Researchers at the University of Massachusetts Boston have come up with a new idea of combining electric power with a combustion engine, which they say may enable electric vehicles to store more energy than gasoline in the same volume, and extend their range.

They say that electric power storage that is part battery part chemical fuel cell may ditch gasoline for good.

Stuart Licht, who conceived the new design along with his colleagues at the university, says that it can store energy more densely than petrol.

Batteries produce electricity from a closed chemical system that is eventually exhausted, and fuel cells use a constant supply of fuel so that they are continually topped up.

Licht insists that his cell has features of both. He says that his cell's anode is made from vanadium boride, which serves double-duty as a fuel too. However, it is held internally, unlike the flowing fuel of a fuel cell.

The researchers say that the vanadium boride reacts with a constant stream of oxygen, as in a fuel cell, provided by the cathode, which brings in a supply of air from outside.

The cell has a theoretical energy capacity of 27 kilowatt hours per litre, compared to 9.7 kilowatt hours per litre for gasoline. Both approaches, however, are limited by practical factors to smaller figures.

Licht believes that his approach may make for a practical energy capacity of about five kilowatt hours per litre.

"But that's two-fold higher than the practical storage capacity of gasoline," New Scientist magazine quoted him as saying.

A research article on the new approach has been published in the journal Chemical Communications.