Electric Cars: Worth the Charge?

We’re shooting off to Mars, because there’s news out this week that the red planet is seismically active and it experiences marsquakes. Katie Haylor has this report...

Katie - NASA's insight mission is tasked with finding out what's going on inside the red planet. In November 2018 the static lander arrived on the surface, and got to work. Now, the publication of several papers worth of data are revealing its findings so far, and the Open University's planetary geoscientist David Rothery gave me the lowdown.

David - Well, in 10 months there have been not far short of 200 separate Marsquakes, and most of them are small events and they appear to be vibrations that travel just through the crust, that's the outermost rocky layer of the planet. And they're not very well understood. But there have been 24 recorded that measure magnitude 3 to magnitude 4 on the Richter scale, which have caused vibrations, which had been strong enough to travel through the crust into the mantle and then back out of the surface where the detector is.

Katie - These Marsquakes are detected by Insights' seismometer sitting on Mars' surface: it is essentially a very sensitive microphone that records the planet's vibrations.

David - They can pinpoint the source of some of these earthquakes. At least two of these appear to be in a region about a thousand kilometres from the Lambda Kerberos fault side. This is where the surface is quite badly fractured, some quite deep chasms there, where people had previously suggested there were earthquakes. So you can see where boulders have tumbled down slopes and bounced through recent sand dunes. So something recently disturbing the ground. Could that be earthquakes? Well now it seems that inference was right because Marsquakes have been pinpointed back to that very region.

Katie - So what's actually causing these Marsquakes?

David - Well, these Marsquakes are not like the big earthquakes we get on the earth, which are at the boundaries between moving plates. Mars's crust and upper mantle is not divided into rigid plates sliding around on a plastic interior like we have on the earth. The quakes on Mars are like what happens inside Earth's continents where stresses just cause some fracturing or some buckling or something like that. So they're relatively small. They're like the biggest quakes that we occasionally get in the UK. But Mars's crust, a rigid outer layer, is under stress, and now and then the stress overcomes the strength of the rock and the rock fractures. And that's a Marsquake.

Katie - Now that we know for sure that Mars is indeed quaking. How does this help us better understand the geology of our planetary neighbour?

David - We'd like a few more quakes before we extrapolate too wildly. But we do know, number one: Mars is active today. Quakes are definitely happening. Previously we inferred them, now we've seen them. It's likely that part of the mantle is mushy because the shaking wave, so-called S waves, do not travel very well at all through part of a mantle. Whereas the compressional waves do travel quite well. So we're beginning to understand the mechanics of inside Mars.

Katie - Looking ahead, could these findings have any impact on, perhaps one day, a base on Mars?

David - What we're learning about the properties of the shallow crust will help because we want to know what we're building on. But some people have been saying on social media: "Oh there are Marsquakes, it's too dangerous to go and put bases there". That's completely untrue. You wouldn't refuse to build a base in the UK because there's occasionally a magnitude 3 earthquake here, or in the middle of Siberia because there's a magnitude 3 earthquake every so often. Mars is perfectly safe seismically. You wouldn't build a base in the bottom of one of the chasms on Kerberos Fossi, because you've got a great big cliff above you and a boulder could fall off if dislodged by a Marsquake. That's common sense. We're not learning from this that we shouldn't go to Mars because Marsquakes occur. We're understanding about the interior of the planet from what Marsquakes can tell us.

We were saddened to hear of the recent death of NASA’s mathematical legend, Katherine Johnson. It was her calculations that got men to the moon, and safely home again. Indeed, some astronauts refused to fly unless she’d personally looked at the figures. Adam Murphy has been reflecting on her contribution to the space race…

Adam - Katherine Johnson, legendary NASA mathematician, passed away on February 24th at the age of 101. Johnson was renowned for her mathematical abilities. She began work at NASA’s predecessor, the National Advisory Committee for Aeronautics, where she was a human computer, reading the black box data from aeroplanes. She spent her time there segregated by both her race, and her gender. Eventually, it was impossible to ignore her mathematical skill and she began assisting with NASA spaceflights, although she still faced pervasive discrimination. She calculated the trajectories rockets needed to be launched at, and even the times at which it was possible to launch them at all. Overcoming the barriers faced by black women in the sciences, Johnson’s work is part of so many iconic moments in NASA’s history. Johnson calculated the trajectory for the rocket, and the launch window for Alan Sheppard’s 1961 mission that made him the first American in space. When electronic computers began to be used at NASA, astronaut John Glenn refused to accept the figures until they had been checked by Johnson, stating “If she says the numbers are good, I’m ready to go”. Johnson was involved in the first mission that put men on the moon, helping to calculate their launch trajectory. And when Apollo 13 announced that “Houston, we have a problem”, Johnson’s work on backup procedures helped to get them home safely. Johnson’s contributions to the history of space travel went relatively unrecognised for decades, but in 2015 she was awarded the Presidential Medal of Freedom by Barack Obama, the highest civilian honour the United States gives. And she and her colleagues were also the focus of the 2016 film Hidden Figures. A fitting honour for someone who’s work has impacted so much of modern science.

