Tesla's current Model S car has batteries with a capacitance of 85 kWh, which enables the car to drive up to 480 km between charges. The company's CEO, Elon Mask, recently said that the company is developing "new battery technology" that will almost double the capacity - and will allow the cars to drive up to 800 km between charges.
Today, China News Network posts an article saying that Tesla's new battery technology is based on graphene. This makes sense as graphene-based battery electrodes can dramatically increase battery charge time and capacity. There are many companies developing this technology and it's likely that Tesla is collaborating with one (or more of these companies).
In 2013, XG Sciences launched a new graphene-based anode materials for Li-Ion batteries that has four times the capacity of conventional anodes. XG says that the new material is available today at commercial scale with an "attractive pricing". In 2014, SiNode Systems signed a joint-development agreement with Merck's AZ Electronic Materials with an aim to commercialize graphene-based materials for lithium-ion batteries.
Angstron Materials recently launched a line of graphene-enhanced anode materials for lithium-ion batteries, called "NANO GCA", which combine high capacity silicon materials with mechanically reinforcing, and electrically conductive graphene.
Tesla is collaborating with Panasonic to build the world's largest Li-Ion battery plant (the Gigafactory) - that by 2020 will produce more Li-Ion batteries annually than were produced worldwide in 2013. This should price battery prices down by more than 30%, according to Tesla.