For a man who has just paid $US6.7 billion ($9.9 billion) for a company in one of the most volatile sectors in global mining that was worth only $US2.4 billion a month ago, Rio Tinto chief executive Jakob Stausholm is remarkably relaxed.

Indeed, he sees his deal to buy Arcadium Lithium as a chance to bring some stability to a commodity that has been a wild roller-coaster ride for the past five years.