What’s actually powering the average electric car? Chemist David Hall works on battery technology at the University of Cambridge, and Chris Smith and Katie Haylor asked him for the lowdown on batteries...

David - Every battery, whether it's a lead acid in your petroleum based vehicle, whether it's a watch battery, or your cell phone's lithium-ion battery, it always has two electrodes. They're solid pieces of material, and they're separated by an electrolyte that's made up of a salt and some sort of a solvent. So lead-acid uses acid dissolved in water. Lithium-ion uses a lithium salt dissolved in an organic solvent, which is carbon based.

Chris - How does it actually make electricity?

David - Batteries use the principle of electrochemistry, where we can convert between chemical energy, and electricity. And we do this by passing current through a wire outside, and then there's a current inside the battery that flows through that electrolyte. That's the movement of those charged particles in the salt.

Chris - So when a battery is charged up versus discharged, what's the chemical difference?

David - So in the case of a lithium-ion battery, basically we take lithium from one material on the positive, and we move it into the layers of the material on the negative side. And that's a very unstable, high energy arrangement, and it wants to get back to how it was before.

Chris - When it's in that unstable state, it's charged?

David - Exactly.

Chris - And when it flows sort of, down the energy hill as it were, to get back to the other material where it's more comfortable, it's discharged?

David - Correct. Exactly.

Chris - So that's why it wants to push electricity around the circuit, because to make that journey, the lithium has got to surrender some charge around the circuit first?

David - Exactly. And it's a much more controlled way to release energy than say, burning fuel, which just releases heat uncontrollably basically.

Chris - And the cars that are being put on the roads that are electric vehicles, do they just use the same technology, the same lithium batteries effectively, that are in my mobile phone?

David - They're very similar in many ways. What's different is the exact components or composition of those materials, especially the positive electrode material. So a lot of phones will have cobalt, whereas modern batteries will have cobalt, nickel, manganese, aluminium in some combination.

Katie - David talking of phones, my mobile phone battery is, ugh, it's really in need of replacement. Why do batteries degrade over time?

David - As you're using your battery, ideally all of these changes, moving lithium from one side to the other is completely reversible, but unfortunately there are these side reactions. You can think of it like how your car rusts with time. It just slowly degrades those materials, and they break down. And you also slowly degrade that organic solvent that I mentioned, releasing gases and oxygen and that sort of thing.

Katie - Can you then tweak the chemistry to try and fix that problem?

David - Absolutely, and this is a huge area of research in the UK and around the world, to understand what exactly is causing those different degradation, parasitic reactions. How can you slow them, or control them, or even just predict them reliably.

Katie - What about habits though? Bad charging habits for batteries. I'm thinking of phones, but I guess with electric cars it must be a similar sort of thing, right?

David - Certainly for phones and laptops, the best thing you can do is make sure they don't get too hot. So don't leave it running full power in your shag carpeting, where it gets really, really hot. Heat is the main thing.

Chris - The guy who invented lithium batteries got the Nobel prize, didn't he? Why are we still married to lithium though, David? Why have we not found an even better chemical or a better way of doing this? Because people say to me, although lithium batteries have made a sort of revolution in storable energy, they're still not without their constraints. As Katie says, her phones clapping out, my laptop will only run for 10 minutes now compared to what used to be five hours.

David - The main concept of lithium ion batteries really hasn't changed. Take lithium out of one side, put it into the negative electrode on the other, but those materials are significantly different than the original ones that got that prize. So modern battery chemistry is actually very different, and you can hold something like two or three times as much energy in the same space. So there is a lot of progress, even within lithium-ion.

Katie - We mentioned charging habits. I'm just curious if you have any advice for charging habits when it comes to an electric vehicle, in terms of the battery?

