The microstructure of the active material of Li‐ion batteries has a crucial influence on local ion‐transport processes but is not yet well characterized. Atom probe tomography (APT), a method combining sub‐nanometer spatial resolution with sub‐parts‐per‐thousand chemical resolution is well suited for 3 D microstructural characterization. Herein, the results of the characterization of lithium (nickel)manganese oxides [L(N)MO] with APT are presented. Structural and chemical defects of different dimensions such as the segregation of Na impurities to grain boundaries and the appearance of a Ni‐rich foreign phase are detected. Furthermore, a lamellar microstructure correlated to fluctuations in the local Li content was observed, and its influence on Li transport in the material is discussed. In defect‐free regions, the lattice planes of LMO are reconstructed for the first time, and the high spatial resolution of APT is revealed. Thus, the results demonstrate the potential of APT for the 3 D microstructural characterization of LMO.

A method to characterize open-cell nanoporous materials with atom probe tomography (APT) has been developed. For this, open-cell nanoporous gold with pore diameters of around 50 nm was used as a model system, and filled by electron beam-induced deposition (EBID) to obtain a compact material. Two different EBID precursors were successfully tested-dicobalt octacarbonyl [Co2(CO)8] and diiron nonacarbonyl [Fe2(CO)9]. Penetration and filling depth are sufficient for focused ion beam-based APT sample preparation. With this approach, stable APT analysis of the nanoporous material can be performed. Reconstruction reveals the composition of the deposited precursor and the nanoporous material, as well as chemical information of the interfaces between them. Thus, it is shown that, using an appropriate EBID process, local chemical information in three dimensions with sub-nanometer resolution can be obtained from nanoporous materials using APT.

Atom probe tomography is routinely used for the characterization of materials microstructures, usually assuming that the microstructure is unaltered by the analysis. When analyzing ionic conductors, however, gradients in the chemical potential and the electric field penetrating dielectric atom probe specimens can cause significant ionic mobility. Although ionic mobility is undesirable when aiming for materials characterization, it offers a strategy to manipulate materials directly in situ in the atom probe. Here, we present experimental results on the analysis of the ionic conductor lithium-manganese-oxide with different atom probe techniques. We demonstrate that, at a temperature of 30 K, characterization of the materials microstructure is possible without measurable Li mobility. Also, we show that at 298 K the material can be deintercalated, in situ in the atom probe, without changing the manganese-oxide host structure. Combining in situ atom probe deintercalation and subsequent conventional characterization, we demonstrate a new methodological approach to study ionic conductors even in early stages of deintercalation.

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Experiments on the room temperature oxidation of tip-shaped tungsten nanowires under an externally applied electric field are reported, yielding the controlled formation of tungsten oxide layers up to several tens of nanometers thick in the high field region at the tip of the nanowires. The initially very fast oxidation reaction is observed to virtually terminate at a field dependent state, defined by a critical field strength of 1.15(2)×109V∕m. Since electric fields of the order of 109V∕m are easily obtained, the observed effect may influence the chemical stability of nanoscaled systems significantly when used in ambient atmosphere.

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