Abstract
Batteries, in particular lithium-ion (Li-ion) batteries, are energy storage devices that are suitable for portable applications (cell phones, laptops) and support the need of using intrinsically diffuse/intermittent renewable energy sources. In order to improve such devices and make them safer, it is crucial to understand and characterize in the most accurate way the constitutive materials and their interfaces. To do so the use of powerful tools is essential especially since nano-architectured materials have been developed. Thus the use of the Transmission Electron Microscope (TEM) is particularly relevant due to its ability to study morphological, structural or chemical properties at this scale. On this basis our project relates to the in situ study of an electrochemical system under operation within a TEM. The first part of this manuscript is devoted to the strategy of the study. Indeed, the technological issues inherent to both the TEM technique and the battery forced us to make some choices based on the state of the art, mostly in terms of materials, technologies or equipment. Thus this project is based on the study of an all solid-state microbattery. The fabrication process of a microbattery by laser deposition, including the synthesis and the study of each active material, is detailed in the second chapter. The third part describes the solutions suggested to solve some of the technological issues encountered. We thus demonstrated the first ex situ TEM observation of "nanobatteries" obtained by cross-sectioning a microbattery using focus ion beam (FIB) in a dual beam SEM. Then, TEM analyses between pristine, cycled, and faulted all solid-state batteries have revealed drastic changes, damages or deterioration mechanisms, never highlighted previously Since it was not possible during the previous experiments to achieve the development of live in situ TEM observation of "nanobatteries" cycled within the microscope, we describe in the last chapter all the configuration modifications made. The new design of the samples allowed us to experiment live in situ TEM cycling and to reveal the last challenges that have to be faced.