Deformation and Chemomechanical Degradation at Solid Electrolyte–Electrode Interfaces

Solid electrolytes in batteries are inevitably subjected to mechanical strains when the active materials undergo chemically induced volume changes. It is difficult to probe these effects in complex battery structures. Thus, we developed a new in situ method to monitor mechanical deformation during electrochemical cycling, using simplified thin-film structures. This approach was applied to polymer electrolytes on V 2 O 5– x thin-film electrodes. Analysis of these deflection measurements was performed with a finite element model. The results indicate that the electrolyte compliance is rate-dependent and that it varies with the polymer molecular weight. Our approach was also employed to investigate interactions between chemical and mechanical changes at the solid electrolyte–electrode interface. Here, in situ stress studies were combined with impedance spectroscopy and ex situ peel tests. These results show that interfacial chemistry changes during electrochemical cycling lead to a significant decrease in the electrolyte–electrode adhesion energy.