When I was doing my PhD, we didn’t have lithium-ion batteries. It wasn’t until 1992 that the first lithium-ion battery was commercialised, and the world started pouring energy into improving them. For the next two decades or so, it was all about lithium.
My work was always parallel to that. For the last 30 years I’ve been involved in investigating how we can improve the chemistry of all sorts of batteries, capacitors, fuel cells, solar cells. I’ve been designing new electrolyte materials – which are the heart of all types of batteries – that improve the ability of ions to move from one electrode to the other and allow the electrochemical reactions that are required to provide electricity.
In particular, I’ve been looking at safer electrolytes. There are fires every other day based around lithium-ion batteries. Obviously, these are hugely important technologies for us to transition into clean energy, but there’s always room for improvement.
It’s important to make these devices safer, to make them last longer, and to get more and more energy out of them. But as we transition to net zero, we’ve got to be careful that the technologies we develop don’t create new problems. We need to make sure that the technologies we’re creating are sustainable, and designed for recycling in a circular economy.
It was only about 10 years ago that people started to look closely at the amount of lithium reserves and all the critical minerals that we need to make the lithium-ion batteries needed for the transition to electrification by 2050. The fact is we don’t have anywhere near enough materials in the ground. The known reserves simply aren’t big enough. And that’s a big problem.
As we transition to net zero, we’ve got to be careful that the technologies we develop don’t create new problems.
Beyond that, the lithium that we’re mining has big implications for the environment. In Australia we’re blessed – we have a lot of spodumene, which is a mineral from where we extract lithium. But the majority of lithium sourced elsewhere comes from the salt lakes of South America, and mining that does not have a nice environmental impact.
So, what’s next? Sodium is in seawater, right? It’s everywhere. That’s the “next big thing” for me.
Sodium batteries are not going to replace lithium, but because of the planet’s demand for more and more energy, we’re going to need to look at multiple technologies. Lithium is great – we’re going to use it. Lead acid is still here 150 years later, and we’re still using it. Flow batteries are being used, and we’re working on improving that. But the sodium-ion for me is the really important one. It’s the same manufacturing process as lithium, it’s very similar chemistry, but it’s far more sustainable.
We’re now seeing companies in China making sodium-ion batteries to demonstrate them in smaller vehicles. I see myself working towards translating that technology with my colleagues in Australia.
Most types of modern batteries generally work on the same principles. It’s the materials that go into them that are different. Then it comes down to how much voltage you can get out of the battery; how much it weighs; and then its capacity – how much energy do you get per kilogram, or per volume.
People talk about energy density, which is the weight and volume. That’s what’s important. The benefit of lithium is that it’s one of the lightest elements on the periodic table. It’s also one of the most energetic elements. Sodium is heavier, and it’s slightly less energetic, so you’re not going to have the same amount of energy coming out of a similar size sodium battery as you get out of a lithium battery, which means you’re not going to drive a car 1000 kilometres on a sodium battery just yet. And you’re probably not going to fly aeroplanes on sodium – you’re probably going to use lithium. But it’s got to be horses for courses.
Most types of modern batteries generally work on the same principles. It’s the materials that go into them that are different.
There’s another important reason that sodium is more sustainable. In a normal lithium battery that we currently use, the actual electrode on the anode side is graphite, a form of carbon. This is something we mine – it’s a critical mineral, which means it’s expensive.
The beauty of sodium is that you can use a much cheaper form of carbon than graphite, called a hard carbon. My colleagues and I are currently working in the lab on producing hard carbon using waste biomass.
One example: we’re carbonising waste textiles and turning them into different carbons with different materials properties, different porosity, different surface chemistry. We’re also using the biochars that you get from bio solids – basically, what comes out of our bodies gets turned into biochar, which we then treat and refine and characterise; control the porosity, the chemistry on surface, the structure; and that becomes the electrode in a battery. This is obviously more sustainable.
Sodium is what makes the juice, if you like, but every material that we combine in the battery has to work efficiently. To this end we’re also working on the cathode material. This is the other end of the battery, and it is the structure that allows sodium to insert in and out as you charge and discharge your battery. For example, the sodium goes into your hard carbon electrodes during charge, and then it goes into the other electrode (the cathode) during discharge. When this happens, the sodium travels through the electrolyte, which is the material in between the two ends of the battery, and that electrolyte can be a liquid, or a solid, or it can be a polymer.
The beauty of sodium is that you can use a much cheaper form of carbon than graphite.
But what’s really important is the interfaces between those components. When that material is touched during the charge and discharge process, chemistry happens. And while that chemistry has to allow ions through, it also has to protect you from reactions that you don’t want to happen, because those ions will lose you energy. We call these “parasitic” reactions, because they destroy the life of the battery.
The magic comes in designing each of these materials – the hard carbon anode, the cathode and the electrolyte – and controlling the reaction that occurs between them at that interface.
My very first ever research project in 1990 was on sodium electrolytes, but then when lithium hit the world, everyone started working on it. Now, at Deakin University, with the help of the Victorian government, I’ve helped establish Australia’s first pre-commercial prototyping facility, where we go from the materials through to the components that go into a battery cell. I’m passionate about translating this technology out of the lab and commercialising sodium batteries – and seeing safer, sustainable batteries become the Next Big Thing.
As told to Graem Sims.