Emerging Electron Microscopy Techniques for Probing Functional Interfaces in Energy Materials

Abstract

Interfaces play a fundamental role in many areas of chemistry. However, their localized nature requires characterization techniques with high spatial resolution in order to fully understand their structure and properties. State‐of‐the‐art atomic resolution or in situ scanning transmission electron microscopy and electron energy‐loss spectroscopy are indispensable tools for characterizing the local structure and chemistry of materials with single‐atom resolution, but they are not able to measure many properties that dictate function, such as vibrational modes or charge transfer, and are limited to room‐temperature samples containing no liquids. Here, we outline emerging electron microscopy techniques that are allowing these limitations to be overcome and highlight several recent studies that were enabled by these techniques. We then provide a vision for how these techniques can be paired with each other and with in situ methods to deliver new insights into the static and dynamic behavior of functional interfaces.

Controlling electrochemical growth of metallic zinc electrodes: Toward affordable rechargeable energy storage systems

“…A few studies report on the crystallographic orientation of Zn deposits obtained with pulsed protocol (192,193). The correlation is, however, not straightforward, unlike what has been shown for Cu deposition-Strong (111), (100), and (101) textures can be achieved respectively by optimization of the pulse parameter (194). In light of the greater crystal anisotropy of Zn than Cu, we speculate that similar quality of texturing can be realized in Zn systems, which warrants further explorations.…”

“…Similarly, the Zn structure shown in Fig. 4C also extends along a low-index zone axis, i.e., [1 ¯ 2 0], allowing the exposure of (002) and (100). The analogy between Li and Zn further suggests that the moss-like Zn electrodeposits are formed in a SEI-dominated regime.…”

“…For example, some claim that Zn 4 SO 4 (OH) 6 •4H 2 O is also detected on electrodeposited Zn metal (97)(98)(99), as opposed to the ZnO observed in other studies as mentioned. Advanced characterization techniques, e.g., high-resolution TEM/scanning TEM, could provide important insights into the SEI of Zn metal to resolve these remaining questions about the nature of SEI and the role it plays in electrodeposition, particularly considering that Zn metal samples are not as sensitive to atmosphere or to beam damage as Li samples are (100).…”

Determination of the embedded electronic states at nanoscale interface via surface-sensitive photoemission spectroscopy

“…Emerging electron microscopy techniques, based on scanning transmission electron microscopy (STEM) and/or electron energy loss spectroscopy (EELS) (such as 4D-STEM, cryo-STEM, and monochromated EELS) are very useful tools for probing functional interfaces in energy materials (as shown typically in Fig. 1 ) 24 , 25 . Spatially resolved EELS is capable of examining the conduction band structure and has been used to study the electronic changes at perovskite oxide heterointerfaces 7 , 26 , 27 .…”

Atomic-Resolution Cryo-STEM Across Continuously Variable Temperatures

“…As atomic-resolution imaging and spectroscopy of crystalline materials at room temperature has become almost routine, the interest in cryogenic electron microscopy for the physical sciences has been renewed (El Baggari & Kourkoutis, 2019; Minor et al, 2019; Zachman et al, 2020). Recent results have demonstrated the potential for cryogenic scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy to explore quantum materials phenomena including low-temperature spin states (Klie et al, 2007), emergent charge density phases (El Baggari et al, 2018), and interface charge transfer (Zhao et al, 2018).…”