UC San Diego

Since the introduction of battery as a new source of energy, great attention has been endeavored to boost the electrochemical performance for meet the impeding energy request. Prelithiation as a facile and effective method to compensate the lithium inventory loss in the initial cycle has progressed considerably both on anode and cathode sides. However, much less research has been devoted to the prelithiation effect on the interface stabilization for long-term cycling of Si-based anodes. An in-depth quantitative analysis of the interface that form during the prelithiation of SiOx is presented here and the results are compared with prelithiaton of Si anodes. Local structure probe combined with detailed electrochemical analysis reveals that a characteristic mosaic interface is formed on both prelithiated SiOx and Si anodes. This mosaic interface containing multiple lithium silicates phases, is fundamentally different from the solid electrolyte interface (SEI) formed without prelithiation. The ideal conductivity and mechanical properties of lithium silicates enable improved cycling stability of both prelithiated anodes. With a higher ratio of lithium silicates due to the oxygen participation, prelithiated SiO1.3 anode improves the initial coulombic efficiency to 94% in full cell and delivers good cycling retention after hundreds cycles under lean electrolyte conditions, which provides the possibility for the application in high loading Si anodes. Understanding the battery materials and its solid electrolyte interphase (SEI) is crucial for the progress of battery technology. Deploying a correlative imaging approach that integrates focused ion beam and electron microscopy offers a comprehensive characterization strategy across multiple length scales. Unraveling the fundamental mechanisms that govern lithium metal deposition and stripping behaviors encounters many challenges, given the reactivity of Li metal and the SEI towards the environment and external characterization probes. In this work, we investigated the reaction mechanisms of these battery materials using various external probes, including Ga+, Xe+, Ar+ ions, and electrons, under different environmental conditions. Our findings reveal that the chemical reactivity of metallic lithium requires appropriate sample preparation, transfer and imaging protocols to access accurate structural and chemistry information. Achieving atomic resolution imaging of pure lithium metal is feasible at room temperature via full inert gas sample transfer (IGST) procedure with normal dosage. The SEI components display significantly higher reactivity than lithium metal to electron beams and requires cryogenic temperature and precise beam dose control for high-resolution imaging. The dosage limit for commonly reported SEI components, such as Li2CO3, LiF, and Li2O, is quantified in this work to elucidate their chemical and structural evolution under electron beam irradiation. Moreover, our study emphasizes the risk of potential misinterpretation of experimental results due to the materials reactivity. This highlights the importance of exercising special attention via protocol to ensure reproducible and reliable characterizations for reactive battery materials.