The K3® IS camera is able to provide simultaneous low-dose imaging via a robust combination of real-time electron counting, a large field of view and the rapid continuous capture of data.
The model 626 cryo-transfer holder has been designed to offer frost-free low-temperature sample transfer, allowing the subsequent imaging of radiation-sensitive frozen samples at high resolution while precisely measuring temperature.
A number of emerging and evolving technologies – critical for energy efficiency and sustainability – are reliant on the ongoing development of improved batteries.
The fundamental properties of Lithium (Li) metal make it an attractive anode material, but one factor limiting its use is the formation and later instability of a solid electrolyte interphase (SEI).
Insight into the exact structure and structural dynamics of the SEI in new battery designs is essential in improving their efficiency, but imaging the SEI has historically proven challenging.
As it is a thin and occasionally heterogeneous layer, high-resolution imaging is required. This layer is also relatively sensitive to the electron beam, however, limiting the applicability of standard HR TEM. The experiment presented here aims to observe the SEI in a new electrolyte.1
Materials and Methods
The lithium metal in the novel electrolyte presented here has been prepared by plunge-freezing on a standard Cu transmission electron microscope (TEM) grid.
The sample’s temperature was maintained below 100 K thanks to the model 626 cryo-transfer holder. Prior to imaging, the sample was placed into an image-corrected Titan ETEM.
The image shown here was collected using a K3 IS camera in counted mode, utilizing a dose rate of 40 e-/Å2 per second until a total dose of 70 e-/Å2 was achieved.
Despite the relatively small pixel size of only 0.54 Å, it was possible to image a large sample area (Figure 1). Data is from the dataset also shown in Figure 4 of Wang et al.1
Figure 1. Cryo-TEM image of Li metal filament with SEI. The full field of view is shown along with a smaller region (blue) showing the amorphous SEI and its interfaces with the crystalline Li and solvent more clearly. The orange region shows the visibility of the lattice fringes that exist only within the Li filament. Green and orange insets show FFTs from the corresponding boxed regions. Image Credit: Gatan Inc.
Figure 1 shows a TEM image depicting a Li filament comprised of a single crystal over the observed region.
The SEI on the Li surface was noted to be amorphous, but the application of a low electron dose and dose rate coupled with the low temperature maintained using the model 626 cryo-transfer holder allowed this sample to be imaged despite its sensitivity to the electron beam
- Wang, H. et al. Dual-Solvent Li-Ion Solvation Enables High-Performance Li-Metal Batteries. Adv. Mater. 33, 2008619 (2021).