CRYOGENIC MICROSCOPIES OF ENERGY STORAGE MATERIALS: INSIGHTS INTO METAL ANODES, SOLID-ELECTROLYTE INTERFACES, AND MXENES

The escalating global energy demand has intensified the pursuit of high energy density storage technologies, focusing on metal anode systems that promise higher energy density at lower cost. This dissertation presents comprehensive research that advances our understanding of energy storage materials, including alkali metal anodes, solid-electrolyte interfaces (SEI), and MXenes through developed cryogenic characterization techniques in batteries.Our research addresses a critical characterization gap by developing and adapting multiple cryogenic techniques specifically for energy materials research applications. By integrating cryogenic plasma focused ion beam (cryo-PFIB), time-of-flight secondary ion mass spectrometry (TOF-SIMS), cryogenic transmission electron microscopy (cryo-TEM), aberration-corrected scanning transmission electron microscopy (AC-STEM), and electron energy loss spectroscopy (EELS), we have developed novel analytical approaches that enable unprecedented insights into environmentally and beam-sensitive energy storage materials. We establish viable protocols for effectively analyzing these materials without introducing artifacts from atomic to micron scales while minimizing beam-induced damage. This positions cryogenic electron microscopy as an effective solution for high-sensitivity detection of light elements (H, Li, and F) and interface studies in energy storage systems. Additionally, we offer strategic approaches for designing low-cost, high-energy-density and safe batteries incorporating sodium metal anodes and solid polymer electrolytes (SPEs). We analyze sodium nucleation and SEI growth mechanisms with SPEs through a systematic approach combining scanning electron nanobeam diffraction (SEND), TOF-SIMS, and cryo-TEM for stable cycling. This enables statistical quantification and mapping of SEI components at the micron scale with nanometer resolution, revealing critical interface characteristics that govern battery performance. Beyond sodium-based systems, we explore monolayer titanium carbonitride MXenes as direct current collectors to replace conventional lithium metal anodes for further increased energy density. Our work provides fundamental insights into structure-property relationships in these MXenes by applying AC-STEM and EELS at the atomic level. These techniques allow us to study defect concentration, surface termination, and oxidation state to elucidate electronic conductivity mechanisms. Furthermore, our cryo-TEM studies point toward a promising direction for investigating lithium nucleation on MXenes. These insights serve as a foundation for developing MXene current collectors in metal anode applications with enhanced stability and performance.

Author dc:creator

• Zhang, Yihui

Advisor dc:contributor.advisor

• Stach, Eric A., EAS

• Materials Engineering

Language dc:language.iso

en

Repository record dc:identifier.uri

https://repository.upenn.edu/handle/20.500.14332/61245

OAI identifier oai:identifier

oai:repository.upenn.edu:20.500.14332/61245