物理化学学报 >> 2019, Vol. 35 >> Issue (5): 509-516.doi: 10.3866/PKU.WHXB201806071

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固体氧化物燃料电池电化学阻抗谱差异化研究方法和分解

施王影,贾川,张永亮,吕泽伟,韩敏芳*()   

  • 收稿日期:2018-05-09 发布日期:2018-10-19
  • 通讯作者: 韩敏芳 E-mail:hanminfang@sina.com
  • 基金资助:
    国家重点研发计划(2017YFB0601901);国家重点研发计划(2017YFB0601903);东莞市科研项目(201460720100025);清华大学自主科研计划(2015THZ0)

Differentiation and Decomposition of Solid Oxide Fuel Cell Electrochemical Impedance Spectra

Wangying SHI,Chuan JIA,Yongliang ZHANG,Zewei Lü,Minfang HAN*()   

  • Received:2018-05-09 Published:2018-10-19
  • Contact: Minfang HAN E-mail:hanminfang@sina.com
  • Supported by:
    the National Key Research and Development Program of China(2017YFB0601901);the National Key Research and Development Program of China(2017YFB0601903);the Research Program of Dongguan, China(201460720100025);the Independent Scientific Research Plan of Tsinghua University, China(2015THZ0)

摘要:

电化学阻抗谱技术(EIS)在固体氧化物燃料电池(SOFC)中已获得广泛应用。在EIS分析过程中,研究者能够清楚地获得燃料电池内部因纯离子(电子)导电引起的欧姆电阻和因电化学过程、扩散作用引起的极化阻抗的大小,但是对于极化阻抗的构成缺乏进一步解析。本文选用传统的Ni-YSZ阳极支撑电池,通过改变测试温度、阳极运行气氛和阴极运行气氛,设计了一套完整的阻抗差异分析(ADIS)实验。并基于弛豫时间分布法(DRT)和阻抗差异分析法,系统地分析并解释了阻抗谱中各频率段对应阻抗的物理或(电)化学含义,将该类型电池阻抗谱以6个RQ并联电路予以拟合,为之后燃料电池性能稳定性的研究奠定基础。

关键词: 固体氧化物燃料电池, 电化学阻抗谱, 阻抗差异分析法, 弛豫时间分布

Abstract:

Benefitting from high-temperature operating conditions, solid oxide fuel cells (SOFCs) exhibit high electricity efficiency and can be coupled with conventional engines such as gas turbines, to achieve cascaded energy utilization. However, high temperature inevitably accelerates material deterioration, and simultaneously complicates the on-line diagnosis of SOFCs. Electrochemical impedance spectroscopy (EIS) is a mature on-line testing technology that is been widely used in SOFC research. Using EIS analyses, researchers can clearly determine the ohmic resistance of pure ion/electron conduction and the magnitude of the polarization impedance of electrochemical processes or diffusion. However, the lack of decomposition of polarization impedance constitutes a limitation for the deeper understanding of SOFC operation. To better utilize information-rich EIS, this work used a typical Ni-Y2O3 stabilized zirconia (Ni-YSZ) anode-supported SOFC and designed a complete set of impedance tests by modifying the test temperature, anode operating atmosphere, and cathode operating atmosphere. In addition, this study combined two advanced impedance spectrum analysis methods: the analysis of differences in impedance spectra (ADIS) and distribution of relaxation time (DRT) methods to allow for a deeper comprehension of the impedance spectrum and obtain the characteristic frequency of each process in the SOFC. Based on the characteristic frequency obtained by the spectral decomposition, this study analyzed and explained the physical or (electro-) chemical origins of the impedance in each frequency band. In addition, the equivalent circuit method (ECM) was adopted to fit the SOFC impedance spectra by 6 (RQ) parallel circuits to summarize the impedance distribution. The ADIS method was more convenient than the DRT method and could be used to initially determine the range of characteristic frequencies. However, it failed to provide a clear decomposition for the high-frequency region of the impedance spectrum. The DRT method can yield a good decomposition of a single impedance spectrum, and the characteristic frequency of Ni-YSZ SOFC was separated into ~2, ~20, ~30, 1 × 103-1.5 × 103, 2 × 103-4 × 103, and ~4 × 104 Hz regions. The highest frequency (~4 × 104) region was dominated by charge transfer impedance at the YSZ/GDC (gadolinia doped ceria) or LSCF/GDC interface. Peaks at 2 × 103-4 × 103 and 1 × 103-1.5 × 103 Hz correspond to the H2 electrochemical reaction at the Ni/YSZ/H2 boundary and O2 reduction at the LSCF/O2 boundary, respectively. The impedance at lower frequencies can be explained by diffusion polarization impedance. In this study, ~20 Hz corresponds to the cathode diffusion impedance, and ~30 Hz corresponds to the anode diffusion resistance. At a frequency of ~2 Hz, the impedance magnitude is influenced by both cathode and anode diffusion. The results of this study combined three methods (ADIS, DRT, and ECM) for SOFC impedance investigations, and lays a foundation for future studies regarding SOFC performance degradation and degradation characteristics based on DRT analysis.

Key words: Solid oxide fuel cell, Electrochemical impedance spectroscopy, Analysis of differences in impedance spectra, Distribution of relaxation time

MSC2000: 

  • O646