Amminex is set to announce a hydrogen storage tank that would meet the EPA goal of 500 km range with a storage volume of 50 L, according to Slashdot. The company stores hydrogen in a pellet of sorts, which is claimed to hold 9% H2 by weight. That's extremely impressive performance. This appears to be the ionic type of hydride storage mechanism, but Amminex doesn't have much technical information on their site (linked below). Other companies, such as Ovonic, have also been working with the different hydride technologies, which potentially provide far better density than compressing or liquefying the gas and could be much safer as well.