David - that's a huge area of research as well, that I've spent many years thinking about, especially how can I charge a vehicle very quickly. And usually the faster you charge it, the more damaging and more destructive it is on it. So you try to make things more conductive, so that ions and electricity can flow more quickly and more easily. And that's really a design aspect for where we think these vehicles will be used, how we think they'll be used.

Chris - So it's just a question really then, of not abusing your battery. Is there technology built into batteries to stop us abusing them?

David - Absolutely, and it's a huge area in engineering to build what we call battery management systems, that regulate the temperature, that try not to pass too much current into one battery too quickly. It's another area of development that the auto makers are really getting better at.

A lot of electric cars have “zero emissions” emblazoned on the side. But they’re only as green as the energy used to charge them. Renewable energy is becoming more available, but not necessarily “on tap” 24/7. For instance, the sun doesn’t shine at night! Kathryn Toghill, from the University of Lancaster, works on one potential solution to this problem, as she explained to Chris Smith and Katie Haylor...

Kathryn - Renewable electricity has been penetrating the market at a significant rate over the last few years. We use a third of it, it's this intermittent energy. So we need some kind of mediator between the energy generation and the use on the grid to actually balance that out. And that's where these batteries come in.

Chris - Is it as simple as the kinds of batteries one puts in a torch, you just have loads and loads of those, and you put them near your wind farm or you put them near your solar array, or even in your house, and you just basically use them like an energy sponge, they soak up any surplus when you don't need it? Is that basically the concept?

Kathryn - That is basically the concept, yes.

Chris - So what's not to like?

Kathryn - The cost of the system is the issue. So the problem with the batteries we've made for these portable technologies like for electric vehicles or for your phone, anything like that, is that they're designed for high power, high usage, they're designed to be lightweight, they're designed for a completely different profile of energy use. Whereas these stationary energy systems, they need to take on large amounts of energy, they need to scale up on a considerably higher scale than your portable systems, and they need to deliver that energy in a smoother way as well.

Chris - I suppose that a weight, when you're talking about a stationary battery that's just parked on a site or even in your utility room, is less of an issue than it is for an electric vehicle where the battery's got to be a certain weight, a minimum, and presumably also got to fit certain specifications because it's got to be a certain size and fit into a certain space in the car. You're less constrained with a domestic or a wind farm system.

Kathryn - Absolutely. Yes, so you've now got a completely different area of chemistry to be exploring because you're not so constrained anymore. The other issue is that what we really want from a stationary storage system is something that has longevity. So now lifetime really matters and the depth of your cycling really matters. So whereas earlier you were talking about your batteries dying very quickly in your phone or in your laptop - we can't have that happening in stationary storage. So that's where the alternatives to what we already have are coming in. That's where new chemistry is being designed.

Chris - Now when you say new chemistry; in other words, we're not just going to take the batteries that work in an electric car and just basically repackage them for domestic use? You could do that, but actually you're saying you could do it better.

Kathryn - Yeah, there'd be no advantage to that. First of all there's going to be high demand for lithium ion, so lithium is not that sustainable if every kind of technology is going to be using it; so where we can switch to a different chemistry, that's a better idea generally. The alternative chemistries we can be using will have a different design entirely as well. So we don't need that high power, we don't need that fast charge capability, so we can start looking at things like flow batteries where you're working with completely different metals and a completely different system design as well.

Chris - So what's a flow battery then?

Kathryn - So a redox flow battery is where all your charge goes into the solution; so where we talked about electrodes and then an electrolyte in between them earlier in normal batteries, your electrodes are what matter and that's where all the charge is kept; but in a flow battery it's all kept in the electrolytes. So you have these chemicals in solution that can take on charge and they can give back charge depending on which way you want your flow to go in your battery. And then you store these solutions in big tanks so they're separate from the electrodes. And that means you can scale up your tanks depending on how much storage you need, or you can scale up the number of electrodes in the middle depending on how much power you need.

Katie - Kathryn, you mentioned that the electrolyte is the important thing here. So what's novel in this area then?

Kathryn - What we use here that's the state of the art is vanadium. So vanadium ions in solution, nothing is solid in there. They are charging and discharging, different states, depending on what you need. But also we are moving away from metal-centred flow batteries as well. So we're trying to look at technologies where we don't have metals in there at all bcause they have two political issues associated with them.

