Electrolytes are salts which flow and so allow the conduction of charge. The simplest household electrolyte is table salt dissolved into water, as is so often used in the kitchen. There are many other commonplace electrolytes such as the oceans and the fluid inside our cells or in our blood. The common feature of all these well-known examples is that they include water as the solvent; the salt (e.g. sodium chloride, NaCl) is dissolved in the water in the sense that the individual ions break apart into positively charged sodium ions (Na+) and negatively charged chloride ions (Cl-). Each of the ions in these examples is surrounded by water molecules. However, there are many types of electrolyte where there is no water solvent: some salts are fluid without any solvent at all (these are called ionic liquids), some salts can be dissolved in other salts, or in other molecules such as polymers. These kind of electrolytes don’t usually occur naturally (although there are examples, ranging from exoplanets to volcanic magma) but they are important for technological applications such as battery electrolytes.
Owing to the charges on the ions, for example positive on the sodium and negative on the chloride in NaCl, interactions between the ions (repulsions and attractions) are quite strong and so are ‘felt’ by the other ions in the electrolyte over long distances. If the electrolyte is ‘dilute’, meaning that there is only a small amount of salt in a large quantity of water, the effect of these interactions reasonably well understood using mathematical theories. But most of the important salts, like those used in batteries or even the ones in the sea or in our bodies, are too concentrated for the known theories to apply well. In this project we are working towards a better understanding of many different sorts of electrolytes from a fundamental perspective – that is to say, we are looking for general principles, that can be explained using physics and maths, that describe the properties of the electrolytes. The results are of use to scientists working in a wide range of other disciplines, ranging from marine chemistry to battery electrolyte development.
