@usert2HgfHk9Ha it's likely a ways off, to be honest, if at all. While many phone manufacturers do want to implement graphene batteries, replacements specifically for the S9 line may or may not be compatible. We will have to wait and see.
Graphine batterie's do not exist yet for smartphones (or really anything else but scientific testing tbh) so if they ever come to exist, it will be a very very long time away.
The Galaxy S9+ will no longer be a flagship at that point and smartphones as we know them will probably be very different.
I'm thinking we will land on Mars before Graphene batteries become main stream.