Mechanisms of Impedance Rise in High-Power Lithium-Ion Cells

Ira Bloom,^a Scott A. Jones,^a Edward G. Polzin,^a Vincent S. Battaglia,^a Gary L. Henriksen,^a Chester G. Motloch,^b Randy B. Wright,^b Rudolph G. Jungst^c, Herbert L. Case^c and Daniel H. Doughty^c

^a Electrochemical Technology Program, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439-4837, USA ^b Idaho National Engineering and Environmental Laboratory, P.O. Box 1625, Idaho Falls, ID 83415, USA ^c Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185, USA

Cells were life-cycled cells using profiles with a 3, 6, or 9% change in state of charge (ΔSOC) at 40, 50, 60, and 70°C. From the voltage response of the cells to the life-cycle profile at each temperature, we separated the overall impedance rise into two simpler terms, R_o (ohmic) and R_p (polarization), using an equivalent circuit model. The R_o data tend to follow the expected trends (40>50>60>70°C). Although the R_p data trends show that R_p can either decrease or increase asymptotically with time, the overall temperature-dependent behavior is similar to that of R_o. We illustrate the types of processes that can occur in one lithium-ion cell chemistry. Based on the initial rates, the processes are complex. The R_o term dominates the observable cell impedance, but R_p adds a non-trivial contribution.

Copyright © 2004 Elsevier Science