In Situ Measurements of Stress-Potential Coupling in Lithiated Silicon

TL;DR

This study combines thermodynamic analysis and in situ experiments to quantify the stress-potential coupling in lithiated silicon electrodes, revealing a significant impact on electrochemical behavior and capacity.

Contribution

It provides the first direct measurement of stress-potential coupling in silicon electrodes, confirming theoretical predictions and highlighting its importance in battery performance.

Findings

Stress-potential coupling estimated at ~60 mV/GPa theoretically.

Experimental measurements show coupling of 100-120 mV/GPa.

Stress influences maximum charge capacity and hysteresis in silicon electrodes.

Abstract

An analysis of the dependence of electric potential on the state of stress of a lithiated-silicon electrode is presented. Based on the Larch\'e and Cahn chemical potential for a solid solution, a thermodynamic argument is made for the existence of the stress-potential coupling in lithiated-silicon; based on the known properties of the material, the magnitude of the coupling is estimated to be ca. 60 mV/GPa in thin-film geometry. An experimental investigation is carried out on silicon thin-film electrodes in which the stress is measured in situ during electrochemical lithiation and delithiation. By progressively varying the stress through incremental delithiation, the relation between stress change and electric-potential change is measured to be 100 - 120 mV/GPa, which is of the same order of magnitude as the prediction of the analysis. The importance of the coupling is discussed in interpreting the hysteresis observed in potential vs. state-of-charge plots, and the role of stress in modifying the maximum charge capacity of a silicon electrode under stress.