  We demonstrate that failure of time-invariance assumption in the modeling of
electrochemical systems by equivalent circuits can lead to the formation of low
frequency "inductive loops" that manifest themselves as positive imaginary
parts of the impedance function. Assuming that the properties of the equivalent
circuits change slowly in time we perform an asymptotic analysis and obtain a
new integral representation of the impedance function that reduces to the
standard one at high frequencies, while exhibiting inductive loops at low
frequencies.
