If anybody else disassembles a cell and wonders what’s inside it — I asked one of the professionals in the field.
Here’s his response (which I also cc’d to BigClive)

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We have an x-ray fluorescence spectrometer that could identify it if we had a sample. As speculation, the hydrogen storage metal can contain rare earths. Mischmetal is typically used as a component in the alloy, and particle diameters are 10-20 microns, so that could be the culprit.

best regards
mark


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