With 9.65 times the energy
With 9.65 times the energy density the Prime would indeed get fantastic mileage. But imagine something like the Hyundai Kona EV or the Chevy Bolt! We could then be seeing almost a 2400 mile range.
At that range the notion of needing gasoline range extending engine.
Let us imagine a battery only half the size of the 1000lb 64KWh battery. We save 500 lbs of weight and still have 1200 miles of range in a car that now weighs about the same as a traditional car with even greater efficiencies that come with having to move less mass.