I expect that at this time of year you might normally be about to fly somewhere. Although the pandemic has grounded most flights, and the climate change concerns of the flygskam movement haven’t gone away, eventually many people will want to resume flying.
When they do, it won’t be on a green plane, which are still many decades off. That hasn’t stopped political attention turning to them, with the UK government last month holding the first meeting of its “jet zero council”, which aspires to make long-haul, net-zero-emission flights a reality.
Whether that is made possible with hydrogen, biofuel or batteries is an open question. This week’s Fix the Planet focuses on an emerging battery technology that is lightweight and so is a natural candidate for anything airborne. You know about the lithium-ion batteries in your phone – read on to learn how lithium-sulphur ones may change our world.
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This two-seater plane could soon come in an electric version with lithium-sulphur batteries. Photo: OXIS
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What’s wrong with the current batteries we’re all using?
Today, lithium-ion is the dominant battery technology for everything from phones and cars to electricity grid-scale storage. It is mature, safe and relatively cheap because of mass manufacturing, largely in Asia. But there are some next-generation battery technologies with properties that may make them better for certain applications. “We think that across the different metrics, cost, energy and power density, safety and operating temperature, there are exciting opportunities for battery chemistries beyond lithium-ion,” says Paul Shearing at University College London (UCL), who is working with the UK-based Faraday Institute to advance some of those alternatives.
OK, what’s so special about lithium-sulphur?
The key material, sulphur, is ubiquitous across Earth, cheap and relatively benign in its environmental impact, says Shearing. The big attraction is that it is lighter weight. The batteries can store more energy per unit weight, known as gravimetric energy density. Another attraction lies in how they can be transported around without any charge. Lithium-ion batteries need to be shipped with around 30 per cent charge, because if they are discharged to 0 volts a reaction can occur between the electrode and current collectors. That doesn’t happen in lithium-sulphur ones because of the different materials involved, meaning battery shipping protocols don’t apply. “That translates to being able to ship them by aviation. Effectively, you have a bag of chemicals rather than a live battery, which has a huge impact in terms of cost and ease of shipping,” says James Robinson at UCL. The batteries can also operate at a wider range of temperatures.
Where are we likely to see these batteries used first?
While strong on gravimetric energy density, lithium-sulphur isn’t so hot on volumetric energy density – how much energy a battery stores in comparison to its volume. That larger size means cars are probably out in the short term because current lithium-ion batteries win on volumetric energy density of around 600-700 watt hours per litre (the hope is lithium-sulphur will get to 500). “In order to be successful in early market applications, lithium-sulphur is addressing things that can benefit from being intrinsically lightweight. That’s probably things that fly. Things that need to be carried around, things like on-person power that might be important for military applications,” says Shearing. There might be uses in trucks and buses where the weight of lithium-ion batteries makes them limiting. Drones and high-altitude satellites are also likely candidates for early use of the technology.
Why aren’t we all using them yet?
There are several technical challenges, including how the metal lithium anode degrades over time. That means work needs to be done on improving the number of cycles the batteries can be charged and used for – the Faraday Institute’s LiSTAR project is targeting about 500 cycles. Shearing thinks that is enough to target some early uses and says in some cases, such as defence uses, it might be possible to get away with much less. And then there is the old bugbear of any new technology: cost. “Because of the enormous economies of scale within the lithium-ion industry, we have our work cut out to develop a cost-competitive technology,” says Shearing. Lithium costs around £100 per kilowatt hour today, but the equivalent for lithium-sulphur is closer to about £200 per kWh.
But progress is being made, right?
The LiSTAR project is a big effort in the UK to make the batteries ready for commercial use. Robinson says that although Asia is a manufacturing hub for lithium-ion, the UK’s skills and companies make it well-placed to be the equivalent for lithium-sulphur. Shearing thinks the cost could eventually be brought down to about £50 per kWh. “I think we can quickly see there is a compelling opportunity,” he says. There are also factories being built and deals being struck. UK firm OXIS Energy is building a lithium-sulphur battery factory in Brazil that should be ready in 2023, and the company has agreed deals to develop a two-seater electric plane and electric buses.
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1.
Changing the materials we use to make solar panels could reduce the time they take to pay back the carbon emissions linked to their manufacturing, new research in the journal Science Advances finds. My colleague Donna Lu has the lowdown.
2.
The pandemic continues to shake up big oil. On 4 August, BP said that by 2030 it will increase its investments in low-carbon technologies tenfold and reduce oil production by 40 per cent. The day before, its peer Shell bought an Australia “ carbon farming” company, Select Carbon, as it diversifies away from fossil fuels.
3.
Stopping a single abandoned road in the Amazon being reopened would avoid a huge amount of carbon being released through deforestation, according to a letter in the journal Science. Allowing highway BR-319 to reopen “will likely accelerate anthropogenic climate change”, write Lucas Ferrante and Philip Martin Fearnside at the National Institute for Research in Amazonia.
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Thanks for reading. I’m off on holiday myself today for a fortnight – by road, not plane – so my next dispatch will be at the start of September. Let me know what you want to read about!
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