Role of residual thermal stress on the electrochemical performance of a solid-state half-cell

Synthesizing a solid electrolyte layer with a positive electrode layer requires a high-temperature sintering process to improve the interface contact between the two layers. This may generate substantial residual thermal stress between the components during cooling. In this study, we develop a theoretical model to investigate the influence of residual thermal stress on the electrochemical performance of a solid-state half-cell (solid electrolyte–positive electrode). The model accounts for the stress–diffusion interaction and electrochemical reaction and is based on the classical plate theory. The numerical results indicate that, although the residual thermal stress could effectively improve the half-cell capacity, the structural mechanical reliability is reduced. The improvement in the battery capacity is found to be highly dependent on the ratio of the thermal expansion coefficients of the solid electrolyte and the positive electrode. The thermal expansion coefficients determine whether the operating temperature needs to be raised or reduced. Additionally, under the influence of residual thermal stress, reasonable control of the thickness of a solid electrolyte can significantly improve battery capacity. Finally, by examining the stress drop at the interface, we found that introducing residual thermal stress is detrimental to the structural mechanical reliability of the half-cell, meaning that the conflicting demands for improved capacity and mechanical reliability seem irreconcilable.