and MMO (mixed metal oxide) coating on the other side of the plate for corrosion protection and electrical performance.
- Laser Welding: Smooth seals and flush surfaces at the seals to provide leak-free assembly of the stack.
- Over 10 years of experience exporting etched components around the world, complete with documentation and COC certification.
With this unique combination of etching experience, coating knowledge, and dependable service, TMNetch is ready to be your trusted partner in fuel cell and electrolyzer technology development.
FAQs About Bipolar Plate Material
What is the function of the bipolar plate in a fuel cell?
Bipolar plates are tasked with four critical functions for fuel cell systems simultaneously. The flow channels distribute hydrogen and oxygen reactants to the surfaces of each cell. The fluid cooling passages remove heat from the fuel cell stack. Finally, bipolar plates provide structural integrity for the entire fuel cell assembly.
What are bipolar plates made of?
Bipolar plate material consists primarily of metals, graphite, and composites. Graphite provides good resistance to chemical attack but is not mechanically tough. The bipolar plate material in PEM fuel cells contains some type of protective coatings to enhance performance.
What is a bipolar plate?
Bipolar plates are thin components that separate the individual fuel cells while electrically connecting them. The ‘bipolar’ name is derived from their dual electrical assignment; one side is positive, while the other is negative. Bipolar plates have etched flow channels designed to distribute reactant gases to the active areas.
Conclusion
Choosing the proper bipolar plate material will affect the performance and longevity of your fuel cell system. The physical requirements for bipolar plate materials in a PEM fuel cell application differ significantly from the alkaline electrolyzer application.
Advanced manufacturing processes, including photochemical etching, allow designs conceived by the designer to be manufactured and formed to contour themselves for applications that may never have been thought possible with more traditional methods of manufacture. Surface treatment techniques allow a battery design to have many properties, including electrical and chemical properties enhanced in parallel.
Contact TMNetch today for enhanced performance over traditional manufacturing.