Engineering the solid-electrolyte interface with sulfur-rich and chlorine-rich materials to protect lithium metal anodes for Li-S batteries

Restricted (Penn State Only)
Author:
Regula, Michael John
Graduate Program:
Chemical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
September 20, 2018
Committee Members:
  • Donghai Wang, Dissertation Advisor
  • Michael John Janik, Committee Chair
  • Donghai Wang, Committee Member
  • Seong Han Kim, Committee Member
  • Sulin Zhang, Outside Member
Keywords:
  • Energy Storage
  • Battery Materials
  • Solid-electrolyte interface
  • Lithium metal anodes
  • Lithium-sulfur batteries
Abstract:
Humans are becoming increasingly dependent on energy to maintain our quality of life. Our energy generation systems are woefully inefficient, which has significant economic and environmental impacts. More fossil fuels need to be burned to meet energy demand for electricity generation and transportation, while intermittent renewable energy sources, like wind and solar, cannot provide energy in a stable manner. Energy storage devices can stabilize and improve the overall efficiency of electricity generation and transportation. Among energy storage devices, batteries have received the most attention. Specifically, the advent of the lithium-ion battery in 1991 helped spur the portable electronics market and kickstart the production of modern all-electric vehicles. For electric vehicles, though, lithium-ion batteries do not have the energy density nor cost effectiveness to make them pervasive in today’s marketplace. A different lithium-based battery chemistry, lithium-sulfur, can meet the energy demands for this application, but many scientific challenges still remain. Sulfur, the high voltage cathode material, is non-conductive and its redox reaction chain with lithium causes rapid drops in battery performance during cycling. Lithium metal, the low voltage anode material, is highly reactive, decomposing electrolyte solvents and lithium-ion conducting salts to form a surface film known as the solid electrolyte interface (SEI). In conventional electrolytes, the SEI composition and morphology is non-uniform across the electrode. Lithium agglomerates during cycling into “dendrite” structures because of non-uniformities in the SEI. Fortunately, the SEI can be engineering with electrolyte additives. In this dissertation, high-sulfur content and high-chlorine content materials are employed as electrolyte additives to protect lithium metal anodes from dendrite formation to enable long-term, stable SEI formation. Well-protected lithium metal anodes directly lead to improvements in lithium-sulfur battery performance. The materials and electrochemical characterization of these additives should be used to guide future studies in lithium metal anode protection and lithium-sulfur battery development.