A coupled electrochemical-mechanical model for all-solid-state lithium batteries with pre-stretched solid polymer electrolytes

Tensile pre-strain presents a promising approach to solving the constraints of solid polymer electrolytes (SPEs) in flexible batteries at room temperatures. In this study, electrochemical impedance spectroscopy and uniaxial tensile tests were conducted on polyethylene oxide (PEO)-based SPEs at various tensile pre-strains within the temperature range of 20–50 °C. Subsequently, a pre-strain and temperature-dependent ionic conductivity model and a viscoelastic-viscoplastic mechanical model considering tensile pre-strain were established for PEO-based SPEs. A fully coupled electrochemical-mechanical model of all-solid-state lithium batteries (ASSLBs) with pre-stretched SPEs was established on this basis. The electrochemical and mechanical properties of ASSLBs utilizing different pre-stretched SPE configurations were investigated. The results indicate that the discharge capacity of the battery can be improved by pre-stretching the SPE. The effects of operating temperature, discharge rate, SPE thickness, and residual stress on the discharge capacity and mechanical properties of ASSLBs were discussed. The results show that appropriately increasing the operating temperature can augment the discharge capacity of the ASSLB while ensuring the mechanical integrity of the SPE. Notably, the discharge capacity improvement effect of batteries with pre-stretched SPE is more obvious. Additionally, pre-stretched SPE can increase the discharge capacity and stabilize the discharge platform of the battery at higher rates. Reducing the thickness of SPE can significantly decrease the internal stress of pre-stretched SPE while increasing the discharge capacity of ASSLBs, thereby improving the mechanical reliability of the cell. Tensile residual stress is detrimental to the mechanical durability of the ASSLB, although it could improve its capacity. This model provides an effective way for performance evaluation and optimization of stretchable ASSLBs under various operational conditions and structural parameters. •Proposed coupled electrochemical-mechanical model for ASSLBs with pre-stretched SPEs•A phenomenological model of ionic conductivity for PEO-based SPEs with tensile pre-strain•The simulated results agree well with the experimental data.•ASSLBs with pre-stretched SPEs have higher capacity.•ASSLB performs better at high temperatures and C-rates when appropriately pre-strained.