Decoupling Electrochemical Reaction and Diffusion Processes in Ionically-Conductive Solids on the Nanometer Scale

Abstract

We have developed a scanning probe microscopy approach to explore voltage-controlled ion dynamics in ionically conductive solids and decouple transport and local electrochemical reactivity on the nanometer scale. Electrochemical strain microscopy allows detection of bias-induced ionic motion through the dynamic (0.1-1 MHz) local strain. Spectroscopic modes based on low-frequency (∼1 Hz) voltage sweeps allow local ion dynamics to be probed locally. The bias dependence of the hysteretic strain response accessed through first-order reversal curve (FORC) measurements demonstrates that the process is activated at a certain critical voltage and is linear above this voltage everywhere on the surface. This suggests that FORC spectroscopic ESM data separates local electrochemical reaction and transport processes. The relevant parameters such as critical voltage and effective mobility can be extracted for each location and correlated with the microstructure. The evolution of these behaviors with the charging of the amorphous Si anode in a thin-film Li-ion battery is explored. A broad applicability of this method to other ionically conductive systems is predicted.

Ferroelectric or non-ferroelectric: Why so many materials exhibit “ferroelectricity” on the nanoscale

“…Recently, it was proposed that application of electric bias to the ionically conductive material will result in ionic motion, and, via Vegard strain, will give rise to the surface displacement. 247 This concept was utilized in Electrochemical Strain Microscopy (ESM), [248][249][250][251] allowing visualization of phenomena such as electrochemical activity on cathode 252 and anode 253 materials, oxides [254][255][256] and semiconductors. Similar to PFM, ESM can be extended to a variety of time-and bias-spectroscopic modes.…”

In situ methods for Li-ion battery research: A review of recent developments

“…This technique, denoted electrochemical strain microscopy (ESM) [35], is based on the application of periodic high frequency voltage-bias between the cathode and anode. The resulting oscillatory surface displacement on top of the thin film battery can then locally be detected by the AFM tip.…”

Chemomechanics of ionically conductive ceramics for electrical energy conversion and storage

“…Synchrotron X-rays [21] and combinations of scanning transmission electron microscopy and electron energy loss spectroscopy (EELS) [20,22] have been successfully used for obtaining localized electronic information on oxide hetero-interfaces. Scanning probe techniques are ideal for studying local electronic, magnetic, or electrochemical properties on surfaces [23][24][25][26]. Even more challenging is to access interfaces buried within multilayered structures.…”