Temperature-Dependent Structural Breathing of Nanoconfined Ionic Liquids for Tunable Ionic Conductivity

The confinement of low-temperature ionic liquids (ILs) within nanoscale geometries presents a unique opportunity to explore their behavior under restricted conditions compared to that of the bulk phase. Here, we report the discovery of a breathing phenomenon and the consequential enhancement of the ionic conductivity observed in ILs subjected to nanoscale confinement. Our experimental and modeling experiment focuses on an IL confined within graphene oxide (GOIL) at temperatures ranging from 253 to 293 K. A surprising structural breathing effect near 283 K emphasizes the confinement's influence on GOIL dynamics. Importantly, GOIL exhibits 3–4 times higher ionic conductivity than that of bulk ILs across different temperatures. The simulation proves that this increase is mainly due to the faster ion transport caused by cation and anion delamination under nanoconfinement. Even at low temperatures (253 K), GOIL demonstrates exceptional ionic conductivity exceeding 1 mS cm–1, rendering it suitable for harsh environment energy storage applications. These findings shed light on the properties of ILs under nanoscale confinement, providing insights into the design of nanomaterials with enhanced performance.