The ambitious goal of reaching a detailed understanding of electrochemical reactions mechanisms within and on the surface of the constituent materials of Li-ion batteries has generated the development of an arsenal of physicochemical characterization techniques, especially in situ or operando, which are the subject of this contribution. Although often unavoidable, they however impose constraints on measurement that are not necessarily in line with the time necessary for a uniform electrochemical reaction and / or balance. It offers in this book a critical analysis of the state of the art in this field for the main characterization methods used in solid electrochemistry the community.