Studies on LiFePO4 as Cathode Material in Li-Ion Batteries

Abstract

Lithium iron phosphate is a promising cathode material for the use in lithium-ion batteries meeting the demands of good stability during cycling and safe operation due to reduced risk of thermal runaway. However, slow solid state diffusion and poor electrical conductivity reduce power capability. For further improvement, the identification of the rate determining processes is necessary. Electrochemical impedance spectroscopy (EIS) has proven to be a powerful tool for the characterization of electrochemical systems. In this contribution a deconvolution of the impedance with the distribution of relaxation times (DRT) is used to obtain a better resolution in frequency domain. Therewith, the cathodic and anodic polarization processes are identified and an impedance model for the cell is proposed.