Understanding Fluoroethylene Carbonate and Vinylene Carbonate Based Electrolytes for Si Anodes in Lithium Ion Batteries with NMR Spectroscopy

Yanting Jin, Nis Julian H. Kneusels, Lauren E. Marbella, Elizabeth Castillo-Martinez, Pieter C.M.M. Magusin, Robert S. Weatherup, Erlendur Jonsson, Tao Liu, Subhradip Paul, Clare P. Grey

    Research output: Contribution to journalArticlepeer-review

    906 Downloads (Pure)

    Abstract

    Fluoroethylene carbonate (FEC) and vinylene carbonate (VC) are widely used as electrolyte additives in lithium ion batteries. Here we analyze the solid electrolyte interphase (SEI) formed on binder-free silicon nanowires (SiNWs) electrodes in pure FEC or VC electrolytes containing 1 M LiPF6 by solid-state nuclear magnetic resonance (ssNMR) with and without dynamic nuclear polarization (DNP) enhancement. We find that the polymeric SEIs formed in pure FEC or VC electrolytes consist mainly of cross-linked polyethylene oxide (PEO) and aliphatic chain functionalities along with additional carbonate and carboxylate species. The formation of branched fragments is further confirmed by 13C-13C correlation NMR experiments. The presence of cross-linked PEO-type polymers in FEC and VC correlates with good capacity retention and high Coulombic efficiencies of the SiNWs. Using 29Si DNP NMR, we are able to probe the interfacial region between SEI and the Si surface for the first time with NMR spectroscopy. Organosiloxanes are identified to form upon cycling, confirming that some of the organic SEI is covalently bonded to the Si surface. We suggest that both the polymeric structure of the SEI and the nature of its adhesion to the redox-active materials are important for electrochemical performance.

    Original languageEnglish
    JournalJournal of the American Chemical Society
    Early online date6 Jul 2018
    DOIs
    Publication statusPublished - 2018

    Fingerprint

    Dive into the research topics of 'Understanding Fluoroethylene Carbonate and Vinylene Carbonate Based Electrolytes for Si Anodes in Lithium Ion Batteries with NMR Spectroscopy'. Together they form a unique fingerprint.

    Cite this