Research On Internal Resistance In Proton Exchange Membrane Fuel Cells With Metal Bipolar Plates

Proton Exchange Membrane Fuel Cell(PEMFC) is a kind of clean and greenelectrochemical power generating device that can be suitable for transportation,portable and backup power. The internal ohmic resistance is an important factormaking voltage loss and limits the power. Especially for the PEMFC with metalbipolar plates, its power density has greatly increased, but the contact resistancebetween bipolar plates and GDL has been a new problem because of their differentmaterials. Therefore, it is significant to do some research on internal resistance in aPEMFC with metal bipolar plates that can decrease ohmic resistance and improve theperformance of fuel cell.First of all, this paper has researched the performance and internal resistance ofentire stack and its working conditions. The results show that (i) different workingcondition(e.g RH, back pressure, water pressure) has an obvious influence on stackvoltage and resistance. When the anodic RH is80%, cathodic RH is100%, stack hasthe best performance;(ii) At1A/cm2current density, the metal bipolar plates stackohmic loss accounts for40.4%of total voltage loss while the graphite plates stack is34.6%;(iii) Internal resistance of membrane accounts for less than20%of total loss.The high contact resistance is the main problem.Secondly, this paper has researched the contact resistance. Results show that (i)the contact resistance decreases very fast with the increasing of pressure in a relativelow pressure, when the pressure close to1Mpa, contact resistance almost keep stable;(ii)the RBP-GDLis13.1mΩ·cm2, RBP-BPis7.5mΩ·cm2;(iii) when the spacing rateincreased from0to40%, contact resistance did not change very much, with thespacing rate continue increasing, the contact resistance begin increasing, especiallyover45%spacing rate, it is increasing sharply.At last, researched the relationship between durability of the stack and internalresistance. The results show that (i) the performance of stack decrease with the increasing of cycles, the internal resistance increase during this time. Internalresistance increased is an important factor lead to stack decreasing;(ii) theperformance decreased14.34%and internal resistance increased32.11%at the800mA/cm2current density from0to2000h. Performance decreasing from ohmicloss accounts for52.04%of the total decrease;(iii) the first cell decreased mostseriously while the10thcell only decreased a little. For the first cell, the decreasefrom ohmic loss accounts for34.49%of it’s total decrease which is less than theentire stack. The uniformity of stack reduced mainly because the membrane, catalystand GDL has been damaged in varying degrees.