Properties of Layered Crystal Structures: Quantum Materials and Battery Cathodes

Abstract

Layered crystal materials possess structural and electronic properties crucial for current and next-generation technologies, particularly in energy storage and electronics. Their layered crystal structure facilitates the intercalation of metals, thereby tuning the materials’ electronic properties. This dissertation investigates two categories of layered crystal materials: the topological insulator Bi2Se3, and sodium-ion battery cathode materials. High-temperature quenching reveals evidence of a previously unreported transition in Bi2Se3, observed through transmission electron microscopy, resistivity, and nuclear magnetic resonance measurements. Intercalation of Bi2Se3 with niobium enables a superconducting transition at low temperatures. Additionally, the observed temperature for this previously unreported transition is significantly higher when intercalated with niobium. In the sodium battery cathode materials NMFO, intercalation of nickel or cobalt enhances the cyclability and reduces internal resistance in sodium-ion coin cell batteries. This enhancement is confirmed through x-ray diffraction, state-of-health measurements, and equivalent circuit modeling of electrochemical impedance spectra. Finally, machine learning techniques can classify and predict future battery performance based on electrochemical impedance spectroscopy data from lithium-ion batteries.