BATTERY T EC H SPECIAL WHAT’ S COMING NEXT
Slow to charge and sometimes dangerous, lithium-ion batteries may not be the best way to power our devices. Nicole Kobie reveals the research that may replace them
Flaming Samsungs aside, most of us lament our batteries for their lifespan and charging time. But what if there was a better way?
Researchers are searching for an alternative to the standard lithiumion, redesigning how batteries work and trying new combinations of chemicals, in the pursuit of a longlasting, fast-charging and safe alternative for smartphones, laptops, electric cars and more.
They’ve come up with a range of ideas, redesigning them from the ground up and substituting new materials. Although chemical challenges and funding complaints mean we’ll likely be stuck with lithium-ion for a while, the future of charging could be just over the horizon. Here’s what researchers are considering – and why.
Problems with batteries
It’s impossible to discuss lithium-ion batteries without acknowledging their apparent propensity to overheat and scorch people – or, in the case of one unlucky Samsung fan, go up in flames and burn their car. Paul Shearing, senior lecturer in chemical engineering at University College London, warned not to get caught up in headlines. While lithium-ion batteries can fail and lead to fires, it isn’t as common as it sounds.
“It’s important to remember the complete ubiquity of lithium-ion batteries across all modern societies, from mobile phones to laptops to satellites to electric vehicles to aeroplanes,” Shearing said. “The chance of failure is really extremely low.” When they do fail, it’s generally due to short circuits in the battery that cause heat and failure within the cell – a process called thermal runaway. Such batteries have safety features to avoid overheating, but manufacturing flaws, corner-cutting, or trying to cram too much battery into a smaller form factor can cause problems.
Another problem with lithium-ion batteries is discharge cycles, which are usually limited to 800, or two years if recharging every day. “The battery is fine for the mobile phone because people tend to upgrade their phones every two years,” said Donald Sadoway, professor of materials chemistry at MIT. “But when it comes to something like automobiles, people are not going to be trading in their automobiles every two years.”
Such batteries have improved over the past decade, but optimisation has remained incremental – leading certain researchers to look not just for tiny improvements, but for the design and materials that will eventually replace lithium-ion.
Possible solutions
Alternatives to lithium-ion need to tick the same boxes, notes Dr Martin Foster, professor of electronic engineering at the University of Sheffield. They need to be better on cost, capacity, charge/discharge rate, size, safety and available capacity. “Most of these can be addressed but only to a certain degree [and] batteries are limited by material fundamentally,” Foster said. “For instance, the lithium-titanate battery we have at Willenhall [an energy storage demonstrator] can be charged/discharged at higher rates than other lithium batteries, but they are more expensive.”
There are a few promising options, however. Shearing’s pick for the best alternative battery design is using solid-state materials instead of liquids, making them safer. Shearing said this involves “replacing some of the fallible liquids that are in the current generation of lithium-ion batteries with folate materials because those are known to be much, much safer”.
Because they’re less of a risk, they’re easier to use in devices without as many safety precautions. Plus, they last longer and are lighter. While Shearing admits they’re currently “precommercial”, Dyson last year bought solid-state battery company Sakti3 for $90 million.
Another way to upgrade batteries is using new materials in place of lithium. Options include sodium-ion, lithium-sulphur, and lithium-air.
Sodium-ion batteries are more likely to find a home in grid storage than consumer devices. They may be cheaper and more stable than lithium versions, but they’re also heavier and have less energy density. Lithiumsulphur has seen investment from carmakers and NASA, which hope to use its increased energy density to power travel, be it down to the shops or far into space.
For our gadgets, researchers are considering air. Last year, University of Cambridge researchers claimed to have boosted energy density by five times using lithium-air versus lithium-ion. Plus, they could be recharged 2,000 times – more than double lithium-ion models. Such results were echoed by an MIT study that used “solid oxygen” cathodes, helping batteries to hold onto energy and capacity for even longer.
Shearing said options such as air and sulphur had “huge promise”, but were, again, “a little way off from commercial reality at the moment”.
MIT’s Sadoway said his eyes are on aluminium to replace lithium-ion because “aluminium is the third-most abundant element in the Earth’s crust,” he explained. “And if we make a battery that’s based on aluminium, it’s going to be cheap.” Researchers at Stanford University unveiled an aluminium-ion version in 2015 that not only charged quickly and withstood 7,500 recharge cycles without capacity loss, but is so safe you can drill through it – making it less risky than lithium-ion and ideal for flexible devices. Similar options include magnesium and iron – anything that’s “abundant and cheap”, Sadoway said.
Beyond material changes, batteries could be completely redesigned – take a look at some of the more unusual ideas on the next page. The wonder material graphene makes an appearance in designs for supercapacitors, an alternative to batteries that store energy electrostatically rather than using chemical reactions, while bio-batteries that use biological structures such as amino acids could provide an alternative infrastructure. Don’t hold your breath, though: much more research is needed.
Why it’s not happening
With all these options available, why are we stuck on lithium-ion? Sadoway pins the stagnation on the battery industry and a lack of funding in innovation, noting that lithium-ion itself didn’t come from that sector, which preferred to stick with its investments in nickel-metal hydride batteries. Instead, it came from Sony, and he sees the same resistance to change now.
“We should be bolder and more imaginative in looking at something beyond lithium-ion,” said Sadoway. “And my fear is that we’re just not doing it.” Instead, manufacturers are focusing on making lithium-ion “incrementally better”. At the same time, the American government has over the past few years slashed research budgets, which remain low aside from life sciences, Sadoway said.
The lack of research funding on new designs or materials means none of the aforementioned options have yet proven to be commercially viable. Sadoway said that could be because they simply don’t work, because we haven’t spent enough money developing them, or because “of the collective IQ problem” – not enough researchers means not enough “intellectual horsepower” to leap the hurdles holding them back.
“The industry is not innovators,” he added. “The industry is focused simply on driving down the costs.” For mobiles and laptops, that’s less of a problem than for electric cars. “If your computer battery dies, you just plug it into the wall,” he said. “But if your car runs out of charge, this is a horrible experience.” In other words, forget the inconvenience of having to carry a power pack to get your older smartphone through the day – much more is being held back by our refusal to upgrade batteries.
Shearing pointed to a laptop that would last a week between charges; a smartphone that lasted for a week; electric vehicles with longer range; or a battery that could charge to full in five minutes. “That would be quite transformative,” he said. “And improvement in batteries will definitely translate into some exciting technology.”