Density isn’t everything. It’s likely a lot cheaper and less environmentally destructive to dig a big hole in the ground than to manufacture a lithium battery.
That is not entirely a given. Large eathworks have important knock effects on the environment and wildlife. We tend to think that dams and such are harmless but they change their surroundings radically. I had experience living next to one which modified the local climate and made a large contribution to the desertification of the place.