A Unifying View of the Constant-Phase-Element and Its Role as an Aging Indicator for Li-Ion Batteries. Issue 8 (1st January 2015)

• Record Type: Journal Article
• Authors: Cuervo-Reyes, Eduardo; Scheller, Christian Philipp; Held, Marcel; Sennhauser, Urs
• Is Part Of: Journal of the Electrochemical Society. Volume 162:Issue 8(2015)
• Page Start: A1585
• Page End: A1591
• Publication Date: 2015-01-01
• Subjects: charge transport -- constant phase element -- disordered media -- impedance spectroscopy -- Li-ion battery aging -- lithium-ion batteries -- stable distributions -- statistical mechanics -- strange diffusion; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0791508jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : Various materials display a constant phase impedance, Z ∝[ i ω] − u, over a wide frequency range. In this paper, we show that this behavior is a natural consequence of charge transport in the macroscopic limit, and that in contrast to the common belief, no assumptions on the "relaxation functions" are required. Our unifying view of the constant-phase-element (CPE) is then employed for analyzing impedance spectra that were recorded during the aging of Li x FePO4 cells. We find and explain a significant correlation between their capacity loss and changes in the exponent ( u ) of the CPE describing cathodic Li-intercalation. Changes in u with the state of charge are also discussed. CPE exponents are shown to be valuable performance indicators for Li-ion batteries.