Computer Simulations of the Impedance Response of Lithium Rechargeable Batteries

A mathematical model is developed to simulate the impedance response of a wide range of lithium rechargeable battery systems. The mathematical model is a macroscopic model of a full‐cell sandwich utilizing porous electrode theory to treat the electrode region and concentrated solution theory for transport processes in solution. Insertion processes are described with charge‐transfer kinetic expressions and solid‐phase diffusion of lithium into the active electrode material. The impedance model assumes steady‐state conditions and a linear response with the perturbation applied about the open‐circuit condition for the battery. The simulated impedance response of a specific system, the lithium‐polymer cell , is analyzed in more detail to illustrate several features of the impedance behavior. Particular attention is paid to the measurement of solid‐phase lithium‐ion diffusion coefficients in the insertion electrodes using impedance techniques. A number of complications that can lead to errors in diffusion‐coefficient measurements based on impedance techniques are discussed. © 2000 The Electrochemical Society. All rights reserved.