Here's a new and well written overview article by Adam Miller on EEstor.
The advance is based on a barium-titanate insulator claimed to increase the specific energy far beyond that achievable with today's ultracapacitor technology. It is claimed that this new advance allows for a specific energy of about 280 watts per kilogram -- more than double that of the most advanced lithium-ion technology and ten times that of lead-acid batteries. This could translate into an electric vehicle capable of traveling up to 500 miles on a five minute charge, compared with current battery technology which offers an average 50-100 range on an overnight charge. As if that weren't enough, the company claims they will be able to mass-produce the units at a fraction of the cost.