Small-Signal Apparent Diffusion Impedance of Intercalation Battery Electrodes

The small-signal apparent diffusion impedance of intercalation battery electrodes is studied on the basis of generalized Poisson–Nernst–Planck equations for planar, cylindrical, and spherical geometry. Compared with conventional treatment in tracking the concentration of neutral intercalation species as chemical diffusion, the present work focuses on the voltage and current terms of intercalating ions and electrons and discusses explicit physical meanings of these electrical terms, in the form of equivalent circuits. It can be shown that the present treatment generates the same results as those from conventional chemical diffusion when the electronic transference number is close to 1. Finally, the correlation between the frequency domain impedance methods and the time domain methods, such as chronoamperometry and chronopotentiometry, is discussed.