High-resolution X-ray computed tomography (CT) has become
an invaluable
tool in battery research for its ability to probe phase distributions
in sealed samples. The Cartesian coordinates used in describing the
CT image stack are not appropriate for understanding radial dependencies,
like that seen in bobbin-type batteries. The most prominent of these
bobbin-type batteries is alkaline Zn–MnO2, which
dominates the primary battery market. To understand material radial
dependencies within these batteries, a method is presented to approximate
the Cartesian coordinates of CT data into pseudo-cylindrical coordinates.
This is important because radial volume fractions are the output of
computational battery models, and this will allow the correlation
of a battery model to CT data. A selection of 10 anodes inside Zn–MnO2 AA batteries are used to demonstrate the method. For these,
the pseudo-radius is defined as the relative distance in the anode
between the central current collecting pin and the separator. Using
these anodes, we validate that this method results in averaged one-dimensional
material profiles that, when compared to other methods, show a better
quantitative match to individual local slices of the anodes in the
polar θ-direction. The other methods tested are methods that
average to an absolute center point based on either the pin or the
separator. The pseudo-cylindrical method also corrects for slight
asymmetries observed in bobbin-type batteries because the pin is often
slightly off-center and the separator often has a noncircular shape.
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