In November 2013 a group of researchers with a grant from the Ministry of Korea did publish a paper in which discusses about a record in energy density for supercapacitor technology. Taking advantage of the greatest conductor available, they claim to achieve an impressive total of 64.18 kW-h/kg. Li-Ion have a range of 100-300kW-h/kg, and it's right now the industry standard for electric vehicles.
Li-Ion battery technology has a span of about 1000-1200 recharging cycles, and permits a relatively fast charging, but in the order or 20 minutes or more for half a charge and with a very powerful charger (the fastest by January 2014, Tesla Motors Supercharger), not available in other territories.
That's in our opinion where Li-Ion is currently creating some unnecessary problems to the EV revolution. For everyday use, 20 minutes of charge and more than 200 km of range, without pollution and free is like a dream for numerous individuals. Nevertheless the planet is huge, and a trip of 1000 km is not rare nowadays. To solve this problem without planning too many 20 minute stops, there are at least two available options keeping CO2, other toxic gases and particles toward the public air at zero (mandatory of course for sustainable development / environmental responsibility, security, quality of life and health).
First would be to standardize batteries with intelligence leaving room for any kind of technology in advance. So any vehicle has the standard space for the battery and accepts a definite quantity of amperes and voltage, then two poles are enough like always to charge and recharge; and technology independent. With this solution, and a battery swap standard for service stations, homes or whatever location, the EV market would advance unstoppable ahead of the anachronistic, dirty combustion.
But the second option is a method to recharge batteries in seconds, with service stations ready to handle great current flow. And here supercapacitors seems the unique viable alternative today, with recharging times in less than 30 seconds and with 98% of the available capacity after 10.000 recharging cycles! These are the newest, amazing numbers published in the aforementioned research. Not obviously for EV but for every possible device that runs on batteries.
Let's add that the key to energy density seems graphene 3D arrangement and the proposed method in the paper is nice but a bit stochastic, so far from ideal lattices, thus the energy density per kilogram could be more with graphene, a one-atom-thick material.
This is where technology might really create a better place to live... electricity production from solar energy is not a problem anymore for thousand years e.g. with mirror based thermosolar plants. Any sector should be willing to invest in this.