What do you mean "what kind of density"? "Similar to lithium batteries" means just that, if you have a lithium battery of a certain size, this will hold an amount of energy similar to that.
A 30% difference would still be classified as "similar", but this would still be a big deal since batteries are just borderline capable to provide electric cars with sufficient charge to be acceptable for most people. A battery that's 30% worse than the best current batteries would be unusable.
He's referring more to a car that could charge in 5 minutes and go 60 miles.
As I have an EV, that's closer to my current scenario of charging (once they put in a charger in the office parking lot) 4 hours and going 90 miles. The tradeoff of reduced distance for superior charge time is...irritating.
60 miles would be just short enough where I would need a gasoline car. That's why I've yet to get a Leaf. Can't afford a Tesla (nor do I want/need a car that big).
Energy density can be given in terms of mass or in terms of volume. In general, if a source of a new interesting battery technology does not describe which one they mean in a comparison, you can assume the worst, that is, that they are comparable to lithium-ion in joules/m^3 (at which lithium ion isn't actually that good).