The plenary lecture this morning was by Peter Bruce, from the University of St Andrews, over on the east coast of Scotland. His message was an appeal to chemists to open their minds in order to save the world from climate change. Free yourselves from thinking of the immediate applications, he said, and this challenge can be faced. “The chemistry to tackle this is still going to be fundamental chemistry,” he says. Chemists should forget the immediate technical challenges.
Stirring stuff. And he had some very good reasons for saying this. Bruce has spent many years looking at ion transport in polymer electrolytes, and along the way has invented a better way to probe the structure of these large crystalline polymers that are otherwise too large to get x-ray crystal structures of.
How can this help climate change? Well these fundamental chemistry advances have found their way into lithium batteries – the things that charge our laptops, mobile phones, as well as powering tiny implantable medical devices of the future.
Bruce is now looking at ways that might – eventually – make the charging and recharging process of batteries much much faster. This process involves lithium ions moving from one material to another. They travel one way when the battery is being used, and when it’s plugged in again to recharge, they hop back over from whence they came. As many of you will know, this can take hours.
Bruce’s work on solid crystalline polymer electrolytes could help. But to understand how these materials work their molecular-scale structure needs to be understood. The problem has been getting single crystals to do crystallography on. So Bruce developed a powder diffraction technique that worked a treat.
He’s also spent a lot of time investigating why and how these crystalline polymers can conduct. The reason is that ions in crystalline polymers hop, which is very different to the way floppy non-crystalline systems work, he says. The conductivities they show are way too low for industry, he says, but doesn’t much care. “Scientifically it opens up new avenues,” he said. And curiosity has led his group to investigate other metals in the same group of the periodic table as lithium.
Next is the challenge of making the energy density of the materials better. To try and get a ten-fold improvement in energy, Bruce has developed a lithium-air battery, where oxygen from air reacts to start the ion motion. It’s a neat idea, and you never know, it could work.