RESUMO
The current sustained demand for "smart" and connected devices has created a need for more miniaturized power sources, hence for microbatteries. Lithium-ion or "lithium-free" all-solid-state thin-film batteries are adapted solutions to this issue. The capability to carry out spatially resolved chemical analysis is fundamental for the understanding of the operation in an all-solid-state microbattery. Classically cumbersome and not straightforward techniques as TEM/STEM/EELS and FIB preparation methods could be used to address this issue. The challenge in this work is to make the characterization of Li-based material possible by coupling ion-milling cross section preparation method and AES techniques to characterize the behavior of a LiCoO2 positive electrode in an all solid state microbattery. The surface chemistry of LiCoO2 has been studied before and after LiPON deposition. Modifications of the chemical environments characteristic of the positive electrode have been reported at different steps of the electrochemical process. An original qualitative and a semiquantitative analysis has been used in this work with the peak deconvolution method based on real, certified reference spectra to better understand the lithiation/delithiation process. This original coupling has demonstrated that a full study of the pristine, cycled, and post mortem positive electrode in a microbattery is also possible. The ion-milling preparation method allows access to a large area, and the resolution of Auger analysis is highly resolved in energy to separate the lithium and the cobalt signals in an accurate way.
RESUMO
This work has examined the elemental distribution and local morphology at the nanoscale of core@shell Ag/Au@SiO2 particles. The characterization of such complex metal/insulator materials becomes more efficient when using an initial cross-section method of preparation of the core@shell nanoparticles (ion milling cross polisher). The originality of this route of preparation allows one to obtain undamaged, well-defined and planar layers of cross-cut nano-objects. Once combined with high-resolution techniques of characterization (XPS, Auger and SEM), the process appears as a powerful way to minimize charging effects and enhance the outcoming electron signal (potentially affected by the topography of the material) during analysis. SEM experiments have unambiguously revealed the hollow-morphology of the metal core, while Auger spectroscopy observations showed chemical heterogeneity within the particles (as silver and gold are randomly found in the core ring). To our knowledge, this is the first time that Auger nano probe spectroscopy has been used and successfully optimized for the study of some complex metal/inorganic interfaces at such a high degree of resolution (≈12 nm). Complementarily, XPS Au 4f and Ag 3d peaks were finally detected attesting the possibility of access to the whole chemistry of such nanostructured assemblies.
