Bipolar plate for proton exchange membrane fuel cell

Abstract

The invention provides an improvement of a proton exchange membrane fuel cell bipolar plate and is characterized in that a middle coolant flow field is made from a flexible graphite plate and the flexible graphite plate is peripherally equipped with a rigid thickness limit frame. The flexibility of the flexible graphite and certain elastic deformation thereof, not only can compensate for the inevitable unevenness deviation caused by the processing of anode flow field plate and cathode flow field plate, and ensure that the flow field plate surfaces are contacted closely and pressed together, so as to effectively reduce the contact resistance between the flow field plates, to achieve the minimized combination of contact resistances and to basically achieve no loss of interface voltage; but also achieve excellent plane thermal conductivity, so as to improve the cooling effect, limit the temperature rising of the cell stack and to achieve good-performance assembled batteries; in addition, since the flexible graphite texture is relatively soft in texture, the depth of a water flow channel can be relatively lower, so that the processing is easier. The combination performance is obviously superior to that of the rigid graphite cooling flow field and that of the flexible graphite reaction gas flow field. The three flow field plates are manufactured separately, so that the flow field can be changed easily and the independent optimization of the flow field can be realized.

Description

technical field [0001] The invention is an improvement on the bipolar plate of the proton exchange membrane fuel cell, especially an improvement on the cooling flow field of the bipolar plate. Background technique [0002] Proton exchange membrane fuel cell (PEMFC) is a power generation device that directly converts the chemical energy in hydrogen fuel and oxidant into electrical energy and its products. PEMFC single cell voltage is very low, about 0.6~0.7V, in order to obtain useful current and voltage, it is necessary to connect multiple single cells in series to form a battery stack. The separator used to separate two adjacent single cells is called a bipolar plate. In order to remove the heat of reaction from the fuel cell stack, a coolant channel is designed in the middle of each bipolar plate. Therefore, the usual bipolar plates are made of The anode plate with flow field, cathode plate and coolant flow field are composed. In order to pass current between the anode o...

AI Technical Summary

Problems solved by technology

This kind of bipolar plate composed of hard material graphite or metal plate, although the plate has high electrical conductivity, but the main disadvantage is: due to the extremely high processing precision of the flow field pattern, the processing of the hard plate with the coolant flow field is complicated , Difficulty, high production cost, for example, using hard graphite plate requires at least three surfaces of mechanical milling, using metal plate or molded graphite plate, the mold suppresses the flow field, not only the mold is complicated, but also because the flow field groove is small and needs to be maintained A certain depth makes it difficult to demould, and the production cost is also high; secondly, the combination of the hard surface and the hard surface of the combined plate makes it difficult to press the hard material tightly, and the inevitable uneven deviation of the plate processing leads to contact The resistance increases, resulting in poor electrical performance of the assembled battery; moreover, the combined structure of the coolant flow field and the plate restricts the change of the flow field of the plate, and the design flexibility of the plate flow field is low

But the bipolar plate of this composition can only be applied to the bipolar plate of the air-cooled fuel cell, and the flexible graphite plate is used as the reaction gas (hydrogen and air) flow field of the bipolar plate, and the deformability of the flexible graphite can be used in the combined cell stack. Pressure during the process will easily deform the original design gas flow field, and the cooling air pressure introduced will also cause deformation of the reaction gas flow field

The deformation of the reactive gas flow field will affect the transmission and diffusion of the reactive gas, resulting in a decrease in battery performance; secondly, in order to prevent the reactive gas flow field from being deformed, the flexible graphite flow field must be deep processed. Due to the constraints of the flexible graphite material, deep processing of the flow field is difficult. Little effect on actual cost reduction

Therefore, although the bipolar plate improves the processing difficulty of the reaction gas flow field, there are other deficiencies that make the actual improvement effect still unsatisfactory, and there is still room for improvement