Cambridge chemists make super-battery breakthrough
Clive Cookson, Science Editor
A breakthrough in electrochemistry at Cambridge university could lead the way to rechargeable super-batteries that pack five times more energy into a given space than today’s best batteries, greatly extending the range of electric vehicles and potentially transforming the economics of electricity storage.
Chemistry professor Clare Grey and her team have overcome technical challenges in the development of lithium-air batteries — the only cells theoretically capable of giving electric cars the range of petrol and diesel vehicles without having to carry excessively bulky and heavy battery packs.
If the technology can be turned from a laboratory demonstrator into a commercial product, it will enable a car to drive from London to Edinburgh on a single charge, with batteries that cost and weigh one-fifth of the lithium-ion cells that power today’s electric cars.
“What we’ve achieved is a significant advance for this technology and suggests whole new areas for research,” said Prof Grey. “We haven’t solved all the problems inherent to this chemistry but our results do show routes forward.”
Researchers around the world are working to make lithium-air batteries viable because they theoretically can store 10 times more energy than rechargeable lithium-ion batteries, which dominate the market.
A research paper published in the journal Science shows that the Cambridge group has overcome some of the practical problems of the technology, particularly the chemical instability that led to a rapid fall-off in performance of the lithium-air cells demonstrated previously.
The basic chemistry of lithium-air batteries is simple. The cell generates electricity by combining lithium with oxygen to form lithium peroxide and is then recharged by applying a current to reverse the reaction. Making these reactions take place reliably over many cycles is the challenge.
The Cambridge scientists adjusted the chemistry to make it more controllable. For example, they converted lithium peroxide to lithium hydroxide (a compound that is easier to work with), they added lithium iodide to the system and they made a very porous “fluffy” electrode from graphene, a form of carbon discovered 12 years ago at Manchester university.
The system demonstrated in the Cambridge lab is 90 per cent efficient, say the researchers, and it can be recharged 2,000 times. But they say at least another decade of work is likely to be required to turn it into a commercial battery for cars and for grid storage — storing the intermittent output of solar and wind generators for use when needed.
The Cambridge research has been funded by the UK Engineering and Physical Sciences Research Council, the US Department of Energy and the EU, with support from Johnson Matthey, the UK advanced materials company.
“We have patented the technology and the intellectual property is owned by Cambridge Enterprise, the university’s commercialisation arm,” said Prof Grey. “We are working with a number of companies to take it forward.”
Clare Grey returned to the UK in 2009 after almost 20 years in the US, mainly at Stony Brook University in New York, to take on one of the country’s top academic science posts: professor and head of inorganic chemistry at Cambridge.
“My family is here and it was an opportunity to set up a research group at the leading British university in my subject,” says Professor Grey, who had been an undergraduate and DPhil student at Oxford in the 1980s. “Stony Brook is a good state university but it is not Cambridge.”
She has built up a 35-strong team at Cambridge, the Grey Group, carrying out research in materials chemistry with a focus on battery technology. They are a diverse group, she says, with researchers from Britain and many other countries.
“We are interested in new methods of understanding what is going on inside batteries and using that fundamental science to improve the system,” she says.
Prof Grey’s own scientific reputation was build on using the analytical technique of nuclear magnetic resonance to investigate chemical structures and reactions, though her interests are much broader now. “I have become interested in the whole energy landscape,” she says.
The lab is working on a wide range of battery technologies. Although lithium-air is a particularly attractive option, because it can pack so much energy into a small cell, she expects the future to feature a diversity of battery types. “I think lithium-air will play a role when fast charging is not essential but others will feature too.”
● Clare Grey has been the Geoffrey Moorhouse Gibson professor in the department of chemistry at Cambridge university since July 2009.
● Her research specialises in applications to material of nuclear magnetic resonance, particularly in rechargeable lithium-ion batteries.
● She graduated with a BA in chemistry — with first class honours — from Oxford university in 1987, and completed her PhD in chemistry there in 1991.
● Her thesis title? A 119Sn and 89Y MAS NMR study of Rare-Earth Pyrochlores.
● She was elected Fellow of the Royal Society in 2011 and won the society’s Davy Prize in 2014 and its Kavli Medal in 2011.