Bipolar plates materials

As we have mentioned before, a bipolar plate serves multiple purposes in a fuel cell sfack. If serves as a current collector, dissipates the heat generated in the fuel cell by conduction through the solid material and by convection through gas channels and cooling channels, and provides the structural strength and support for the thin MEAs in the stack. Selection of a material that satisfies all these requirements is to some extent challenging and requires extensive analysis depending on the applications. 

There are a number of materials that satisfy a majority of these requirements, namely, metals with and without coatings, metal alloys, carbon-based materials such as graphite, and metal and carbon composites. 

A brief discussion of the most competent bipolar plate materials that are attractive in terms of meeting all the requirements is given here. 

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The bipolar plate material of the PAFC is graphite. A portion of it has a carefully controlled porosity that sei ves as a resei voir for phosphoric acid and provides ffow channels for distribution of the fuel and oxidant. The plates are elec tronically conductive but impervious to gas crossover. 

The anode material in SOF(7s is a cermet (rnetal/cerarnic composite material) of 30 to 40 percent nickel in zirconia, and the cathode is lanthanum rnanganite doped with calcium oxide or strontium oxide. Both of these materials are porous and mixed ionic/electronic conductors. The bipolar separator typically is doped lanthanum chromite, but a metal can be used in cells operating below 1073 K (1472°F). The bipolar plate materials are dense and electronically conductive. 

Progress and Challenges in the Development of Bipolar Plate Materials... 

Mepsted, G. O., and J. M. Moore. 2003. Performance and durability of bipolar plate materials. In Handbook of fuel cells—Fundamentals, technologies, and applications, ed. W. Vielstich, H. A. Gasteiger, and A. Lamm. Vol. 3 Fuel cell technologies and applications, 286-293 (chap. 24). New York John Wiley Sons. 

Kumar, A., and R. G. Reddy. 2002. PEM fuel cell bipolar plate—Materials selection, design and integration. In Fundamentals of advanced materials and energy conversion proceedings, ed. D. Chandra and R. G. Bautista, 41-53. Seattle, WA IMS. 

Wang, H., and J. A. Turner. 2004. Investigation of a duplex stainless steel as polymer electrolyte membrane fuel cell bipolar plate material. Journal of Power Sources. 128 193-200. 

Graphite-based composites and metal/alloy materials both have their own advantages and drawbacks. Current research interests in bipolar plate materials include both graphite composites and coated metals. No doubt progress on these materials will eventually lead to substantial reduction in the volume and cost of the fuel cell stack. 

Mepsted, G.O. and Moore, J.M., Performance and durability of bipolar plate materials, in Handbook of Fuel Cells Fundamentals, Technology, and Applications, 1st ed., Vielstich, W., Lamm, A., and Gasteiger, H.A., Eds., John Wiley Sons, West Sussex, England, 2003, p. 286. 

Wang, H., Sweikart, M.A., and Turner, J.A., Stainless steel as bipolar plate material for polymer electrolyte membrane fuel cells, J. Power Sources, 115, 243, 2003. 

Silva, R.R et al., Surface conductivity and stability of metallic bipolar plate materials for polymer electrolyte fuel cells, Electrochim. Acta, 51, 3592, 2006. 

Wang, Y. and Northwood, D.O., An investigation into polypyrrole-coated 316L stainless steel as a bipolar plate material for PEM fuel cells, J. Power Sources, 163(1), 500, 2006. 

Develop bipolar plate materials/configurations to meet various users unique requirements. 

Figure 1. Infrared Images of Carbon Composite Bipolar Plate Material Samples...

During this period, the mechanical properties of the carbon composite bipolar plate material were assessed, including measurements of uniformity and defect distribution by infrared imaging. The results indicate good material uniformity and substantial resistance to torsional stresses. Significant improvement in the wetting of the material was demonstrated after a simple oxidation treatment. 

Evaluate the performance of the bipolar plate materials through fuel cell stack testing... 

Developed improved bipolar plate materials, exhibiting improved material properties and low-cost ingredients... 

Table 1 shows preliminary materials properties measured on non-optimized bipolar plate materials produced through initial development work at PFCT Comparisons with published DOE goals are made in the table. Sealing of the plate through - through plate permeability is accomplished through the application... 

As mentioned in Table 9-2, different perovskite compounds are used as cathode or bipolar plates materials. 

Bipolar plate materials have historically been metals coated with corrosion-resistant layers or graphite with a seal treatment (to lower the gas permeability). In recent years, major efforts have been made for developing RP bipolar plates. The new plates usually have molded-in gas flow channels so that they can be fabricated rapidly and cost-effectively. However, the cost of bipolar plates ( 10/plate with 400 cm ) today is still too high to be applied to automotive and other civil power applications, and the conductivity is marginal. 

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