Envia Systems, a Californian company with prototyping and production facilities in China, has developed a lithium-ion battery with roughly twice as much energy per gram as present batteries.

Envia Systems found that by including manganese in a mix of materials for the cathode better energy densities could be achieved. The team then boosted the performance of the anode by incorporating silicon along with the usual graphite.

Silicon anodes swell and, until now, have been disintegrated by being charged and recharged as few as ten times. By encasing the silicon in a carbon coating and interlacing the carbon fibres, the Envia team produced a battery which they have shown can be cycled more than 400 times.

The slim, energy-dense batteries could reduce the number needed per car by half. In addition, at $125 per kilowatt-hour, the batteries are less than half the cost of current batteries. And, because the batteries can be slimmer, they are easier to keep cool – reducing the risk of "thermal runaway" in the event of an accident.

A Nissan Leaf, with the Envia batteries, could travel almost 500 kilometres on a single charge, compared with about 130 kilometres with current batteries.

Envia's co-founder and chief technology officer, Sujeet Kumar, said that "We expect Envia's next generation lithium-ion battery will revolutionize the [electric vehicle] industry by eliminating the three remaining barriers to mass adoption: cost, range and safety. The ability to drive up to 300 miles on a single charge will eliminate 'range anxiety.'"