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This content will become publicly available on February 16, 2019

Title: Fluoroethylene Carbonate Induces Ordered Electrolyte Interface on Silicon and Sapphire Surfaces as Revealed by Sum Frequency Generation Vibrational Spectroscopy and X-ray Reflectivity

Here, the cyclability of silicon anodes in lithium ion batteries (LIBs) is affected by the reduction of the electrolyte on the anode surface to produce a coating layer termed the solid electrolyte interphase (SEI). One of the key steps for a major improvement of LIBs is unraveling the SEI’s structure-related diffusion properties as charge and discharge rates of LIBs are diffusion-limited. To this end, we have combined two surface sensitive techniques, sum frequency generation (SFG) vibrational spectroscopy, and X-ray reflectivity (XRR), to explore the first monolayer and to probe the first several layers of electrolyte, respectively, for solutions consisting of 1 M lithium perchlorate (LiClO 4) salt dissolved in ethylene carbonate (EC) or fluoroethylene carbonate (FEC) and their mixtures (EC/FEC 7:3 and 1:1 wt %) on silicon and sapphire surfaces. Our results suggest that the addition of FEC to EC solution causes the first monolayer to rearrange itself more perpendicular to the anode surface, while subsequent layers are less affected and tend to maintain their, on average, surface-parallel arrangements. This fundamental understanding of the near-surface orientation of the electrolyte molecules can aid operational strategies for designing high-performance LIBs.
ORCiD logo [1] ;  [2] ;  [1] ;  [3] ;  [3] ;  [4] ; ORCiD logo [2] ; ORCiD logo [1]
  1. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  3. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States)
  4. Stanford Univ., Stanford, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH1123; AC02-76SF00515
Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 18; Journal Issue: 3; Journal ID: ISSN 1530-6984
American Chemical Society
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
Country of Publication:
United States
electrolyte additives; Lithium ion batteries; sum frequency generation vibrational spectroscopy; X-ray reflectivity
OSTI Identifier: