Relaxation Impedance - The Nature of Inductive and capacitive Behaviour in Low Frequency Impedance Spectra of Corroding Electrodes, Batteries and Fuel Cells

Kurzfassung

Some electrochemical systems may exhibit small inductive contributions to the overall frequency response, especially at low frequencies. Prominent examples are for instance corroding electrodes of Aluminium and Zirconium in the presence of chloride ions, mild steel in the presence of CO2 at low pH value, high temperature fuel cells under certain load conditions, PEM fuel cells in the presence of CO in the fuel or rechargeable batteries under high current charging/discharging conditions. A lot of different mechanisms are discussed in the literature explaining very special situations, leading to inductive behaviour of electrochemical systems. On the other hand, a very universal mechanism, the Relaxation Impedance, is able to explain the above examples and - beyond that - the appearance of low frequency capacitive loops in conjunction with the PEM membrane water balance. Although some principal considerations can be found in literature, a comprehensive and thoroughly treatment is still outstanding so far.