RE:Hey RiotintoeSooner, I won't carry on with conjecture about their partnership with Sumitomo concerning their Winu project. For several reasons, the project seemed like a piece of low-hanging fruit for Rio to handle on their own. I would like to point out though, the information released through Rio Tinto concerning Sumitomo I think goes a long way and explaining the reason why. They will more than likely be collaborating on other projects in the future...
"The parties have also entered into a letter of intent to develop a broader strategic partnership to work together to explore opportunities for commercial, technical and strategic collaboration across copper, other base metals and lithium."