2, Nova Research, Inc., Alexandria, Virginia, United States
3, Argonne National Laboratory, Argonne, Illinois, United States
4, Naval Surface Warfare Center–Carderock Division, West Bethesda, Maryland, United States
Synthesis and crystal engineering of metal oxides typically focuses on creating single-phase materials. Our team emphasizes the importance of disorder as a means to increase the electrochemical charge-storage performance of transition-metal oxides, including when the materials are inherently disordered thanks to high surface-to-volume nanoscale expression within three-dimensional electrode architectures. Establishing structure when the energy-relevant material is nanoscale, disordered, and already incorporated as the functional component in a device-ready macroscale form-factor imparts challenges for structure determination. But when disorder serves to amplify performance, structural characterization becomes a necessary challenge. Amorphous and/or nanoparticulate phases are difficult to characterize via neutron or X-ray scattering because of broad Bragg peaks, so we turn to total scattering analyses that allow atomistic modeling of these difficult to characterize—but functionally important—composites via differential pair distribution function (DPDF) analyses. Two pseudocapacitive systems will be discussed as fabricated by electroless deposition of conformal, ultrathin films: (1) ~10 nm–thick manganese oxide on carbon nanofoam paper in which the oxide “paint” can be crystal engineered in-situ via ion exchange and thermal processing and (2) ~3 nm–thick ruthenium dioxide on silica fiber paper, in which electrical conductivity of the electrode can be tuned over three orders of magnitude by calcining without ripening the ruthenia nanoparticles that comprise the conductive shell. The effects of rearranging in-situ the structural order/disorder of the charge-storing oxide will be tracked by the pseudocapacitance or faradiac (battery-like) performance of the device-ready electrodes.