electrodeimpedantie

Electrode impedantie, or electrode impedance, is the opposition that an electrode–electrolyte interface presents to alternating current. It is a complex quantity Z(ω) = Re[Z] + i Im[Z], described by its magnitude |Z| and phase angle ∠Z, which vary with frequency ω. The impedance reflects several physical processes at the interface, including solution resistance Rs in the electrolyte, charge-transfer resistance Rct associated with electron transfer across the interface, the double-layer capacitance Cdl formed by ion charges at the electrode surface, and diffusion effects described by Warburg impedance.

Measurement and interpretation of electrode impedance are commonly performed with electrochemical impedance spectroscopy (EIS). EIS applies small sinusoidal perturbations over a wide frequency range and records the response, yielding data in Nyquist plots (imaginary vs real part) or Bode plots (|Z| and ∠Z vs frequency). Impedance data are often fitted with equivalent circuits, such as the Randles circuit, which consists of Rs in series with a parallel branch of Rct and Cdl, and may include a Warburg element to represent diffusion or a constant phase element (CPE) to model non-ideal capacitive behavior.

Applications of electrode impedance span batteries, supercapacitors, fuel cells, corrosion studies, electrochemical sensors, and neural interfaces. Impedance analysis provides insight into internal resistance, interfacial kinetics, and capacitive storage, informing design, conditioning, and performance assessment.

Factors influencing impedance include electrode material and surface area, surface roughness and cleanliness, electrolyte conductivity, temperature, and polarization effects. Accurate interpretation requires appropriate experimental setup (electrodes and geometry) and careful modeling to separate contributions from solution, charge transfer, and diffusion.