Spatial and Time-Resolved Aging Behaviors of Silicon-Based Electrodes

The improvements in secondary battery provided by next-generation electrode materials including silicon are offset by their rapid degradation due to the undesirable (electro)chemical reactions, taking place at electrode surface in contact with a reactive electrolyte, which form the unstable and heterogeneous solid-electrolyte interphase (SEI). Understanding the complex reactions taking place in each phase, as well as the compositional, morphological, and structural formation and evolution of the SEI, therefore, is essential to the development of mitigation strategies enabling safe and longer battery life.^1-3 Over the decades of battery R&D, many analytical techniques have been developed to characterize the properties of battery components and understand cell failure mechanisms, but most often, these techniques are applied ex-situ to a component of the battery that has been harvested from a disassembled cell after testing. While informative, ex-situ analyses cannot elucidate detailed changes happening to the cell during testing, thus potentially failing to provide critical information about correlated processes underpinning the cell behavior and performance.⁴<br/>Our newly developed in-situ vibrational spectroscopic techniques demonstrate reproducible and reliable performance over multiple cycles in terms of both electrochemistry and spectroscopy, which enables us to monitor the surface chemistry and structural changes on/in the electrode and to gain a fundamental and mechanistic understanding of the electrochemical behavior and performance of lithium-ion batteries.^5,6 Specifically, we have investigated spatial and time-resolved heterogeneous aging behaviors of silicon-based electrodes during calendar aging, such as active material structural and chemical changes (e.g., silicon and carbon structure changes and fluorinated carbon formation), SEI species (e.g., LiF, Li₂CO₃, LiOH, Li₂O and LiEDC) growth and change, and heterogeneous aging behaviors of SEI species and electrode components across the electrode. Ultimately, we aim to develop in-situ multi-modal characterization techniques—a combination of in-situ vibrational spectroscopy and in-situ gas chromatography with flame ionization detection—enabling a holistic understanding of the battery.<br/><br/><b>References</b><br/>1. S.-D. Han <i>et al.</i>, “Intrinsic Properties of Individual Inorganic Silicon-Electrolyte Interphase Constituents,” <i>ACS Appl. Mater. Interfaces</i> <b>2019</b>, <i>11</i>, 46993.<br/>2. Z. Yang, S.-D. Han <i>et al.</i>, “A New Mechanism of Stabilizing SEI of Si Anode Driven by Crosstalk Behavior and Its Potential for Developing High Performance Si-based Batteries,” <i>Energy Stor. Mater.</i> <b>2023</b>, <i>55</i>, 436.<br/>3. G. M. Carroll, S.-D. Han <i>et al.</i>, “Control of Nanoparticle Dispersion, SEI Composition, and Electrode Morphology Enables Long Cycle Life in High Silicon Content Nanoparticle-based Composite Anodes for Lithium-ion Batteries,” <i>J. Mater. Chem. A</i> <b>2023</b>, <i>11</i>, 5257.<br/>4. S.-D. Han <i>et al.</i>, “Batteries: Materials Principles and Characterization Methods; Chapter 4. Vibrational Spectroscopy for Batteries,” <i>IOP Publishing Ltd.</i> <b>2021</b>.<br/>5. S.-D. Han <i>et al.</i>, “Probing the Evolution of Surface Chemistry at the Silicon-Electrolyte Interphase via <i>In-situ</i> Surface-Enhanced Raman Spectroscopy,” <i>J. Phys. Chem. Lett.</i> <b>2020</b>, <i>11</i>, 286.<br/>6. S.-D. Han <i>et al.</i>, “Effect of Coated Pitch-carbon Properties on Electrochemical Behavior and Performance of Silicon Nanoparticle Anode,” <b>2024</b>, under revision.