To be honest, I am not too fuss or concern of what they use in...

To be honest, I am not too fuss or concern of what they use in submarine, it is only a small fleet around the world.
Even all are converted to lithium, it is not a quantity that will make whole lot difference to the demand of Li.
Just curious how are they going to get charge in the middle of the ocean & their long voyage.
I hope not float on the surface charge from the solar panel install to the top of the submarines.