Behind the scenes of Britain's battery revolution

“When you go to buy an electric car, the battery is the component that controls almost everything you care about. It’s half the build cost. Its capacity governs the driving range. The car’s packaging – whether it can carry five people and luggage – depends absolutely on the 800kg lump down below. The performance, ride and handling are all down to weight and weight distribution. Same with stuff like styling and seating position. In truth, the battery is the pacing item for the whole electric transport industry.”

Not that this is new. Electric cars have been around for more than a century, Greenwood reminds me. In 1910 they were more popular than petrol cars but the 1920s emergence of Shell (which helped create a fuel standard and an infrastructure) and Ricardo (which helped refine the combustion process) led to the supremacy of liquid-fuelled cars. 

This era might have lasted longer but for the rising awareness of CO2 and its greenhouse effects, fast-rising concerns about air quality, the fears of non-oil nations about energy security and, of course, Dieselgate. Greenwood is interesting on these subjects – “The ‘ban all diesels’ conclusion is an oversimplification,” he says – but in the end he sees their effects as the drivers that make his own work so urgent and important. 

Two distinct kinds of batteries have emerged, he explains. The type used in Nissan Leaf-type models stores a lot of energy to give a long range but charges and discharges relatively slowly. Then there’s the higher-power type, usually smaller and better suited to a Toyota Prius-style hybrid, which discharges more quickly for short-term acceleration and accepts charge more easily from regenerative braking. Both types have made huge progress in the past few years. 

Just eight years ago, Greenwood explains, an average electric car’s battery cost around £780/kilowatt hour (kWh). Nowadays the figure is around £155/kWh, which means the cost has fallen four-fifths. At the same time that battery’s energy density has doubled. 

“If I’d built you an electric car in 2010 and replaced it with one using today’s technology, you could expect it to go twice as far with a battery costing a fifth as much,” he says. 

“This incredible progress, in a nutshell, has made electric cars into the viable products they were not just eight years ago.” 

Unfortunately the meteoric rate of progress is unlikely to continue, he says. The quick wins have come from improved cell packaging, manufacturing economies and reductions in materials costs. The next steps will have to be delivered by innovation. 

Fortunately, Britain has bodies like the WMG enterprise and the government-academia-industry Faraday Foundation, a 10-year co-operative set up last year and in which Greenwood is also heavily involved, to pick up the baton. Faraday is backed initially by £237 million from the government and is already investigating highly promising solid-state and lithium anode battery technology. Studies are looking at how batteries degrade in use, boosting computer modelling as an aid to battery development and improving recycling techniques. Participants are determined to avoid what happened with nickel-metal hydride battery technology, which was discovered in Oxford but sold in difficult economic times to a Japanese developer that made billions. 

To answer everybody’s burning question – how quickly will batteries develop from here on? – Greenwood quotes from the Advanced Propulsion Centre’s electric energy road map. On a 10 to 20-year cycle we can expect costs to halve again and energy density to double. But the biggest progress is predicted to be on power density, says Greenwood. Today’s average figure of 3kW per kilogram is tipped to quadruple to 12. 

“We see technologies in Formula 1 and other racing that promise such figures,” he reveals. “At present they wouldn’t live long enough for production, but we see ways of fixing that.” 

For the nearer future Greenwood sees lithium ion batteries carrying developments for the next 8-10 years. A cheaper, slightly larger sodium ion technology could also come into play, but if the lithium anode and solid-state technology under development at Faraday comes to fruition, the reward could be a spectacular tenfold improvement in efficiency. Greenwood, ever the modest academic, refers to “an order of magnitude”. 

It’s late. Everyone else left the lab two hours ago but Greenwood’s unquenchable optimism and love of the subject remains. 

“It’s like the Wild West at present,” he says. “Battery progress is where engines were in the 1920s and 1930s. You’re not sure what’ll happen next, but you know it’ll be exciting.”

Who’ll pay to charge electric cars?

An optimist on nearly every aspect of the electric car, Professor Dave Greenwood has concerns about how the economics of car charging will work when electric cars become common. At present, he says, when you pull into a public car park to recharge, the cost of the parking often outweighs the cost of the charge, sometimes by 10 times. 

“Revenue raised by the Treasury on liquid fuels is significant,” says Greenwood, “but it has been falling and will continue to do so. Government will want to do something about that. On top of that, someone, somewhere needs to make a profit out of keeping charging points running otherwise they won’t bother. The problem is in differentiating between household energy and energy for cars. The electron doesn’t know if it’s flowing into a house or a car — you can hardly have red ones and blue ones.” Loading the cost of electricity could create energy poverty in less well-off households, says Greenwood. And loading the cost of old-tech cars to pay for the new ones risks penalising lower-income drivers who are likely to be the owner of older cars.