If this is a real and documented concern, please provide sources so I can take a look.
Otherwise, no, batteries will not hold a charge for decades. Landmines and unexploded ordinance are analog. They will last as long as the mechanisms and explosive payload aren’t damaged, or corroded.
No amount of copium is going to clear those minefields, or save the coming generations Ukrainians, who will continue to be maimed and killed by these for the foreseeable future…
The only real hope, is that there is a significant technological development that that both dramatically expedites the complete mapping of minefields, and allows demining personel to rapidily destroy the ordinace, while being outside of the blast and shrapnel radius.