New insights into ionic liquids may improve energy storage

Conductive liquids are vitally important to energy storage, as energy reservoir devices must contain a medium through which charged particles can move in order to operate. In most current battery systems, this role, called the electrolyte, is fulfilled by solutions. But these can cause problems: the conductivity can be low, and depends on the concentration of the charged species dissolved in the solution, and if flammable solvents are used, the electrolyte itself can be flammable or even explosive, as has happened with lithium ion batteries in laptops, electric vehicles and aircraft in recent years.

Ionic liquids offer an alternative to solutions. Often molten salts, these also contain mobile charged particles. Some enery storage researchers are looking to room temperature ionic liquids (RTILs) as an alternative as molten salts tend to be so hot that they cause more problems.

But the conductivity of RTILs is itself paradoxical. They are good conductors because they contain a very high concentration of ions, but this density of conductors should mean that positive and negative ions are close enough together that they cancel each other out; in theory, they should combine to create neutral particles which do not conduct electricity. The lack of understanding of why this does not happen has been a block for scientist trying to formulate RTILs with optional properties for energy storage or other applications.