Boosting the mobility of ions in nanoporous confinement by applying a gate voltage

The mobility of ions under confinement in nanoporous materials is central to many electrochemical energy transformation and storage devices. By using ionic liquids (ILs) and metal-organic frameworks (MOFs) as well-defined, regular nanoporous host, the dynamic ion properties are explored in detail. Here, we demonstrate that applying a gate-voltage allows to considerably enhance the ion mobility. The experiments based on MOF films show a conductivity increase of up to 35%. Molecular dynamic simulations show that the gate-voltage-field causes layers of increased and decreased ion concentrations, parallel to the charge transfer direction. In these layers, the ion mobility can be up to 2.5 times larger than in the bulk phase or without an additional gate-voltage field. Thus, these layers of highly-mobile ions resemble gate-voltage-induced ion highways, causing the experimentally observed higher conductance. The study provides deeper insights into ion dynamics in nanopores, provides a method for enhanced ion mobilities and may help designing advanced electrochemical devices with improved dynamics and larger power-output.