Understanding fluorine-free electrolytes via small-angle X-ray scattering

Scientific Achievement

We compare the solvation phenomenon of sodium tetraphenylborate (NaBPh4) salt dissolved in organic solvents of propylene carbonate (PC), 1,2-dimethoxyethane (DME), acetonitrile (ACN) and tetrahydrofuran (THF) by SAXS/WAXS measurement and MD simulation.

Significance and Impact

Fluorine-free electrolytes have attracted great attention because of its low-cost and environmental friendliness. However, so far, little is known about the solution structures of these electrolytes. This work emphasizes the importance of global and local structural analysis of fluorine-free sodium electrolytes, which will provide valuable clues for understanding the structure-performance relationship of electrolytes.

Research Detail

  • A unique structural feature is found in this salt-concentrated PC electrolyte by SAXS. Two characteristic peaks at 0.4 and 0.76 Å-1 emerged in concentrated NaBPh4/PC solution while only one peak at ~0.76 Å-1 can be found in NaBPh4 solutions using other solvents such as DME, ACN, and THF.
  • This two-peak phenomenon is mainly caused by the short-range stacking between bulky BPh4- anions (clusters). The distances between clusters contribute to the unique peak at ~0.4 Å-1.
  • Raman spectroscopy and MD simulations further confirm that there is a large population of CIPs in the concentrated NaBPh4/PC electrolyte.

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DOI: 10.1016/j.jechem.2022.02.043  

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