Washing may leach out the compounds you want to see, so why would you like to wash the material ?? EDS will give you the information about the amount and dispersion of sulfides in the separator as it is, so don't modify it.

Alain

Thanks Alain for your description. I got the idea as you suggested. I will follow it.

Sumair

There would be significant quantities of lithium Polysulfide trapped in the coating of the separator. You can scan for both sulfur and oxygen species using EDX. Comparison of This would give you an understanding of which particles are sulfur based but don't arise from electrolyte salt (which contains oxygen based compounds)