Spatially resolved structural order in low-temperature liquid electrolyte
Yujun Xie, Jingyang Wang, Benjamin H. Savitzky, Zheng Chen, Yu Wang, Sophia B. Betzler, Karen C. Bustillo, Kristin A. Persson, Yi Cui, Lin‐Wang Wang, Colin Ophus, Peter Ercius, Haimei Zheng
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 (LiPF 6 ) 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 + -(PF 6 − ) n ( n > 2) local structural order induced by high LiPF 6 salt concentration.