arXiv subjects

S. D. Matson

Publications and source records attributed to S. D. Matson.

2 recordsLinked to original sources

arXiv2023

Epitaxial NaxCoO2 Thin Films via Molecular-Beam Epitaxy and Topotactic Transformation: a Model System for Sodium Intercalation

Renewable energy sources such as solar and wind are critical to combatting global warming. Nevertheless, their intermittent energy generation requires the development of large-scale grid energy storage, in contrast to the on-demand generation of coal-based power plants. Sodium-ion batteries offer a promising potential technology, yet because sodium ions are larger than lithium ions, sodium-ion intercalation results in more drastic structural rearrangements. An improved understanding of structural dynamics and ionic diffusion pathways is crucial to developing more durable sodium-ion batteries. Here we synthesize epitaxial NaxCoO2 by using molecular-beam epitaxy and topotactic transformation. In the synthesized epitaxial films, the CoO2 layers are canted with respect to the film surface, allowing electrochemical extraction of sodium ions, which we confirm via ex-situ x-ray diffraction. We anticipate the epitaxial thin films reported here to enable future operando studies of interfaces, subtle lattice distortions, and microstructure during electrochemical cycling.

cond-mat.mtrl-sci↗

arXiv2021

Interaction and transformation of metastable defects in intercalation materials

Non-equilibrium defects often dictate macroscopic functional properties of materials. In intercalation hosts, widely used in rechargeable batteries, high-dimensional defects largely define reversibility and kinetics1,2,3,4. However, transient defects briefly appearing during ionic transport have been challenging to capture, limiting the understanding of their life cycle and impact. Here, we overcome this challenge and track operando the interaction and impact of metastable defects within NaxNi1-xMnyO2 intercalation hosts in a charging sodium-ion battery. Three-dimensional coherent X-ray imaging3,4,5 reveals transformation and self-healing of a metastable domain boundary, glissile dislocation loop, and stacking fault. A local strain gradient suggests a quantifiable difference in ion diffusion, coincident with the macroscopic change in diffusion coefficient. Analysis of the unexpected4,6 defect anisotropy highlights the importance of mesostructure, suggesting a possible control approach and disputing the rigidity of the framework layers. The shared nature of oxygen framework layers makes our results applicable to a wide range of intercalation materials.

cond-mat.mtrl-sci↗