Visualizing Battery Reactions and Processes by Using In Situ and In Operando Microscopies

Abstract

Based on traditional electronic, X-ray, and optical microscopies, novel tools and methodologies have been developed to monitor batteries in situ or in operando. This review surveys the recent development of several types of in situ and in operando microscopy and their utilization in studying batteries. The article is organized mainly by the in situ and in operando techniques used (X-ray microscopy, electron microscopy, scanning probe microscopy, etc.) rather than the chemical reactions that govern battery behavior. We compare different methodologies to illustrate their advantages and disadvantages in the study of different systems and problems and, at the end of the article, discuss generalized principles for the selection of methodologies and possible future directions.

Exploring Flow Characteristics in Vanadium Redox‐Flow Batteries: Optical Measurements and CFD Simulations

“…However, with the current setup of the optical measurements, the electrolyte behavior at the fiber level is not recordable. To do so other visualization and modeling techniques such as X-ray imaging are applicable [21,30]. As the experimental results for thickened water and PE differ only slightly, the potential of the optical measurements is emphasized by allowing to observe the transport process in the test half-cell of the original fluid and carbon felt electrode material for the VFB.…”

Side‐View Operando Optical Microscopy Analysis of a Graphite Anode to Study Its Kinetic Hysteresis

“…For example, it allows us to utilize an electrochemical cell configuration similar to a real battery, which consists of liquid electrolytes and conventional electrodes fabricated on Cu or Al current collectors. Basically, in both cases, the interactions between charge transfer and diffusion of lithium ions are governed by the active materials in the electrodes rather than by the electrolytes . In contrast, the configurations of many spectroscopic analyses and scanning and transmission electron microscopes obfuscate this underlying mechanism owing to relatively large electrolyte contents in their minuscule devices, which lead to electrolyte‐dominant reactions during the operando analysis.…”

“…Basically,i nb oth cases,t he interactions between charge transfer and diffusion of lithium ions are governed by the active materials in the electrodes rather than by the electrolytes. [13][14][15] In contrast, the configurations of many spectroscopic analyses and scanning and transmission electron microscopeso bfuscate this underlying mechanism owing to relativelyl arge electrolyte contents in their minuscule devices, which lead to electrolyte-dominant reactions during the operando analysis.Graphite anodesa re still the most promising candidates for commercial application in lithium-ion batteries (LIBs), but retaining their kinetics on repeatedc harge-discharge cycles is a scientificchallenge. [16,17] In particular,understanding their kinetics at the electrode level is crucial to satisfy the high demand for rapid-charging batteries with the current LIB systems.…”

“…Basically,i nb oth cases,t he interactions between charge transfer and diffusion of lithium ions are governed by the active materials in the electrodes rather than by the electrolytes. [13][14][15] In contrast, the configurations of many spectroscopic analyses and scanning and transmission electron microscopeso bfuscate this underlying mechanism owing to relativelyl arge electrolyte contents in their minuscule devices, which lead to electrolyte-dominant reactions during the operando analysis.…”

In‐Operando Mapping of pH Distribution in Electrochemical Processes

“…Various methods have been used to visualize processes occurring in electrochemical cells, including electron, X‐ray, and optical microscopy . To visualize the chemical boundary layer, fluorescence and electrogenerated luminescence methods have been reported .…”