It seems that the deuterium fuell cell2 puts out a diffrent used up deuterium fuel cell then the deuterium fuel cell. There is no recipe to use it.

They give the same used up cell.
Just like Uranium and Plutonium give the same used up cell, and Thorium and Thorium-Plutonium give the same used up cell.

if they give different cells, it's possible that you're using other mods, and one of them changes the result item. Since Deuterium fuel cell 2 is new for 1.0, it's possible that whatever other mod is changing the result for the first one, (And the author) doesn't know about the second.

I mean, that's a guess, I'm not sure why other mods would change a used up fuel cell item.

Angeles Industries seems to break it.