Understanding and improving the behavior of interfaces is essential to the development of safer and high performance Li-based batteries regardless of their range of applications. Indirect methods such as impedance spectroscopy or direct methods such as the live in situ observation of batteries cycled within a scanning electron microscope (in situ SEM) are used to determine the interface microstructure/composition evolution upon cycling. These methods are used to establish a direct link between interface properties and batteries performance; they also enable us to spot local interface defects that are crucial to the development of 2D solid-state microbattery, for instance. Indeed, this technology is of interest in powering the new generation of microelectromechanical systems (MEMS). Here, we demonstrate 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 LiCoO2/solid electrolyte/SnO Li-ion batteries have revealed drastic changes such as the presence, depending on the battery fabrication process, of both cavities within the solid electrolyte layers and low wetting points between the electrolyte and the negative electrode. Moreover, post-mortem TEM observations of cycled microbatteries have revealed a rapid deterioration of the interface upon cycling because of the migration of the chemical elements between stacked layers. Such findings are involved both in the improvement of the reliability of the 2D all solid-state battery assembling process and in the enhancement of their cycling performances. Such achievements constitute the technical platform for our future targets namely the development of live in situ TEM observation of “nanobatteries” cycled within the microscope.

A biomimetic composite of nanohydroxyapatite (nHap) and semicrystalline polyamide 6,9 (PA 6,9) was synthesized by thermally induced phase separation. The nHap powder was dispersed in a polymer matrix with a low ratio ranging 1-10 wt %. The mean size of the nHap, determined by scanning electron microscopy (SEM) was approximately 100-200 nm (length), 40-60 nm (width). Physicochemical analyses were performed in order to characterize the PA 6,9 and nHap separately on the one hand, and the PA 6,9/nHap composites on the other hand. Differential scanning calorimetry (DSC) and dynamic mechanical analyses (DMA) have pointed out an optimization of the composite physical properties as a function of nHap content till a limit value of 5 wt %. Above this value, the mechanical properties decreased. Four main parameters have been found to influence the composite physical properties improvement: the fillers content, the physical structure of the polymeric matrix, the particles dispersion and the physical interaction strength between organic and inorganic phases. The dynamic mechanical properties of this biomimetic nanocomposite were compared with human cortical bone.

In this paper, we detailed the formation/evolution of precipitates in alcoholic media containing Co(II+) and Li(+) species, together with the evolution of the composition and structure/texture of the resulting solid phases during the aging process at controlled constant temperature. While the end product is found to be well-crystallized HT-LiCoO(2), its formation is shown to result from a two-step process enlisting the initial fast precipitation of β-HCoO(2) and then its slow dissolution followed by recrystallization of the lithium-containing material. These results were obtained through combined X-ray diffraction, Raman and IR spectroscopy, elemental and oxidation-state analysis, and high-resolution transmission electron microscopy/selected-area electron diffraction observations. Depending on the cationic concentration, the size of the precipitated material can be controlled within the nanometric range. The electrochemical performances of these aged materials are slightly improved compared to those of the directly precipitated ones that we previously reported. The main limitation of these materials remains the presence of surface protons.