Looks to me like a case of a typo or an "invention" in a somewhat reliable source being spread around. All searches for it bring up the exact same information, on Lithium in a periodic table, with a description that states the salt lithium chloride is one of the most lyproscopic materials known.
If the homework came from a textbook, you might be able to make a pretty big stink with the publisher about plagarism. If the teacher made up the homework, your brother could put the teacher on the spot for not being very dilligent with information sources.
If it is a scientific term, there would exist more than one sentence using it, and a definition somewhere. So, I would say that it's a word so obscure, that it technically doesn't exist
