Using X-Ray Scattering to Elucidate the Microstructural Instability of 3D Bicontinuous Nanoporous Metal Scaffolds for Use in an Aperiodic 3D Tricontinuous Conductor-Insulator-Conductor Nanocapacitor.

The development of three-dimensional aperiodic energy storage devices is in part impeded by the lack of appropriate aperiodic templates that can withstand the thermal conditions required to deposit energy storage materials within their void space. Herein, the feasibility of an aperiodic three-dimensional architecture for energy storage is demonstrated for the first time by constructing a tricontinuous conductor-insulator-conductor (CIC) nanocapacitor on an aperiodic nanoporous gold scaffold. To accomplish this, the scaffold was characterized using in situ small-angle X-ray scattering (SAXS) during exposure to a thermal environment, revealing that its microstructure eventually stabilizes after undergoing a phase of rapid coarsening, indicating a departure from the 1/4 time-dependent power-law coarsening behavior usually observed at the early stage of the coarsening process. Using this stability regime, we created the CIC by intentionally precoarsening and stabilizing the scaffold before depositing two dissimilar metal oxide films in its void space by atomic layer deposition. Current-voltage characteristics and electrochemical impedance spectroscopy measurements revealed that the un-optimized 3D CIC outperformed its 2D counterpart by ∼4× in terms of capacitance. This proof-of-concept device will pave the way to the development of aperiodic three-dimensional energy storage systems with enhanced energy and power densities.