Coupling between Voltage Profiles and Mechanical Deformations in LAGP Solid Electrolyte during Li Plating and Stripping

Solid electrolytes show a great promise to use Li metal as an anode for high-energy all-solid-state batteries. However, the practical performance of these batteries suffers from severe chemo-mechanical degradation at the solid electrolyte-Li metal electrode interface. It is critical to understand the governing forces behind the chemical and mechanical deformations during battery operation. The buried interface between Li metal and solid electrolyte presents challenges to probe dynamic changes in the interface during battery cycling. In this study, we establish an in operando experimental system by utilizing digital image correlation (DIC). In operando DIC measurements provided temporal and spatial resolution of chemo-mechanical deformations in the LAGP solid electrolyte during the symmetrical cell cycling. The study reports experimental evidence for the correlation between overpotentials and mechanical deformations in the interface. The increase in strains in the interphase layer coincides with the increase in overpotential. At the later cycles, large shear strains (∼0.75%) were generated in the middle of the solid electrolyte where fractures were detected by ex situ micro X-ray computed tomography. This work highlights the mechanical deformations in the LAGP/Li interface and its coupling with the electrochemical behavior of the battery.