As the company, Aion V, is really not releasing info on what their "graphene battery" really is, my guess is that it's not an actual total graphene battery, where graphene is used to STORE the electrical energy, but is rather what's called a "graphene enhanced" battery, which many companies are working on. Essentially, that means using graphene on one of the electrodes to take advantage of its conductivity and huge surface area.
That's not at all a bad thing! But the reality may be a LOT more down to Earth than implied in this article.
Here's a good primer: