Bipolar plates stainless steels

The fuel cell components have thicknesses as follows the anode is 0.8-1.5mm thick the cathode, 0.4-1.5 mm, the matrix, 0.5-1 mm. In a fuel cell of the filter-press type, the individual cells are separated by bipolar plates made of nickel-plated stainless steel, contacting the anode with their nickel side, and the cathode with their steel side. All structural parts are made of nickel or nickel-plated steel. In a working fuel cell, the temperature of the outer part of the matrix electrolyte is lower than that of the inner part, so that in the outer part the electrolyte is solidified. This provides for tight sealing around the periphery of the individual fuel cells. 

The bipolar plates are made from either Type 310 or Type 316 stainless steel, which is coated on the fuel side with nickel and aluminized in the seal area around the edge of the plates. Both internally and externally manifolded stacks have been developed. 

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. 

Planar geometry Although there are variations in detail, the design of the planar or flat plate cell, and how cells are interconnected are essentially as illustrated in Fig. 4.27. The construction may involve a self-supporting, coated electrolyte or, if the operating temperature permits, the anode-electrolyte-cathode structure may be supported on a stainless steel bipolar plate. 

Ni-state-of-the-art anodes contain Cr to eliminate the problem of sintering. However, Ni-Cr anodes are susceptible to creep, while Cr can be lithiated by the electrolyte and consumes carbonate, leading to efforts to decrease Cr. State-of-the-art cathodes are made of lithiated-NiO. Dissolution of the cathode is probably the primary life-limiting constraint of MCFCs, particularly under pressurised operation. The present bipolar plate consists of the separator, the current collectors, and the seal. The bipolar plates are usually fabricated from thin sheets of a stainless steel alloy coated on one side by a Ni layer, which is stable in the reducing environment of the anode. On the cathode side, contact electrical resistance increases as an oxide layer builds up (US DOE, 2002 Larminie et al., 2003 Yuh et al., 2002). 

Bipolar plates are currently made from milled graphite or gold-coated stainless steel. Ongoing research is aiming to replace these materials with polymers or low-cost steel alloys, which will allow the use of low-cost production techniques. Even today, bipolar plates can be produced at 200 /kW, if the production volume... 

A special stainless steel was developed in Australia and patented (Jaffray, 1999). Production costs and endurance of the resulting flat plate design (Foger etal, 2000) were improved relative to that of the firm s initial all-ceramic design. The bipolar plates and interconnects were stainless steel. The cell had operational difficulties, and has been discontinued. The firm has just established a UK division, to compete in Europe. 

The MEAs of the MCFC are sandwiched between stainless steel or nickel bipolar plates, which collect current from, and distribute fuel/steam and oxidant air plus recirculated anode gas via the porous electrode structures to, the chemical reactions at the electrolyte/gas interfaces. Figure 5.1. In the long-anode, narrow-cathode, rectangular MTU fuel cell, fuel utilisation is about 80%, oxygen utilisation about 50%. 

Alternative materials for bipolar plates include graphite, stainless steels, titanium and aluminium, all with a developed fabrication technique, and coating technique if needed. Major competitors UTC Fuel Cells has an active fuel cell bus programme, but give sparse details of its flow plate and other technology. (See UTC web site.)... 

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. 

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. 

Makkus, R.C. et al.. Use of stainless steel for cost competitive bipolar plates in the SPFC, J. Power Sources, 86, 274, 2000. 

The bipolar plates (Fig. 3.20) providing electric contact between cells and forming impermeable channels for gas transport are in most SOFC designs made of ferritic stainless steel (low thermal expansion coefficient), although at the highest operating temperatures, more advanced (and expensive) metal structures must be used. 

Austenitic stainless steels like 31 OS, 316, or 316L are typically used for the construction of cathode and anode current collectors and bipolar separator plates. Corrosion of these steel components is a major lifetime-limiting factor in MCFC. The corrosion behavior of stainless steel components in molten carbonate conditions has been studied extensively during the past decade. Research is being aimed at increasing the corrosion resistance of these components by altering the alloy composition or by surface modification techniques. ... 

The most suitable materials result to be non-porous graphite, metals (aluminum, stainless steel, titanium, and nickel), and composite sohds. Graphite made nonporous by impregnation with impermeable substance was early used for bipolar plates, but its applicability is limited by difficulties in machining and consequent costs. The metal plates present the obvious advantages of high robustness and low... 

Abo El, Enin SA, Abdel-Salam OE, El-Abd H, Amin AM (2008) New electroplated aluminum bipolar plate for PEM fuel cells. J Power Sources 177 131-136 Feng K, Shen Y, Sun H, Liu D, An Q, Cai X, Chu PK (2009) Conductive amorphous carbon-coated 316L stainless steel as bipolar plates in polymer electrolyte membrane fuel cells. Int J Hydrogen Energ 34 6771-6777... 

It is well known that nncoated stainless steel bipolar plates exhibit high transition impedances dne to formation of an oxide layer by corrosion under fuel cell operation conditions. 

Depending on operation temperature the material chosen for the bipolar plate is graphite (or graphite composites) or iron-based alloys (stainless steel) for low- and medium-temperature fuel cells (PEFC, PAFC, MCFC) and chromium or ceramic-based materials for the high-temperature systems (SOFC). In SOFC, for sealing reasons, tubular concepts have also been developed (see Section 8.1.4.6). 

Bipolar Plate (iatercoimect) (La, Sr, Ca)Cr03 Alloys (Y2O3) Stainless Steel... 

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