Comment by pfdietz

About lithium: DT fusion needs mostly Li-6. If it were separated, batteries would work just fine with Li-7.

I recall a story of some lab that was trying to make a lithium-based neutron detector. It wouldn't work, and when they investigated they discovered the lithium they had bought was almost pure Li-7. It was surplus sold back into the chemicals market from the US hydrogen bomb program (which needed Li-6).