From the Walkman to the electric car

Mr. Novák, in recent days you were in Ulm in southern Germany, where a conference on battery research was taking place exactly when the Nobel Prizes in the natural sciences were being announced. Was the timing of the conference coincidental?

That absolutely was a coincidence. And it was also a coincidence that one could meet the future Nobel laureate Stanley Whittingham there. On Wednesday, the day the Nobel Prize for Chemistry was to be announced, he delivered his lecture at 8:30 during the morning session. So, shortly before the Nobel Prize was announced at 11:50.

Even Whittingham himself had hardly learned about it any earlier; this is the usual procedure of the Nobel Committee. I did notice that he left the room twice for phone calls. After that, he had to keep it to himself for another half hour.

And then?

At 11:50, I was sitting on the stage where I was chairing the continuing morning session. I looked at my phone to see who had received the Nobel Prize in Chemistry. And at first I could hardly believe it. Even though for me the topic of lithium-ion batteries was one of the frontrunners for the prize, and thus clearly Whittingham, it was still surreal that I had the Nobel Prize winner sitting in front of me in the audience.

Then I briefly interrupted the series of talks and announced the Nobel Prize from the stage. That was a great joy for me.

So it was clear to you: If lithium-ion batteries are the topic, then Whittingham is one of the laureates. Does that also apply to the other two, John Goodenough and Akira Yoshino?

Yes. Even though over the decades there has been a lot of research by very many people, these three are a very good selection of the people who were involved in this development.

What is your memory of these decades of battery research?

What this award honours is a development that began in 1976. At that time, Stanley Whittingham built a rechargeable battery with lithium; it was already known theoretically that it has some suitable property. A battery consists essentially of the two electrodes – the cathode and the anode – and the electrolyte. The mostly liquid electrolyte helps the lithium ions move back and forth between cathode and anode, one way when it's charging, the other way when it's discharging. Whittingham was the first to identify a material with which a well-functioning cathode could be implemented: titanium disulphide.

So Whittingham built the first lithium-ion battery?

You can say that. But today's lithium-ion batteries are composed of different materials. Already three years later came another advance, when John Goodenough showed in 1979 that cobalt dioxide is still better suited as a material for the cathode.

But on the anode side, there was still a problem. At that time, they were made of pure lithium or lithium-aluminium alloys. That seemed a natural choice, but it wasn’t ideal. Akira Yoshino therefore tried out various materials that could serve as a carrier for lithium ions. It was found in petroleum coke, which being a waste product of petroleum processing is very low-priced, and with special treatment is suitable for the anodes. The first lithium-ion battery based on this design came on the market in 1991.

Why did it take Whittingham and Goodenough until 1991?

Research and development simply picked up in the late 1980s and early 1990s, when the miniaturisation of electronic devices came along. I remember that Sony needed a small, powerful battery to develop that era's wave of portable devices – Walkman, Discman, video cameras. In my view, among other things, we have the Discman to thank for lithium-ion batteries!

And how has the research and development for lithium-ion batteries proceeded since 1991?

Since 1991, there have been no groundbreaking changes, but rather constant improvements. There has been and continues to be a great deal of research on the exact composition of cathode and anode materials. In the cathode, for both economic and ethical reasons, there is an effort to keep the proportion of cobalt as low as possible. You choose other compositions that have a somewhat higher energy density. And the anodes are no longer made from coke, but rather from graphite. That is now standard. Some are already made from a mixture of graphite and silicon.

Up to 90 percent of the battery research at PSI, or maybe even more, is research on lithium-ion batteries. Among other things, for more than two decades already we have had a successful collaboration with the company Imerys Graphite & Carbon in Ticino, which has a significant share of the graphite market. With Imerys, we are doing research on graphite-electrodes for lithium-ion batteries.

Is the battery in a smartphone today exactly the same as the one in an electric car?

Not quite. Today there are various types of lithium-ion batteries, which are optimised depending on the application: With smartphone batteries, the priority is on the energy density – accepting the downside of a service life of only around two years. Conversely, for electromobility you want to develop batteries with high reliability and long service life. Elsewhere, again, you might want high power. All this can be achieved through small differences in mechanical design and choice of materials: For example, the thickness of the electrode, the porosity of the materials, even small differences in the composition of the electrolyte and electrode materials can selectively improve a desired property.

Do you also want to get 97 years old like Goodenough and then receive the Nobel Prize?

Oh, I want to keep it rolling. And go on doing science.
 

Interview: Paul Scherrer Institute/Laura Hennemann