Interview by James Webster for the University of Oxford Science Blog
You specialise in ‘interface science’. For the uninitiated, like myself, what does that mean?
Interface science is hugely important, but at the same time, it’s difficult to understand. When two surfaces meet, it’s where a lot of interesting chemistry happens.
If you think about your material, you have the ‘bulk’ and the ‘surface/interface’. The ‘bulk’ is where we have most of the material, all the atoms in ordered rows. It’s fairly easy to predict how that will behave. When you have two materials interfacing, you have a lot of that bulk on either side. And that gets in the way of trying to measure them.
The problem comes at interfaces where the surface interacts with other things. And that’s where it gets trickier.
For example, my work on batteries. In a lithium ion battery, you have an electrode in contact with liquid electrolyte. The reaction you want to happen is for lithium ions to travel from one electrode to the other. But you also get side reactions, like electrolyte decomposing or your electrode dissolving. These side reactions are why batteries stop holding as much charge. Like you see after about a year of using your phone, the battery just doesn’t go as far as it used to.
We want to be able to measure down to really small levels, like nanometre or even angstrom sensitivity at these interfaces. That means developing special techniques to do that.
And what kind of impacts and innovations can we expect to see coming out of this area?
Look at electric vehicles. People want the same kind of performance from electric cars as with petrol. They want it to last at least 10 years, have similar performance, and comparable cost. Two of the big problems with batteries at the moment is that they’re expensive and their total lifetime isn’t long enough.
If we can take that really close look at what’s going wrong, using some of these new techniques, we can try to find solutions for some of those problems.
What have been some of the milestones of the career that’s brought you to Oxford?
At heart, I’m a problem-solver, that’s why I got into engineering. So solving the problem of longer-lasting batteries, even a bit at a time, is exciting.
I did my PhD and undergraduate degree at Cambridge, in Engineering. I stayed to do a research fellowship, then I went to Berkeley in California for two years on the Marie Curie Fellowship, which was my route into looking at batteries.
To begin with, I was working on electronic devices, but then started to look more at the materials, like graphene.
Over in Berkeley they have a synchrotron facility that allowed for some really high sensitive techniques to look at those materials. A synchrotron is a big donut-shaped building where they spin electrons close to the speed of light to produce x-rays. I’ve spent a lot of my career hanging around different synchrotron facilities.
Basically, you use x-rays to illuminate the material you’re looking at. Then you can see the photoelectrons coming off it, which tells you a lot about its surface chemistry.
Using thin materials, like the graphene I’d been working with, I found a way to use this to look at higher pressure materials. For example, like the liquids you might find in batteries.
After Berkeley I went back to Cambridge and then I moved on to Manchester. For my research there I started working with the diamond synchrotron in Harwell, near Oxford, and that’s part of why I’ve ended up here.
So, you did your undergrad and PhD at Cambridge, you’ve also worked in Berkeley and Manchester, and now you’re at Oxford. How have you found moving between those places?
The US system was very different. Partly because I was going from a university system to a national lab. It was a lot more open, both in discussing ideas and sharing equipment.
Though, on return to the UK, I’ve found universities have moved in the same direction. There’s been a successful push to open things up and make resources more widely available.
Coming from Cambridge, did you get any light-hearted grief from friends for coming to Oxford? And how have you found Oxford, generally?
I did. But I got my just desserts I think, because I did some of that joshing when I was at Cambridge. We had a few people who had come from Oxford, so I was winding them up about that. And then they took it upon themselves to remind me of this when I turned the other way.
A lot of things are superficially very similar between the two, of course. I have to adjust my language, sometimes I’ll find myself in the middle of tutorials talking about ‘supervisions’, so some little things take a while to get used to. But I’m getting there!
They’re both great places to do science, so there have been no major surprises and I’m settling in well.
One of your big projects is the ominously titled ‘What Lies Beneath’ with the Faraday Institution. Tell us about that?
That one has only really just started. The funding came through just before I came to Oxford and we’ve just had our first post-doc start with us about a week ago here. What’s nice is that Oxford has lots of battery research, equipment and colleagues (like Peter Bruce and Mauro Pasta) to lend expertise.
That project still involves a collaboration with Manchester and with the Diamond Light Source at Harwell, so we’re keeping strong links with that excellent facility and I have some students based down there.
And what’s the overall goal of that project?
We are trying to look at the interfaces in batteries, which are buried. That ‘bulk’ I mentioned earlier? That hides a lot of the reactions.
So we’re looking at both solid state batteries and liquid cells, working to understand those lifespan issues.
