Thermofisher Axia ChemiSEM User Manual

APPLICATION NOTE

Assessment of contaminants
within battery materials via
Axia ChemiSEM

Introduction

Contamination is a major issue in the battery manufacturing
process. From production of the cathode, anode, and battery
cell to battery module assembly and testing, contaminants
are a concern at every stage of the process. The existence
of contaminants in the battery can cause a wide range of
problems—lowering materials usage efficiency, accelerating
cell degradation, and even causing internal shorts. As a result,
it is essential for materials scientists to obtain a thorough
understanding of the contaminants that enter the battery
manufacturing process.

The combination of a scanning electron microscope (SEM) and
energy dispersive X-ray spectroscopy (EDS) can be used to
probe both structure and elemental information of contaminants
in battery materials. However, battery contaminants generally
have a low concentration level, and image acquisition times can
be long when studying these contaminants using conventional
EDS. In this application note, we introduce a fast and simple
method for characterizing these contaminants via the Thermo
Scientific
bring speed and simplicity to materials micro-structural analysis
and defect discovery.

™

Axia™ ChemiSEM, a new SEM platform designed to

100 μm

OC

Al

Mg Ti Co

Figure 1. Large-scale navigation montage image obtained by collecting neighboring frames to generate a low magnification image for point-and-click
navigation. 750 µm x 370 µm. Acquisition parameter s: acc voltage 20 keV, beam cur rent 0.13 uA.

Large-scale navigation

With the Axia ChemiSEM, identification of the presence of
contaminants can be rapidly achieved within a large field of
view—thanks to the system’s full integration of different imaging
modalities including live-quantitative elemental mapping and
conventional SEM imaging. The image in Figure 1 shows a
navigation image acquired on the surface of a lithium cobalt
oxide (LiCoO

) cathode via A xia ChemiSEM.

2

This large-scale overview of the sample with EDS data included
is collected within 15 minutes. Traditionally, a grayscale
image with morphological information and contrast based
on backscattered electron signal cannot provide enough
information to identify regions of interest for contamination
analysis. The main reason for this limitation is that a
backscattered electron image only provides a compositional
contrast based on the atomic number, and oftentimes the
compositional contrast between two different elements is too
similar to be observed in grayscale.

With the quantitative elemental information provided by Axia
ChemiSEM, however, the large-scale overview already shows
some foreign elements, such as magnesium (Mg), aluminum
(Al), and titanium (Ti), as well as their position. The large-scale
overview serves as a navigation image that can be used to
easily move to the region of interest where the contaminants are
present to run a more detailed characterization.

Combined SEM-EDS analysis

Using the navigation image as a reference, the user can
simply click on the point of interest to drive the stage to it.
This process significantly decreases time-to-data for each
suspected contaminant. To further demonstrate this ability to
hone in on specific regions, the characterization of one area of
interest highlighted in Figure 1 is presented in Figure 2. Using
conventional SEM imaging, the backscattered electron image,
which offers a first level of feedback on the composition, does
not provide enough information to identify the contaminant.

By contrast, Axia ChemiSEM provides near instant access
to quantitative elemental information every time a grayscale
image is acquired since X-ray detection is always on. X-rays
are acquired and processed in the background during the
acquisition of the grayscale image to obtain quantitative
elemental information, different from the raw signal usually
acquired from a traditional EDS gross counts mapping analysis.
This constant access to elemental information translates to a
seamless characterization experience where no time is wasted
waiting for data.

The quantitative elemental map presented in Figure 2 was
collected simultaneously during the conventional SEM image
acquisition. To view this result, the user simply needs to activate
the quantitative elemental view. There is no need to re-acquire
the data as one would need do with a conventional EDS system.

5 μm

5 μm

OC

Al

Mg Ti Co

Figure 2. Traditional backscatte red electr on image (top) of the region of
interest and quantitative elemental mapping (bottom) obtained with an
acquisition of 80 seconds. (Acquisition parameters: acc voltage 10 keV,
beam cu rrent 0.76 nA, dwell time 5 us).

To obtain a better view of the distribution of each element, the
user can generate a complete set of images highlighting one
element at a time, as shown in Figure 3. Besides Co, the main
element from LiCoO

, the results also show the presence of

2

the elements Al, Mg, and Ti within the electrode, which are
unexpected. These contaminants could have been introduced
during the cathode materials synthesis, mixing, or coating
processes as the battery was manufactured. The user stays
focused on searching for the odd elements, which easily stand
out, leading to a more intuitive and accurate discovery process.

Co

5 μm

Point analyses

To further identify these contaminants, point analyses have
been executed to obtain the exact quantification of the elements
present in the contamination with the focus on Al as an example.
All of the conventional EDS functions are fully integrated into
the Axia ChemiSEM user interface with no need to switch to a
different software. (The location of the point analyzed is shown
with a red dot in the first image from the top of Figure 3.)

70

60

50

5 μm

Al

40

30

20

Atomic Percentage (%)

10

0

Figure 4. Contamination composition quantified at different acquisition
conditions (10 keV and 0.76 nA, 5 keV and 0.28 nA, 3 keV and 0.16 nA).

C O Al Co

Points quantification

10 keV
5 kV
3kV

Elements

5 μm

Mg

5 μm

Ti

Figure 3. The first image on the top shows the distribution of the cobalt
(Co) which is part of the battery matrix. The other three images highlight
the distribution of aluminum (Al), magnesium (Mg) an d titanium ( Ti)
contamination, respectively. The red dot in the top image shows the location
where further analysis will be performed.

In order to exclude the interaction volume effects on the
quantitative results of the contaminant’s composition, both
accelerating voltage and beam current have been reduced and
the same point analysis has been performed. Figure 4 compares
the analysis of that point as a function of acceleration voltage.

Axia ChemiSEM’s enhanced graphical user interface provides
automated system alignments, allowing the user to change the
analysis parameters without manual adjustments for fast and
easy analyses. In short order, point analyses using three different
characterization conditions have been acquired, lowering the
accelerating voltage up to the minimum required to identify the
contaminant’s composition and excite the Al k-line (1.4866 keV),
as shown in Figure 4. The obtained results are comparable,
regardless of accelerating voltage.

The fact that the contaminant’s composition remains consistent
proves that a certain amount of Al is embedded in the LiCoO

,

2

which likely means that the Al element was reacting with the
precursor used to synthesize LiCoO

during the sintering

2

process. As a result of this analysis, the researcher would be
able to determine that the raw materials for LiCoO

synthesis

2

or the equipment involved in the sintering process need to be
carefully examined to eliminate this contaminant.

Conclusion

A thorough assessment of the contaminants within battery
materials is critical to assuring battery quality and performance.
Using the Thermo Scientific Axia ChemiSEM, large-scale
SEM-EDS mapping was employed to quickly and easily identify
contaminants and then move directly into detailed quantitative
EDS analysis to more precisely pinpoint the distribution of
each contaminant. Point analyses were then performed to
obtain the exact quantification of each element present in the
contamination.

With the Axia ChemiSEM, SEM imaging and EDS are no longer
separate workflows, but an integrated process designed
to rapidly move from discovery to analysis that generates
accurate results. Live EDS technology together with the Axia
ChemiSEM’s automatic alignment function allows for a smooth
user experience and efficient characterization of the battery
electrode. Using the Axia ChemiSEM for fast and simple SEM­EDS contaminant analysis, battery manufacturers can improve
the efficiency of their research—reducing contaminants during
the manufacturing process and improving battery performance.

Find out more at thermofisher.com/Axia-ChemiSEM

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