Chris - Kathryn, if I may: if you've got a battery system that's built around a liquid, you're saying the electrolyte is the charged thing and the electrodes are less important, that sounds to me very much like the petrol that we put in a car tank. So have we not got a really nice solution here which uses much of the infrastructure we already have for dispensing an energy-rich fuel into a car? You could just fill up your car battery with a charged electrolyte, and then when the charge has been used up you drain that depleted electrolyte out and replace it with some replete, charged electrolyte again.

Kathryn - It is not a crazy idea actually. But unfortunately vanadium flow batteries and most flow batteries, the energy density is too low. So you're looking at something that's ten times less dense in energy than a lithium ion battery. So it wouldn't be feasible because petrol has a very high energy density, even though the system is quite inefficient. But there are people researching... so up in Glasgow, for example, there are people who have been researching these new materials which would deliver very high energy density# liquid electrolytes. So that could be an option in the future. But it's quite far away at the moment.

Chris - And what about price, Kathryn? Because I've been talking to some people who live in, for instance, remote parts of Australia. They're very reliant on solar, for example. And so for them, the ability to store a lot of charge in a decent battery, it can be a life-changing thing. But how much does it cost to install a rig for say a domestic setup?

Kathryn - It depends on the rig you have, but you're looking at installing it coupled with solar, that would influence the cost as well. And then you've got your battery management system. So there's lots of different components, it's not all dependent on the battery itself. But you're looking at tens of thousands of pounds for a home storage system.

Chris - Pretty pricey then.

Kathryn - But it's equivalent to an electric vehicle.

Chris - But then I suppose if you've got the electric car parked in the garage and the stationary battery in the utility room, are we getting to the point where everyone's basically got their own power station at home? Is this not overkill?

Kathryn - I don't... I personally wouldn't want to cycle my car battery because that battery is not designed to do many cycles. I would want that load of a long lifetime for a home battery storage system to be on something that's designed for that purpose.

How can the batteries inside electric cars be recycled, once they reach end of life? We need to plan for this, because the industry will struggle to continue to source the materials needed to make new cars and batteries if we haven’t got a way to supplement supplies of raw materials. Megan McGregor spoke to Birmingham University’s Gavin Harper about the way forward...

Gavin - If you take a battery and you were able to slice it apart very carefully without contaminating the materials in the battery, and if you were able to scrape off the cathode material from the electrode, and then you might apply some processes to improve its quality, and then coat that material straight into a new battery, that is direct recycling. And the benefit of that process is that it's not just about recovering the raw materials that go into the battery, it's also about preserving the structure in the cathode materials. And obviously a lot of energy, a lot of effort, goes into creating that structure of the cathode material.

Megan - It seems to me to assume that the battery chemistry will stay fairly constant. Are the recycling possibilities if down the line the battery chemistry changes? So for example, the amount of a material that's required goes up or down?

Gavin - I think the main challenge at the moment is around cobalt. Batteries with high cobalt content are very energy dense, which is good from the perspective that it gives the electric vehicles a really good range. The challenges around sourcing cobalt mean that there's a real push to try and reduce its use in electric vehicle batteries. Cobalt largely comes from the Democratic Republic of Congo. The conditions in which it's mined would cause a lot of concern. Children that are working in mining and the sort of unregulated industry that runs alongside of the sort of mainstream mining industry. There's work that's ongoing at the moment to look at, first of all, if you've got for example, a range of different cobalt chemistries and you've mixed everything together, how can you segregate those different cathode materials in a direct recycling process? So that is step one. And then secondly, there's work ongoing to look at if you've got chemistry of one cobalt formulation, can you reformulate that into a different battery chemistry by adjusting the mix? And I think they're both really interesting avenues of exploration for direct recycling.

Megan - And is it possible in future that if we manage to reduce the cobalt concentration in future batteries, that it may become desirable to recycle the batteries of today more immediately, because of their high cobalt concentrations?

Gavin - Yeah. So I think there's a real tension between recycling and reuse. And if we think about how the market for recycled batteries might operate, if a battery comes out of a car and it's still got useful life in it, then that has an economic value. And so our normal approach would be to reuse that battery and extract the most life out of it, you know, squeeze the pips out of it as it were. However, you could imagine a situation in the future where the supply of cobalt was constrained, either because of the supply chain or processing capability or the mining. And in that situation it might be advantageous to recycle batteries early that are of a high cobalt chemistry. If you had a technique whereby you could produce more batteries with a lower cobalt chemistry from the same resource, I think you can look at what's optimum from a resource allocation and resource efficiency angle. But then that's obviously going to run into the buffer of real world economics.