Advances in understanding li battery mechanisms using impedance spectroscopy

Abstract

The use of impedance spectroscopy in the field of modern batteries is demonstrated on three systems: lithium ion batteries represented by lithium iron phosphate (LFP) and lithium cobalt oxide (LCO) electrodes, a porous carbon cathode in contact with polysulfides and a metallic lithium anode exhibiting dendritic growth. In all cases, systematic experiments are shown where the type and composition of electrochemical cell is varied in order to identify the main processes contributing to the impedance response. The experiments are upgraded with appropriate models, using mainly the transmission line approach. The approach allows establishment of clear correlations between the composition and morphology of electrodes on one hand and the measured impedance features on the other. As the transmission line models are based on the use of physically well-defined elements, the approach allows a quantitative description of the main processes (diffusion, reaction, migration across films and contacts) taking place in modern battery electrodes.