Bipolar plate materials can be roughly divided into three categories:carbon materials,metal materials and composite materials of metal and carbon.
(1)Carbon materials.Carbonaceous materials include graphite,molded carbon materials,and expanded(flexible)graphite.Conventional bipolar plates use dense graphite that is machined to form gas flow channels.·Graphite bipolar plate has stable chemical properties and low contact resistance with MEA.
(2)Metal materials.Metal materials such as aluminum,nickel,titanium and stainless steel can be used to make bipolar plates.The metal bipolar plate is easy to process,can be manufactured in batches,has low cost,thin thickness,and has high volume specific power and specific energy of the battery.
(3)Composite materials.If the contact resistance between the bipolar plate and the MEA is large,the polarization loss caused by the ohmic resistance is large,and the operation efficiency is reduced.Among the various bipolar plate materials commonly used,the contact resistance of graphite materials is small,and non-conductive oxide films are formed on the surfaces of stainless steel and titanium to increase the contact resistance.
