Lithium ion batteries are ubiquitous in modern society, powering all of our portable (and not so portable) technology – from smartphones, smart forks and smart salt dispensers (www.mysmalt.com) to electric vehicles and off-grid energy storage devices. However, while the increase in our demand and reliance on technology shows no signs of slowing down, improvements to the energy storage capacity of current state-of-the-art Li-ion batteries are becoming limited. So, new families of materials with inherently greater capacities are required to replace those currently used, in order to more effectively meet the world’s energy storage demands. While many promising new families of materials exist, not much is currently known about their structure and physical properties, leaving many important questions unanswered regarding their safety, capacity and long-term stability.
The problem is – many of these questions relate to the structure on the atomic scale, so how do we answer them when we can’t possibly see anything that small – even with powerful microscopes?
The answer: we make the materials ring, using nuclear magnetic resonance (NMR) spectroscopy.
NMR is an exceptionally powerful technique for studying these materials on the atomic scale, and is a key part of my research. The nuclei at the centre of most atoms possess a property called spin, which means that they behave like a tiny magnet in the presence of an external magnetic field. They can align with this field or against it, and will flip between these two states with a characteristic resonant frequency – a specific note which is highly sensitive to the atom’s immediate surroundings within the material’s structure. The variety of chemical environments (the surroundings of a particular atom) means that many such frequencies will be present in these compounds. We can cause the atoms to resonate (or ring) at their characteristic frequencies by zapping the material with radio waves – just like we might strike a bell or a tuning fork to make it chime – and separate out the various notes as they ring to identify the different local environments within the structure.
Using techniques such as NMR, we can learn more about exciting new battery materials, and hence continue to improve on the current battery technology – keeping our smart salt dispensers dispensing salt for even longer.
NanoDTC PhD Student 2016