Thesis Format
Integrated Article
Degree
Doctor of Philosophy
Program
Mechanical and Materials Engineering
Supervisor
Sun, Xueliang
Abstract
All-solid-state batteries (ASSBs) offer opportunities to achieve high energy density, long life, and excellent safety, making them promising for electric vehicles. However, ASSBs still face several key challenges: (1) sluggish lithium-ion transport in solid-state electrolytes (SSEs) and interfaces between SSEs and electrodes; (2) electrochemical stability between SSEs and electrodes; (3) limited cycling stability. To address these challenges, the approach focuses on three key approaches: (1) developing new electrolytes to enhance ionic conductivity and stability; (2) creating artificial electrodeelectrolyte interfaces to enhance cathode kinetic behavior; (3) advanced characterization and theoretical calculations to help understand the ion transport and mechanisms of stability. In this thesis, SSEs based on thiosilicate and borohydride were developed, and utilized composite cathode, to enhance ion transport and electrochemical stability. First, amorphous 5Li2S-3SiS2 SSE was synthesized, which has a unique dimer structure that lowers lithium diffusion energy barriers and boosts conductivity to 1.2 mS/cm. Next, this SSE was enhanced by adding closo-type complex hydride Li2B9H9-Li2B12H12, improving conductivity to 2 mS/cm and reducing lithium dendrite growth. Hydroborate electrolytes, LiBH4-LiI-LixMOy (M=P, C) were also explored. Due to the B-O electrostatic effect, these SSEs exhibit high ionic conductivity. Additionally, these materials demonstrate good chemical stability with chalcogen (Se, S, Li₂S) cathodes and Li metal anodes. Finally, a universal surface chemistry was discovered for designing the dynamic surface of high-loading Li₂S cathode. Advanced characterization techniques, including synchrotron, NMR, and theoretical calculations, have been employed to study the local structure of the amorphous SSEs, as well as interface transportation and chemical stability.
Summary for Lay Audience
With the development of battery technology, there is a growing emphasis on enhancing both the safety and energy density of the battery. At present, achieving further increases in the energy density and safety of commercial liquid lithium-ion battery systems poses challenges. Due to inherent safety issues and theoretical capacities. Effectively, the development of lithium-ion batteries has encountered a bottleneck. Using solid-state electrolytes (SSEs) instead of organic electrolytes is one of the most effective ways to improve energy density and safety. All-solid-state batteries (ASSBs) use non-flammable solid electrolytes and lithium metal anodes, which greatly improve battery performance and become an ideal power source for electric vehicles and large-scale energy storage. The design for high performance of ASSBs is our target.
To overcome these issues, my research focuses on three key strategies: (1) developing new electrolytes that improve ion conductivity and electrode stability, (2) creating artificial interfaces within the battery to boost ion transport and stability, and (3) using advanced methods to study ion transport and stability mechanisms. In this thesis, new types of solid-state electrolytes (SSEs) using thiosilicate and borohydride that offer high ionic conductivity and outstanding electrode stability were developed. ASSBs using these newly developed SSEs exhibit promising electrochemical performance. Lastly, the LiFeS2 modification layer enables the Li-S batteries to achieve high active material utilization and impressive energy density. Overall, all findings presented in the thesis would make sizable contributions to the development of high-performance ASSLBs.
Recommended Citation
Hao, Xiaoge, "Investigation of Ion Transport and Stability in Solid-State Electrolytes for High-Performance All-Solid-State Batteries" (2024). Electronic Thesis and Dissertation Repository. 10421.
https://ir.lib.uwo.ca/etd/10421