Electrochemical impedance spectroscopy alternative signal

ABSTRACT State determination of Li-ion cells is often accomplished with Electrochemical Impedance Spectroscopy (EIS). The measurement results are in frequency domain and used to describe the state of a Li-ion cell by parameterizing impedance-based models. Since EIS is a costly measurement method, an alternative method for the parameterization of impedance-based models with time-domain data easier to record is presented in this work. For this purpose the model equations from the impedance-based models are transformed from frequency domain into time domain. As an excitation signal a current step is applied. The resulting voltage step responses are the model equations in time domain. They are presented for lumped and derived for distributed electrical circuit elements, i.e. Warburg impedance, Constant Phase Element and RCPE. A resulting technique is the determination of the inner resistance from an impedance spectrum which is performed on measurement data. 

Electrochemical impedance spectroscopy (EIS) is also commonly employed for analysis of enzymatic electrode systems [11], EIS is performed by overlaying a range of alternating current (AC) perturbation signals to an electrode that is under direct current (DC) bias. A Nyquist plot is then generated, and variations of the frequency response can then be used to interpret limiting mechanisms associated with charge transfer. 

Impedance spectroscopy is a versatile electrochemical tool, helpful to characterize the intrinsic dielectric properties of various materials. The basis of this technique is the measurement of the impedance (opposition to alternating current) of a system, in response to an exciting signal over a range of frequencies (Bard and Faulkner, 2001). 

The authors of this paper propose for the first time an updated, prospective method for impedance spectroscopy based on an essentially new design of the electrode system. In this case, the electrode system is replaced by an extended electric conductor immersed into the electrolyte. An alternating voltage is applied to the ends of the conductor connected directly to a measuring device. This signal induces two identical and electrochemically conjugated electrodes at the both ends of the conductor. The polarity of these electrodes is variable by fed frequency. They come in contact at the non-polarized centre of the extended conductor. The linear coordinate of the non-polarized centre is estimated on the condition of a conjugation of cathodic and anodic process ... 

---