Probing Highly Sensitive Hard-Soft Interfaces in Energy Devices by Low-Dose Cryo-(S)TEM

Energy storage and conversion devices such as batteries [1], electrolyzers [2], and fuel cells [3], are becoming increasingly important as society shifts to renewable energy production and electrification of transportation. Interfaces between materials within these devices often dictate their overall properties, with length scales for relevant features at these interfaces approaching the atomic scale. Electron microscopy is therefore well suited for studying these important features. Many materials used within next-generation energy storage devices, however, are highly sensitive to high-energy electron probes, such as solid polymer electrolytes (SPEs) within lithium metal batteries (LMBs) and thin-film ion-conducting ionomers and electrode materials within water electrolyzers, making high-resolution characterization of these materials challenging or impossible using conventional (scanning) transmission electron microscopy ((S)TEM) methods.<br/><br/>Here, we will discuss cryogenic (S)TEM (cryo-(S)TEM) techniques that allow highly beam-sensitive materials at hard-soft interfaces in energy devices to be characterized at high resolution. First, we will discuss how automated, low-dose cryo-TEM imaging allows heterogeneous thin-film ionomer properties such as morphology and coverage to be measured statistically as a function of position across an electrode structure. We will additionally discuss how low-dose STEM imaging and electron energy-loss spectroscopy (EELS) allow novel nanoscale structural, compositional, and bonding information to be measured at interfaces between SPEs and high-voltage cathodes (HVCs) in LMBs. These techniques provide access to information typically inaccessible to conventional techniques, and as a result, will help generate a more complete understanding of these hard-soft interfaces critical to energy devices, therefore aiding in design of next-generation devices with improved properties.<br/> <br/>References:<br/>[1] J.M. Tarascon and M. Armand, <i>Nature</i> <b>414</b>, 359 (2001).<br/>[2] K. Ayers et al., <i>Annu Rev Chem Biomol Eng</i> <b>10</b>, 219 (2019).<br/>[3] D.A. Cullen et al., <i>Nat Energy</i> <b>6</b>, 462 (2021).<br/> <br/>This material is based upon work supported by the U.S. Department of Energy, Office of Science Energy Earthshot Initiative as part of the Center for Ionomer-based Water Electrolysis at Lawrence Berkeley National Laboratory under contract #DE-AC02-05CH11231, as well as by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (ORNL, managed by UT-Battelle, LLC for the U.S. Department of Energy) under Contract no. DEAC05-00OR22725. In addition, the electron microscopy portion of this research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory.