In situ investigation of water on MXene interfaces.

A continuum of water populations can exist in nanoscale layered materials, which impacts transport phenomena relevant for separation, adsorption, and charge storage processes. Quantification and direct interrogation of water structure and organization are important in order to design materials with molecular-level control for emerging energy and water applications. Through combining molecular simulations with ambient-pressure X-ray photoelectron spectroscopy, X-ray diffraction, and diffuse reflectance infrared Fourier transform spectroscopy, we directly probe hydration mechanisms at confined and nonconfined regions in nanolayered transition-metal carbide materials. Hydrophobic (K+) cations decrease water mobility within the confined interlayer and accelerate water removal at nonconfined surfaces. Hydrophilic cations (Li+) increase water mobility within the confined interlayer and decrease water-removal rates at nonconfined surfaces. Solutes, rather than the surface terminating groups, are shown to be more impactful on the kinetics of water adsorption and desorption. Calculations from grand canonical molecular dynamics demonstrate that hydrophilic cations (Li+) actively aid in water adsorption at MXene interfaces. In contrast, hydrophobic cations (K+) weakly interact with water, leading to higher degrees of water ordering (orientation) and faster removal at elevated temperatures.

Scalable Manufacturing of Hybrid Solid Electrolytes with Interface Control.

Hybrid solid electrolytes are promising alternatives for high energy density metallic lithium batteries. Scalable manufacturing of multi-material electrolytes with tailored transport pathways can provide an avenue toward controlling Li stripping and deposition mechanisms in all-solid-state devices. A novel roll-to-roll compatible coextrusion device is demonstrated to investigate mesostructural control during manufacturing. Solid electrolytes with 25 and 75 wt % PEO-LLZO compositions are investigated. The coextrusion head is demonstrated to effectively process multimaterial films with strict compositional gradients in a single pass. An average manufacturing variability of 5.75 ± 1.2 µm is observed in the thickness across all the electrolytes manufactured. Coextruded membranes with 1 mm stripes show the highest room temperature conductivity of 8.8 × 10-6 S cm-1 compared to the conductivity of single-material films (25 wt %, 1.2 × 10-6 S cm-1; 75 wt %, 1.8 × 10-6 S cm-1). Distribution of relaxation times and effective mean field theory calculations suggest that the interface generated between the two materials possesses high ion-conducting properties. Computational simulations are used to further substantiate the influence of macroscale interfaces on ion transport.