In situ and operando force‐based atomic force microscopy for probing local functionality in energy storage materials

Abstract

Electrochemical energy storage is the key enabling component of electric vehicles and solar‐/wind‐based energy technologies. The enhancement of energy stored requires the detailed understanding of charge storage mechanisms and local electrochemical and electromechanical phenomena over a variety of length scales from atoms to full cells. Classical electrochemical techniques, such as voltammetry, represent the macroscopic electrochemical properties, and consequently do not allow to extract important information about local electrochemical reactions, ions adsorption, intercalations, and transport. Understanding, controlling, and tuning the local electrochemical functionalities in functional energy materials require in situ/operando techniques which limit the use of structural and functional characterization techniques that provide local information. Here, force‐based atomic force microscopies (AFMs) have provided novel insights into locally probing electrochemical mechanisms on tens of nanometer and even molecular length scales and provide a viable pathway to probe electrochemical processes in situ/operando. In this review, we highlight the contributions in the development and application of force‐based AFM methods to elucidate the local charge storage mechanism in a variety of energy‐related materials. We will focus in particular on methods or AFM modalities in a liquid electrolyte environment.

Elucidation of the Charging Mechanisms and the Coupled Structural–Mechanical Behavior of Ti3C2Tx (MXenes) Electrodes by In Situ Techniques

“…The main tool for in situ morphological characterizations of MXene electrodes is AFM. [ 60 ] Come et al. employed contact resonance (CR) frequency AFM imaging [ 61 ] to quantify the elastic properties of Ti 3 C 2 T x (MXene) paper electrodes during electrochemical cycling.…”

Future Directions for Electrochemical Capacitors

“…Another recent development has been the use of atomic force microscopy (AFM) with an in situ electrochemical cell. The advantage here is the ability to determine the electrode volume change at the nanometer level as a function of applied potential (Figure c). The development of scanning electrochemical microscopy (SECM) is certain to have an impact on understanding the electrode–electrolyte interface as it enables one to determine local electrode reactivity and kinetic parameters of the electrochemical processes by recording the current flowing through an ultramicroprobe electrode (the tip), while controlling the tip-electrode distance (Figure d).…”

“…The advantage here is the ability to determine the electrode volume change at the nanometer The development of advanced in situ analytical techniques to understand fundamental electrochemical processes and structural effects down to the nanoscale level will help in better understanding the ion adsorption and electron transfer in (pseudo)capacitive materials. level as a function of applied potential 16 (Figure 1c). The development of scanning electrochemical microscopy (SECM) is certain to have an impact on understanding the electrode− electrolyte interface as it enables one to determine local electrode reactivity and kinetic parameters of the electrochemical processes by recording the current flowing through an ultramicroprobe electrode (the tip), while controlling the tip-electrode distance 17 (Figure 1d).…”

Molecular-Resolution Imaging of Interfacial Solvation of Electrolytes for Lithium-Ion Batteries by Frequency Modulation Atomic Force Microscopy

“…In recent years, the solvation structure at the solid/liquid interface has been investigated by X-ray reflectometry − and sum frequency generation. − For example, X-ray reflectometry can precisely measure the one-dimensional structure of solvation shells in the direction perpendicular to the interface, but it cannot provide information in the plane parallel to the interface; thus, it is difficult to evaluate the solvation structure in a specific area of concern. There is also a growing interest in the evaluation of high-resolution solid/liquid interfaces using atomic force microscopy . Especially, the solid/liquid interface measurement method using frequency modulation atomic force microscopy (FM-AFM), which has an atomic resolution in liquid, has made great progress in recent years.…”

“…There is also a growing interest in the evaluation of high-resolution solid/ liquid interfaces using atomic force microscopy. 13 Especially, the solid/liquid interface measurement method using fre- Initially, FM-AFM imaging in liquid was mainly focused on the solid/water interface, such as the hydration structure on the surface of mica 14−16 and highly oriented pyrolytic graphite. 17 However, recently, molecular scale structures at the interface between liquids other than aqueous solutions, such as ionic liquids, and solids have also been investigated.…”