Additive-Specific SEI Nanostructures on Silicon Anodes Revealed by Cryo-TEM and EELS under Suppressed Bulk Alloying.
basic_science · Level V
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- Record sourced from PubMed, PMID 41964587.
- Also identified by DOI 10.1021/acs.nanolett.6c00141.
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Abstract
Silicon anodes suffer from unstable solid electrolyte interphases (SEI) that drive capacity fade. Here, using low-dose cryogenic TEM and EELS under suppressed bulk Li-Si alloying (0.1 V vs Li/Li<sup>+</sup> cutoff, 10 cycles), we resolve the atomic-scale SEI nanostructures induced by fluoroethylene carbonate (FEC), ethylene sulfite (ES), and lithium difluorophosphate (LiPO<sub>2</sub>F<sub>2</sub>). FEC forms a dense ∼20 nm LiF-rich nanocrystal scaffold, ES produces a 10-20 nm heterogeneous mosaic of LiF/Li<sub>2</sub>SO<sub>4</sub> within an organic-rich matrix, and LiPO<sub>2</sub>F<sub>2</sub> yields an ultrathin (∼10 nm) inorganic-dominated but brittle layer. Despite being the thickest, the FEC-derived SEI delivers the best long-term cycling stability. Mechanistically, optimal performance arises from a balanced architecture that combines strong electronic insulation, efficient Li<sup>+</sup> transport across grain boundaries, and mechanical coherence rather than minimized thickness alone. These findings identify composition and nanostructural continuity as key regulators of interfacial stability in silicon anodes.