Operando X-Ray Diffraction and EIS on NCA Battery Cathodes

Abstract

In recent decades, lithium-ion batteries (LIB) have revolutionized the portable electronics industry and the emerging market of electric vehicles (EVs) and hybrid electric vehicles (HEVs). Significant efforts have been devoted to fundamental and commercial research and development of layered oxide cathodes with small structural deformation upon lithium intercalation and de-intercalation. Towards this end, there is a need to couple modern electroanalytical techniques with advanced structural characterization methods. Here I discuss current progress to complement electrochemical impedance spectroscopy (EIS) with in operando x-ray methods, focusing on correlating time-dependent measurements in order to add structural information to the electrochemical models. EIS is widely used as a measure of kinetics and interface properties in a wide variety of systems. In a battery system, correlating the impedance parameters to the cycling efficiency of the cell, helps predicting the likelihood of battery failures. While EIS is a very powerful analysis tool, the interpretation of the data is non-trivial, as they can`t be fit by a unique model. In this study, we investigate the structural behavior of LiNi0.80Co0.15Al0.05O2 (NCA) cathode material, of particular interest as it exhibits high structural stability. We aim to gain additional structural information from x-ray diffraction methods in order to unambiguity model the EIS data.