Electrochemical accumulator impedance

Adsorption impedance — The current flowing in an electrochemical system splits into two parts at an interface the charge either transfers across, (-> faradaic current) or gets accumulated at the two sides of the boundary (- non-faradaic or - charging current) the related impedance elements are called - Faraday impedance and non-Faraday impedances, respectively. The latter element is an essentially capacitive element its lossy character is related to the slow kinetics of - adsorption- related processes involved. 

The power of electrochemical impedance spectroscopy (EIS) is well acknowledged and widely used in various systems [130, 131]. The history of impedance of porous, distributed electrodes in liquid electrolytes goes back to the early 1960s (see Refs. 132, 133), and some later works [134, 135]. In the context of accumulators, interpretation of electrode impedance was already long ago considered as a promising way to acquire information on the current state of the electrodes [136]. The same refers to the study of corrosion [137, 138]. Nowadays,... 

Impedance spectroscopy has been used for a wide and versatile field of applications (Macdonald, 1987a Rubinstein, 1995), as for example the measurement of the grain boundary and bulk resistances of polycrystalline solids (Bard, 1980) and of ionic conductors, the characterization of corrosion in metals and alloys, the charging and discharging behavior of accumulators, the aging of electrochemical sensors, the quality inspection of coatings or the investigation ofporous structures (Bates, 1988 Candy, 1981 Keiser, 1976 Rubinstein, 1995), etc. 

The atmospheric corrosion occurs frequently under thin electrolyte layers (TELs) or even adsorbed layers. The thickness of electrolyte has important role on corrosion phenomena such as the mass transport of dissolved oxygen, the accumulation of corrosion products, and the hydration of dissolved metal ions. The corrosion behavior of pure magnesium was investigated under aerated and de-aerated TELs with various thicknesses by means of cathodic polarization curve, electrochemical impedance spectroscopy (EIS) and EN measurements (Zhang et al, 2008). 

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