Spatially resolved structural order in low-temperature liquid electrolyte

Yujun Xie; Jingyang Wang; Benjamin H Savitzky; Zheng Chen; Yu Wang; Sophia Betzler; Karen Bustillo; Kristin Persson; Yi Cui; Lin-Wang Wang; Colin Ophus; Peter Ercius; Haimei Zheng

doi:10.1126/sciadv.adc9721

Spatially resolved structural order in low-temperature liquid electrolyte

Sci Adv. 2023 Jan 13;9(2):eadc9721. doi: 10.1126/sciadv.adc9721. Epub 2023 Jan 13.

Authors

Yujun Xie^{1

2

3}, Jingyang Wang^{3

4}, Benjamin H Savitzky², Zheng Chen⁵, Yu Wang³, Sophia Betzler³, Karen Bustillo², Kristin Persson^{6

7}, Yi Cui⁴, Lin-Wang Wang³, Colin Ophus², Peter Ercius^{2

3}, Haimei Zheng^{3

7}

Affiliations

¹ Department of Nuclear Engineering, University of California, Berkeley, Berkeley, CA 94720, USA.
² National Center for Electron Microscopy, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
³ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
⁴ Department of Materials Science and Engineering, Stanford University, Palo Alto, CA 94305, USA.
⁵ Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT 06511, USA.
⁶ Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
⁷ Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA 94720, USA.

PMID: 36638171
DOI: 10.1126/sciadv.adc9721

Abstract

Determining the degree and the spatial extent of structural order in liquids is a grand challenge. Here, we are able to resolve the structural order in a model organic electrolyte of 1 M lithium hexafluorophosphate (LiPF₆) dissolved in 1:1 (v/v) ethylene carbonate:diethylcarbonate by developing an integrated method of liquid-phase transmission electron microscopy (TEM), cryo-TEM operated at -30°C, four-dimensional scanning TEM, and data analysis based on deep learning. This study reveals the presence of short-range order (SRO) in the high-salt concentration domains of the liquid electrolyte from liquid phase separation at the low temperature. Molecular dynamics simulations suggest the SRO originates from the Li⁺-(PF₆^-)_n (n > 2) local structural order induced by high LiPF₆ salt concentration.