By analyzing Electrochemical Impedance Spectroscopy(EIS) in applications of dynamic proton exchange membrane fuel cell(PEMFC),bottlenecks which restrict EIS tool development have been pointed out in this paper.Though the high-frequency resistance in EIS is largely accepted as cell inner-resistance,this can only be applied for cell with low current.The low-frequency resistance is difficult to be realized due to its relation with mass transfer.Furthermore,the improved Randles equivalent circuits are built up ...