Theoretical and Experimental Analysis of Porous Electrodes for Lithium-Ion Batteries by Electrochemical Impedance Spectroscopy Using a Symmetric Cell

The purpose of this study was to understand the electrochemical behavior of the interface between porous electrodes and electrolytes of lithium-ion batteries. We propose a new analytical approach that is a combination of the transmission line model theory for cylindrical pores and electrochemical impedance spectroscopy using symmetric cells. Mathematical model and experimental impedance behavior results agree with each other. By mathematically fitting the experimental impedance plots, the individual internal resistance components of the actual porous electrode/electrolyte interface could be described as the following four parameters: electric resistance (R-e), electrolyte bulk resistance, (R-sol), ionic resistance in pores (R-ion), and charge-transfer resistance for lithium intercalation (R-ct). In actual electrodes, the R-ion obtained in this study is a characteristic parameter of the porous electrode/electrolyte interface that is important to consider for thick electrodes. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.057207jes] All rights reserved.