Synthesis and Characterization of Nitride Solid-State Electrolytes for All-Solid-State Lithium Metal Batteries

Weihan Li, Western University

Abstract

All-solid-state lithium metal batteries offer a potential solution to conventional lithium-ion battery limitations, encompassing safety concerns, restricted voltage windows, cycling performance instability, and suboptimal energy density. Utilizing lithium metal anodes and high-capacity cathode materials, these batteries can attain energy densities surpassing 500 Wh/kg, rendering them a promising candidate for electric vehicles necessitating extended driving ranges. Notwithstanding recent advancements, the realization of long-term cycling stability in all-solid-state lithium metal batteries continues to pose challenges, primarily due to the persistent difficulty in mitigating lithium dendrite growth at elevated areal capacities (>3 mAh/cm²) and high cycling rates (>4 C). This thesis seeks to tackle persisting obstacles and foster progress in all-solid-state lithium metal batteries through: a) the innovation of lithium-stable nitride solid-state electrolytes tailored for all-solid-state lithium metal batteries; b) the realization of practical all-solid-state lithium metal battery applications; and c) the utilization of synchrotron X-ray analytical techniques for in-depth characterization of solid-state electrolyte-lithium metal interfaces, thereby augmenting fundamental comprehension. This research develops a series of nitride-based SSEs and processing methodologies aimed at mitigating lithium dendrite growth, while maintaining high stability at increased current densities and areal capacities. Ultimately, by leveraging tailored interface engineering strategies, this work demonstrates practical all-solid-state lithium metal batteries exhibiting high areal capacity (>4 mAh/cm²), rapid charging capabilities (4 C), extended cycling life (5000 cycles), and feasible pouch cell implementations. Utilizing advanced X-ray and electron imaging analytical techniques, this thesis elucidates the interphases' compositions, crystal and local structures, and corresponding distribution parallel and perpendicular to interfaces, as well as the stability of SSE-lithium metal interfaces during electrochemical cycling. In summary, this thesis serves as a critical contribution to advancing all-solid-state lithium metal batteries towards achieving high energy density, thereby addressing the rapidly evolving demands of the electric vehicle market.