Solid state batteries are where you have solid electrolytes. Those aren’t really commercially available yet, but they have very high energy density and can also be safer as the electrolytes aren’t flammable. But when you have these two thick solids, it’s even harder to probe. So we’re looking at ways to thin down the electrodes, and also looking deeper and using ‘hard x-rays’.
This is the first time this is being done with working batteries. Previously, you’d pull the surfaces apart to get a better look, but the chemistry is changed by separating them.
So you can’t look at what’s happening while the battery’s charging or discharging.
And what might the impact be of this kind of research? How’s it going to change how we look at batteries and electric vehicles?
The blue sky part of the research is new techniques to get a closer look at the interfaces and chemistry.
Practically, we hope to understand why we’re getting degradation in higher capacity materials.
There are new materials that could provide better performance and be cheaper. But they may also be less stable and interact in new ways with the electrodes, so we really want to understand why that is.
And these are batteries that are close to market already, so it can have a real impact on the industry.
You grew up in Chelmsford, right? Would it be okay to say a little about your journey from there to Cambridge and then to here? What got you into engineering?
I was born in Chelmsford and went to the local grammar school. Chelmsford’s actually where Marconi founded his first radio factory. So a lot of the local industry was related to telecommunications.
What got me into engineering was a very passionate design and technology teacher, who had a keen interest in electronics. She was really good at running after school activities that were great for involving you and keeping your interest up. She was one of the most defining teachers I had, definitely. She encouraged me to get involved in a local engineering scheme as a hobby too, and to seriously pursue a path to a career in the field.
It probably helped having a dad who was a physicist and worked as an electronic engineer for a local company too.
Oxford has a rich history of work on batteries, with John B. Goodenough, who pioneered the Lithium Ion battery, recently being awarded a Nobel Prize. How does your work build upon that history?
Absolutely. We’re working with very similar materials. The cathode materials we’re still looking at, 30-odd years on, are still based on that structure, tweaked for higher capacity.
He had a huge impact on the commercially viable lithium ion battery and his work is still very pertinent to the real batteries we’re working on.
Many of his former students and colleagues are active at Oxford; there’s Bill David in Chemistry here, who I work with at Diamond, and Peter Bruce here in Materials as well.
Obviously, electric cars and thus lithium ion batteries are a hot button topic at the moment, any insights on what the future holds for them, based on your work?
Not just my work – look at government policy. We’re committed to all cars being zero emission by 2040. Electric vehicles look like the most promising solution. Which is why things like the Faraday Institution have been founded.
In terms of what we’re doing, we want to make these new higher capacity materials viable for the next generation of batteries, to make them more stable and offer longer lifetimes. We expect that in about 5 to 10 years that these new materials could be used in real world batteries.
For solid state batteries too, I can’t give an exact estimate, but it could be up to 20 years before we see them used in cars or phones. But we could see them used in smaller portable devices sooner!
Talking of timescale, what do you think we’re looking at for when electric cars might meet people’s expectations, compared to petrol?
You’re not going to wake up overnight and find that suddenly batteries have twice the capacity. But those kind of advancements are coming, and our work is helping get there.
Gradually those little steps will keep building up and they’ll become cheaper, they’ll last longer and that kind of thing.
The more unpredictable thing is if we’ll have a breakthrough where suddenly we find a new kind of material that will completely change the game.
Obviously, I can’t say when or even if that will happen, but it’s the kind of thing that can only happen if we do the research and better understand what’s going on with the materials.
What one thing about your research we haven’t covered yet that you think is important and interesting?
Beyond the batteries, we’re working on how we might be able to make other technologies to be more sustainable. For example, the synthesis of fuels and chemicals.
There’s an increasing interest in this idea of green chemistry. So, how do you capture waste products from industry or vehicles (like CO2) and turn them into something useful? Basically, how do we close the ‘carbon loop’?
This will be one of the few ways to make some technologies sustainable – but we’re not going to see batteries powering planes any time soon.
Where do you want your career at Oxford to take you? Where will this research take you?
Firstly, I’m hoping to build up the strength of my group to address some of these problems! Oxford’s full of like-minded people, so it’s a great environment to do that.
And I’m hoping some of the techniques we’re developing, will really give the validation that we’re doing important work.
And what would you say to people considering studying engineering, electronics or materials?
‘Do it!’ I think people should definitely consider it if they like problem-solving and understanding how the world works.
In terms of personal qualities, you need a lot of resilience and persistence. The nature of research is that things often go wrong and it’s easy to give up and call it a day, but often those are the times where, if you just keep going, you can make it work or learn why it wasn’t working. So many of the things we’ve understood in history aren’t from well-designed experiments that went well, but from when they didn’t go well. Just keep pushing on.