不同稳态操作条件和变载下燃料电池短堆交流阻抗谱分析：温度变化和动态变化

AC impedance characteristics of a 2 kW PEMfuel cell stack under different operating conditions and load changes

Xiqiang Yan

Ming Hou

Liyan Sun

Dong Liang

Qiang Shen

Hongfei Xu

Pingwen Ming

BaolianYi

Abstract

This paper mainly presents the AC impedancecharacteristics of a 2 kW PEMFC stack under different operating conditions andload changes． The AC impedances of the fuel cell stack are examined by a fuelcell impedance meter． Air stoichiometry， air humidity， and operationtemperature are shown to have significant effects on the AC impedance of stack．When air stoichiometry decreases， themass transfer resistance of stack increases obviously， but the influences onother resistances are very slight． Theair humidity and operation temperature mainly influence the charge transferresistance of stack． The influences of load changes on the AC impedance ofstack are also investigated， and the results of which show that it is quitenecessary to adjust the humidity of reactant gas according to the fuel cellload changes during fuel cell running． The AC impedance diagnosis of stack canprovide some useful information for the running of fuel cell stack．

the active area of each cell is 270cm 2

Fig． 1． The AC impedance spectra of  20－cells stack at 135A． 0．5A／cm2

Fig． 2． The Bode plots of stack at 135A，  60 ◦ C， and RH ＝ 80％．

Fig． 3． Equivalent circuit for impedance  analysis on fuel cell stack．

Fig． 4． AC impedance spectra and its  fitting curve of 20－cell stack at 135A．

Fig． 5． AC impedance spectra of stack  with different current densities．

Fig． 6． AC impedance spectra of stack  with different air stoichiometries at 500mAcm −2

Fig． 7． The performance curve of stack  with different air stoichiometries

Fig． 8． The dependence of the ohmic  resistance （R Ω ）， the charge transfer resistance （R ct ）， and mass transfer  resistance （R mt ） with different stoichiometries at 500mAcm −2

Fig． 9． AC impedance spectra of stack  with different RHs at 500mAcm −2

Fig． 10． The performance curve of fuel  cell stack with different RHs．

Fig． 11． The dependence of the ohmic  resistance （R Ω ）， the charge transfer resistance （R ct ）， and mass transfer  resistance （R mt ） with different RHs at 500mAcm −2

Fig． 12． AC impedance spectra of stack  with different operating temperatures at 500mAcm −2 ．

Fig． 13． The performance curve of stack  with different operating temperatures．

Fig． 14． The dependence of the ohmic  resistance （R Ω ）， the charge transfer resistance （R ct ）， and mass transfer  resistance （R mt ） with different operating temperatures at 500mAcm −2

唯一的一张图，Rct在Rmt之上的图。

室温性能不佳不一定是Rmt，很有可能是Rct，你可可看你的电池如何。

Fig． 15． AC impedance changes of stack  with loading changes

60度 60％RH 2kHz

As seen in Fig． 12（这里可能是改动文章的时候没有更新，应该是Fig． 15）， the impedance of stack gradually increases at state of  idle speed （current about 5A） and gradually decreases at relative high load  （current above 81A）．

Conclusions

The AC impedance characteristics of the  2kW PEM fuel cell stack under various operating conditions and load changes  are measured and the optimal operation conditions of fuel cell stack are  obtained． The results of the AC impedance show that air stoichiometry， air  humidity， and operation temperature have obvious effects on AC impedance of  stack． When air stoichiometry decreases， the mass transfer resistance of  stack increases obviously， but the influences on other resistances are very  slight． The stack humidity and operation temperature mainly influence the  charge transfer resistance of stack． Furthermore， the influences of load  changes on the AC impedance are investigated． The AC impedance of stack gradually  increases at state of idle speed （current about 5A） and gradually decreases  at relative high load （current above 81A）． Therefore， it is quite necessary to  adjust the humidity of reactant gas according to the fuel cell load changes  during running． The AC impedance diagnosis of stack could provide some useful  information for fuel cell stack， especially in vehicular application．