Correlative In-Situ Liquid Cell Electrochemistry TEM and Cryogenic APT of Liquid-Solid Interfaces

Liquid cell transmission electron microscopy (LCTEM) allows for solution phase dynamic processes to be visualised and probed at the nanoscale at unprecedented temporal and spatial resolutions in comparison to other liquid microscopy techniques such as light and physical probe microscopes. Additionally, MEMS based biasing sample holder chip design has provided a platform to perform electrochemical experiments to replicate battery cycling experiments within the electron microscope.<br/>While these experiments have been useful for gaining a micro and nanoscale in-situ understanding of electrochemical processes that occur at solid-liquid interfaces of battery materials, the current spatial resolution of liquid processes within the TEM is still not capable of resolving and quantifying complex dynamic nanoscale structures at atomic resolutions. As a result, the performance of electrochemical systems is currently limited due to a lack of understanding of complex interactions that occur between mobile species and electrode materials. Finding a correlative high-resolution characterisation method which is compatible with both the liquid and solid component of the interface is of great importance to gain a fundamental understanding of these processes at an atomic level.<br/>Cryogenic focused ion beam (FIB) preparation and atom probe tomography (APT) has allowed researchers to investigate the native liquid-solid interfaces of samples by vitrifying the liquid phase at the near to atomic scale. In this presentation we will present how one can combine in-situ electrochemistry LCTEM with site specific cryogenic atom probe tomography. We investigate Li based solid electrode interfaces and dendrites formed during the lithiation cycling.<br/>While there have been numerous examples in recent years of room temperature correlative TEM and APT, there has been no such examples of correlative LCTEM-APT or correlative cryogenic TEM-APT. The primary reason for this is the difficulty in transferring, preparing, and maintaining specimens in **cryogenic conditions**. In this study, the liquid in the LCTEM chips are cryogenically vitrified following in-situ electrochemical LCTEM experiments, in order to allow APT needle samples to be created from the liquid-solid interface of interest. Recent advances in vacuum cryo transfer module technology, and cryogenic FIB site specific sample preparation workflows, have allowed for this type of correlative cryogenic multi-microscopy approach to be realised.