In situ AFM Observations of Li-Oxygen Electrochemical Reactions

TL;DR

This paper presents a new enclosed in situ AFM cell enabling real-time high-resolution imaging of Li2O2 growth in Li-O2 batteries under controlled, air-free conditions, advancing mechanistic understanding of discharge product formation.

Contribution

The development of a fully enclosed, environment-controlled AFM cell allows for real-time observation of Li2O2 morphology during battery discharge, providing new insights into reaction mechanisms.

Findings

Different Li2O2 morphologies observed under various conditions

Enclosed AFM cell enables real-time imaging in controlled environments

Supports multiple proposed mechanisms for Li-O2 reactions

Abstract

The morphologies of crystalline lithium peroxide (Li2O2) discharge products in Li-O2 batteries have been shown to exhibit a dependency on subtle variations within the battery cell-operating environment including exposure to ambient air, moisture, or additives. As a result, imaging battery discharge products in real time under carefully controlled environmental conditions is a challenging obstacle for complete mechanistic understanding of Li2O2 growth and deposition during discharge in metal-air batteries. Here, we report the design of a completely enclosed cell for high-resolution in situ AFM imaging of Li-O2 battery discharge products. The air-and moisture-free electrochemical cell environment enabled the observation of different product morphologies during AFM imaging when LiTFSI in oxygen-saturated tetraethylene glycol dimethyl ether (tetraglyme) solvent was employed. This in situ AFM cell development brings complimentary information to various proposed mechanisms for lithium oxygen reaction.