Scientists at the University of Cambridge have reported that they have made a significant advance in the practical development of a lithium-air battery – regarded by many as the “ultimate” battery.

The scientists have overcome several of the problems holding back the development of these devices in building a working laboratory demonstrator of a lithium-air battery which has very high energy density, is more than 90% efficient, and, to date, can be recharged more than 2000 times.

Lithium-air (or “lithium-oxygen”) batteries have been described as the “ultimate” battery because of their theoretical energy density, which is ten times that of a lithium-ion battery. Such a high energy density is comparable to that of gasoline – and would enable an electric car with a battery that is a fifth the cost and a fifth the weight of those currently on the market to drive about 650 kilometres on a single charge.

In a conventional lithium-air battery, the cell generates electricity by combining lithium with oxygen from the air to form lithium peroxide; it is recharged by applying a current to reverse the reaction. The difficulty has been making these reactions take place reliably over many cycles.

The Cambridge scientists have achieved this by converting lithium peroxide to lithium hydroxide, which is much easier to work with, adding lithium iodide to the system and making a very porous “fluffy” electrode from graphene.

The scientists are working with a number of companies to commercialise the technology but expect that it will be a decade before it is widely available.