Hmm, Co60 is a fission product?
University researchers create battery powered by waste isotopes
"The team tested battery designs with two radioactive isotope sources—cesium-137 and cobalt-60, both of which are fission products found in used nuclear fuel."
https://www.ans.org/news/2025-03-03/article-6806/university-researchers-create-battery-powered-by-waste-isotopes/