Study On Bipolar Plates And Flow Fields Of PEM Fuel Cells

Due to the prospects for attaining high power density and energy conversionefficiency, the proton exchange membrane fuel cell (PEMFC) is one of the mostpromising power sources for future electric vehicles. Bipolar plates of PEMFC areone of the critical components which have a major impact not only on theperformance of the stack but also on the cost and have been choke points ofindustrialization.The majority of PEMFC stack producers utilize bipolar plate based on graphite,carbon composites or metals (principally, stainless steel). Each of these materials hascharacteristics that are beneficial for fuel cell applications, but are limited by others.An idea bipolar plate would incorporate the merits of these materials, such that itwould be high in electrical conductivity and corrosion protection, of low density butwith high mechanical strength, impermeable to reactant gases, chemically inert,thermal conductivity, and allow for ease of manufacture.A novel composite bipolar plate is studied and prepared in this thesis, which isadopted stainless steel plate as its supporting plate and flexible graphite plate as itsflow field plate. The composite bipolar plate combined advantages with graphite andmetal plates, which meets the conditions of an idea bipolar plate.The effect of thin stainless steel plate on performance of PEM fuel cell has beenstudied. Coating systems for metal plates are including electroplate, electrolessplating, ion eject and etc. The contact resistance between the flexible graphite plateand the coated stainless steel plate has been investigated. At the same time, theflexible graphite flow field plate has been discussed, including gas penetrability,component and body resistance. The dimensions of flow field also have an importanteffect on performance of PEM fuel cell. Stack assembled with composite plates has been used for engine, which furtherconfirmsreliability of the composite plate.