Sodium Sulphide is going to be huge if it works. Dirt cheap. Basically salt + waste + magic.
Sodium is easy part, but Sulfur might be a problem. I read article that most of it comes from by product of oil refining. As such if we stop refining as much oil we might need to find new sources. And it is also used in fertilizers and many industrial processes... Add extra demand for batteries and things start to look lot less rosy.
Calcium sulfate (and I suppose other sulfates) are quite common.