RESUMEN
All-solid-state batteries (SSBs) are attracting widespread attention as next-generation energy storage devices, potentially offering increased power and energy densities and better safety than liquid electrolyte-based Li-ion batteries. Significant research efforts are currently underway to develop stable and high-performance bulk-type SSB cells by optimizing the cathode microstructure and composition, among others. Electronically conductive additives in the positive electrode may have a positive or negative impact on cyclability. Herein, it is shown that for high-loading (pelletized) SSB cells using both a size- and surface-tailored Ni-rich layered oxide cathode material and a lithium thiophosphate solid electrolyte, the cycling performance is best when low-surface-area carbon black is introduced.
RESUMEN
LiCo0.8Fe0.2MnO4 has been investigated as an active material for the positive electrode in lithium-ion batteries (LIBs) with a discharge potential of around 5 V (vs. Li+|Li). After synthesis by a Pechini based sol-gel route, the structural and morphological properties have been investigated by X-ray diffraction, scanning electron microscopy, 7Li MAS NMR spectroscopy, and 57Fe Mössbauer spectroscopy. With galvanostatic cycling, it was possible to obtain a specific discharge capacity of 117 mA h g-1, which is more than 80% of the theoretical capacity. The lithium extraction/insertion mechanism has been characterized by in situ synchrotron powder diffraction. The reversible oxidation process of Fe3+ to Fe4+ has been observed by in situ Mössbauer spectroscopy and in situ XAS measurements.
RESUMEN
A systematic study on charging of carbon thin films under intense electron-beam irradiation was performed in a transmission electron microscope to identify the underlying physics for the functionality of hole-free phase plates. Thin amorphous carbon films fabricated by different deposition techniques and single-layer graphene were studied. Clean thin films at moderate temperatures show small negative charging while thin films kept at an elevated temperature are stable and not prone to beam-generated charging. The charging is attributed to electron-stimulated desorption (ESD) of chemisorbed water molecules from the thin-film surfaces and an accompanying change of work function. The ESD interpretation is supported by experimental results obtained by electron-energy loss spectroscopy, hole-free phase plate imaging, secondary electron detection and x-ray photoelectron spectroscopy as well as simulations of the electrostatic potential distribution. The described ESD-based model explains previous experimental findings and is of general interest to any phase-related technique in a transmission electron microscope.
RESUMEN
SnP2O7 was prepared by a sol-gel route. The structural changes of tin pyrophosphate during the electrochemical lithiation were followed by using in situ XRD measurements that reveal the existence of a crystalline phase at the beginning of the discharge process. Nevertheless, it becomes amorphous after the full discharge as a result of a conversion reaction leading to the formation of LixSny alloys. The electrochemical tests show a high capacity with high retention upon cycling. To better understand the reaction mechanism of SnP2O7 with Li, several techniques were applied, such as ex situ(119)Sn Mössbauer and ex situ(7)Li and (31)P NMR spectroscopies with which we can follow the changes in the local environment of each element during cycling.