Abstract
X-ray absorption spectroscopy (XAS) is a synchrotron-based, element-specific, short-range structural method largely used in the study of materials, already widely employed for the study of the electrochemical processes in battery systems. The high penetration of the X-rays makes XAS particularly suited for the study of battery materials under operando conditions using specifically developed in situ electrochemical cells. In this paper, the application of XAS to the study of battery materials carried out at Institut Charles Gerhardt Montpellier (France) will be outlined, illustrating the type of information provided by XAS. The challenging study of the sodiation of followed individually and simultaneously at both metals will be also presented in order to highlight the typical advantages of this technique even when it is pushed at its technical limits.