Scientists have developed a groundbreaking new class of organic materials that conduct ions with the same efficiency as liquids, defying the conventional understanding of electrochemistry. This remarkable discovery, published in Science, challenges the long-held belief that freezing or crystallizing a liquid hinders ion movement. The team, led by Professor Paul McGonigal from Oxford Chemistry, has created state-independent electrolytes (SIEs) that maintain exceptional ionic conductivity across liquid, liquid-crystal, and solid states.
The secret lies in the unique molecular structure of these SIEs. Each molecule boasts a flat, disc-shaped core surrounded by long, flexible side chains, resembling a wheel with soft bristles. This design ensures that positive charges are evenly distributed, preventing tight binding with negatively charged partners. Consequently, negative ions can move freely, flowing through the side chains. In the solid state, these organic ions naturally stack into rigid columns, akin to static rollers in a car wash, while still providing ample space for negative ions to move freely, akin to their liquid counterparts.
This dynamic, ordered structure enables negatively charged ions to move through the solid state with the same ease as in the liquid form, without a sharp decrease in ionic conductivity. PhD student Juliet Barclay, the first author of the study, expresses the significance of this discovery: "As a PhD student, it’s incredibly rewarding to discover something that changes how we think materials can work. We’ve shown that organic materials can be engineered so that the movement of ions doesn’t ‘freeze out’ when the material solidifies. This opens new possibilities for safer, lightweight solid-state devices that work efficiently over wide temperature ranges."
The potential applications of these state-independent electrolytes are vast. They could be added to devices as a liquid at a slightly elevated temperature, making good contact with electrodes, and then cooled to ambient temperature for safe, solid-state operation without losing ionic conductivity. This innovation could revolutionize batteries, sensors, and electrochromic devices, leveraging the lightweight and flexible properties of organic materials, which can be sourced renewably.
The Oxford research team is now focused on enhancing the conductivity and versatility of these materials, as well as exploring their use in electronic devices for computing. This groundbreaking discovery not only challenges conventional electrochemistry but also paves the way for safer, more efficient, and sustainable technologies.
