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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.

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.

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Mixed transition‐metal ferrites with the chemical formula MFe2O4 (M=Co, Ni), synthesized through an inverse co‐precipitation route, were characterized by using scanning electron microscopy and powder X‐ray diffraction, which demonstrate phase‐pure compounds with particle sizes of about 100 nm. Cyclic voltammetry investigations in lithium half‐cells revealed a difference between the first cycle and the following charge–discharge cycles, which is characteristic for conversion‐type electrode systems. To understand the mechanism of the electrochemical reaction in the first cycle, in situ X‐ray absorption spectroscopy was performed during cycling at a charge–discharge rate of C/10. During the first discharge process, the crystalline Co and Ni ferrites undergo reduction. A coexistence of binary metal oxides (CoO/NiO and Fe2O3) and metallic phases were observed during the discharge. At the end of discharge, only the existence of metallic nanoclusters was observed. In the subsequent charging process, Fe was found to undergo complete oxidation in both ferrites. In contrast, almost 60 % of the Co or Ni remained in the metallic state at the end of the charge (end of first cycle). This incomplete oxidation of Co and Ni in the applied voltage range could be the main reason behind the irreversible capacity loss and low coulombic efficiency often reported for these conversion electrode systems.

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