  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.
