Mechanistic Insights into High Performance All-Solid-State Li-S Batteries
Abstract
All-solid-state lithium-sulfur batteries (ASSLSBs) have emerged as a highly promising energy storage solution for next-generation applications, particularly electric vehicles. ASSLSBs offer several advantages compared to their lithium-ion battery counterparts, including economic feasibility, high theoretical energy density, and intrinsic safety. However, despite their potential, there remain significant challenges that hinder the widespread adoption of ASSLSB technology. The first part of this thesis focuses on investigating the reaction mechanism of ASSLSBs, with a particular focus on their discharge products. Advanced characterization techniques such as X-ray absorption spectroscopy and time-of-flight secondary ion mass spectroscopy are employed to probe the discharge products of ASSLSBs. Contrary to previous reports that suggest the formation of only lithium sulfide (Li2S), we discover that the discharge products of ASSLSBs consist of a mixture of Li2S and lithium disulfide (Li2S2). Building on this insight, we propose a strategy to induce a Li2S2-dominant discharge product while incorporating a trace mount of solid-state catalyst. This approach leads fully reversible ASSLSBs with long cycle life. The second part of this thesis investigates the relationship between the sulfide solid-state electrolyte (SSE) degradation in the cathode composite and the resulting impact on the electrochemical behavior of ASSLSBs. We reveal that the electrochemical performance of ASSLSBs is influenced by the type of SSE used in the cathode composite, primarily due to variations in their degradation products. In summary, this thesis provides valuable insights into the fundamental aspects of ASSLSBs and offers feasible strategies to improve their performance. The findings presented in this thesis contribute to the development of next-generation energy storage technologies, paving the way for the widespread adoption of ASSLSB technology in various applications and devices.