University of Cambridge scientists have developed a working laboratory demonstrator of a lithium-oxygen battery that has very high energy density (storage capacity per unit volume), is more than 90% efficient, and can be recharged more than 2000 times (so far), showing how several of the problems holding back the development of more powerful batteries could be solved.Lithium-oxygen (lithium-air) batteries have been touted as the “ultimate” battery due to their theoretical energy density, which is ten times higher than a lithium-ion battery. Such a high energy density would be comparable to that of gasoline — allowing for an electric car with a battery that is a fifth the cost and a fifth the weight of those currently on the market and that could drive about 666 km (414 miles) on a single charge.