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FEATURE: The race to make EV batteries better

Rich McEachran

(Credit: iStock)
(Credit: iStock)

The UK is phasing out new combustion engines by 2030, but the switch to electric vehicles is going to require battery innovation to improve the consumer charging experience.

As part of the UK government’s ambitious bid to reach net zero by 2050, it’s targeting a ban on sales of new petrol and diesel cars from 2030. But the current state of the charging infrastructure and experience could put the brakes on the electric vehicle (EV) transition. 
Following a freedom of information request submitted by DevicePilot, a service monitoring and management platform for EV charge-point operators, it was revealed that, although 2022 should be a record-breaking year for EV infrastructure investment in the UK, the roll-out of charging points leaves much to be desired.

Fifty-two per cent of councils didn’t spend a single penny on EV charging points in the 12 months before the freedom of information request. And 60% of councils received complaints about the availability and reliability of existing charging points over the same period. And 46% of councils admitted that they didn’t know how many charging points would be installed in 2022.

According to the data, on 9 March 2022, there were 18,693 points installed across the UK with the number of devices at these stations totalling 29,820 and a total of 50,261 connectors. 

While Zap-Map points out that the number of charging points has been growing rapidly over the past few years, much more will need to be done. And it’s not just a case of the UK installing thousands more charging stations. 

According to a study from the University of California published in the journal Nature Energy in May 2021, 18% of EV owners surveyed between 2015 and 2019 had switched back to traditional combustion engines simply because of a poor charging experience. 
Improving infrastructure needs to go hand-in-hand with improvements in EV technology. 
So what might help the UK achieve its electric dream?

The speed challenge

Data from Zap-Map showed that the UK had 16,775 fast chargers and 7,609 slow chargers as of 9 March. The rest of the 29,820 devices were rapid and ultra-rapid chargers.
It’s the slow ones that are arguably the more critical of the two. These can be installed in home owners’ drives and the chargers are left plugged in for long periods – a typical EV battery of 60kWh takes just under eight hours to charge when using a 7kW home charging point. Slow chargers put less demand on the grid, resulting in grid stabilisation. They are also installed on streets, but digging up pavements can be inconvenient and, with parking spaces being like gold dust in some cities, there’s reluctance among councils to invest in EV chargers and take parking spaces away from non-EV drivers.

Nonetheless, fast chargers are still important, as EV drivers rely on them when on long journeys. These are the ones you find at service stations and supermarkets. Some sites will need to invest in new connectors to support high-speed charging, and costs can end up running into millions of pounds, which can discourage investment. 

Fast chargers also present a big logistical challenge. Drivers are used to pulling into a petrol station, filling up an empty tank in a matter of minutes and going around 400 miles before needing to refill. But a charge of 30 minutes using fast chargers – typically 50kW – will only provide a driving range of around 87 miles. This isn’t conducive to travelling long distances. 
Having to stop more often to charge the battery means more charge-discharge cycles and this will degrade the battery more quickly, decreasing its life cycle. A bit like how continually charging your smartphone and then draining it isn’t good for the lifespan of the battery.
For an EV to have a longer range, though, a battery needs to be larger and the electrode material needs to be considerably thicker, so the longer it takes to charge, says Neil Dasgupta, an associate professor of mechanical engineering at the University of Michigan. “The thicker the battery, the harder it is to charge because lithium ions are forced to travel deeper inside the material,” he adds.

At the eponymous Dasgupta Research Group, Dasgupta and a team of researchers have found a way to potentially address the trade-off between charging time and driving range by using laser manufacturing techniques to drill holes into the graphite anodes (negative electrodes) of EV batteries. “This essentially creates a highway, which allows lithium ions to get inside thicker electrodes more quickly,” explains Dasgupta. 

The results? They showed that a laser patterning process can be used to fully charge batteries in 10 minutes, according to Dasgupta. Whereas using conventional fast methods to charge an EV battery in 10 minutes degrades it so much that it might only last for 50 cycles, the Dasgupta Research Group concluded that the laser patterning process has the potential to improve an EV battery’s capacity retention. 

If the industry can commercialise efficient fast charging of EV batteries, then it should be a game-changer as it’ll improve the charging experience. Drivers will then be less likely to switch back to traditional combustion engine vehicles. The ultimate aim is to be able to charge a car as quickly as filling up a tank. 

Better batteries 

Consumer adoption of EVs will likely remain low, however, until the purchase cost can be brought down. A survey of 3,400 UK consumers carried out by Impact Utilities found that 48% were put off buying an EV as their next car because of the cost. 
One way to drive down costs and boost public acceptance is by making EV batteries more sustainable and cutting the use of cobalt and nickel. 

Peter Baker is an instrument scientist at ISIS Neutron and Muon Source. He’s also co-investigator of the FutureCat Project at the UK’s flagship battery research programme, the Faraday Institution – the project is focused on improving cathode design so that batteries can hold charge for longer.

Baker uses muons to analyse the atomic structure of materials. Research by the FutureCat project points towards sodium-ion batteries as being potentially cheaper alternatives to lithium-ion ones. They would also eliminate the ethical and environmental quandary of mining lithium, cobalt and nickel, as these metals aren’t required. 

Yet, it’s likely to be some years before sodium-ion batteries are packed into cars. While they perform better over time, sodium ions are significantly larger than lithium ions – around three times the mass – so a sodium-ion battery is heavier than a lithium-ion battery. This would inhibit uptake by EV manufacturers, who want to keep their vehicles as light as possible to maximise the range. Sodium-ion batteries also have a lower energy density. In lithium-ion batteries, it’s cobalt that helps to stabilise the structure and allows for the high energy density. 

The solution for now is likely to be battery packs that combine both lithium-ion and sodium-ion cells. Chinese battery manufacturer CATL unveiled just this last July and claimed it charges more quickly than a conventional lithium-ion battery and also boasts greater thermal stability. 

More research is needed into battery chemistries to develop alternatives to traditional materials without sacrificing energy density and to improve an EV’s range, stresses Baker. There’s also the issue of addressing concerns relating to charging. Thirty-four per cent of the 3,400 UK consumers surveyed said that how far they travel on a charge had stopped them from purchasing an EV.  

“EVs work most effectively when they’re not charged regularly,” says Baker. “But the public expectation is still set by combustion engine vehicles, which only need refuelling once the tank is empty. EV batteries need to improve to meet this expectation.”

The main advantage of advances in battery chemistries would be that, if EV batteries can hold their charge for longer, then drivers will obviously be able to go further without needing to charge their vehicle as often and this would reduce the pressure on the infrastructure. “Better batteries won’t eliminate the need for EV charging stations in the future, but they may limit the number of stations needed and ensure they’re better utilised,” says Baker. 

“People are always likely to be travelling away from home, while there are plenty of people who won’t be able to charge at home because of where they live – or at least that won’t be a cheap option for them,” he adds. While improvements in battery charging and technology should help to drive the adoption of EVs, any innovation will still need to keep in mind the needs of the grid.  

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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.

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