Local probing of ionic diffusion by electrochemical strain microscopy: spatial resolution and signal formation mechanisms

TL;DR

This paper analyzes the mechanisms of electrochemical strain microscopy (ESM) for probing ionic diffusion at nanometer scales, developing analytical models and comparing ESM with classical electrochemical techniques to enable high-resolution spatial studies.

Contribution

It provides an analytical description of ESM signal formation in frequency and time domains and demonstrates its potential for sub-10 nanometer resolution in studying Li-ion dynamics.

Findings

ESM signal formation mechanisms are analytically described.

ESM can achieve sub-10 nanometer spatial resolution.

Comparison shows ESM's advantages over classical electrochemical methods.

Abstract

Electrochemical insertion-deintercalation reactions are typically associated with significant change of molar volume of the host compound. This strong coupling between ionic currents and strains underpins image formation mechanisms in electrochemical strain microscopy (ESM), and allows exploring the tip-induced electrochemical processes locally. Here we analyze the signal formation mechanism in ESM, and develop the analytical description of operation in frequency and time domains. The ESM spectroscopic modes are compared to classical electrochemical methods including potentiostatic and galvanostatic intermittent titration (PITT and GITT), and electrochemical impedance spectroscopy (EIS). This analysis illustrates the feasibility of spatially resolved studies of Li-ion dynamics on the sub-10 nanometer level using electromechanical detection.