Microscope image showing charged and discharged graphene electrodes Tao Liu, Clare Grey andGabriella Bocchetti

An efficient lithium-oxygen (Li-O2) battery that can be recharged more than 2,000 times could make truly long-distance electric cars possible for the first time.

Chemical engineers at the University of Cambridge said their 'breathing' battery was the first of its type to last more than a few charge cycles. In previous systems, the lithium reaction with the batteries' electrolyte caused the lithium anode to become clogged and inactive.


The team's innovations, published in Science, resolve that critical flaw; their battery includes a highly porous graphene electrode, made from one-atom-thick sheets of carbon atoms and an electrolyte made from the organic solvent dimethoxyethane, mixed with the salt lithium iodide.

This means that the main byproduct of the battery's reaction is lithium hydroxide, which decomposes easily when the battery is charged, rather than coating the anode.

Lithium-air batteries are regarded as one of the best hopes for long-distance electric cars, due to their great density. Because oxygen is readily available in air, they don't have to carry one of their ingredients around, and lithium itself is a low-density material. This means that a lithium-oxygen battery could store as much energy per kilogram as a petrol engine, allowing an electric car equipped with such a battery to potentially drive for 800km between charges, according to Nature.

We're not quite there yet, however; the Cambridge University team's prototype is merely a laboratory demonstration of the technology, not a ready-for-market battery, and the researchers say that a practical implementation is still a decade away.


However, senior author Professor Clare Grey says that "what we’ve achieved is a significant advance for this technology and suggests whole new areas for research -- we haven’t solved all the problems inherent to this chemistry, but our results do show routes forward towards a practical device".

The porous graphene electrode gives this design comparable efficiency to a lithium-ion battery, and also greatly increases the battery's capacity, albeit only at certain very specific rates of charge and discharge. The demonstrator currentlyu requires pure oxygen, rather than air, and the team has yet to find a way to prevent the electrode from growing lithium dendrites, which can cause short-circuits and even explode the battery.

First author Dr. Tao Liu said that "there’s still a lot of work to do, but what we’ve seen here suggests that there are ways to solve these problems -- maybe we’ve just got to look at things a little differently."