UBC Theses and Dissertations
Development and characterization of the anode-free lithium metal battery electrode Zhou, Bingxin
Although great effort has been devoted to the investigation of lithium metal batteries (LMBs) and numerous papers are published, the deposition and corrosion behavior of lithium is still not fully understood and requires further investigations. Moreover, the characterization and data interpretation in the literature can be very misleading or ambiguous. In this thesis, the deposition behavior of lithium at a carbon host, the decoupling of impedance of the solid-electrolyte interface (SEI) and plated lithium, and the impact of electrolytes on the lithium corrosion behavior are presented. Firstly, pure hollow core-carbon spheres (PHCCSs) are prepared and applied onto the Cu current collector, which is then used to investigate the deposition behavior of lithium. This type of structure is selected because the nano-carbon-based materials are widely reported as lithium host materials in LMBs, while contradictory claims are reported as to where the lithium plating occurs. It is demonstrated that the lithium shows some initial and limited intercalation into the PHCCSs and then plates on the external carbon walls and the top surface of the carbon coating during the charging process. No evidence of lithium plating inside the hollow core space is found. Secondly, a combined electrochemical quartz crystal microbalance (EQCM) and electrochemical impedance spectroscopy (EIS) study is conducted to decouple the various contributions to the impedance response of an anode free battery. This decoupling is achieved by a comparison of the evolution of EIS spectra in 2- and 3- electrode cells during the Li plating/striping processes. The observed high and low frequency loops of the impedance spectra can be unambiguously assigned to the charge transfer of the SEI and the plated lithium layers, respectively. Finally, inspired by the capacity performance in the lithium bis(fluorosulfonyl)imide- lithium bis(trifluoromethanesulfonyl)imide-dimethyl ether-dioxolane (LiFSI-LiTFSI-DME-DOL) electrolyte system, the impact of electrolytes on lithium corrosion behavior is investigated systematically. Results show the key point of minimizing capacity loss during open circuit voltage (OCV) is the coordination of insoluble particles and polymers in the SEI layer. A “less-soluble particle-polymer symbiosis” (LSPPS) concept is thus proposed and validated by the preparation and performance evaluation of modified electrolytes.
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