4 research outputs found
Facilitating the systematic nanoscale study of battery materials by atom probe tomography through in-situ metal coating
Through its capability for 3D mapping of Li at the nanoscale, atom probe
tomography (APT) is poised to play a key role in understanding the
microstructural degradation of lithium-ion batteries (LIB) during successive
charge and discharge cycles. However, APT application to materials for LIB is
plagued by the field induced delithiation (deintercalation) of Li-ions during
the analysis itself that prevents the precise assessment of the Li
distribution. Here, we showcase how a thin Cr-coating, in-situ formed on APT
specimens of NMC811 in the focused-ion beam (FIB), preserves the sample's
integrity and circumvent this deleterious delithiation. Cr-coated specimens
demonstrated remarkable improvements in data quality and virtually eliminated
premature specimen failures, allowing for more precise measurements via.
improved statistics. Through improved data analysis, we reveal substantial
cation fluctuations in commercial grade NMC811, including complete grains of
LiMnO. The current methodology stands out for its simplicity and
cost-effectiveness and is a viable approach to prepare battery cathodes and
anodes for systematic APT studies
A versatile and reproducible cryo-sample preparation methodology for atom probe studies
Repeatable and reliable site-specific preparation of specimens for atom probe
tomography (APT) at cryogenic temperatures has proven challenging. A
generalized workflow is required for cryogenic-specimen preparation including
lift-out via focused-ion beam and in-situ deposition of capping layers, to
strengthen specimens that will be exposed to high electric field and stresses
during field evaporation in APT, and protect them from environment during
transfer into the atom probe. Here, we build on existing protocols, and
showcase preparation and analysis of a variety of metals, oxides and supported
frozen liquids and battery materials. We demonstrate reliable in-situ
deposition of a metallic capping layer that significantly improve the atom
probe data quality for challenging material systems, particularly battery
cathode materials which are subjected to delithiation during the atom probe
analysis itself. Our workflow designed is versatile and transferable widely to
other instruments
In-situ metallic coating of atom probe specimen for enhanced yield, performance, and increased field-of-view
Atom probe tomography requires needle-shaped specimens with a diameter
typically below 100 nm, making them both very fragile and reactive, and defects
(notches at grain boundaries or precipitates) are known to affect the yield and
data quality. The use of a conformal coating directly on the sharpened specimen
has been proposed to increase yield and reduce background. However, to date,
these coatings have been applied ex-situ and mostly are not uniformly. Here, we
report on the controlled focused ion beam in-situ deposition of a thin metal
film on specimens immediately after specimen preparation. Different metallic
targets e.g. Cr were attached to a micromanipulator via a conventional lift-out
method and sputtered using the Ga or Xe ions. We showcase the many advantages
of coating specimens from metallic to non-metallic materials. We have
identified an increase in data quality and yield, an improvement of the mass
resolution, as well as an increase in the effective field-of-view enabling
visualization of the entire original specimen, including the complete surface
oxide layer. The ease of implementation of the approach makes it very
attractive for generalizing its use across a very wide range of atom probe
analyses