Graphene is one of those things you hear so much about but never actually see it go anywhere.
Really hope it takes off. But as per your question - pretty sure the answer is that Purism will use the best battery that they can find that properly fits the form factor of whatever device is in-question.
I imagine that if Samsung really does come forward with this new battery type, it’ll be exclusive to their devices for a little while before they’ll allow the individual sale of them to other device manufacturers anyway.
I mean, that’s speculative - it’d make sense, but I really have no idea, I mean batteries are batteries so they may just sell them on the open market right away for all I know. You’d have to ask Samsung’s marketing team.
Lets hope these batteries aren’t too 
though, like some of their older designs 